diff --git a/MIM-104D/MIM-104D-set.xml b/MIM-104D/MIM-104D-set.xml
index 00cd04a..042ec5a 100644
--- a/MIM-104D/MIM-104D-set.xml
+++ b/MIM-104D/MIM-104D-set.xml
@@ -378,7 +378,7 @@
         <damage type="double">100</damage>
     </sam>
 
-        <enemies>
+    <enemies>
         <e1 userarchive="y" type="string">target1</e1>
         <e2 userarchive="y" type="string">target2</e2>
         <e3 userarchive="y" type="string">target3</e3>
@@ -395,6 +395,17 @@
 
     <priority type="int">0</priority>
     <priority0 type="int">1</priority0>
+
+    <instrumentation>
+        <datalink>
+            <data type="int">0</data>
+            <power type="bool">true</power>
+            <channel type="int">1212</channel>
+            <power_prop type="string">/instrumentation/datalink/power</power_prop>
+            <channel_prop type="string">instrumentation/datalink/channel</channel_prop>
+            <receive_period type="double">1</receive_period>
+        </datalink>
+    </instrumentation>
 	
     <nasal>
         <!--emesary><file>Aircraft/S-300/Nasal/emesary.nas</file></emesary>
@@ -418,7 +429,11 @@
         <armament>
             <file>Aircraft/MIM-104D/Nasal/guided-missiles.nas</file>
         </armament>
+        <datalink>
+            <file>Aircraft/MIM-104D/Nasal/datalink.nas</file>
+        </datalink>
 		<fire_control>
+            <file>Aircraft/MIM-104D/Nasal/fire-control-custom.nas</file>
 			<file>Aircraft/MIM-104D/Nasal/fire-control.nas</file>
 		</fire_control>
     </nasal>
diff --git a/MIM-104D/Nasal/datalink.nas b/MIM-104D/Nasal/datalink.nas
new file mode 100644
index 0000000..7b88482
--- /dev/null
+++ b/MIM-104D/Nasal/datalink.nas
@@ -0,0 +1,681 @@
+#### Datalink
+
+# Copyright 2020-2021 Colin Geniet.
+# Licensed under the GNU General Public License 2.0 or any later version.
+
+
+#### Usage
+
+### Generalities
+#
+# The datalink protocol consists of a core protocol which implements a notion
+# of datalink channel, and extensions which allow transmitting actual data.
+
+### Core protocol usage:
+#
+# Define the following properties (must be defined at nasal loading time).
+# * Mandatory
+#   /instrumentation/datalink/power_prop                path to property indicating if datalink is on
+#   /instrumentation/datalink/channel_prop              path to property containing datalink channel
+#   (the channel property can contain anything, and is transmitted/compared as a string).
+# * Optional
+#   /instrumentation/datalink/receive_period = 1        receiving loop update rate
+#
+# Optional: Re-define the function
+#   datalink.can_transmit(callsign, mp_prop, mp_index)
+#
+# This function should return 'true' when the given aircraft is able to transmit over datalink to us.
+# For instance, it can be used to check line of sight and maximum range.
+# The default implementation always returns true (always able to transmit).
+# Arguments are callsign, property node /ai/models/multiplayer[i], index of the former node.
+#
+#
+# API:
+# - get_data(callsign)
+#     Returns all datalink information about 'callsign' as an object, or nil if there is none.
+#     This object must not be modified.
+#     It contains the following methods:
+#       callsign(): The aircraft callsign (same as the argument of get_data()).
+#       index():    The aircraft index in /ai/models/multiplayer[i].
+#       on_link():  Returns a bool indicating whether 'callsign' is connected to this aircraft through datalink.
+#
+#     Extensions can define other methods in this object.
+#
+# - get_connected_callsigns() / get_connected_indices()
+#     Returns a vector containing all callsigns, resp. indices
+#     in /ai/models/multiplayer[i], of aircrafts connected on datalink.
+#     Both vectors use the same order, i.e. get_connected_callsigns()[i]
+#     and get_connected_indices()[i] correspond to the same aircraft.
+#     Furthermore this order is stable (the relative order of two aircrafts
+#     does not change as long as neither disconnects from multiplayer).
+#
+# - get_all_callsigns()
+#     Returns a vector containing all callsigns of aircraft with any associated data.
+#     There is no guarantee on the order of callsigns.
+#
+# - send_data(data, timeout=nil)
+#     Send data on the datalink. 'data' is a hash of the form
+#       {
+#           <extension_name>: <extension_data>,
+#           ...
+#       }
+#     If 'timeout' is set, clear_data() will be called after this delay.
+#     Data sent with send_data() is deleted at the next call of send_data(), or by clear_data().
+#
+# - clear_data()
+#     Clear data transmitted by this aircraft.
+#
+# Important note:
+# After a send_data(), and until the next send_data() or clear_data(),
+# the datalink behaves as if you are continuously sending the same data.
+# Thus, it is important to
+#   1. either call send_data() regularly
+#   2. or set the timeout argument of send_data()
+
+### Extensions
+
+### Aircraft contacts (extension name: "contacts")
+#
+# This extension allows to simulate an aircraft transmitting information about
+# another aircraft (typically one tracked on radar). The position data is not
+# actually transmitted (since everyone can access it from simulator internals).
+#
+## Receiving data
+# This extension adds the following methods to the result of get_data("A"):
+#       tracked():          A bool indicating that some aircraft "B" connected on datalink
+#                           is transmitting information about aircraft "A".
+#       iff():              One of IFF_UNKNOWN, IFF_HOSTILE, IFF_FRIENDLY, or nil if tracked() is false.
+#                           Indicates the result of IFF interrogation of "A" by "B"
+#                           IFF_UNKNOWN means that e.g. no IFF interrogation was performed.
+#       tracked_by():       The callsign of the transmitting aircraft ("A"), or nil if tracked() is false.
+#       tracked_by_index(): The index of the transmitting aircraft, or nil if tracked() is false.
+#                           The index refers to property nodes /ai/models/multiplayer[i].
+#       is_known():         Equivalent to (on_link() or tracked()).
+#                           Indicates if the position of this aircraft is supposed to be known
+#                           (i.e. whether or not it should be displayed on a HSD or whatever).
+#       is_friendly():      Equivalent to (on_link() or iff() == IFF_FRIENDLY).
+#       is_hostile():       Equivalent to (!on_link() and iff() == IFF_HOSTILE).
+#
+## Sending data
+# usage: send_data({ contacts: <contacts>, ...}, ...)
+# where <contacts> is a vector of hashes of the form { callsign: <callsign>, [iff: <iff>,] }.
+# <callsign> is the multiplayer callsign of the tracked aircraft.
+# <iff> (optional) is one of IFF_UNKNOWN, IFF_HOSTILE, IFF_FRIENDLY
+
+### Datalink identifier (extension name: "identifier")
+#
+# This extension allows each aircraft on datalink to transmit a personal
+# identifier, e.g. the number of the aircraft in a flight.
+#
+## Receiving data
+# This extension adds the method identifier() to the result of get_data(),
+# which returns the identifier, or nil if there is none).
+#
+## Sending data
+# Set the identifier with send_data({"identifier": <identifier>, ...});
+# The identifier must be a string. It must not contain '!'.
+
+### Coordinate transmission (extension name: "point")
+#
+# This extension allows each aircraft to broadcast a coordinate (geo.Coord object).
+#
+## Receiving data
+# This extension adds the method point() to the result of get_data(),
+# which results the transmitted geo.Coord object, or nil if there is none.
+#
+## Sending data
+# Transmit a geo.Coord object <coord> with send_data({"point": <coord>, ...});
+
+
+#### Protocol:
+#
+# Data is transmitted on MP generic string[7], with the following format:
+#   <channel>(!<data>)+
+#
+# <channel> is a hash of the datalink channel. See hash_channel() and check_channel_hash().
+# Each <data> block corresponds to data sent by an extension.
+# It starts with a prefix uniquely defining the extension.
+# The rest of the block can contain any character (including non-ascii) except '!'.
+#
+# Remark: '!' as separator is specifically chosen to allow encoding with emesary.Transfer<type>.
+#
+# The current extension prefixes are the following:
+#   contacts:   C
+#   identifier: I
+#   point:      P
+
+#### Extensions API
+#
+# Creating a new extension is done with
+#   register_extension(name, prefix, object, encode, decode)
+# name                      the extension name, used as key in the 'data' argument of send_data().
+# prefix                    the protocol prefix.
+# class                     contact class parent.
+#   A class from which all contact objects will inherit.
+#   It must have an init() method, which is called whenever a contact is created.
+#
+# encode(data)              extension encoding function.
+#   Must return the encoding of the extension data (i.e. <data> when calling
+#   send_data({name: <data>})) into a string, which may use any character except '!'.
+#   The extension prefix must not be part of the encoded string.
+#
+# decode(aircrafts_data, callsign, index, string)      extension decoding function.
+#   'aircrafts_data' is a hash from callsigns to contact objects (see below).
+#   'callsign' is the callsign of the aircraft which transmitted this data.
+#   'index' is the index of the aircraft which transmitted this data.
+#   'string' is the data encoded by encode() and transmitted through datalink.
+
+#   Each contact in 'data' inherits from the core 'Contact' class, and the extension 'class'.
+#   decode() is expected to modify 'aircrafts_data', by possibly editing
+#   existing contacts and adding new ones.  It should be careful when
+#   overwriting existing data in these contacts, including its own: decode()
+#   will be called several time on the same 'aircrafts_data' (once for each
+#   transmitting aircraft).
+#   The modified 'aircrafts_data' hash must be returned.
+#
+# decode() may use the following helper functions:
+#   add_if_missing(aircrafts_data, callsign):
+#     Create a new contact object for 'callsign' and add it to 'aircrafts_data',
+#     unless an entry for 'callsign' already exists. Returns the modified hash.
+
+
+
+#### Version and changelog
+# current: v1.1.0, minimum compatible: v1.0.0
+#
+## v1.1.0:
+# Allow external transmission restrictions
+# Make transmitting contact IFF optional
+# Ensure personal identifier has no '!'
+# '\n' is redundant for printf()
+# Fix separator character in documentation
+# Fix error when sending unknown extension
+#
+## v1.0.1:
+# Add is_known(), is_friendly(), is_hostile() helpers to extension "contacts".
+#
+## v1.0.0: Initial version
+# - Core protocol for datalink channel.
+# - Extensions "contacts", "identifier", and "point".
+
+
+
+### Parameters
+#
+# Remark: most parameters need to be the same on all aircrafts.
+
+# Index of multiplayer string used to transmit datalink info.
+# Must be the same for all aircrafts.
+var mp_string = 7;
+var mp_path = "sim/multiplay/generic/string["~mp_string~"]";
+
+var channel_hash_period = 600;
+
+var receive_period = getprop("/instrumentation/datalink/receive_period") or 1;
+
+# Should be overwitten to add transmission restrictions.
+var can_transmit = func(contact, mp_prop, mp_index) {
+    return 1;
+}
+
+### Properties
+
+var input = {
+    power:      getprop("/instrumentation/datalink/power_prop"),
+    channel:    getprop("/instrumentation/datalink/channel_prop"),
+    ident:      getprop("/instrumentation/datalink/identifier_prop"),
+    mp:         mp_path,
+    models:     "/ai/models",
+    callsign:   "/sim/multiplay/callsign",
+};
+
+foreach (var name; keys(input)) {
+    if (input[name] != nil) {
+        input[name] = props.globals.getNode(input[name], 1);
+    }
+}
+
+
+
+#### Core protocol implementation
+
+### Channel hash (based on iff.nas)
+#
+# Channel is hashed with current time (rounded to 10min) and own callsign.
+
+var clean_callsign = func(callsign) {
+    return damage.processCallsign(callsign);
+}
+
+var my_callsign = func {
+    return clean_callsign(input.callsign.getValue());
+}
+
+# Time, rounded to 'channel_hash_period'. This is used to hash channel.
+var get_time = func {
+    return int(math.floor(systime() / channel_hash_period) * channel_hash_period);
+}
+
+# Previous / next time (with channel_hash_period interval).
+# This is used to give a bit of margin on the time check.
+# (will work if system clocks are coordinated within 10min).
+var get_prev_time = func { return get_time() - channel_hash_period; }
+var get_next_time = func { return get_time() + channel_hash_period; }
+
+var parse_hexadecimal = func(str) {
+    var res = 0;
+    for (var i=0; i<size(str); i+=1) {
+        res *= 10;
+        var c = str[i];
+        if (c >= 48 and c < 58) {
+            # digit
+            res += c - 48;
+        } elsif (c >= 65 and c < 71) {
+            # upper case letter
+            res += c - 55;
+        } elsif (c >= 97 and c < 103) {
+            # lower case letter
+            res += c - 87;
+        }
+    }
+    return res;
+}
+
+var _hash_channel = func(time, callsign, channel) {
+    # 5 hex digits (2^20) fit in 3 chars for emesary int encoding.
+    var hash = parse_hexadecimal(left(md5(time ~ callsign ~ channel), 5));
+    return emesary.TransferInt.encode(hash, 3);
+}
+
+# Hash channel (when sending).
+var encode_channel = func(channel) {
+    return _hash_channel(get_time(), my_callsign(), channel);
+}
+
+# Check that the hash transmitted by aircraft 'callsign' is correct for 'channel'.
+var check_channel = func(hash, callsign, channel) {
+    return hash == _hash_channel(get_time(), callsign, channel)
+        or hash == _hash_channel(get_prev_time(), callsign, channel)
+        or hash == _hash_channel(get_next_time(), callsign, channel);
+}
+
+### Contact object
+var Contact = {
+    new: func(callsign) {
+        var c = {
+            # contact_parents is the list of all classes from which contacts inherit (for extensions).
+            parents: contact_parents,
+            _callsign: callsign,
+        };
+        # Initialize all inherited classes.
+        foreach (var class; contact_parents) {
+            call(class.init, [], c, nil, nil);
+        }
+        return c;
+    },
+    init: func { me._on_link = 0; },
+
+    callsign: func { return me._callsign; },
+    index: func { return callsign_to_index[me._callsign]; },
+    on_link: func { return me._on_link; },
+    set_on_link: func(b) { me._on_link = b; },
+};
+
+### Extensions
+var extensions = {};
+var extension_prefixes = {};
+var max_prefix_length = 0;
+var contact_parents = [Contact];
+
+var register_extension = func(name, prefix, class, encode, decode) {
+    if (contains(extensions, name)) {
+        printf("Datalink: double registration of extension '%s'. Skipping.", name);
+        return -1;
+    }
+    if (contains(extension_prefixes, prefix)) {
+        printf("Datalink: double registration of extension prefix '%s'. Skipping.", name);
+        return -1;
+    }
+    extensions[name] = { prefix: prefix, encode: encode, decode: decode, };
+    extension_prefixes[prefix] = name;
+    max_prefix_length = math.max(max_prefix_length, size(prefix));
+    append(contact_parents, class);
+
+    return 0;
+}
+
+
+var data_separator = "!";
+
+
+### Transmission
+
+var clear_data = func {
+    send_data({});
+}
+
+var clear_timer = maketimer(1, clear_data);
+clear_timer.singleShot = 1;
+
+# Send data through datalink.
+#
+# timeout: if set, sent data will be cleared after this time (other aircrafts
+# won't receive it anymore). Useful if 'send_data' is not called often.
+var send_data = func(data, timeout=nil) {
+    if (!input.power.getBoolValue()) {
+        last_data = {};
+        input.mp.setValue("");
+        return;
+    }
+
+    # First encode channel
+    var str = encode_channel(input.channel.getValue());
+
+    # Then all extensions
+    last_data = data;
+    foreach(var ext; keys(data)) {
+        # Skip missing extensions with a warning
+        if (!contains(extensions, ext)) {
+            printf("Warning: unknown datalink extension %s in send_data().", ext);
+            continue;
+        }
+        str = str ~ data_separator ~ extensions[ext].prefix ~ extensions[ext].encode(data[ext]);
+    }
+
+    input.mp.setValue(str);
+
+    if (timeout != nil) {
+        clear_timer.restart(timeout);
+    }
+}
+
+# Used internally to update the channel/identifier while keeping the same data.
+# Does not touch timeout.
+var last_data = {};
+var resend_data = func {
+    send_data(last_data);
+}
+
+# Very slow timer to ensure the channel hash is updated regularly.
+# Only relevant if you never call send_data();
+var hash_update_timer = maketimer(channel_hash_period/2, resend_data);
+hash_update_timer.start();
+
+
+### Receiving
+
+# callsign to data hash
+var aircrafts_data = {};
+# List of callsigns / indices connected on datalink (index is for /ai/models/multiplayer[i]).
+var connected_callsigns = [];
+var connected_indices = [];
+
+# Maintain callsign to multiplayer index hash
+# (doesn't cost much since we already iterate over MP models).
+var callsign_to_index = {};
+
+
+var get_data = func(callsign) {
+    return aircrafts_data[callsign];
+}
+
+var get_connected_callsigns = func {
+    return connected_callsigns;
+}
+
+var get_connected_indices = func {
+    return connected_indices;
+}
+
+var get_all_callsigns = func {
+    return keys(aircrafts_data);
+}
+
+# Helper for modifying aircrafts_data.
+var add_if_missing = func(aircrafts_data, callsign) {
+    if (!contains(aircrafts_data, callsign)) {
+        aircrafts_data[callsign] = Contact.new(callsign);
+    }
+    return aircrafts_data;
+}
+
+var receive_loop = func {
+    var my_channel = input.channel.getValue();
+
+    aircrafts_data = {};
+    connected_callsigns = [];
+    connected_indices = [];
+
+    var mp_models = input.models.getChildren("multiplayer");
+    foreach(var mp; mp_models) {
+        var idx = mp.getIndex();
+        if (!mp.getValue("valid")) continue;
+        var callsign = mp.getValue("callsign");
+        if (callsign == nil) continue;
+
+        callsign_to_index[callsign] = idx;
+
+        var data = mp.getValue(mp_path);
+        if (data == nil) continue;
+
+        # Split channel part and data part
+        var tokens = split(data_separator, data);
+
+        # Check channel
+        if (!check_channel(tokens[0], callsign, my_channel)) continue;
+
+        # We check this _after_ the channel. Checking the channel is quite cheap,
+        # and we don't know how slow this function is, it might have a get_cart_ground_intersection()
+        if (!can_transmit(callsign, mp, idx)) continue;
+
+        # Add to list of connected aircrafts.
+        append(connected_callsigns, callsign);
+        append(connected_indices, idx);
+        # Add to data
+        aircrafts_data = add_if_missing(aircrafts_data, callsign);
+        aircrafts_data[callsign].set_on_link(1);
+
+        # Parse extensions data
+        for (var i=1; i<size(tokens); i+=1) {
+            var extension = nil;
+            # Identify extension prefix.  This is not very clever code, but
+            # realistically it doesn't matter since prefixes are very short.
+            var len = 1;
+            for (; len <= max_prefix_length; len += 1) {
+                if (len > size(tokens)) break;
+                var prefix = left(tokens[i], len);
+                if (contains(extension_prefixes, prefix)) {
+                    extension = extension_prefixes[prefix];
+                    break;
+                }
+            }
+            # Unknown extension, skip
+            if (extension == nil) continue;
+            # Remove prefix
+            var data = substr(tokens[i], len);
+            # Decode
+            aircrafts_data = extensions[extension].decode(aircrafts_data, callsign, data);
+        }
+    }
+}
+
+var receive_timer = maketimer(receive_period, receive_loop);
+
+
+# Start / stop listener
+setlistener(input.power, func (node) {
+    if (node.getBoolValue()) {
+        receive_timer.start();
+        resend_data();  # Sets channel/identifier
+    } else {
+        receive_timer.stop();
+        aircrafts_data = {};
+        clear_data();
+    }
+}, 1, 0);
+
+# Listener to resend data so as to update the channel.
+setlistener(input.channel, resend_data);
+
+
+
+#### Extensions
+
+## Identifier
+
+var ContactIdentifier = {
+    init: func {
+        me._identifier = nil;
+    },
+    set_identifier: func(ident) {
+        me._identifier = ident;
+    },
+    identifier: func {
+        return me._identifier;
+    },
+};
+
+var encode_identifier = func(ident) {
+    # Force string conversion
+    ident = ""~ident;
+
+    if (find("!", ident) >= 0) {
+        printf("Datalink: Identifier is not allowed to contain '!': %s.", ident);
+        return "";
+    } else {
+        return ident;
+    }
+}
+
+var decode_identifier = func(aircrafts_data, callsign, str) {
+    aircrafts_data = add_if_missing(aircrafts_data, callsign);
+    aircrafts_data[callsign].set_identifier(str);
+    return aircrafts_data;
+}
+
+register_extension("identifier", "I", ContactIdentifier, encode_identifier, decode_identifier);
+
+
+
+## Contacts
+
+# IFF status transmitted over datalink.
+var IFF_UNKNOWN = 0;      # Unknown status
+var IFF_HOSTILE = 1;      # Considered hostile (no response to IFF).
+var IFF_FRIENDLY = 2;     # Friendly, because positive IFF identification.
+#   This is also the priority order for IFF reports in case of conflicts:
+#   e.g. a contact will be reported as friendly if anyone on datalink reports it as friendly.
+
+var ContactTracked = {
+    init: func {
+        me._tracked_by = nil;
+        me._iff = IFF_UNKNOWN;
+    },
+    set_tracked_by: func(callsign) {
+        me._tracked_by = callsign;
+    },
+    set_iff: func(iff) {
+        # Priority order on IFF values (friendly, then hostile, then no data).
+        me._iff = math.max(me._iff, iff);
+    },
+    tracked: func {
+        return me._tracked_by != nil;
+    },
+    tracked_by: func {
+        return me._tracked_by;
+    },
+    tracked_by_index: func {
+        return (me._tracked_by != nil) ? callsign_to_index[me._tracked_by] : nil;
+    },
+    iff: func {
+        return me._iff;
+    },
+    is_known: func {
+        return me.on_link() or me.tracked();
+    },
+    is_friendly: func {
+        return me.on_link() or me.iff() == IFF_FRIENDLY;
+    },
+    is_hostile: func {
+        return !me.on_link() and me.iff() == IFF_HOSTILE;
+    },
+};
+
+# Contact encoding: callsign + bits
+# callsign: the callsign encoded with emesary.TransferString
+# bits: bitfield |xxxxxxff| (left is most significant)
+#   f: IFF, x: unused
+#   encoded with emesary.TransferByte
+# Additional values may be appended for extensions.
+
+var encode_contact = func(contact) {
+    # Encode bitfield
+    var bits = contact["iff"] != nil ? contact.iff : IFF_UNKNOWN;
+
+    return emesary.TransferString.encode(clean_callsign(contact.callsign))
+        ~ emesary.TransferByte.encode(bits);
+}
+
+var decode_contact = func(str) {
+    var res = {};
+    var dv = emesary.TransferString.decode(str, 0);
+    res.callsign = dv.value;
+    dv = emesary.TransferByte.decode(str, dv.pos);
+    var bits = dv.value;
+    res.iff = math.mod(bits, 4);
+    return res;
+}
+
+# Special character, won't be used by emesary encoding.
+var contacts_separator = "#";
+
+var encode_contacts = func(contacts) {
+    var str = "";
+    foreach (var contact; contacts) {
+        str = str~encode_contact(contact)~contacts_separator;
+    }
+    return str;
+}
+
+var decode_contacts = func(aircrafts_data, callsign, str) {
+    var contacts = split(contacts_separator, str);
+    foreach (var contact; contacts) {
+        if (contact == "") continue;
+        var res = decode_contact(contact);
+        aircrafts_data = add_if_missing(aircrafts_data, res.callsign);
+        aircrafts_data[res.callsign].set_iff(res.iff);
+        aircrafts_data[res.callsign].set_tracked_by(callsign);
+    }
+    return aircrafts_data;
+}
+
+register_extension("contacts", "C", ContactTracked, encode_contacts, decode_contacts);
+
+
+
+## Coordinate
+
+var ContactPoint = {
+    init: func {
+        me._point = nil;
+    },
+    set_point: func(point) {
+        me._point = point;
+    },
+    point: func {
+        return me._point;
+    },
+};
+
+var encode_point = func(coord) {
+    return emesary.TransferCoord.encode(coord);
+}
+
+var decode_point = func(aircrafts_data, callsign, str) {
+    var coord = emesary.TransferCoord.decode(str, 0).value;
+    aircrafts_data = add_if_missing(aircrafts_data, callsign);
+    aircrafts_data[callsign].set_point(coord);
+    return aircrafts_data;
+}
+
+register_extension("point", "P", ContactPoint, encode_point, decode_point);
\ No newline at end of file
diff --git a/MIM-104D/Nasal/fire-control-custom.nas b/MIM-104D/Nasal/fire-control-custom.nas
new file mode 100644
index 0000000..077fba6
--- /dev/null
+++ b/MIM-104D/Nasal/fire-control-custom.nas
@@ -0,0 +1,44 @@
+
+################### SAM INFO
+
+var setupTime = 300;#minimum 'launcher_tilt_time' secs no matter what, due to anim and stuff.
+var reload_time = 900;
+var launcher_final_tilt_deg  = 45;
+var launcher_start_tilt_deg  =  0;
+var launcher_tilt_time       = 15;
+var sam_align_to_target      =  0;
+var launcher_align_to_target =  1;
+var align_speed_dps          = 20;
+var radar_elevation_above_terrain_m = 25;
+var radar_lowest_pitch       = -5;# 0.5 degs = roughly 925 feet at 20 nm, 25 feet at half a nm. # 0.35 = roughly 925 feet at 20 nm, 25 feet at half a nm.
+
+#reaction tme for s-300p is 28 secs acording to http://www.astronautix.com/s/s-300p.html
+# sounds a bit high for pmu, as its 4 secs for s-400
+
+################### CIWS INFO
+
+var ciws_installed =   0;
+var ciws_domain_nm = 1.50; #range where it can kill
+var ciws_chance    = 0.20; #chance to get a kill at 0nm distance
+var ciws_burst_rounds = 60;#how many rounds in a burst
+var ciws_shell = 15;#from lookup table in damage.nas
+var ROUNDS_init       = 30;
+var ROUNDS = ROUNDS_init;#CIWS bursts remaining
+
+################### MISSILE INFO
+
+var NUM_MISSILES = 3; # total carried minus 1
+var missile_name = "GEM";
+var missile_brevity = "GEM/T";
+var missile_max_distance = 43; #max distance of target in nm when it will fire
+var missile_min_distance = 0.5; #minimum distance in nm when it will fire
+var lockon_time = 12; #time in seconds it takes to lock on and get a firing solution on a target
+var fire_minimum_interval = 7;# time since last track was initiated till a new can be initiated
+var same_target_max_missiles = 1;# max number of missiles in air against same target
+
+var isInEngagementEnvelope = func (target_radial_airspeed, target_ground_distance, target_relative_altitude) {
+	return 1;
+}
+
+var midflight = nil;
+
diff --git a/MIM-104D/Nasal/fire-control.nas b/MIM-104D/Nasal/fire-control.nas
index fcbd063..58c42a7 100644
--- a/MIM-104D/Nasal/fire-control.nas
+++ b/MIM-104D/Nasal/fire-control.nas
@@ -20,49 +20,6 @@ var ACTIVE_MISSILE = 0;
 var semi_active_track = nil;# with multiple missiles flying in semi-active-radar mode, this can change rather fast. Which means pilots wont get a steady tone, but disrupted tones. (tradeoff)
 var mutexLock = thread.newlock();
 
