RT-359A-style transponder
The 1970s-80s Cessna transponder: the amber REPLY jewel, the function knob (OFF, SBY, ON, ALT), ID, DIM, TEST, the code in four windows with a knurled knob under each digit. The older RT-459A, gray in its beige frame with four drums turned by their levers, is the second model.
- Modeled on
- ARC RT-359A-style transponder, and the older RT-459A (the 300 / 400 series of a 1970s-80s Cessna)
- 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
Variants
RT-359A (black)v1.0
Black faceplate: REPLY, the function knob, ID, DIM, TEST, the code in four windows, a knurled knob under each digit.
Picker: MODEL > RT-359A (black)
RT-459A (gray)v1.0
Gray in its beige frame: REPLY, ID, the function knob, DIM, TST; the code on four drums turned by the black levers under them.
MODEL > RT-459A (gray)
Features
- The code on four digits (0-7), each with its own knob (RT-359A) or lever (RT-459A); a digit turned is sent to the simulator's transponder at once
- Function knob OFF, SBY, ON, ALT, following the simulator mode
- Amber REPLY jewel lit while replying (simulated radar sweeps) or identing
- ID: ident; TEST (TST on the RT-459A): the REPLY lamp while held; DIM only turns
- x359A and XPDR (x459A, 400 XPDR) printed as the real ones, the models disguised; no maker name
- Dark without avionics power; the faceplate takes the red flood light at night
On the iPad
- Drag round a code knob (RT-359A), or drag a lever up or down (RT-459A), to turn that digit
- Tap the function knob for the next stop, or drag round it to step either way
- Tap ID to ident; press and hold TEST
Settings
- Model: RT-359A (black) or RT-459A (gray) (picker variant)
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 |
Sends
| When you… | MSFS | X-Plane |
|---|---|---|
| A code digit turned (the whole code) | XPNDR_SET | sim/cockpit2/radios/actuators/transponder_code |
| The function knob: OFF, SBY, ON, ALT | SimVar write: TRANSPONDER STATE:1 | sim/cockpit2/radios/actuators/transponder_mode |
| ID | 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.
