Technical data

13773-001
23-50
Page 1
AUDIO INTEGRATING
1. DESCRIPTION
This section covers the portion of the system which controls the output of the communications and naviga-
tion receivers into the flight crew headphones and speakers, and the output of the flight crew microphones
into the communications transmitters. Included are the audio control panel, audio jacks, cockpit loud
speaker, and push-to-talk (PTT) switch.
The Audio Control Unit provides audio amplification, audio selection, marker beacon control, and a voice
activated intercom system for the cabin speaker, headsets, and microphones. The system allows audio
switching for up to three transceivers (COM 1, COM 2, and COM3) and five receivers (NAV 1, NAV2, ADF,
DME, and MKR). Push-buttons select the receiver audio source provided to the headphones. A fail-safe
mode connects the pilot headphone and microphone to COM 1 if power is removed or if the Mic Selector
switch is turned to the OFF position. The audio control unit is located on the center console, center-high.
Audio jacks are mounted on the center console. The pilot and co-pilot audio jacks are mounted inside the
center console arm rest, the passenger audio jacks are mounted on the top, rear of the center console.
Push-To-Talk (PTT) switches, mounted on the control yolks, allow the pilot and co-pilot to transmit over the
selected transceiver.
2. MAINTENANCE PRACTICES
A. Garmin GMA 340 Audio Control Unit (See Figure 23-501)
(1) Removal - Garmin GMA 340 Audio Control Unit
CAUTION: Ensure electrical power to airplane is off prior to performing maintenance.
(a) Insert allen wrench into front panel bolt hole and engage allen bolt.
(b) Turn locking screw counterclockwise to loosen locking cam. Cam will move the trans-
ceiver unit out 1/4” and disengage from the electrical connectors.
(c) Pull audio control unit from mounting tray
(2) Installation - Garmin GMA 340 Audio Control Unit
(a) With light to medium pressure, push audio control unit into mounting tray to engage elec-
trical connectors.
(b) Insert allen wrench into front panel bolt hole and engage allen bolt.
(c) Turn bolt clockwise to tighten locking cam.
(3) Inspection/Check - Garmin GMA 340 Audio Control Unit
CAUTION: Verify proper operation of marker beacon under VFR conditions.
(a) After installing audio control unit conduct a performance flight test to ensure satisfactory
performance of audio and maker beacon receiver functions. Verify proper operation of the
maker lamps and marker audio including marker audio mute function. Check proper oper-
ation of the sensitivity selection (using the SENS button) by flying towards the outer
marker position initially using HI sensitivity. When OM audio is just barely audible, switch-
ing to LO sensitivity should reduce or eliminate the audio.
(b) The following adjustments can be made via access holes in top cover of the audio panel:
1
Marker beacon audio level
2
Airplane radio speaker output level
3
Pilot PA microphone speaker output level
30 Nov 2000