-################### SAM INFO
-
-var setupTime = 300;#minimum 'launcher_tilt_time' secs no matter what, due to anim and stuff.
-var reload_time = 900;
-var launcher_final_tilt_deg  = 45;
-var launcher_start_tilt_deg  =  0;
-var launcher_tilt_time       = 15;
-var sam_align_to_target      =  0;
-var launcher_align_to_target =  1;
-var align_speed_dps          = 20;
-var radar_elevation_above_terrain_m = 25;
-var radar_lowest_pitch       = -5;# 0.5 degs = roughly 925 feet at 20 nm, 25 feet at half a nm. # 0.35 = roughly 925 feet at 20 nm, 25 feet at half a nm.
-
-#reaction tme for s-300p is 28 secs acording to http://www.astronautix.com/s/s-300p.html
-# sounds a bit high for pmu, as its 4 secs for s-400
-
-################### CIWS INFO
-
-var ciws_installed =   0;
-var ciws_domain_nm = 1.50; #range where it can kill
-var ciws_chance    = 0.20; #chance to get a kill at 0nm distance
-var ciws_burst_rounds = 60;#how many rounds in a burst
-var ciws_shell = 15;#from lookup table in damage.nas
-var ROUNDS_init       = 30;
-var ROUNDS = ROUNDS_init;#CIWS bursts remaining
-
-################### MISSILE INFO
-
-var NUM_MISSILES = 3; # total carried minus 1
-var missile_name = "GEM";
-var missile_brevity = "GEM/T";
-var missile_max_distance = 43; #max distance of target in nm when it will fire
-var missile_min_distance = 0.5; #minimum distance in nm when it will fire
-var lockon_time = 12; #time in seconds it takes to lock on and get a firing solution on a target
-var fire_minimum_interval = 7;# time since last track was initiated till a new can be initiated
-var same_target_max_missiles = 1;# max number of missiles in air against same target
-
-var isInEngagementEnvelope = func (target_radial_airspeed, target_ground_distance, target_relative_altitude) {
-	return 1;
-}
-
-var midflight = nil;
-
 
 ##########################################################################
 ######################## Common SAM code       ###########################
@@ -70,6 +27,8 @@ var midflight = nil;
 
 ################### VARIOUS
 
+setprop("sim/multiplay/generic/float[7]", 0);# tracking radar vert rotation
+setprop("sim/multiplay/generic/float[8]", 0);# tracking radar horiz rotation
 setprop("sim/multiplay/generic/float[5]", 0);# launcher vert rotation
 setprop("sim/multiplay/generic/float[6]", 0);# launcher horiz rotation
 var start_time = systime();
@@ -130,7 +89,7 @@ var buildTargetList = func {
 };
 
 var lookup = func (sign) {
-	
+
 	foreach (tgt ; targetsV2.vector) {
 		if (tgt.callsign == sign) {
 			return tgt;
@@ -168,9 +127,11 @@ var scan = func() {
 	buildTargetList();
 
 	if ( getprop("/carrier/sunk") == 1 or getprop("/carrier/disabled") == 1) {
+		setprop("sim/multiplay/generic/string[6]", "");
+		datalink.clear_data();
 		return;
 	}
-	
+
 	if (systime() - start_time < setupTime ) {
 		printf("Seconds till activation: %.1f", setupTime - (systime() - start_time));
 		setprop("sam/timeleft", setupTime - (systime() - start_time));
@@ -184,8 +145,11 @@ var scan = func() {
 			setprop("sim/multiplay/generic/float[5]", launcher_final_tilt_deg);
 		}
 		setprop("sim/multiplay/generic/float[6]", 0);
+		setprop("sim/multiplay/generic/float[7]", 0);
+		setprop("sim/multiplay/generic/float[8]", 0);
 		setprop("sim/multiplay/generic/string[6]", "");
 		setprop("/sim/multiplay/generic/int[2]", 1);
+		datalink.clear_data();
 		return;
 	}
 	setprop("sim/multiplay/generic/float[5]", launcher_final_tilt_deg);
@@ -214,12 +178,12 @@ var scan = func() {
 	}
 	prio_vector = sort(prio_vector, func (a,b) {if (a[2]>b[2]){return -1;} elsif (a[2]<b[2]) {return 1;} else {return 0;}});
 	foreach(var mp; prio_vector) {
-		
+
 		#### DO WE HAVE FIRING SOLUTION... ####
 		# is plane in range, do we still have missiles, and is a missile already inbound, and has it been 4 seconds since the last missile launch?
 		var trigger = mp[1];
 		#print("dist to target = " ~ dist_to_target);
-		
+
 		var lu = lookup(mp[0].getNode("callsign").getValue());
 		if ( launch_in_progress == 0 and trigger == true and lu != nil and lu.in_air < same_target_max_missiles and !lu.tracking and ACTIVE_MISSILE <= NUM_MISSILES and ( systime() - missile_delay_time > fire_minimum_interval ) ) { #
 			#### ... FOR THE MISSILE ####
@@ -229,7 +193,7 @@ var scan = func() {
 			armament.contact = radar_logic.Contact.new(mp[0], AIR);
 			launch_in_progress = 1;
 			missile_launch(mp[0], systime(), my_pos);
-			
+
 		} elsif ( ciws_installed and trigger == -1 and ROUNDS > 0 and ( systime() - ciws_delay_time > 1.0 ) and lu != nil) {
 			#### ... FOR THE CIWS ####
 			var contact = radar_logic.Contact.new(mp[0], AIR);
@@ -263,7 +227,7 @@ var scan = func() {
 				reloading = 1;
 				reload_starting = systime();
 			}
-		} 
+		}
 		if (lu != nil and lu.tracking) {
 			radarOn = 1;
 		}
@@ -309,8 +273,10 @@ var clearSingleLock = func () {
 	thread.lock(mutexLock);
 	if (semi_active_track == nil) {
 		setprop("sim/multiplay/generic/string[6]", "");
+		datalink.clear_data();
 	} else {
 		setprop("sim/multiplay/generic/string[6]", left(md5(semi_active_track), 4));
+		datalink.send_data({"contacts":[{"callsign":semi_active_track,"iff":0}]});
 	}
 	thread.unlock(mutexLock);
 }
@@ -326,7 +292,7 @@ var fire_control = func(mp, my_pos) {
 	var ufo_pos = geo.Coord.new().set_latlon(mp.getNode("position/latitude-deg").getValue(),mp.getNode("position/longitude-deg").getValue(),(mp.getNode("position/altitude-ft").getValue() * FT2M));
 	var target_distance = my_pos.direct_distance_to(ufo_pos);
 	var target_altitude = mp.getNode("position/altitude-ft").getValue();
-	
+
 	# is this plane a friend or foe?
 	var lu = lookup(mp.getNode("callsign").getValue());
 	if ( lu == nil ) { return [mp,false,0,0]; }
@@ -335,11 +301,11 @@ var fire_control = func(mp, my_pos) {
 	var target_ground_distance = my_pos.distance_to(ufo_pos);
 	var target_heading = mp.getNode("orientation/true-heading-deg").getValue();
 	var relative_bearing = math.abs(geo.normdeg180(ufo_pos.course_to(my_pos) - target_heading));
-	
+
 	var target_relative_altitude = target_altitude - my_pos.alt()*M2FT;
 	var target_radial_airspeed = math.abs(math.abs(((relative_bearing / 90 ) - 1) * target_airspeed));#200kt against us = 200kt, 200kt at angle of us = 0kt, 200kt away from us = 200kt
 	var target_relative_pitch = vector.Math.getPitch(my_pos, ufo_pos);
-	
+
 
