KT 76A-style transponder
The older Bendix/King-style transponder: the code on four drums, each turned by its own knob, the rotary mode knob, and IDENT under the amber reply light.
- Modeled on
- Bendix/King KT 76A-style transponder
- Category
- Radios and panels
- Size
- 2 × 1 cells
- Version
- 1.0 · 2026-10-19
- Plan
- Pro
- Simulators
- MSFS 2020 · MSFS 2024 · X-Plane 11 · X-Plane 12
Features
- Four code drums with a white digit each, set by the knob under them (0-7, wrapping)
- Mode knob: OFF, SBY, ON, ALT, TST
- Amber reply lamp that glows when replying (simulated radar sweeps), identing, or in TST; it is also the IDENT button
- The drums show the new code right away, until the simulator confirms it
- At night the faceplate, keys and knobs take the red flood light while the display keeps its own colors, dimmed; the glareshield's warm light falls on the faceplate too when its dimmer is up (Settings > Dimmers > Glareshield, off by default)
On the iPad
- Drag a code knob to turn its digit; tap it for the next digit
- Tap the mode knob for the next stop or drag around it
- Tap the reply light / IDENT to ident
Keys and controllers
Map any of these to a key, a game controller's button or axis, or a MIDI knob (how):
- Transponder IDENT
- Transponder STBY
- Transponder ALT
Simulator data
What the Hub reads from the simulator for this instrument, and what the instrument sends back. Names are the simulators' own: MSFS SimVars and events, X-Plane datarefs and commands.
Reads
| Value | MSFS | X-Plane |
|---|---|---|
| Transponder code as its four digits (e.g. 1200) (code) | TRANSPONDER CODE:1 (number) | sim/cockpit2/radios/actuators/transponder_code |
| Transponder mode: 0 off, 1 standby, 2 test, 3 on, 4 altitude (enum) | TRANSPONDER STATE:1 (number) | sim/cockpit2/radios/actuators/transponder_mode |
| Transponder identing (1/0) (bool) | TRANSPONDER IDENT:1 (bool) | sim/cockpit2/radios/indicators/transponder_id |
Sends
| When you… | MSFS | X-Plane |
|---|---|---|
| Each step of a code knob (the full new code) | XPNDR_SET | sim/cockpit2/radios/actuators/transponder_code |
| Mode knob | SimVar write: TRANSPONDER STATE:1 | sim/cockpit2/radios/actuators/transponder_mode |
| Tapping the reply light / IDENT | XPNDR_IDENT_ON | sim/transponder/transponder_ident |
Add-on aircraft with their own systems may use other variables; the Hub reads the standard ones.
Changes
The instrument's version counts what its faces share (the case, the mechanism, the data, the sounds); a face's own version counts that face alone.
- 1.0 2026-10-19
- First numbered version.
