KT 76C-style transponder
A classic Bendix/King-style transponder with orange gas-discharge digits: type the code on the 0-7 keys, choose the mode with the rotary knob, IDT to ident. The display shows FL, the mode, the code and the reply light.
- Modeled on
- Bendix/King KT 76C-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
- Code typed on the 0-7 keys: digits blink until the fourth, then it's sent; CLR removes the last digit; entry times out after 4 s
- Rotary mode knob: OFF, SBY, TST, ON, ALT
- FL with the pressure altitude in hundreds of feet in ALT
- R shown while replying (simulated radar sweeps) or identing
- TST lights all segments (888, 8888); display dark when OFF
- VFR key sets the VFR code (again: the previous code)
- Squawking 7500 asks for confirmation
- Gas-discharge digits dimmed at night; dark without avionics power; the faceplate takes the red flood light and, when its dimmer is up, the glareshield's warm light (Settings > Dimmers > Glareshield, off by default)
On the iPad
- Tap the 0-7 keys to type a code
- Tap the mode knob for the next stop, or drag around it to step either way
- Tap IDT to ident; tap VFR for the VFR code; tap CLR to delete a digit
Settings
- App Settings > Transponder: 'Transponder VFR code' 1200 (US) or 7000 (Europe), shared by every transponder's VFR key
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 |
| Pressure altitude (ft) | PRESSURE ALTITUDE (feet) | sim/flightmodel2/position/pressure_altitude |
Sends
| When you… | MSFS | X-Plane |
|---|---|---|
| Fourth digit typed, or VFR key | XPNDR_SET | sim/cockpit2/radios/actuators/transponder_code |
| Turning or tapping the mode knob (0 OFF, 1 SBY, 2 TST, 3 ON, 4 ALT) | SimVar write: TRANSPONDER STATE:1 | sim/cockpit2/radios/actuators/transponder_mode |
| IDT key | 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.