 	# can the radar see it?
 	var data_link_match = false;
@@ -349,7 +315,7 @@ var fire_control = func(mp, my_pos) {
 #			#print('tgt confirmed via datalink');
 #		}
 #	}
-	
+
 	var visible = radar_logic.isNotBehindTerrain(mp);
 
 
@@ -358,9 +324,10 @@ var fire_control = func(mp, my_pos) {
 		var radarSeeTarget = 1;
 		if ( data_link_match == false ) {
 			if ( visible[0] == false ) {radarSeeTarget = 0 }
-			if ( target_relative_pitch < radar_lowest_pitch ) { radarSeeTarget = 0 } # 
+			if ( target_relative_pitch < radar_lowest_pitch ) { radarSeeTarget = 0 } #
 			if ( target_distance*M2NM > 1.0 and visible[1] and math.abs(target_radial_airspeed) < 20 ) {radarSeeTarget = 0 } # i.e. notching with terrain behind
 		}
+
 		if (radarSeeTarget and rand() > target_distance*M2NM / ciws_domain_nm) {
 			var score = 0;
 			var priority = getprop("priority");
@@ -386,26 +353,26 @@ var fire_control = func(mp, my_pos) {
 	if ( data_link_match == false ) {
 		if (target_airspeed < 60) {return [mp,false,0,0];}
 		if ( visible[0] == false ) { return [mp,false,0,0]; }
-		if ( target_relative_pitch < radar_lowest_pitch ) { return [mp,false,0,0]; } # 
+		if ( target_relative_pitch < radar_lowest_pitch ) { return [mp,false,0,0]; } #
 		if ( visible[1] and math.abs(target_radial_airspeed) < 20 ) { return [mp,false,0,0]; } # i.e. notching, landed aircraft
 	}
-	
+
 	if ( target_distance * M2NM > missile_max_distance ) { return [mp,false,0,0]; }
 
-	
-	
-	
+
+
+
 	# is the plane within the engagement envelope?
 	# the numbers after target_radial_airspeed are ( offset_of_engagement_envelope / speed_to_apply_that_offset )
 	# larger offset means it wont fire until the plane is closer.
 	# for visualization: https://www.desmos.com/calculator/gw570fa9km
-	
-	if (!isInEngagementEnvelope(target_radial_airspeed, target_ground_distance, target_relative_altitude) ) { return [mp,false,0,0]; }	
 
-	
+	if (!isInEngagementEnvelope(target_radial_airspeed, target_ground_distance, target_relative_altitude) ) { return [mp,false,0,0]; }
+
+
 
 	var the_dice = rand();
-	
+
 	if ( the_dice > 0.20 ) {
 		var score = 0;
 		var priority = getprop("priority");
@@ -452,7 +419,7 @@ var reload = func(force = 1) {
 	if (ROUNDS == 0 or force == 1) {
 		ROUNDS = ROUNDS_init;
 		print("Reloaded with "~(ROUNDS)~" bursts.");
-	}	
+	}
 	setprop("sam/missiles",(NUM_MISSILES+1-ACTIVE_MISSILE));
 	setprop("sam/bursts", ROUNDS);
 	reloading = 0;
@@ -484,6 +451,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 	}
 	var ufo_pos = geo.Coord.new().set_latlon(mp.getNode("position/latitude-deg").getValue(),mp.getNode("position/longitude-deg").getValue(),(mp.getNode("position/altitude-ft").getValue() * 0.3048));
 	var target_bearing = my_pos.course_to(ufo_pos);
+	var target_pitch   = vector.Math.getPitch(my_pos, ufo_pos);
 	var info = mp.getNode("callsign").getValue();
 	var lu = lookup(mp.getNode("callsign").getValue());
 	if (getprop("sam/timeleft") != 0) {
@@ -501,6 +469,8 @@ var missile_launch = func(mp, launchtime, my_pos) {
 			setprop("sim/multiplay/generic/float[6]", target_bearing-getprop("orientation/heading-deg"));
 			theMissile.rail_head_deg = getprop("sim/multiplay/generic/float[6]");
 		}
+		setprop("sim/multiplay/generic/float[7]", target_pitch);
+		setprop("sim/multiplay/generic/float[8]", target_bearing-getprop("orientation/heading-deg"));
 		if (sam_align_to_target) {
 			setprop("/orientation/heading-deg",target_bearing);
 		}
@@ -515,7 +485,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 			settimer(autoreload, reload_time);
 			reloading = 1;
 			reload_starting = systime();
-		}		
+		}
 		if (lu != nil) {
 			append(lu.missiles, theMissile);
 			lu.in_air += 1;
@@ -542,15 +512,19 @@ var missile_launch = func(mp, launchtime, my_pos) {
 	} else {
 		info = info~" (tracking)";
 		if (systime()-missile_release_time > 1.5) {
+			var tgt_dir = target_bearing-getprop("orientation/heading-deg");
+			var max_dir = launch_update_time*align_speed_dps;
 			if (launcher_align_to_target) {
 				# now smoothly rotate launcher:
-				var tgt_dir = target_bearing-getprop("orientation/heading-deg");
 				var cur_dir = getprop("sim/multiplay/generic/float[6]");
 				var move_dir = geo.normdeg180(tgt_dir-cur_dir);
-				var max_dir = launch_update_time*align_speed_dps;
 				move_dir = math.clamp(move_dir, -max_dir, max_dir);
 				setprop("sim/multiplay/generic/float[6]", cur_dir+move_dir);
 			}
+			var cur_dir2 = getprop("sim/multiplay/generic/float[8]");
+			var move_dir2 = geo.normdeg180(tgt_dir-cur_dir2);
+			move_dir2 = math.clamp(move_dir2, -max_dir, max_dir);
+			setprop("sim/multiplay/generic/float[8]", cur_dir2+move_dir2);
 			if (sam_align_to_target) {
 				var tgt_dir = target_bearing;
 				var cur_dir = getprop("orientation/heading-deg");
@@ -564,6 +538,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 		setprop("sam/info", info);
 		if (mp.getNode("callsign") != nil and mp.getNode("callsign").getValue() != nil and mp.getNode("callsign").getValue() != "") {
 	        setprop("sim/multiplay/generic/string[6]", left(md5(mp.getNode("callsign").getValue()), 4));
+	        datalink.send_data({"contacts":[{"callsign":mp.getNode("callsign").getValue(),"iff":0}]});
 	    } else {
 	        clearSingleLock();
 	    }
@@ -571,6 +546,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 			lu.tracking = 1;
 		}
 	}
+
 	settimer( func { missile_launch(mp, launchtime, my_pos); },launch_update_time);
 }
 
diff --git a/MIM-104D/gui/dialogs/prio.xml b/MIM-104D/gui/dialogs/prio.xml
index 072157e..cabac21 100644
--- a/MIM-104D/gui/dialogs/prio.xml
+++ b/MIM-104D/gui/dialogs/prio.xml
@@ -5,8 +5,8 @@
   	<layout>vbox</layout>
   	<draggable>true</draggable>
     <resizable>false</resizable>
-    <width>125</width>
-    <height>200</height>
+    <width>150</width>
+    <height>250</height>
 
     <group>
     	<empty><stretch>1</stretch></empty>
@@ -144,5 +144,23 @@
                 <script>setprop("priority",6);setprop("priority6",1);setprop("priority0",0);setprop("priority1",0);setprop("priority2",0);setprop("priority3",0);setprop("priority4",0);setprop("priority5",0);</script>
             </binding>
         </radio>
+        <input>
+            <row>7</row>
+            <col>0</col>
+            <width>75</width>
+            <height>25</height>
+            <label>DLNK</label>
+            <property>instrumentation/datalink/channel</property>
+            <live>true</live>
+            <halign>right</halign>
+            <binding>
+                <command>dialog-apply</command>
+            </binding>
+            <color>
+                <red>0.75</red>
+                <green>0.75</green>
+                <blue>1.0</blue>
+            </color>
+        </input>
     </group>
 </PropertyList>
\ No newline at end of file
diff --git a/S-200/S-200-set.xml b/S-200/S-200-set.xml
index 8d36a73..bd1387e 100644
--- a/S-200/S-200-set.xml
+++ b/S-200/S-200-set.xml
@@ -38,11 +38,6 @@
                 <splash type="bool">true</splash>
                 <path>gui/1.png</path>
             </preview>
-            <preview>
-                <type>exterior</type>
-                <splash type="bool">true</splash>
-                <path>gui/2.png</path>
-            </preview>
         </previews>
 
         <current-view>
@@ -226,6 +221,8 @@
                 <MAW-bearing type="double">0</MAW-bearing>
                 <MAW-active type="bool">false</MAW-active>
                 <spike type="bool">false</spike>
+				
+                
             </armament>
     </payload>
 
@@ -275,6 +272,17 @@
 
     <priority type="int">1</priority>
     <priority1 type="int">1</priority1>
+
+    <instrumentation>
+        <datalink>
+            <data type="int">0</data>
+            <power type="bool">true</power>
+            <channel type="int">1212</channel>
+            <power_prop type="string">/instrumentation/datalink/power</power_prop>
+            <channel_prop type="string">instrumentation/datalink/channel</channel_prop>
+            <receive_period type="double">1</receive_period>
+        </datalink>
+    </instrumentation>
 	
