GMA 340-style audio panel

The 172's audio panel in the style of a GMA 340: marker beacon lamps, the receiver keys and the COM 1 / COM 2 MIC selector, each lit when it is on in the simulator. It's a 2 x 1 stack unit that also fits in a free rack (it's one of a new rack's default units).

Modeled on: Garmin GMA 340-style audio panel (as in X-Plane 12's Cessna 172 SP GNS panel)
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

O / M / I marker lamps (blue, amber, white): the one received lights up and glows
COM1 and COM2 keys lit while that radio is heard (receiving) in the simulator
DME, NAV1, NAV2 and ADF1 keys lit when that audio is on in the simulator
COM1 MIC / COM2 MIC: the radio transmitting has its key lit
MKR MUTE key lit while the marker audio is muted
HI / LO sensitivity bars toggled by SENS (shown only; no simulator counterpart)
PILOT and COPILOT volume knobs, the blank keys and ADF2 drawn as on the real unit but inert
At night the faceplate, keys and knobs take the red flood light; the lamps keep their own color, dimmed
Lamps go dark when the aircraft's avionics power is off

On the iPad

Tap COM1 or COM2 to listen to (or stop listening to) that radio
Tap DME, NAV1, NAV2 or ADF1 to toggle that audio
Tap COM1 MIC or COM2 MIC to pick the radio you transmit on
Tap MKR MUTE to mute or unmute the marker audio
Tap SENS to switch the marker sensitivity indicator between HI and LO (display only)

Keys and controllers

Map any of these to a key, a game controller's button or axis, or a MIDI knob (how):

Transmit on COM 1
Transmit on COM 2
Audio NAV 1
Audio NAV 2
Audio DME
Audio ADF
Audio MKR

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
Audio panel keys lit, one bit each (AudioBit: nav1, nav2, dme, adf, mkr, spkr) (bitfield)	`NAV SOUND:1 (bool)NAV SOUND:2 (bool)DME SOUND (bool)ADF SOUND:1 (bool)MARKER SOUND (bool)SPEAKER ACTIVE (bool)`	`sim/cockpit2/radios/actuators/audio_selection_nav1sim/cockpit2/radios/actuators/audio_selection_nav2sim/cockpit2/radios/actuators/audio_dme_enabledsim/cockpit2/radios/actuators/audio_selection_adf1sim/cockpit2/radios/actuators/audio_marker_enabled`
COM transmitting: 1, 2, 0 none (enum)	`COM TRANSMIT:1 (bool)COM TRANSMIT:2 (bool)`	`sim/cockpit2/radios/actuators/audio_com_selection`
Marker beacon: 0 none, 1 outer, 2 middle, 3 inner (enum)	`MARKER BEACON STATE (number)`	`sim/cockpit2/radios/indicators/outer_marker_litsim/cockpit2/radios/indicators/middle_marker_litsim/cockpit2/radios/indicators/inner_marker_lit`
COM1 heard (1/0) (bool)	`COM RECEIVE:1 (bool)`	`sim/cockpit2/radios/actuators/audio_selection_com1`
COM2 heard (1/0) (bool)	`COM RECEIVE:2 (bool)`	`sim/cockpit2/radios/actuators/audio_selection_com2`

Sends

When you…	MSFS	X-Plane
COM1 / COM2 key: +1 / +2 to start listening, -1 / -2 to stop	`COM1_RECEIVE_SELECTCOM2_RECEIVE_SELECT`	`sim/cockpit2/radios/actuators/audio_selection_com1sim/cockpit2/radios/actuators/audio_selection_com2`
DME, NAV1, NAV2, ADF1, MKR MUTE keys (the AudioBit index of that key)	`RADIO_VOR1_IDENT_TOGGLERADIO_VOR2_IDENT_TOGGLERADIO_DME1_IDENT_TOGGLERADIO_ADF_IDENT_TOGGLEMARKER_SOUND_TOGGLETOGGLE_SPEAKER`	`sim/cockpit2/radios/actuators/audio_selection_nav1sim/cockpit2/radios/actuators/audio_selection_nav2sim/cockpit2/radios/actuators/audio_dme_enabledsim/cockpit2/radios/actuators/audio_selection_adf1sim/cockpit2/radios/actuators/audio_marker_enabled`
COM1 MIC (1) or COM2 MIC (2)	`COM1_TRANSMIT_SELECTCOM2_TRANSMIT_SELECT`	`sim/cockpit2/radios/actuators/audio_com_selection (6 = COM1, 7 = COM2)`