This page is currently migrating to support 2.2 release, it is under progess, not completed yet.

What is it ?

LotAtc can display transponder and IFF for DCS.

  • It is working for AI using specific unit names in DCS editor.
  • For human pilots, you need to use UniversRadio or SRS and use its transponder function. See following chapter to configure it.

Depending of plane/helicopter capabilities, LotAtc can use MODE1, MODE3 or MODE4. See Wikipedia article for more information.

What I need for AI?

To use transponder AI, you must respect a specific syntax for unit names in DCS editor (note that is the same than UniversRadio for better compatibility).

Add the special string below at the unit name from DCS mission editor, it will be parsed by LotAtc (and not displayed in the name).

Entry Name Format
MODE1 Mode 1 2 digit
MODE3 Mode 3/C 4 digit
MODE4 Mode 4 2 letters, FR for friendly, any others for no friendly

MODE1, MODE3, MODE4 are all optionnals.


  • A F/A-18C called Bones #IFF:7721FR : A F/A-18C friendly called Bones with transponder set to 7721
  • A Su-27 called Kodiac #IFF:(12)7712 : A Su-27 with transponder 7712, mode1 to 12
  • A A-10C called Shark #IFF:7512 : A A-10C with transponder 7512

To make a correspondance between code and name, see below for more information.

What I need for human pilots?

  • LotAtc connected to UniversRadio using UR ATC Desk or SRS
  • DCS human pilots using UniversRadio/SRS
    • For planes with working internal transponder features like A-10C, C-101EB, F-5E3, M2000C and UH-1H… You can use it in-cockpit
    • For planes with no transponder features, use UR Transponder panel or SRS overlay

Configure LotAtc

For AI support

Nothing, should be displayed directly if units have correct names in DCS!

For human pilots support


  • Enable UniversRadio in Radio panel
  • Set your location (AWACS, ground radar, tower…)

That’s all, LotAtc client will begin to scan around your radar location by asking for UniversRadio all transponders around. It takes some seconds to scan all 360° (around 6s).


SRS must be activated in config.lua file and activated on SRS server, then all is done!

For dedicated server

If you are using multiples instances with SRS/LotAtc on same computer, you must set different port for SRS-LotAtc communication to use transponder functions.

For LotAtc, in config.custom.lua:

  • srs_transponder_port : 10712 by default, you have to choose another port and set the same on SRS server
  • srs_server : by default, you can set a different address if SRS server is not on same server

For SRS:

  • open SRS Server.cfg and set same port than srs_transponder_port to LOTATC_EXPORT_PORT=10712

How I see transponder values ?

  • In contact properties, there is a transponder line
  • By customizing labels with the %(transponder) item

Add transponder table to automatically fill names from code

If you want to automatically fill names for friend unit for a specific transponder code, you can use the Saved Games\DCS\Mods\services\LotAtc\userdb\transponders\(blue or red)\*.json files to do so (on the server).

Example of file:

    "enable": false,
    "transponders" : {
        "7123" : "test",
        "7124" : "test2"

Use enable item to activate or not the file.

LotAtc can make association between a mode 1 or mode 3 (or both) and some special attributes to set to the corresponding item. It works with any item, AI or humans.

For example, you have two files, first is containing a list of mode3 of all the squad:

    "transponders" : [
            "mode3": 7123,
            "name": "Bones 11",
            "type": "F/A-18C",
            "callsign": "BN11",
            "onboard": "011"
            "mode3": 7124,
            "name": "Bones 12",
            "type": "F/A-18C",
            "callsign": "BN12"

With this file, attributes will be set for units with matching mode3 transponders.

Then, we have another file (can be the same) with mission table:

    "transponders" : [
            "mode1": 12,
            "comment": "North CAP",
            "mode1": 23,
            "comment": "SEAD on TGT A",
            "classification": {
                "classification": "friend",
                "dimension": "air",
                "sub_dimension": "fighter"

With this file, attributes will be set for units with matching mode1 transponders.

So a plane with IFF mode1 to 23 and mode3 7124 will receive attributes on LotAtc due to its mode 1 and mode 3:

        "name": "Bones 12",
        "type": "F/A-18C",
        "callsign": "BN12"
        "comment": "SEAD on TGT A",
        "classification": {
            "classification": "friend",
            "dimension": "air",
            "sub_dimension": "fighter"

Each entry on the file have:

  • a match entry: mode1, mode2, mode3, modeS
  • list of properties to change (you can use one or severals)
Property Name Description
name Name of the unit  
type Type of the unit  
callsign Callsign of the unit  
comment Comment field of the unit  
onboard Onboard number of the unit  
classification Classification field see classification

Last item must not have comma at end

Files in blue directory will only affect blue coalition contacts. Red for… red…

Special codes

LotAtc handles special codes that are standardized, if you put 7700 as mode3, LotAtc will display EMER and blink. Special codes are:

Mode 3 Display Name
7700 EMER Emergency
7600 RDO Radio problem
7400 QRA Quick Response Alert mode
7500 HJCK HiJacked

More help