     <nasal>
         <notifications>
@@ -296,7 +304,11 @@
         <armament>
             <file>Aircraft/S-200/Nasal/guided-missiles.nas</file>
         </armament>
+        <datalink>
+            <file>Aircraft/S-200/Nasal/datalink.nas</file>
+        </datalink>
 		<fire_control>
+            <file>Aircraft/S-200/Nasal/fire-control-custom.nas</file>
 			<file>Aircraft/S-200/Nasal/fire-control.nas</file>
 		</fire_control>
     </nasal>
diff --git a/S-200/gui/1.png b/S-200/gui/1.png
index 47f1067..fc7f5bd 100644
Binary files a/S-200/gui/1.png and b/S-200/gui/1.png differ
diff --git a/S-200/thumbnail.jpg b/S-200/thumbnail.jpg
index 96a389a..6855dbc 100644
Binary files a/S-200/thumbnail.jpg and b/S-200/thumbnail.jpg differ
diff --git a/S-75/Nasal/datalink.nas b/S-75/Nasal/datalink.nas
new file mode 100644
index 0000000..7b88482
--- /dev/null
+++ b/S-75/Nasal/datalink.nas
@@ -0,0 +1,681 @@
+#### Datalink
+
+# Copyright 2020-2021 Colin Geniet.
+# Licensed under the GNU General Public License 2.0 or any later version.
+
+
+#### Usage
+
+### Generalities
+#
+# The datalink protocol consists of a core protocol which implements a notion
+# of datalink channel, and extensions which allow transmitting actual data.
+
+### Core protocol usage:
+#
+# Define the following properties (must be defined at nasal loading time).
+# * Mandatory
+#   /instrumentation/datalink/power_prop                path to property indicating if datalink is on
+#   /instrumentation/datalink/channel_prop              path to property containing datalink channel
+#   (the channel property can contain anything, and is transmitted/compared as a string).
+# * Optional
+#   /instrumentation/datalink/receive_period = 1        receiving loop update rate
+#
+# Optional: Re-define the function
+#   datalink.can_transmit(callsign, mp_prop, mp_index)
+#
+# This function should return 'true' when the given aircraft is able to transmit over datalink to us.
+# For instance, it can be used to check line of sight and maximum range.
+# The default implementation always returns true (always able to transmit).
+# Arguments are callsign, property node /ai/models/multiplayer[i], index of the former node.
+#
+#
+# API:
+# - get_data(callsign)
+#     Returns all datalink information about 'callsign' as an object, or nil if there is none.
+#     This object must not be modified.
+#     It contains the following methods:
+#       callsign(): The aircraft callsign (same as the argument of get_data()).
+#       index():    The aircraft index in /ai/models/multiplayer[i].
+#       on_link():  Returns a bool indicating whether 'callsign' is connected to this aircraft through datalink.
+#
+#     Extensions can define other methods in this object.
+#
+# - get_connected_callsigns() / get_connected_indices()
+#     Returns a vector containing all callsigns, resp. indices
+#     in /ai/models/multiplayer[i], of aircrafts connected on datalink.
+#     Both vectors use the same order, i.e. get_connected_callsigns()[i]
+#     and get_connected_indices()[i] correspond to the same aircraft.
+#     Furthermore this order is stable (the relative order of two aircrafts
+#     does not change as long as neither disconnects from multiplayer).
+#
+# - get_all_callsigns()
+#     Returns a vector containing all callsigns of aircraft with any associated data.
+#     There is no guarantee on the order of callsigns.
+#
+# - send_data(data, timeout=nil)
+#     Send data on the datalink. 'data' is a hash of the form
+#       {
+#           <extension_name>: <extension_data>,
+#           ...
+#       }
+#     If 'timeout' is set, clear_data() will be called after this delay.
+#     Data sent with send_data() is deleted at the next call of send_data(), or by clear_data().
+#
+# - clear_data()
+#     Clear data transmitted by this aircraft.
+#
+# Important note:
+# After a send_data(), and until the next send_data() or clear_data(),
+# the datalink behaves as if you are continuously sending the same data.
+# Thus, it is important to
+#   1. either call send_data() regularly
+#   2. or set the timeout argument of send_data()
+
+### Extensions
+
+### Aircraft contacts (extension name: "contacts")
+#
+# This extension allows to simulate an aircraft transmitting information about
+# another aircraft (typically one tracked on radar). The position data is not
+# actually transmitted (since everyone can access it from simulator internals).
+#
+## Receiving data
+# This extension adds the following methods to the result of get_data("A"):
+#       tracked():          A bool indicating that some aircraft "B" connected on datalink
+#                           is transmitting information about aircraft "A".
+#       iff():              One of IFF_UNKNOWN, IFF_HOSTILE, IFF_FRIENDLY, or nil if tracked() is false.
+#                           Indicates the result of IFF interrogation of "A" by "B"
+#                           IFF_UNKNOWN means that e.g. no IFF interrogation was performed.
+#       tracked_by():       The callsign of the transmitting aircraft ("A"), or nil if tracked() is false.
+#       tracked_by_index(): The index of the transmitting aircraft, or nil if tracked() is false.
+#                           The index refers to property nodes /ai/models/multiplayer[i].
+#       is_known():         Equivalent to (on_link() or tracked()).
+#                           Indicates if the position of this aircraft is supposed to be known
+#                           (i.e. whether or not it should be displayed on a HSD or whatever).
+#       is_friendly():      Equivalent to (on_link() or iff() == IFF_FRIENDLY).
+#       is_hostile():       Equivalent to (!on_link() and iff() == IFF_HOSTILE).
+#
+## Sending data
+# usage: send_data({ contacts: <contacts>, ...}, ...)
+# where <contacts> is a vector of hashes of the form { callsign: <callsign>, [iff: <iff>,] }.
+# <callsign> is the multiplayer callsign of the tracked aircraft.
+# <iff> (optional) is one of IFF_UNKNOWN, IFF_HOSTILE, IFF_FRIENDLY
+
+### Datalink identifier (extension name: "identifier")
+#
+# This extension allows each aircraft on datalink to transmit a personal
+# identifier, e.g. the number of the aircraft in a flight.
+#
+## Receiving data
+# This extension adds the method identifier() to the result of get_data(),
+# which returns the identifier, or nil if there is none).
+#
+## Sending data
+# Set the identifier with send_data({"identifier": <identifier>, ...});
+# The identifier must be a string. It must not contain '!'.
+
+### Coordinate transmission (extension name: "point")
+#
+# This extension allows each aircraft to broadcast a coordinate (geo.Coord object).
+#
+## Receiving data
+# This extension adds the method point() to the result of get_data(),
+# which results the transmitted geo.Coord object, or nil if there is none.
+#
+## Sending data
+# Transmit a geo.Coord object <coord> with send_data({"point": <coord>, ...});
+
+
+#### Protocol:
+#
+# Data is transmitted on MP generic string[7], with the following format:
+#   <channel>(!<data>)+
+#
+# <channel> is a hash of the datalink channel. See hash_channel() and check_channel_hash().
+# Each <data> block corresponds to data sent by an extension.
+# It starts with a prefix uniquely defining the extension.
+# The rest of the block can contain any character (including non-ascii) except '!'.
+#
+# Remark: '!' as separator is specifically chosen to allow encoding with emesary.Transfer<type>.
+#
+# The current extension prefixes are the following:
+#   contacts:   C
+#   identifier: I
+#   point:      P
+
+#### Extensions API
+#
+# Creating a new extension is done with
+#   register_extension(name, prefix, object, encode, decode)
+# name                      the extension name, used as key in the 'data' argument of send_data().
+# prefix                    the protocol prefix.
+# class                     contact class parent.
+#   A class from which all contact objects will inherit.
+#   It must have an init() method, which is called whenever a contact is created.
+#
+# encode(data)              extension encoding function.
+#   Must return the encoding of the extension data (i.e. <data> when calling
+#   send_data({name: <data>})) into a string, which may use any character except '!'.
+#   The extension prefix must not be part of the encoded string.
+#
+# decode(aircrafts_data, callsign, index, string)      extension decoding function.
+#   'aircrafts_data' is a hash from callsigns to contact objects (see below).
+#   'callsign' is the callsign of the aircraft which transmitted this data.
+#   'index' is the index of the aircraft which transmitted this data.
+#   'string' is the data encoded by encode() and transmitted through datalink.
+
+#   Each contact in 'data' inherits from the core 'Contact' class, and the extension 'class'.
+#   decode() is expected to modify 'aircrafts_data', by possibly editing
+#   existing contacts and adding new ones.  It should be careful when
+#   overwriting existing data in these contacts, including its own: decode()
+#   will be called several time on the same 'aircrafts_data' (once for each
+#   transmitting aircraft).
+#   The modified 'aircrafts_data' hash must be returned.
+#
+# decode() may use the following helper functions:
+#   add_if_missing(aircrafts_data, callsign):
+#     Create a new contact object for 'callsign' and add it to 'aircrafts_data',
+#     unless an entry for 'callsign' already exists. Returns the modified hash.
+
+
+
+#### Version and changelog
+# current: v1.1.0, minimum compatible: v1.0.0
+#
+## v1.1.0:
+# Allow external transmission restrictions
+# Make transmitting contact IFF optional
+# Ensure personal identifier has no '!'
+# '\n' is redundant for printf()
+# Fix separator character in documentation
+# Fix error when sending unknown extension
+#
+## v1.0.1:
+# Add is_known(), is_friendly(), is_hostile() helpers to extension "contacts".
+#
+## v1.0.0: Initial version
+# - Core protocol for datalink channel.
+# - Extensions "contacts", "identifier", and "point".
+
+
+
+### Parameters
+#
+# Remark: most parameters need to be the same on all aircrafts.
+
+# Index of multiplayer string used to transmit datalink info.
+# Must be the same for all aircrafts.
+var mp_string = 7;
+var mp_path = "sim/multiplay/generic/string["~mp_string~"]";
+
+var channel_hash_period = 600;
+
+var receive_period = getprop("/instrumentation/datalink/receive_period") or 1;
+
+# Should be overwitten to add transmission restrictions.
+var can_transmit = func(contact, mp_prop, mp_index) {
+    return 1;
+}
+
+### Properties
+
+var input = {
+    power:      getprop("/instrumentation/datalink/power_prop"),
+    channel:    getprop("/instrumentation/datalink/channel_prop"),
+    ident:      getprop("/instrumentation/datalink/identifier_prop"),
+    mp:         mp_path,
+    models:     "/ai/models",
+    callsign:   "/sim/multiplay/callsign",
+};
+
+foreach (var name; keys(input)) {
+    if (input[name] != nil) {
+        input[name] = props.globals.getNode(input[name], 1);
+    }
+}
+
+
+
+#### Core protocol implementation
+
+### Channel hash (based on iff.nas)
+#
+# Channel is hashed with current time (rounded to 10min) and own callsign.
+
+var clean_callsign = func(callsign) {
+    return damage.processCallsign(callsign);
+}
+
+var my_callsign = func {
+    return clean_callsign(input.callsign.getValue());
+}
+
+# Time, rounded to 'channel_hash_period'. This is used to hash channel.
+var get_time = func {
+    return int(math.floor(systime() / channel_hash_period) * channel_hash_period);
+}
+
+# Previous / next time (with channel_hash_period interval).
+# This is used to give a bit of margin on the time check.
+# (will work if system clocks are coordinated within 10min).
+var get_prev_time = func { return get_time() - channel_hash_period; }
+var get_next_time = func { return get_time() + channel_hash_period; }
+
+var parse_hexadecimal = func(str) {
+    var res = 0;
+    for (var i=0; i<size(str); i+=1) {
+        res *= 10;
+        var c = str[i];
+        if (c >= 48 and c < 58) {
+            # digit
+            res += c - 48;
+        } elsif (c >= 65 and c < 71) {
+            # upper case letter
+            res += c - 55;
+        } elsif (c >= 97 and c < 103) {
+            # lower case letter
+            res += c - 87;
+        }
+    }
+    return res;
+}
+
+var _hash_channel = func(time, callsign, channel) {
+    # 5 hex digits (2^20) fit in 3 chars for emesary int encoding.
+    var hash = parse_hexadecimal(left(md5(time ~ callsign ~ channel), 5));
+    return emesary.TransferInt.encode(hash, 3);
+}
+
+# Hash channel (when sending).
+var encode_channel = func(channel) {
+    return _hash_channel(get_time(), my_callsign(), channel);
+}
+
+# Check that the hash transmitted by aircraft 'callsign' is correct for 'channel'.
+var check_channel = func(hash, callsign, channel) {
+    return hash == _hash_channel(get_time(), callsign, channel)
+        or hash == _hash_channel(get_prev_time(), callsign, channel)
+        or hash == _hash_channel(get_next_time(), callsign, channel);
+}
+
+### Contact object
+var Contact = {
+    new: func(callsign) {
+        var c = {
+            # contact_parents is the list of all classes from which contacts inherit (for extensions).
+            parents: contact_parents,
+            _callsign: callsign,
+        };
+        # Initialize all inherited classes.
+        foreach (var class; contact_parents) {
+            call(class.init, [], c, nil, nil);
+        }
+        return c;
+    },
+    init: func { me._on_link = 0; },
+
+    callsign: func { return me._callsign; },
+    index: func { return callsign_to_index[me._callsign]; },
+    on_link: func { return me._on_link; },
+    set_on_link: func(b) { me._on_link = b; },
+};
+
+### Extensions
+var extensions = {};
+var extension_prefixes = {};
+var max_prefix_length = 0;
+var contact_parents = [Contact];
+
+var register_extension = func(name, prefix, class, encode, decode) {
+    if (contains(extensions, name)) {
+        printf("Datalink: double registration of extension '%s'. Skipping.", name);
+        return -1;
+    }
+    if (contains(extension_prefixes, prefix)) {
+        printf("Datalink: double registration of extension prefix '%s'. Skipping.", name);
+        return -1;
+    }
+    extensions[name] = { prefix: prefix, encode: encode, decode: decode, };
+    extension_prefixes[prefix] = name;
+    max_prefix_length = math.max(max_prefix_length, size(prefix));
+    append(contact_parents, class);
+
+    return 0;
+}
+
+
+var data_separator = "!";
+
+
+### Transmission
+
+var clear_data = func {
+    send_data({});
+}
+
+var clear_timer = maketimer(1, clear_data);
+clear_timer.singleShot = 1;
+
+# Send data through datalink.
+#
+# timeout: if set, sent data will be cleared after this time (other aircrafts
+# won't receive it anymore). Useful if 'send_data' is not called often.
+var send_data = func(data, timeout=nil) {
+    if (!input.power.getBoolValue()) {
+        last_data = {};
+        input.mp.setValue("");
+        return;
+    }
+
+    # First encode channel
+    var str = encode_channel(input.channel.getValue());
+
+    # Then all extensions
+    last_data = data;
+    foreach(var ext; keys(data)) {
+        # Skip missing extensions with a warning
+        if (!contains(extensions, ext)) {
+            printf("Warning: unknown datalink extension %s in send_data().", ext);
+            continue;
+        }
+        str = str ~ data_separator ~ extensions[ext].prefix ~ extensions[ext].encode(data[ext]);
+    }
+
+    input.mp.setValue(str);
+
+    if (timeout != nil) {
+        clear_timer.restart(timeout);
+    }
+}
+
+# Used internally to update the channel/identifier while keeping the same data.
+# Does not touch timeout.
+var last_data = {};
+var resend_data = func {
+    send_data(last_data);
+}
+
+# Very slow timer to ensure the channel hash is updated regularly.
+# Only relevant if you never call send_data();
+var hash_update_timer = maketimer(channel_hash_period/2, resend_data);
+hash_update_timer.start();
+
+
+### Receiving
+
+# callsign to data hash
+var aircrafts_data = {};
+# List of callsigns / indices connected on datalink (index is for /ai/models/multiplayer[i]).
+var connected_callsigns = [];
+var connected_indices = [];
+
+# Maintain callsign to multiplayer index hash
+# (doesn't cost much since we already iterate over MP models).
+var callsign_to_index = {};
+
+
+var get_data = func(callsign) {
+    return aircrafts_data[callsign];
+}
+
+var get_connected_callsigns = func {
+    return connected_callsigns;
+}
+
+var get_connected_indices = func {
+    return connected_indices;
+}
+
+var get_all_callsigns = func {
+    return keys(aircrafts_data);
+}
+
+# Helper for modifying aircrafts_data.
+var add_if_missing = func(aircrafts_data, callsign) {
+    if (!contains(aircrafts_data, callsign)) {
+        aircrafts_data[callsign] = Contact.new(callsign);
+    }
+    return aircrafts_data;
+}
+
+var receive_loop = func {
+    var my_channel = input.channel.getValue();
+
+    aircrafts_data = {};
+    connected_callsigns = [];
+    connected_indices = [];
+
+    var mp_models = input.models.getChildren("multiplayer");
+    foreach(var mp; mp_models) {
+        var idx = mp.getIndex();
+        if (!mp.getValue("valid")) continue;
+        var callsign = mp.getValue("callsign");
+        if (callsign == nil) continue;
+
+        callsign_to_index[callsign] = idx;
+
+        var data = mp.getValue(mp_path);
+        if (data == nil) continue;
+
+        # Split channel part and data part
+        var tokens = split(data_separator, data);
+
+        # Check channel
+        if (!check_channel(tokens[0], callsign, my_channel)) continue;
+
+        # We check this _after_ the channel. Checking the channel is quite cheap,
+        # and we don't know how slow this function is, it might have a get_cart_ground_intersection()
+        if (!can_transmit(callsign, mp, idx)) continue;
+
+        # Add to list of connected aircrafts.
+        append(connected_callsigns, callsign);
+        append(connected_indices, idx);
+        # Add to data
+        aircrafts_data = add_if_missing(aircrafts_data, callsign);
+        aircrafts_data[callsign].set_on_link(1);
+
+        # Parse extensions data
+        for (var i=1; i<size(tokens); i+=1) {
+            var extension = nil;
+            # Identify extension prefix.  This is not very clever code, but
+            # realistically it doesn't matter since prefixes are very short.
+            var len = 1;
+            for (; len <= max_prefix_length; len += 1) {
+                if (len > size(tokens)) break;
+                var prefix = left(tokens[i], len);
+                if (contains(extension_prefixes, prefix)) {
+                    extension = extension_prefixes[prefix];
+                    break;
+                }
+            }
+            # Unknown extension, skip
+            if (extension == nil) continue;
+            # Remove prefix
+            var data = substr(tokens[i], len);
+            # Decode
+            aircrafts_data = extensions[extension].decode(aircrafts_data, callsign, data);
+        }
+    }
+}
+
+var receive_timer = maketimer(receive_period, receive_loop);
+
+
+# Start / stop listener
+setlistener(input.power, func (node) {
+    if (node.getBoolValue()) {
+        receive_timer.start();
+        resend_data();  # Sets channel/identifier
+    } else {
+        receive_timer.stop();
+        aircrafts_data = {};
+        clear_data();
+    }
+}, 1, 0);
+
+# Listener to resend data so as to update the channel.
+setlistener(input.channel, resend_data);
+
+
+
+#### Extensions
+
+## Identifier
+
+var ContactIdentifier = {
+    init: func {
+        me._identifier = nil;
+    },
+    set_identifier: func(ident) {
+        me._identifier = ident;
+    },
+    identifier: func {
+        return me._identifier;
+    },
+};
+
+var encode_identifier = func(ident) {
+    # Force string conversion
+    ident = ""~ident;
+
+    if (find("!", ident) >= 0) {
+        printf("Datalink: Identifier is not allowed to contain '!': %s.", ident);
+        return "";
+    } else {
+        return ident;
+    }
+}
+
+var decode_identifier = func(aircrafts_data, callsign, str) {
+    aircrafts_data = add_if_missing(aircrafts_data, callsign);
+    aircrafts_data[callsign].set_identifier(str);
+    return aircrafts_data;
+}
+
+register_extension("identifier", "I", ContactIdentifier, encode_identifier, decode_identifier);
+
+
+
+## Contacts
+
+# IFF status transmitted over datalink.
+var IFF_UNKNOWN = 0;      # Unknown status
+var IFF_HOSTILE = 1;      # Considered hostile (no response to IFF).
+var IFF_FRIENDLY = 2;     # Friendly, because positive IFF identification.
+#   This is also the priority order for IFF reports in case of conflicts:
+#   e.g. a contact will be reported as friendly if anyone on datalink reports it as friendly.
+
+var ContactTracked = {
+    init: func {
+        me._tracked_by = nil;
+        me._iff = IFF_UNKNOWN;
+    },
+    set_tracked_by: func(callsign) {
+        me._tracked_by = callsign;
+    },
+    set_iff: func(iff) {
+        # Priority order on IFF values (friendly, then hostile, then no data).
+        me._iff = math.max(me._iff, iff);
+    },
+    tracked: func {
+        return me._tracked_by != nil;
+    },
+    tracked_by: func {
+        return me._tracked_by;
+    },
+    tracked_by_index: func {
+        return (me._tracked_by != nil) ? callsign_to_index[me._tracked_by] : nil;
+    },
+    iff: func {
+        return me._iff;
+    },
+    is_known: func {
+        return me.on_link() or me.tracked();
+    },
+    is_friendly: func {
+        return me.on_link() or me.iff() == IFF_FRIENDLY;
+    },
+    is_hostile: func {
+        return !me.on_link() and me.iff() == IFF_HOSTILE;
+    },
+};
+
+# Contact encoding: callsign + bits
+# callsign: the callsign encoded with emesary.TransferString
+# bits: bitfield |xxxxxxff| (left is most significant)
+#   f: IFF, x: unused
+#   encoded with emesary.TransferByte
+# Additional values may be appended for extensions.
+
+var encode_contact = func(contact) {
+    # Encode bitfield
+    var bits = contact["iff"] != nil ? contact.iff : IFF_UNKNOWN;
+
+    return emesary.TransferString.encode(clean_callsign(contact.callsign))
+        ~ emesary.TransferByte.encode(bits);
+}
+
+var decode_contact = func(str) {
+    var res = {};
+    var dv = emesary.TransferString.decode(str, 0);
+    res.callsign = dv.value;
+    dv = emesary.TransferByte.decode(str, dv.pos);
+    var bits = dv.value;
+    res.iff = math.mod(bits, 4);
+    return res;
+}
+
+# Special character, won't be used by emesary encoding.
+var contacts_separator = "#";
+
+var encode_contacts = func(contacts) {
+    var str = "";
+    foreach (var contact; contacts) {
+        str = str~encode_contact(contact)~contacts_separator;
+    }
+    return str;
+}
+
+var decode_contacts = func(aircrafts_data, callsign, str) {
+    var contacts = split(contacts_separator, str);
+    foreach (var contact; contacts) {
+        if (contact == "") continue;
+        var res = decode_contact(contact);
+        aircrafts_data = add_if_missing(aircrafts_data, res.callsign);
+        aircrafts_data[res.callsign].set_iff(res.iff);
+        aircrafts_data[res.callsign].set_tracked_by(callsign);
+    }
+    return aircrafts_data;
+}
+
+register_extension("contacts", "C", ContactTracked, encode_contacts, decode_contacts);
+
+
+
+## Coordinate
+
+var ContactPoint = {
+    init: func {
+        me._point = nil;
+    },
+    set_point: func(point) {
+        me._point = point;
+    },
+    point: func {
+        return me._point;
+    },
+};
+
+var encode_point = func(coord) {
+    return emesary.TransferCoord.encode(coord);
+}
+
+var decode_point = func(aircrafts_data, callsign, str) {
+    var coord = emesary.TransferCoord.decode(str, 0).value;
+    aircrafts_data = add_if_missing(aircrafts_data, callsign);
+    aircrafts_data[callsign].set_point(coord);
+    return aircrafts_data;
+}
+
+register_extension("point", "P", ContactPoint, encode_point, decode_point);
\ No newline at end of file
diff --git a/S-75/Nasal/fire-control-custom.nas b/S-75/Nasal/fire-control-custom.nas
new file mode 100644
index 0000000..bcae39e
--- /dev/null
+++ b/S-75/Nasal/fire-control-custom.nas
@@ -0,0 +1,54 @@
+
+################### SAM INFO
+
+var setupTime = 300;#minimum 'launcher_tilt_time' secs no matter what, due to anim and stuff.
+var reload_time = 400;
+var launcher_final_tilt_deg  = 35;
+var launcher_start_tilt_deg  = 35;
+var launcher_tilt_time       =  0;
+var sam_align_to_target      =  0;
+var launcher_align_to_target =  1;
+var align_speed_dps          = 20;
+var radar_elevation_above_terrain_m = 25;
+var radar_lowest_pitch       = 3.5;# 0.5 degs = roughly 925 feet at 20 nm, 25 feet at half a nm. # 0.35 = roughly 925 feet at 20 nm, 25 feet at half a nm.
+
+#reaction tme for s-300p is 28 secs acording to http://www.astronautix.com/s/s-300p.html
+# sounds a bit high for pmu, as its 4 secs for s-400
+
+################### CIWS INFO
+
+var ciws_installed =   0;
+var ciws_domain_nm = 1.50; #range where it can kill
+var ciws_chance    = 0.20; #chance to get a kill at 0nm distance
+var ciws_burst_rounds = 60;#how many rounds in a burst
+var ciws_shell = 15;#from lookup table in damage.nas
+var ROUNDS_init       = 30;
+var ROUNDS = ROUNDS_init;#CIWS bursts remaining
+
+################### MISSILE INFO
+
+var NUM_MISSILES = 5; # total carried minus 1
+var missile_name = "Volga-M";
+var missile_brevity = "5Ya23";
+var missile_max_distance = 36; #max distance of target in nm when it will fire
+var missile_min_distance = 3.5; #minimum distance in nm when it will fire
+var lockon_time = 12; #time in seconds it takes to lock on and get a firing solution on a target
+var fire_minimum_interval = 7;# time since last track was initiated till a new can be initiated
+var same_target_max_missiles = 2;# max number of missiles in air against same target
+
+var isInEngagementEnvelope = func (target_radial_airspeed, target_ground_distance, target_relative_altitude) {
+	return 1;
+}
+
+var midflight = func (struct) {
+	if (struct.guidance == "semi-radar") {
+		# This makes the SAM system keep lock on target when missile in-flight and no longer tracking the target.
+		# Usage is to make the RWR lock sound go off in targets cockpit.
+		thread.lock(mutexLock);
+		semi_active_track = struct.callsign;
+		thread.unlock(mutexLock);
+	}
+	return {};
+};
+
+
diff --git a/S-75/Nasal/fire-control.nas b/S-75/Nasal/fire-control.nas
index d6189a6..58c42a7 100644
--- a/S-75/Nasal/fire-control.nas
+++ b/S-75/Nasal/fire-control.nas
@@ -20,58 +20,6 @@ var ACTIVE_MISSILE = 0;
 var semi_active_track = nil;# with multiple missiles flying in semi-active-radar mode, this can change rather fast. Which means pilots wont get a steady tone, but disrupted tones. (tradeoff)
 var mutexLock = thread.newlock();
 
