190-01878-02
GMA 342/345 Installation Manual
Rev. 5
Page 4-10
4.6.7 Tel Audio I/O
4.6.8 Headset Outputs
Garmin recommends that stereo headsets and stereo jacks be used to fully utilize the 3D audio features of
the GMA 342/345. A true mono headset will work correctly with the GMA 342/345, but only mono (left
channel) audio will be heard, and 3D audio will not be available (even if enabled). The GMA 342/345 will
detect the mono headset (if stereo jacks are used), and automatically switch to mono operation. 3D audio
is not available with mono headsets or in installations that use mono jacks for the headsets.
In aircraft systems that are wired with stereo headset jacks, if a true mono headset is plugged into the jack,
the right audio channel is shorted to ground. In this condition the GMA 342/345 will detect the right
channel short, and turn off the right channel audio to the headset output to protect the GMA 342/345
headset output from driving a signal into a short (and also for internal audio routing determined by the
mono headset plugged into the headset jack).
In aircraft systems that use mono headset jacks, and are wired correctly (if used, mono jacks should always
use left channel audio and headset lo), 3D audio will not be available, and only left channel audio for
Table 4-13 TEL Audio/XCVR 3 I/O (GMA 342/345 2-COM unit only)
Pin
Connector
Pin Name
Description
I/O
3
J3401
XCVR 3 AUDIO IN (WIRED TEL)
Telephone Audio Input
IN
4
J3401
XCVR 3 AUDIO LO (WIRED TEL)
Ground Reference for Telephone
--
5
J3401
XCVR 3 MIC OUT HI (WIRED TEL) TEL MIC Audio Output
OUT
Table 4-14 TEL Audio I/O (GMA 345 3-COM unit only)
Pin
Connector
Pin Name
Description
I/O
25
J3401
WIRED TEL AUDIO IN HI
Telephone Audio Input
(GMA 345 3-COM unit only)
IN
26
J3401
WIRED TEL AUDIO IN LO
Ground Reference for Telephone
(GMA 345 3-COM unit only)
--
27
J3401
WIRED TEL MIC OUT HI
TEL MIC Audio Output
(GMA 345 3-COM unit only)
OUT
28
J3401
WIRED TEL MIC OUT LO
Ground Reference for Telephone
(GMA 345 3-COM unit only)
--