-################### SAM INFO
-
-var setupTime = 300;#minimum 'launcher_tilt_time' secs no matter what, due to anim and stuff.
-var reload_time = 400;
-var launcher_final_tilt_deg  = 35;
-var launcher_start_tilt_deg  = 35;
-var launcher_tilt_time       =  0;
-var sam_align_to_target      =  0;
-var launcher_align_to_target =  1;
-var align_speed_dps          = 20;
-var radar_elevation_above_terrain_m = 25;
-var radar_lowest_pitch       = 3.5;# 0.5 degs = roughly 925 feet at 20 nm, 25 feet at half a nm. # 0.35 = roughly 925 feet at 20 nm, 25 feet at half a nm.
-
-#reaction tme for s-300p is 28 secs acording to http://www.astronautix.com/s/s-300p.html
-# sounds a bit high for pmu, as its 4 secs for s-400
-
-################### CIWS INFO
-
-var ciws_installed =   0;
-var ciws_domain_nm = 1.50; #range where it can kill
-var ciws_chance    = 0.20; #chance to get a kill at 0nm distance
-var ciws_burst_rounds = 60;#how many rounds in a burst
-var ciws_shell = 15;#from lookup table in damage.nas
-var ROUNDS_init       = 30;
-var ROUNDS = ROUNDS_init;#CIWS bursts remaining
-
-################### MISSILE INFO
-
-var NUM_MISSILES = 5; # total carried minus 1
-var missile_name = "Volga-M";
-var missile_brevity = "5Ya23";
-var missile_max_distance = 36; #max distance of target in nm when it will fire
-var missile_min_distance = 3.5; #minimum distance in nm when it will fire
-var lockon_time = 12; #time in seconds it takes to lock on and get a firing solution on a target
-var fire_minimum_interval = 7;# time since last track was initiated till a new can be initiated
-var same_target_max_missiles = 2;# max number of missiles in air against same target
-
-var isInEngagementEnvelope = func (target_radial_airspeed, target_ground_distance, target_relative_altitude) {
-	return 1;
-}
-
-var midflight = func (struct) {
-	if (struct.guidance == "semi-radar") {
-		# This makes the SAM system keep lock on target when missile in-flight and no longer tracking the target.
-		# Usage is to make the RWR lock sound go off in targets cockpit.
-		thread.lock(mutexLock);
-		semi_active_track = struct.callsign;
-		thread.unlock(mutexLock);
-	}
-	return {};
-};
-
 
 ##########################################################################
 ######################## Common SAM code       ###########################
@@ -79,6 +27,8 @@ var midflight = func (struct) {
 
 ################### VARIOUS
 
+setprop("sim/multiplay/generic/float[7]", 0);# tracking radar vert rotation
+setprop("sim/multiplay/generic/float[8]", 0);# tracking radar horiz rotation
 setprop("sim/multiplay/generic/float[5]", 0);# launcher vert rotation
 setprop("sim/multiplay/generic/float[6]", 0);# launcher horiz rotation
 var start_time = systime();
@@ -139,7 +89,7 @@ var buildTargetList = func {
 };
 
 var lookup = func (sign) {
-	
+
 	foreach (tgt ; targetsV2.vector) {
 		if (tgt.callsign == sign) {
 			return tgt;
@@ -177,9 +127,11 @@ var scan = func() {
 	buildTargetList();
 
 	if ( getprop("/carrier/sunk") == 1 or getprop("/carrier/disabled") == 1) {
+		setprop("sim/multiplay/generic/string[6]", "");
+		datalink.clear_data();
 		return;
 	}
-	
+
 	if (systime() - start_time < setupTime ) {
 		printf("Seconds till activation: %.1f", setupTime - (systime() - start_time));
 		setprop("sam/timeleft", setupTime - (systime() - start_time));
@@ -193,8 +145,11 @@ var scan = func() {
 			setprop("sim/multiplay/generic/float[5]", launcher_final_tilt_deg);
 		}
 		setprop("sim/multiplay/generic/float[6]", 0);
+		setprop("sim/multiplay/generic/float[7]", 0);
+		setprop("sim/multiplay/generic/float[8]", 0);
 		setprop("sim/multiplay/generic/string[6]", "");
 		setprop("/sim/multiplay/generic/int[2]", 1);
+		datalink.clear_data();
 		return;
 	}
 	setprop("sim/multiplay/generic/float[5]", launcher_final_tilt_deg);
@@ -223,12 +178,12 @@ var scan = func() {
 	}
 	prio_vector = sort(prio_vector, func (a,b) {if (a[2]>b[2]){return -1;} elsif (a[2]<b[2]) {return 1;} else {return 0;}});
 	foreach(var mp; prio_vector) {
-		
+
 		#### DO WE HAVE FIRING SOLUTION... ####
 		# is plane in range, do we still have missiles, and is a missile already inbound, and has it been 4 seconds since the last missile launch?
 		var trigger = mp[1];
 		#print("dist to target = " ~ dist_to_target);
-		
+
 		var lu = lookup(mp[0].getNode("callsign").getValue());
 		if ( launch_in_progress == 0 and trigger == true and lu != nil and lu.in_air < same_target_max_missiles and !lu.tracking and ACTIVE_MISSILE <= NUM_MISSILES and ( systime() - missile_delay_time > fire_minimum_interval ) ) { #
 			#### ... FOR THE MISSILE ####
@@ -238,7 +193,7 @@ var scan = func() {
 			armament.contact = radar_logic.Contact.new(mp[0], AIR);
 			launch_in_progress = 1;
 			missile_launch(mp[0], systime(), my_pos);
-			
+
 		} elsif ( ciws_installed and trigger == -1 and ROUNDS > 0 and ( systime() - ciws_delay_time > 1.0 ) and lu != nil) {
 			#### ... FOR THE CIWS ####
 			var contact = radar_logic.Contact.new(mp[0], AIR);
@@ -272,7 +227,7 @@ var scan = func() {
 				reloading = 1;
 				reload_starting = systime();
 			}
-		} 
+		}
 		if (lu != nil and lu.tracking) {
 			radarOn = 1;
 		}
@@ -318,8 +273,10 @@ var clearSingleLock = func () {
 	thread.lock(mutexLock);
 	if (semi_active_track == nil) {
 		setprop("sim/multiplay/generic/string[6]", "");
+		datalink.clear_data();
 	} else {
 		setprop("sim/multiplay/generic/string[6]", left(md5(semi_active_track), 4));
+		datalink.send_data({"contacts":[{"callsign":semi_active_track,"iff":0}]});
 	}
 	thread.unlock(mutexLock);
 }
@@ -335,7 +292,7 @@ var fire_control = func(mp, my_pos) {
 	var ufo_pos = geo.Coord.new().set_latlon(mp.getNode("position/latitude-deg").getValue(),mp.getNode("position/longitude-deg").getValue(),(mp.getNode("position/altitude-ft").getValue() * FT2M));
 	var target_distance = my_pos.direct_distance_to(ufo_pos);
 	var target_altitude = mp.getNode("position/altitude-ft").getValue();
-	
+
 	# is this plane a friend or foe?
 	var lu = lookup(mp.getNode("callsign").getValue());
 	if ( lu == nil ) { return [mp,false,0,0]; }
@@ -344,11 +301,11 @@ var fire_control = func(mp, my_pos) {
 	var target_ground_distance = my_pos.distance_to(ufo_pos);
 	var target_heading = mp.getNode("orientation/true-heading-deg").getValue();
 	var relative_bearing = math.abs(geo.normdeg180(ufo_pos.course_to(my_pos) - target_heading));
-	
+
 	var target_relative_altitude = target_altitude - my_pos.alt()*M2FT;
 	var target_radial_airspeed = math.abs(math.abs(((relative_bearing / 90 ) - 1) * target_airspeed));#200kt against us = 200kt, 200kt at angle of us = 0kt, 200kt away from us = 200kt
 	var target_relative_pitch = vector.Math.getPitch(my_pos, ufo_pos);
-	
+
 
 	# can the radar see it?
 	var data_link_match = false;
@@ -358,7 +315,7 @@ var fire_control = func(mp, my_pos) {
 #			#print('tgt confirmed via datalink');
 #		}
 #	}
-	
+
 	var visible = radar_logic.isNotBehindTerrain(mp);
 
 
@@ -367,9 +324,10 @@ var fire_control = func(mp, my_pos) {
 		var radarSeeTarget = 1;
 		if ( data_link_match == false ) {
 			if ( visible[0] == false ) {radarSeeTarget = 0 }
-			if ( target_relative_pitch < radar_lowest_pitch ) { radarSeeTarget = 0 } # 
+			if ( target_relative_pitch < radar_lowest_pitch ) { radarSeeTarget = 0 } #
 			if ( target_distance*M2NM > 1.0 and visible[1] and math.abs(target_radial_airspeed) < 20 ) {radarSeeTarget = 0 } # i.e. notching with terrain behind
 		}
+
 		if (radarSeeTarget and rand() > target_distance*M2NM / ciws_domain_nm) {
 			var score = 0;
 			var priority = getprop("priority");
@@ -395,26 +353,26 @@ var fire_control = func(mp, my_pos) {
 	if ( data_link_match == false ) {
 		if (target_airspeed < 60) {return [mp,false,0,0];}
 		if ( visible[0] == false ) { return [mp,false,0,0]; }
-		if ( target_relative_pitch < radar_lowest_pitch ) { return [mp,false,0,0]; } # 
+		if ( target_relative_pitch < radar_lowest_pitch ) { return [mp,false,0,0]; } #
 		if ( visible[1] and math.abs(target_radial_airspeed) < 20 ) { return [mp,false,0,0]; } # i.e. notching, landed aircraft
 	}
-	
+
 	if ( target_distance * M2NM > missile_max_distance ) { return [mp,false,0,0]; }
 
-	
-	
-	
+
+
+
 	# is the plane within the engagement envelope?
 	# the numbers after target_radial_airspeed are ( offset_of_engagement_envelope / speed_to_apply_that_offset )
 	# larger offset means it wont fire until the plane is closer.
 	# for visualization: https://www.desmos.com/calculator/gw570fa9km
-	
-	if (!isInEngagementEnvelope(target_radial_airspeed, target_ground_distance, target_relative_altitude) ) { return [mp,false,0,0]; }	
 
-	
+	if (!isInEngagementEnvelope(target_radial_airspeed, target_ground_distance, target_relative_altitude) ) { return [mp,false,0,0]; }
+
+
 
 	var the_dice = rand();
-	
+
 	if ( the_dice > 0.20 ) {
 		var score = 0;
 		var priority = getprop("priority");
@@ -461,7 +419,7 @@ var reload = func(force = 1) {
 	if (ROUNDS == 0 or force == 1) {
 		ROUNDS = ROUNDS_init;
 		print("Reloaded with "~(ROUNDS)~" bursts.");
-	}	
+	}
 	setprop("sam/missiles",(NUM_MISSILES+1-ACTIVE_MISSILE));
 	setprop("sam/bursts", ROUNDS);
 	reloading = 0;
@@ -493,6 +451,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 	}
 	var ufo_pos = geo.Coord.new().set_latlon(mp.getNode("position/latitude-deg").getValue(),mp.getNode("position/longitude-deg").getValue(),(mp.getNode("position/altitude-ft").getValue() * 0.3048));
 	var target_bearing = my_pos.course_to(ufo_pos);
+	var target_pitch   = vector.Math.getPitch(my_pos, ufo_pos);
 	var info = mp.getNode("callsign").getValue();
 	var lu = lookup(mp.getNode("callsign").getValue());
 	if (getprop("sam/timeleft") != 0) {
@@ -510,6 +469,8 @@ var missile_launch = func(mp, launchtime, my_pos) {
 			setprop("sim/multiplay/generic/float[6]", target_bearing-getprop("orientation/heading-deg"));
 			theMissile.rail_head_deg = getprop("sim/multiplay/generic/float[6]");
 		}
+		setprop("sim/multiplay/generic/float[7]", target_pitch);
+		setprop("sim/multiplay/generic/float[8]", target_bearing-getprop("orientation/heading-deg"));
 		if (sam_align_to_target) {
 			setprop("/orientation/heading-deg",target_bearing);
 		}
@@ -524,7 +485,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 			settimer(autoreload, reload_time);
 			reloading = 1;
 			reload_starting = systime();
-		}		
+		}
 		if (lu != nil) {
 			append(lu.missiles, theMissile);
 			lu.in_air += 1;
@@ -551,15 +512,19 @@ var missile_launch = func(mp, launchtime, my_pos) {
 	} else {
 		info = info~" (tracking)";
 		if (systime()-missile_release_time > 1.5) {
+			var tgt_dir = target_bearing-getprop("orientation/heading-deg");
+			var max_dir = launch_update_time*align_speed_dps;
 			if (launcher_align_to_target) {
 				# now smoothly rotate launcher:
-				var tgt_dir = target_bearing-getprop("orientation/heading-deg");
 				var cur_dir = getprop("sim/multiplay/generic/float[6]");
 				var move_dir = geo.normdeg180(tgt_dir-cur_dir);
-				var max_dir = launch_update_time*align_speed_dps;
 				move_dir = math.clamp(move_dir, -max_dir, max_dir);
 				setprop("sim/multiplay/generic/float[6]", cur_dir+move_dir);
 			}
+			var cur_dir2 = getprop("sim/multiplay/generic/float[8]");
+			var move_dir2 = geo.normdeg180(tgt_dir-cur_dir2);
+			move_dir2 = math.clamp(move_dir2, -max_dir, max_dir);
+			setprop("sim/multiplay/generic/float[8]", cur_dir2+move_dir2);
 			if (sam_align_to_target) {
 				var tgt_dir = target_bearing;
 				var cur_dir = getprop("orientation/heading-deg");
@@ -573,6 +538,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 		setprop("sam/info", info);
 		if (mp.getNode("callsign") != nil and mp.getNode("callsign").getValue() != nil and mp.getNode("callsign").getValue() != "") {
 	        setprop("sim/multiplay/generic/string[6]", left(md5(mp.getNode("callsign").getValue()), 4));
+	        datalink.send_data({"contacts":[{"callsign":mp.getNode("callsign").getValue(),"iff":0}]});
 	    } else {
 	        clearSingleLock();
 	    }
@@ -580,6 +546,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 			lu.tracking = 1;
 		}
 	}
+
 	settimer( func { missile_launch(mp, launchtime, my_pos); },launch_update_time);
 }
 
diff --git a/S-75/S-75-set.xml b/S-75/S-75-set.xml
index 619f717..83a1eb6 100644
--- a/S-75/S-75-set.xml
+++ b/S-75/S-75-set.xml
@@ -368,6 +368,17 @@
 
     <priority type="int">1</priority>
     <priority1 type="int">1</priority1>
+
+    <instrumentation>
+        <datalink>
+            <data type="int">0</data>
+            <power type="bool">true</power>
+            <channel type="int">1212</channel>
+            <power_prop type="string">/instrumentation/datalink/power</power_prop>
+            <channel_prop type="string">instrumentation/datalink/channel</channel_prop>
+            <receive_period type="double">1</receive_period>
+        </datalink>
+    </instrumentation>
 	
     <nasal>
         <notifications>
@@ -389,7 +400,11 @@
         <armament>
             <file>Aircraft/S-75/Nasal/guided-missiles.nas</file>
         </armament>
+        <datalink>
+            <file>Aircraft/S-75/Nasal/datalink.nas</file>
+        </datalink>
 		<fire_control>
+            <file>Aircraft/S-75/Nasal/fire-control-custom.nas</file>
 			<file>Aircraft/S-75/Nasal/fire-control.nas</file>
 		</fire_control>
     </nasal>
diff --git a/S-75/gui/dialogs/prio.xml b/S-75/gui/dialogs/prio.xml
index 072157e..cabac21 100644
--- a/S-75/gui/dialogs/prio.xml
+++ b/S-75/gui/dialogs/prio.xml
@@ -5,8 +5,8 @@
   	<layout>vbox</layout>
   	<draggable>true</draggable>
     <resizable>false</resizable>
-    <width>125</width>
-    <height>200</height>
+    <width>150</width>
+    <height>250</height>
 
     <group>
     	<empty><stretch>1</stretch></empty>
@@ -144,5 +144,23 @@
                 <script>setprop("priority",6);setprop("priority6",1);setprop("priority0",0);setprop("priority1",0);setprop("priority2",0);setprop("priority3",0);setprop("priority4",0);setprop("priority5",0);</script>
             </binding>
         </radio>
+        <input>
+            <row>7</row>
+            <col>0</col>
+            <width>75</width>
+            <height>25</height>
+            <label>DLNK</label>
+            <property>instrumentation/datalink/channel</property>
+            <live>true</live>
+            <halign>right</halign>
+            <binding>
+                <command>dialog-apply</command>
+            </binding>
+            <color>
+                <red>0.75</red>
+                <green>0.75</green>
+                <blue>1.0</blue>
+            </color>
+        </input>
     </group>
 </PropertyList>
\ No newline at end of file
diff --git a/SA-6/Nasal/datalink.nas b/SA-6/Nasal/datalink.nas
new file mode 100644
index 0000000..7b88482
--- /dev/null
+++ b/SA-6/Nasal/datalink.nas
@@ -0,0 +1,681 @@
+#### Datalink
+
+# Copyright 2020-2021 Colin Geniet.
+# Licensed under the GNU General Public License 2.0 or any later version.
+
+
+#### Usage
+
+### Generalities
+#
+# The datalink protocol consists of a core protocol which implements a notion
+# of datalink channel, and extensions which allow transmitting actual data.
+
+### Core protocol usage:
+#
+# Define the following properties (must be defined at nasal loading time).
+# * Mandatory
+#   /instrumentation/datalink/power_prop                path to property indicating if datalink is on
+#   /instrumentation/datalink/channel_prop              path to property containing datalink channel
+#   (the channel property can contain anything, and is transmitted/compared as a string).
+# * Optional
+#   /instrumentation/datalink/receive_period = 1        receiving loop update rate
+#
+# Optional: Re-define the function
+#   datalink.can_transmit(callsign, mp_prop, mp_index)
+#
+# This function should return 'true' when the given aircraft is able to transmit over datalink to us.
+# For instance, it can be used to check line of sight and maximum range.
+# The default implementation always returns true (always able to transmit).
+# Arguments are callsign, property node /ai/models/multiplayer[i], index of the former node.
+#
+#
+# API:
+# - get_data(callsign)
+#     Returns all datalink information about 'callsign' as an object, or nil if there is none.
+#     This object must not be modified.
+#     It contains the following methods:
+#       callsign(): The aircraft callsign (same as the argument of get_data()).
+#       index():    The aircraft index in /ai/models/multiplayer[i].
+#       on_link():  Returns a bool indicating whether 'callsign' is connected to this aircraft through datalink.
+#
+#     Extensions can define other methods in this object.
+#
+# - get_connected_callsigns() / get_connected_indices()
+#     Returns a vector containing all callsigns, resp. indices
+#     in /ai/models/multiplayer[i], of aircrafts connected on datalink.
+#     Both vectors use the same order, i.e. get_connected_callsigns()[i]
+#     and get_connected_indices()[i] correspond to the same aircraft.
+#     Furthermore this order is stable (the relative order of two aircrafts
+#     does not change as long as neither disconnects from multiplayer).
+#
+# - get_all_callsigns()
+#     Returns a vector containing all callsigns of aircraft with any associated data.
+#     There is no guarantee on the order of callsigns.
+#
+# - send_data(data, timeout=nil)
+#     Send data on the datalink. 'data' is a hash of the form
+#       {
+#           <extension_name>: <extension_data>,
+#           ...
+#       }
+#     If 'timeout' is set, clear_data() will be called after this delay.
+#     Data sent with send_data() is deleted at the next call of send_data(), or by clear_data().
+#
+# - clear_data()
+#     Clear data transmitted by this aircraft.
+#
+# Important note:
+# After a send_data(), and until the next send_data() or clear_data(),
+# the datalink behaves as if you are continuously sending the same data.
+# Thus, it is important to
+#   1. either call send_data() regularly
+#   2. or set the timeout argument of send_data()
+
+### Extensions
+
+### Aircraft contacts (extension name: "contacts")
+#
+# This extension allows to simulate an aircraft transmitting information about
+# another aircraft (typically one tracked on radar). The position data is not
+# actually transmitted (since everyone can access it from simulator internals).
+#
+## Receiving data
+# This extension adds the following methods to the result of get_data("A"):
+#       tracked():          A bool indicating that some aircraft "B" connected on datalink
+#                           is transmitting information about aircraft "A".
+#       iff():              One of IFF_UNKNOWN, IFF_HOSTILE, IFF_FRIENDLY, or nil if tracked() is false.
+#                           Indicates the result of IFF interrogation of "A" by "B"
+#                           IFF_UNKNOWN means that e.g. no IFF interrogation was performed.
+#       tracked_by():       The callsign of the transmitting aircraft ("A"), or nil if tracked() is false.
+#       tracked_by_index(): The index of the transmitting aircraft, or nil if tracked() is false.
+#                           The index refers to property nodes /ai/models/multiplayer[i].
+#       is_known():         Equivalent to (on_link() or tracked()).
+#                           Indicates if the position of this aircraft is supposed to be known
+#                           (i.e. whether or not it should be displayed on a HSD or whatever).
+#       is_friendly():      Equivalent to (on_link() or iff() == IFF_FRIENDLY).
+#       is_hostile():       Equivalent to (!on_link() and iff() == IFF_HOSTILE).
+#
+## Sending data
+# usage: send_data({ contacts: <contacts>, ...}, ...)
+# where <contacts> is a vector of hashes of the form { callsign: <callsign>, [iff: <iff>,] }.
+# <callsign> is the multiplayer callsign of the tracked aircraft.
+# <iff> (optional) is one of IFF_UNKNOWN, IFF_HOSTILE, IFF_FRIENDLY
+
+### Datalink identifier (extension name: "identifier")
+#
+# This extension allows each aircraft on datalink to transmit a personal
+# identifier, e.g. the number of the aircraft in a flight.
+#
+## Receiving data
+# This extension adds the method identifier() to the result of get_data(),
+# which returns the identifier, or nil if there is none).
+#
+## Sending data
+# Set the identifier with send_data({"identifier": <identifier>, ...});
+# The identifier must be a string. It must not contain '!'.
+
+### Coordinate transmission (extension name: "point")
+#
+# This extension allows each aircraft to broadcast a coordinate (geo.Coord object).
+#
+## Receiving data
+# This extension adds the method point() to the result of get_data(),
+# which results the transmitted geo.Coord object, or nil if there is none.
+#
+## Sending data
+# Transmit a geo.Coord object <coord> with send_data({"point": <coord>, ...});
+
+
+#### Protocol:
+#
+# Data is transmitted on MP generic string[7], with the following format:
+#   <channel>(!<data>)+
+#
+# <channel> is a hash of the datalink channel. See hash_channel() and check_channel_hash().
+# Each <data> block corresponds to data sent by an extension.
+# It starts with a prefix uniquely defining the extension.
+# The rest of the block can contain any character (including non-ascii) except '!'.
+#
+# Remark: '!' as separator is specifically chosen to allow encoding with emesary.Transfer<type>.
+#
+# The current extension prefixes are the following:
+#   contacts:   C
+#   identifier: I
+#   point:      P
+
+#### Extensions API
+#
+# Creating a new extension is done with
+#   register_extension(name, prefix, object, encode, decode)
+# name                      the extension name, used as key in the 'data' argument of send_data().
+# prefix                    the protocol prefix.
+# class                     contact class parent.
+#   A class from which all contact objects will inherit.
+#   It must have an init() method, which is called whenever a contact is created.
+#
+# encode(data)              extension encoding function.
+#   Must return the encoding of the extension data (i.e. <data> when calling
+#   send_data({name: <data>})) into a string, which may use any character except '!'.
+#   The extension prefix must not be part of the encoded string.
+#
+# decode(aircrafts_data, callsign, index, string)      extension decoding function.
+#   'aircrafts_data' is a hash from callsigns to contact objects (see below).
+#   'callsign' is the callsign of the aircraft which transmitted this data.
+#   'index' is the index of the aircraft which transmitted this data.
+#   'string' is the data encoded by encode() and transmitted through datalink.
+
+#   Each contact in 'data' inherits from the core 'Contact' class, and the extension 'class'.
+#   decode() is expected to modify 'aircrafts_data', by possibly editing
+#   existing contacts and adding new ones.  It should be careful when
+#   overwriting existing data in these contacts, including its own: decode()
+#   will be called several time on the same 'aircrafts_data' (once for each
+#   transmitting aircraft).
+#   The modified 'aircrafts_data' hash must be returned.
+#
+# decode() may use the following helper functions:
+#   add_if_missing(aircrafts_data, callsign):
+#     Create a new contact object for 'callsign' and add it to 'aircrafts_data',
+#     unless an entry for 'callsign' already exists. Returns the modified hash.
+
+
+
+#### Version and changelog
+# current: v1.1.0, minimum compatible: v1.0.0
+#
+## v1.1.0:
+# Allow external transmission restrictions
+# Make transmitting contact IFF optional
+# Ensure personal identifier has no '!'
+# '\n' is redundant for printf()
+# Fix separator character in documentation
+# Fix error when sending unknown extension
+#
+## v1.0.1:
+# Add is_known(), is_friendly(), is_hostile() helpers to extension "contacts".
+#
+## v1.0.0: Initial version
+# - Core protocol for datalink channel.
+# - Extensions "contacts", "identifier", and "point".
+
+
+
+### Parameters
+#
+# Remark: most parameters need to be the same on all aircrafts.
+
+# Index of multiplayer string used to transmit datalink info.
+# Must be the same for all aircrafts.
+var mp_string = 7;
+var mp_path = "sim/multiplay/generic/string["~mp_string~"]";
+
+var channel_hash_period = 600;
+
+var receive_period = getprop("/instrumentation/datalink/receive_period") or 1;
+
+# Should be overwitten to add transmission restrictions.
+var can_transmit = func(contact, mp_prop, mp_index) {
+    return 1;
+}
+
+### Properties
+
+var input = {
+    power:      getprop("/instrumentation/datalink/power_prop"),
+    channel:    getprop("/instrumentation/datalink/channel_prop"),
+    ident:      getprop("/instrumentation/datalink/identifier_prop"),
+    mp:         mp_path,
+    models:     "/ai/models",
+    callsign:   "/sim/multiplay/callsign",
+};
+
+foreach (var name; keys(input)) {
+    if (input[name] != nil) {
+        input[name] = props.globals.getNode(input[name], 1);
+    }
+}
+
+
+
+#### Core protocol implementation
+
+### Channel hash (based on iff.nas)
+#
+# Channel is hashed with current time (rounded to 10min) and own callsign.
+
+var clean_callsign = func(callsign) {
+    return damage.processCallsign(callsign);
+}
+
+var my_callsign = func {
+    return clean_callsign(input.callsign.getValue());
+}
+
+# Time, rounded to 'channel_hash_period'. This is used to hash channel.
+var get_time = func {
+    return int(math.floor(systime() / channel_hash_period) * channel_hash_period);
+}
+
+# Previous / next time (with channel_hash_period interval).
+# This is used to give a bit of margin on the time check.
+# (will work if system clocks are coordinated within 10min).
+var get_prev_time = func { return get_time() - channel_hash_period; }
+var get_next_time = func { return get_time() + channel_hash_period; }
+
+var parse_hexadecimal = func(str) {
+    var res = 0;
+    for (var i=0; i<size(str); i+=1) {
+        res *= 10;
+        var c = str[i];
+        if (c >= 48 and c < 58) {
+            # digit
+            res += c - 48;
+        } elsif (c >= 65 and c < 71) {
+            # upper case letter
+            res += c - 55;
+        } elsif (c >= 97 and c < 103) {
+            # lower case letter
+            res += c - 87;
+        }
+    }
+    return res;
+}
+
+var _hash_channel = func(time, callsign, channel) {
+    # 5 hex digits (2^20) fit in 3 chars for emesary int encoding.
+    var hash = parse_hexadecimal(left(md5(time ~ callsign ~ channel), 5));
+    return emesary.TransferInt.encode(hash, 3);
+}
+
+# Hash channel (when sending).
+var encode_channel = func(channel) {
+    return _hash_channel(get_time(), my_callsign(), channel);
+}
+
+# Check that the hash transmitted by aircraft 'callsign' is correct for 'channel'.
+var check_channel = func(hash, callsign, channel) {
+    return hash == _hash_channel(get_time(), callsign, channel)
+        or hash == _hash_channel(get_prev_time(), callsign, channel)
+        or hash == _hash_channel(get_next_time(), callsign, channel);
+}
+
+### Contact object
+var Contact = {
+    new: func(callsign) {
+        var c = {
+            # contact_parents is the list of all classes from which contacts inherit (for extensions).
+            parents: contact_parents,
+            _callsign: callsign,
+        };
+        # Initialize all inherited classes.
+        foreach (var class; contact_parents) {
+            call(class.init, [], c, nil, nil);
+        }
+        return c;
+    },
+    init: func { me._on_link = 0; },
+
+    callsign: func { return me._callsign; },
+    index: func { return callsign_to_index[me._callsign]; },
+    on_link: func { return me._on_link; },
+    set_on_link: func(b) { me._on_link = b; },
+};
+
+### Extensions
+var extensions = {};
+var extension_prefixes = {};
+var max_prefix_length = 0;
+var contact_parents = [Contact];
+
+var register_extension = func(name, prefix, class, encode, decode) {
+    if (contains(extensions, name)) {
+        printf("Datalink: double registration of extension '%s'. Skipping.", name);
+        return -1;
+    }
+    if (contains(extension_prefixes, prefix)) {
+        printf("Datalink: double registration of extension prefix '%s'. Skipping.", name);
+        return -1;
+    }
+    extensions[name] = { prefix: prefix, encode: encode, decode: decode, };
+    extension_prefixes[prefix] = name;
+    max_prefix_length = math.max(max_prefix_length, size(prefix));
+    append(contact_parents, class);
+
+    return 0;
+}
+
+
+var data_separator = "!";
+
+
+### Transmission
+
+var clear_data = func {
+    send_data({});
+}
+
+var clear_timer = maketimer(1, clear_data);
+clear_timer.singleShot = 1;
+
+# Send data through datalink.
+#
+# timeout: if set, sent data will be cleared after this time (other aircrafts
+# won't receive it anymore). Useful if 'send_data' is not called often.
+var send_data = func(data, timeout=nil) {
+    if (!input.power.getBoolValue()) {
+        last_data = {};
+        input.mp.setValue("");
+        return;
+    }
+
+    # First encode channel
+    var str = encode_channel(input.channel.getValue());
+
+    # Then all extensions
+    last_data = data;
+    foreach(var ext; keys(data)) {
+        # Skip missing extensions with a warning
+        if (!contains(extensions, ext)) {
+            printf("Warning: unknown datalink extension %s in send_data().", ext);
+            continue;
+        }
+        str = str ~ data_separator ~ extensions[ext].prefix ~ extensions[ext].encode(data[ext]);
+    }
+
+    input.mp.setValue(str);
+
+    if (timeout != nil) {
+        clear_timer.restart(timeout);
+    }
+}
+
+# Used internally to update the channel/identifier while keeping the same data.
+# Does not touch timeout.
+var last_data = {};
+var resend_data = func {
+    send_data(last_data);
+}
+
+# Very slow timer to ensure the channel hash is updated regularly.
+# Only relevant if you never call send_data();
+var hash_update_timer = maketimer(channel_hash_period/2, resend_data);
+hash_update_timer.start();
+
+
+### Receiving
+
+# callsign to data hash
+var aircrafts_data = {};
+# List of callsigns / indices connected on datalink (index is for /ai/models/multiplayer[i]).
+var connected_callsigns = [];
+var connected_indices = [];
+
+# Maintain callsign to multiplayer index hash
+# (doesn't cost much since we already iterate over MP models).
+var callsign_to_index = {};
+
+
+var get_data = func(callsign) {
+    return aircrafts_data[callsign];
+}
+
+var get_connected_callsigns = func {
+    return connected_callsigns;
+}
+
+var get_connected_indices = func {
+    return connected_indices;
+}
+
+var get_all_callsigns = func {
+    return keys(aircrafts_data);
+}
+
+# Helper for modifying aircrafts_data.
+var add_if_missing = func(aircrafts_data, callsign) {
+    if (!contains(aircrafts_data, callsign)) {
+        aircrafts_data[callsign] = Contact.new(callsign);
+    }
+    return aircrafts_data;
+}
+
+var receive_loop = func {
+    var my_channel = input.channel.getValue();
+
+    aircrafts_data = {};
+    connected_callsigns = [];
+    connected_indices = [];
+
+    var mp_models = input.models.getChildren("multiplayer");
+    foreach(var mp; mp_models) {
+        var idx = mp.getIndex();
+        if (!mp.getValue("valid")) continue;
+        var callsign = mp.getValue("callsign");
+        if (callsign == nil) continue;
+
+        callsign_to_index[callsign] = idx;
+
+        var data = mp.getValue(mp_path);
+        if (data == nil) continue;
+
+        # Split channel part and data part
+        var tokens = split(data_separator, data);
+
+        # Check channel
+        if (!check_channel(tokens[0], callsign, my_channel)) continue;
+
+        # We check this _after_ the channel. Checking the channel is quite cheap,
+        # and we don't know how slow this function is, it might have a get_cart_ground_intersection()
+        if (!can_transmit(callsign, mp, idx)) continue;
+
+        # Add to list of connected aircrafts.
+        append(connected_callsigns, callsign);
+        append(connected_indices, idx);
+        # Add to data
+        aircrafts_data = add_if_missing(aircrafts_data, callsign);
+        aircrafts_data[callsign].set_on_link(1);
+
+        # Parse extensions data
+        for (var i=1; i<size(tokens); i+=1) {
+            var extension = nil;
+            # Identify extension prefix.  This is not very clever code, but
+            # realistically it doesn't matter since prefixes are very short.
+            var len = 1;
+            for (; len <= max_prefix_length; len += 1) {
+                if (len > size(tokens)) break;
+                var prefix = left(tokens[i], len);
+                if (contains(extension_prefixes, prefix)) {
+                    extension = extension_prefixes[prefix];
+                    break;
+                }
+            }
+            # Unknown extension, skip
+            if (extension == nil) continue;
+            # Remove prefix
+            var data = substr(tokens[i], len);
+            # Decode
+            aircrafts_data = extensions[extension].decode(aircrafts_data, callsign, data);
+        }
+    }
+}
+
+var receive_timer = maketimer(receive_period, receive_loop);
+
+
+# Start / stop listener
+setlistener(input.power, func (node) {
+    if (node.getBoolValue()) {
+        receive_timer.start();
+        resend_data();  # Sets channel/identifier
+    } else {
+        receive_timer.stop();
+        aircrafts_data = {};
+        clear_data();
+    }
+}, 1, 0);
+
+# Listener to resend data so as to update the channel.
+setlistener(input.channel, resend_data);
+
+
+
+#### Extensions
+
+## Identifier
+
+var ContactIdentifier = {
+    init: func {
+        me._identifier = nil;
+    },
+    set_identifier: func(ident) {
+        me._identifier = ident;
+    },
+    identifier: func {
+        return me._identifier;
+    },
+};
+
+var encode_identifier = func(ident) {
+    # Force string conversion
+    ident = ""~ident;
+
+    if (find("!", ident) >= 0) {
+        printf("Datalink: Identifier is not allowed to contain '!': %s.", ident);
+        return "";
+    } else {
+        return ident;
+    }
+}
+
+var decode_identifier = func(aircrafts_data, callsign, str) {
+    aircrafts_data = add_if_missing(aircrafts_data, callsign);
+    aircrafts_data[callsign].set_identifier(str);
+    return aircrafts_data;
+}
+
+register_extension("identifier", "I", ContactIdentifier, encode_identifier, decode_identifier);
+
+
+
+## Contacts
+
+# IFF status transmitted over datalink.
+var IFF_UNKNOWN = 0;      # Unknown status
+var IFF_HOSTILE = 1;      # Considered hostile (no response to IFF).
+var IFF_FRIENDLY = 2;     # Friendly, because positive IFF identification.
+#   This is also the priority order for IFF reports in case of conflicts:
+#   e.g. a contact will be reported as friendly if anyone on datalink reports it as friendly.
+
+var ContactTracked = {
+    init: func {
+        me._tracked_by = nil;
+        me._iff = IFF_UNKNOWN;
+    },
+    set_tracked_by: func(callsign) {
+        me._tracked_by = callsign;
+    },
+    set_iff: func(iff) {
+        # Priority order on IFF values (friendly, then hostile, then no data).
+        me._iff = math.max(me._iff, iff);
+    },
+    tracked: func {
+        return me._tracked_by != nil;
+    },
+    tracked_by: func {
+        return me._tracked_by;
+    },
+    tracked_by_index: func {
+        return (me._tracked_by != nil) ? callsign_to_index[me._tracked_by] : nil;
+    },
+    iff: func {
+        return me._iff;
+    },
+    is_known: func {
+        return me.on_link() or me.tracked();
+    },
+    is_friendly: func {
+        return me.on_link() or me.iff() == IFF_FRIENDLY;
+    },
+    is_hostile: func {
+        return !me.on_link() and me.iff() == IFF_HOSTILE;
+    },
+};
+
+# Contact encoding: callsign + bits
+# callsign: the callsign encoded with emesary.TransferString
+# bits: bitfield |xxxxxxff| (left is most significant)
+#   f: IFF, x: unused
+#   encoded with emesary.TransferByte
+# Additional values may be appended for extensions.
+
+var encode_contact = func(contact) {
+    # Encode bitfield
+    var bits = contact["iff"] != nil ? contact.iff : IFF_UNKNOWN;
+
+    return emesary.TransferString.encode(clean_callsign(contact.callsign))
+        ~ emesary.TransferByte.encode(bits);
+}
+
+var decode_contact = func(str) {
+    var res = {};
+    var dv = emesary.TransferString.decode(str, 0);
+    res.callsign = dv.value;
+    dv = emesary.TransferByte.decode(str, dv.pos);
+    var bits = dv.value;
+    res.iff = math.mod(bits, 4);
+    return res;
+}
+
+# Special character, won't be used by emesary encoding.
+var contacts_separator = "#";
+
+var encode_contacts = func(contacts) {
+    var str = "";
+    foreach (var contact; contacts) {
+        str = str~encode_contact(contact)~contacts_separator;
+    }
+    return str;
+}
+
+var decode_contacts = func(aircrafts_data, callsign, str) {
+    var contacts = split(contacts_separator, str);
+    foreach (var contact; contacts) {
+        if (contact == "") continue;
+        var res = decode_contact(contact);
+        aircrafts_data = add_if_missing(aircrafts_data, res.callsign);
+        aircrafts_data[res.callsign].set_iff(res.iff);
+        aircrafts_data[res.callsign].set_tracked_by(callsign);
+    }
+    return aircrafts_data;
+}
+
+register_extension("contacts", "C", ContactTracked, encode_contacts, decode_contacts);
+
+
+
+## Coordinate
+
+var ContactPoint = {
+    init: func {
+        me._point = nil;
+    },
+    set_point: func(point) {
+        me._point = point;
+    },
+    point: func {
+        return me._point;
+    },
+};
+
+var encode_point = func(coord) {
+    return emesary.TransferCoord.encode(coord);
+}
+
+var decode_point = func(aircrafts_data, callsign, str) {
+    var coord = emesary.TransferCoord.decode(str, 0).value;
+    aircrafts_data = add_if_missing(aircrafts_data, callsign);
+    aircrafts_data[callsign].set_point(coord);
+    return aircrafts_data;
+}
+
+register_extension("point", "P", ContactPoint, encode_point, decode_point);
\ No newline at end of file
diff --git a/SA-6/Nasal/fire-control-custom.nas b/SA-6/Nasal/fire-control-custom.nas
new file mode 100644
index 0000000..ef81a26
--- /dev/null
+++ b/SA-6/Nasal/fire-control-custom.nas
@@ -0,0 +1,55 @@
+
+
+################### SAM INFO ###################
+
+var setupTime = 300;#minimum 'launcher_tilt_time' secs no matter what, due to anim and stuff.
+var reload_time = 600;
+var launcher_final_tilt_deg  = 33;
+var launcher_start_tilt_deg  =  0;
+var launcher_tilt_time       = 15;
+var sam_align_to_target      =  0;
+var launcher_align_to_target =  1;
+var align_speed_dps          = 20;
+var radar_elevation_above_terrain_m = 10;#estimate
+var radar_lowest_pitch       = 0.1;# 0.5 degs = roughly 925 feet at 20 nm, 25 feet at half a nm. # 0.35 = roughly 925 feet at 20 nm, 25 feet at half a nm.
+
+#reaction tme for s-300p is 28 secs acording to http://www.astronautix.com/s/s-300p.html
+# sounds a bit high for pmu, as its 4 secs for s-400
+
+################### CIWS INFO ###################
+
+var ciws_installed =   0;
+var ciws_domain_nm = 1.50; #range where it can kill
+var ciws_chance    = 0.20; #chance to get a kill at 0nm distance
+var ciws_burst_rounds = 60;#how many rounds in a burst
+var ciws_shell = 15;#from lookup table in damage.nas
+var ROUNDS_init       = 30;
+var ROUNDS = ROUNDS_init;#CIWS bursts remaining
+
+################### MISSILE INFO - http://www.astronautix.com/k/kub.html ###################
+
+var NUM_MISSILES = 2; # total carried minus 1
+var missile_name = "m3m9";
+var missile_brevity = "3M9";
+var missile_max_distance = 18; #max distance of target in nm when it will fire
+var missile_min_distance = 0.5; #minimum distance in nm when it will fire
+var lockon_time = 24; #time in seconds it takes to lock on and get a firing solution on a target
+var fire_minimum_interval = 7;# time since last track was initiated till a new can be initiated
+var same_target_max_missiles = 2;# max number of missiles in air against same target
+
+var isInEngagementEnvelope = func (target_radial_airspeed, target_ground_distance, target_relative_altitude) {
+	return 1;
+}
+
+var midflight = func (struct) {
+	if (struct.guidance == "semi-radar") {
+		# This makes the SAM system keep lock on target when missile in-flight and no longer tracking the target.
+		# Usage is to make the RWR lock sound go off in targets cockpit.
+		thread.lock(mutexLock);
+		semi_active_track = struct.callsign;
+		thread.unlock(mutexLock);
+	}
+	return {};
+};
+
+
diff --git a/SA-6/Nasal/fire-control.nas b/SA-6/Nasal/fire-control.nas
index 024013b..58c42a7 100644
--- a/SA-6/Nasal/fire-control.nas
+++ b/SA-6/Nasal/fire-control.nas
@@ -1,4 +1,4 @@
-################### GLOBALS ###################
+################### GLOBALS
 
 var false = 0;
 var true = 1;
@@ -20,58 +20,6 @@ var ACTIVE_MISSILE = 0;
 var semi_active_track = nil;# with multiple missiles flying in semi-active-radar mode, this can change rather fast. Which means pilots wont get a steady tone, but disrupted tones. (tradeoff)
 var mutexLock = thread.newlock();
 
-################### SAM INFO ###################
-
-var setupTime = 300;#minimum 'launcher_tilt_time' secs no matter what, due to anim and stuff.
-var reload_time = 600;
-var launcher_final_tilt_deg  = 33;
-var launcher_start_tilt_deg  =  0;
-var launcher_tilt_time       = 15;
-var sam_align_to_target      =  0;
-var launcher_align_to_target =  1;
-var align_speed_dps          = 20;
-var radar_elevation_above_terrain_m = 10;#estimate
-var radar_lowest_pitch       = 0.1;# 0.5 degs = roughly 925 feet at 20 nm, 25 feet at half a nm. # 0.35 = roughly 925 feet at 20 nm, 25 feet at half a nm.
-
-#reaction tme for s-300p is 28 secs acording to http://www.astronautix.com/s/s-300p.html
-# sounds a bit high for pmu, as its 4 secs for s-400
-
-################### CIWS INFO ###################
-
-var ciws_installed =   0;
-var ciws_domain_nm = 1.50; #range where it can kill
-var ciws_chance    = 0.20; #chance to get a kill at 0nm distance
-var ciws_burst_rounds = 60;#how many rounds in a burst
-var ciws_shell = 15;#from lookup table in damage.nas
-var ROUNDS_init       = 30;
-var ROUNDS = ROUNDS_init;#CIWS bursts remaining
-
-################### MISSILE INFO - http://www.astronautix.com/k/kub.html ###################
-
-var NUM_MISSILES = 2; # total carried minus 1
-var missile_name = "m3m9";
-var missile_brevity = "3M9";
-var missile_max_distance = 18; #max distance of target in nm when it will fire
-var missile_min_distance = 0.5; #minimum distance in nm when it will fire
-var lockon_time = 24; #time in seconds it takes to lock on and get a firing solution on a target
-var fire_minimum_interval = 7;# time since last track was initiated till a new can be initiated
-var same_target_max_missiles = 2;# max number of missiles in air against same target
-
-var isInEngagementEnvelope = func (target_radial_airspeed, target_ground_distance, target_relative_altitude) {
-	return 1;
-}
-
-var midflight = func (struct) {
-	if (struct.guidance == "semi-radar") {
-		# This makes the SAM system keep lock on target when missile in-flight and no longer tracking the target.
-		# Usage is to make the RWR lock sound go off in targets cockpit.
-		thread.lock(mutexLock);
-		semi_active_track = struct.callsign;
-		thread.unlock(mutexLock);
-	}
-	return {};
-};
-
 
 ##########################################################################
 ######################## Common SAM code       ###########################
@@ -79,6 +27,8 @@ var midflight = func (struct) {
 
 ################### VARIOUS
 
+setprop("sim/multiplay/generic/float[7]", 0);# tracking radar vert rotation
+setprop("sim/multiplay/generic/float[8]", 0);# tracking radar horiz rotation
 setprop("sim/multiplay/generic/float[5]", 0);# launcher vert rotation
 setprop("sim/multiplay/generic/float[6]", 0);# launcher horiz rotation
 var start_time = systime();
@@ -139,7 +89,7 @@ var buildTargetList = func {
 };
 
 var lookup = func (sign) {
-	
+
 	foreach (tgt ; targetsV2.vector) {
 		if (tgt.callsign == sign) {
 			return tgt;
@@ -177,9 +127,11 @@ var scan = func() {
 	buildTargetList();
 
 	if ( getprop("/carrier/sunk") == 1 or getprop("/carrier/disabled") == 1) {
+		setprop("sim/multiplay/generic/string[6]", "");
+		datalink.clear_data();
 		return;
 	}
-	
+
 	if (systime() - start_time < setupTime ) {
 		printf("Seconds till activation: %.1f", setupTime - (systime() - start_time));
 		setprop("sam/timeleft", setupTime - (systime() - start_time));
@@ -193,8 +145,11 @@ var scan = func() {
 			setprop("sim/multiplay/generic/float[5]", launcher_final_tilt_deg);
 		}
 		setprop("sim/multiplay/generic/float[6]", 0);
+		setprop("sim/multiplay/generic/float[7]", 0);
+		setprop("sim/multiplay/generic/float[8]", 0);
 		setprop("sim/multiplay/generic/string[6]", "");
 		setprop("/sim/multiplay/generic/int[2]", 1);
+		datalink.clear_data();
 		return;
 	}
 	setprop("sim/multiplay/generic/float[5]", launcher_final_tilt_deg);
@@ -223,12 +178,12 @@ var scan = func() {
 	}
 	prio_vector = sort(prio_vector, func (a,b) {if (a[2]>b[2]){return -1;} elsif (a[2]<b[2]) {return 1;} else {return 0;}});
 	foreach(var mp; prio_vector) {
-		
+
 		#### DO WE HAVE FIRING SOLUTION... ####
 		# is plane in range, do we still have missiles, and is a missile already inbound, and has it been 4 seconds since the last missile launch?
 		var trigger = mp[1];
 		#print("dist to target = " ~ dist_to_target);
-		
+
 		var lu = lookup(mp[0].getNode("callsign").getValue());
 		if ( launch_in_progress == 0 and trigger == true and lu != nil and lu.in_air < same_target_max_missiles and !lu.tracking and ACTIVE_MISSILE <= NUM_MISSILES and ( systime() - missile_delay_time > fire_minimum_interval ) ) { #
 			#### ... FOR THE MISSILE ####
@@ -238,7 +193,7 @@ var scan = func() {
 			armament.contact = radar_logic.Contact.new(mp[0], AIR);
 			launch_in_progress = 1;
 			missile_launch(mp[0], systime(), my_pos);
-			
+
 		} elsif ( ciws_installed and trigger == -1 and ROUNDS > 0 and ( systime() - ciws_delay_time > 1.0 ) and lu != nil) {
 			#### ... FOR THE CIWS ####
 			var contact = radar_logic.Contact.new(mp[0], AIR);
@@ -272,7 +227,7 @@ var scan = func() {
 				reloading = 1;
 				reload_starting = systime();
 			}
-		} 
+		}
 		if (lu != nil and lu.tracking) {
 			radarOn = 1;
 		}
@@ -318,8 +273,10 @@ var clearSingleLock = func () {
 	thread.lock(mutexLock);
 	if (semi_active_track == nil) {
 		setprop("sim/multiplay/generic/string[6]", "");
+		datalink.clear_data();
 	} else {
 		setprop("sim/multiplay/generic/string[6]", left(md5(semi_active_track), 4));
+		datalink.send_data({"contacts":[{"callsign":semi_active_track,"iff":0}]});
 	}
 	thread.unlock(mutexLock);
 }
@@ -335,7 +292,7 @@ var fire_control = func(mp, my_pos) {
 	var ufo_pos = geo.Coord.new().set_latlon(mp.getNode("position/latitude-deg").getValue(),mp.getNode("position/longitude-deg").getValue(),(mp.getNode("position/altitude-ft").getValue() * FT2M));
 	var target_distance = my_pos.direct_distance_to(ufo_pos);
 	var target_altitude = mp.getNode("position/altitude-ft").getValue();
-	
+
 	# is this plane a friend or foe?
 	var lu = lookup(mp.getNode("callsign").getValue());
 	if ( lu == nil ) { return [mp,false,0,0]; }
@@ -344,11 +301,11 @@ var fire_control = func(mp, my_pos) {
 	var target_ground_distance = my_pos.distance_to(ufo_pos);
 	var target_heading = mp.getNode("orientation/true-heading-deg").getValue();
 	var relative_bearing = math.abs(geo.normdeg180(ufo_pos.course_to(my_pos) - target_heading));
-	
+
 	var target_relative_altitude = target_altitude - my_pos.alt()*M2FT;
 	var target_radial_airspeed = math.abs(math.abs(((relative_bearing / 90 ) - 1) * target_airspeed));#200kt against us = 200kt, 200kt at angle of us = 0kt, 200kt away from us = 200kt
 	var target_relative_pitch = vector.Math.getPitch(my_pos, ufo_pos);
-	
+
 
 	# can the radar see it?
 	var data_link_match = false;
@@ -358,7 +315,7 @@ var fire_control = func(mp, my_pos) {
 #			#print('tgt confirmed via datalink');
 #		}
 #	}
-	
+
 	var visible = radar_logic.isNotBehindTerrain(mp);
 
 
@@ -367,9 +324,10 @@ var fire_control = func(mp, my_pos) {
 		var radarSeeTarget = 1;
 		if ( data_link_match == false ) {
 			if ( visible[0] == false ) {radarSeeTarget = 0 }
-			if ( target_relative_pitch < radar_lowest_pitch ) { radarSeeTarget = 0 } # 
+			if ( target_relative_pitch < radar_lowest_pitch ) { radarSeeTarget = 0 } #
 			if ( target_distance*M2NM > 1.0 and visible[1] and math.abs(target_radial_airspeed) < 20 ) {radarSeeTarget = 0 } # i.e. notching with terrain behind
 		}
+
 		if (radarSeeTarget and rand() > target_distance*M2NM / ciws_domain_nm) {
 			var score = 0;
 			var priority = getprop("priority");
@@ -395,26 +353,26 @@ var fire_control = func(mp, my_pos) {
 	if ( data_link_match == false ) {
 		if (target_airspeed < 60) {return [mp,false,0,0];}
 		if ( visible[0] == false ) { return [mp,false,0,0]; }
-		if ( target_relative_pitch < radar_lowest_pitch ) { return [mp,false,0,0]; } # 
+		if ( target_relative_pitch < radar_lowest_pitch ) { return [mp,false,0,0]; } #
 		if ( visible[1] and math.abs(target_radial_airspeed) < 20 ) { return [mp,false,0,0]; } # i.e. notching, landed aircraft
 	}
-	
+
 	if ( target_distance * M2NM > missile_max_distance ) { return [mp,false,0,0]; }
 
-	
-	
-	
+
+
+
 	# is the plane within the engagement envelope?
 	# the numbers after target_radial_airspeed are ( offset_of_engagement_envelope / speed_to_apply_that_offset )
 	# larger offset means it wont fire until the plane is closer.
 	# for visualization: https://www.desmos.com/calculator/gw570fa9km
-	
-	if (!isInEngagementEnvelope(target_radial_airspeed, target_ground_distance, target_relative_altitude) ) { return [mp,false,0,0]; }	
 
-	
+	if (!isInEngagementEnvelope(target_radial_airspeed, target_ground_distance, target_relative_altitude) ) { return [mp,false,0,0]; }
+
+
 
 	var the_dice = rand();
-	
+
 	if ( the_dice > 0.20 ) {
 		var score = 0;
 		var priority = getprop("priority");
@@ -461,7 +419,7 @@ var reload = func(force = 1) {
 	if (ROUNDS == 0 or force == 1) {
 		ROUNDS = ROUNDS_init;
 		print("Reloaded with "~(ROUNDS)~" bursts.");
-	}	
+	}
 	setprop("sam/missiles",(NUM_MISSILES+1-ACTIVE_MISSILE));
 	setprop("sam/bursts", ROUNDS);
 	reloading = 0;
@@ -493,6 +451,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 	}
 	var ufo_pos = geo.Coord.new().set_latlon(mp.getNode("position/latitude-deg").getValue(),mp.getNode("position/longitude-deg").getValue(),(mp.getNode("position/altitude-ft").getValue() * 0.3048));
 	var target_bearing = my_pos.course_to(ufo_pos);
+	var target_pitch   = vector.Math.getPitch(my_pos, ufo_pos);
 	var info = mp.getNode("callsign").getValue();
 	var lu = lookup(mp.getNode("callsign").getValue());
 	if (getprop("sam/timeleft") != 0) {
@@ -510,6 +469,8 @@ var missile_launch = func(mp, launchtime, my_pos) {
 			setprop("sim/multiplay/generic/float[6]", target_bearing-getprop("orientation/heading-deg"));
 			theMissile.rail_head_deg = getprop("sim/multiplay/generic/float[6]");
 		}
+		setprop("sim/multiplay/generic/float[7]", target_pitch);
+		setprop("sim/multiplay/generic/float[8]", target_bearing-getprop("orientation/heading-deg"));
 		if (sam_align_to_target) {
 			setprop("/orientation/heading-deg",target_bearing);
 		}
@@ -524,7 +485,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 			settimer(autoreload, reload_time);
 			reloading = 1;
 			reload_starting = systime();
-		}		
+		}
 		if (lu != nil) {
 			append(lu.missiles, theMissile);
 			lu.in_air += 1;
@@ -551,15 +512,19 @@ var missile_launch = func(mp, launchtime, my_pos) {
 	} else {
 		info = info~" (tracking)";
 		if (systime()-missile_release_time > 1.5) {
+			var tgt_dir = target_bearing-getprop("orientation/heading-deg");
+			var max_dir = launch_update_time*align_speed_dps;
 			if (launcher_align_to_target) {
 				# now smoothly rotate launcher:
-				var tgt_dir = target_bearing-getprop("orientation/heading-deg");
 				var cur_dir = getprop("sim/multiplay/generic/float[6]");
 				var move_dir = geo.normdeg180(tgt_dir-cur_dir);
-				var max_dir = launch_update_time*align_speed_dps;
 				move_dir = math.clamp(move_dir, -max_dir, max_dir);
 				setprop("sim/multiplay/generic/float[6]", cur_dir+move_dir);
 			}
+			var cur_dir2 = getprop("sim/multiplay/generic/float[8]");
+			var move_dir2 = geo.normdeg180(tgt_dir-cur_dir2);
+			move_dir2 = math.clamp(move_dir2, -max_dir, max_dir);
+			setprop("sim/multiplay/generic/float[8]", cur_dir2+move_dir2);
 			if (sam_align_to_target) {
 				var tgt_dir = target_bearing;
 				var cur_dir = getprop("orientation/heading-deg");
@@ -573,6 +538,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 		setprop("sam/info", info);
 		if (mp.getNode("callsign") != nil and mp.getNode("callsign").getValue() != nil and mp.getNode("callsign").getValue() != "") {
 	        setprop("sim/multiplay/generic/string[6]", left(md5(mp.getNode("callsign").getValue()), 4));
+	        datalink.send_data({"contacts":[{"callsign":mp.getNode("callsign").getValue(),"iff":0}]});
 	    } else {
 	        clearSingleLock();
 	    }
@@ -580,6 +546,7 @@ var missile_launch = func(mp, launchtime, my_pos) {
 			lu.tracking = 1;
 		}
 	}
+
 	settimer( func { missile_launch(mp, launchtime, my_pos); },launch_update_time);
 }
 
diff --git a/SA-6/SA-6-set.xml b/SA-6/SA-6-set.xml
index b559e1b..229ce52 100644
--- a/SA-6/SA-6-set.xml
+++ b/SA-6/SA-6-set.xml
@@ -356,7 +356,7 @@
         <damage type="double">100</damage>
     </sam>
 
-        <enemies>
+    <enemies>
         <e1 userarchive="y" type="string">target1</e1>
         <e2 userarchive="y" type="string">target2</e2>
         <e3 userarchive="y" type="string">target3</e3>
@@ -373,6 +373,17 @@
 
     <priority type="int">0</priority>
     <priority0 type="int">1</priority0>
+
+    <instrumentation>
+        <datalink>
+            <data type="int">0</data>
+            <power type="bool">true</power>
+            <channel type="int">1212</channel>
+            <power_prop type="string">/instrumentation/datalink/power</power_prop>
+            <channel_prop type="string">instrumentation/datalink/channel</channel_prop>
+            <receive_period type="double">1</receive_period>
+        </datalink>
+    </instrumentation>
 	
     <nasal>
         <notifications>
@@ -394,7 +405,11 @@
         <armament>
             <file>Aircraft/SA-6/Nasal/guided-missiles.nas</file>
         </armament>
+        <datalink>
+            <file>Aircraft/SA-6/Nasal/datalink.nas</file>
+        </datalink>
 		<fire_control>
+            <file>Aircraft/SA-6/Nasal/fire-control-custom.nas</file>
 			<file>Aircraft/SA-6/Nasal/fire-control.nas</file>
 		</fire_control>
     </nasal>
diff --git a/SA-6/Sounds/launch.wav b/SA-6/Sounds/launch.wav
new file mode 100644
index 0000000..0b3c83b
Binary files /dev/null and b/SA-6/Sounds/launch.wav differ
diff --git a/SA-6/Sounds/sound.xml b/SA-6/Sounds/sound.xml
new file mode 100644
index 0000000..331471a
--- /dev/null
+++ b/SA-6/Sounds/sound.xml
@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<PropertyList>
+    <fx>
+        <launch>
+            <name>missile</name>
+            <path>Aircraft/SA-6/Sounds/launch.wav</path>
+            <mode>once</mode>
+            <condition>
+                <property>payload/armament/m3m9/sound-fire-on-off</property>
+            </condition>
+            <reference-dist>50</reference-dist>
+            <max-dist>15000</max-dist>
+            <position>
+                <x> 0.01 </x>
+                <y> 0.01 </y>
+                <z> 0.01 </z>
+            </position>
+            <volume>
+                <factor>1</factor>
+                <max>1</max>
+            </volume>
+        </launch>
+    </fx>
+</PropertyList>
diff --git a/SA-6/gui/dialogs/prio.xml b/SA-6/gui/dialogs/prio.xml
index 072157e..cabac21 100644
--- a/SA-6/gui/dialogs/prio.xml
+++ b/SA-6/gui/dialogs/prio.xml
@@ -5,8 +5,8 @@
   	<layout>vbox</layout>
   	<draggable>true</draggable>
     <resizable>false</resizable>
-    <width>125</width>
-    <height>200</height>
+    <width>150</width>
+    <height>250</height>
 
     <group>
     	<empty><stretch>1</stretch></empty>
@@ -144,5 +144,23 @@
                 <script>setprop("priority",6);setprop("priority6",1);setprop("priority0",0);setprop("priority1",0);setprop("priority2",0);setprop("priority3",0);setprop("priority4",0);setprop("priority5",0);</script>
             </binding>
         </radio>
+        <input>
+            <row>7</row>
+            <col>0</col>
+            <width>75</width>
+            <height>25</height>
+            <label>DLNK</label>
+            <property>instrumentation/datalink/channel</property>
+            <live>true</live>
+            <halign>right</halign>
+            <binding>
+                <command>dialog-apply</command>
+            </binding>
+            <color>
+                <red>0.75</red>
+                <green>0.75</green>
+                <blue>1.0</blue>
+            </color>
+        </input>
     </group>
 </PropertyList>
\ No newline at end of file