Section 2-Audio Panel Description; Unit Features; Intercom System; Digital Voice Recorder - Garmin GMA 347 Maintenance Manual

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SECTION 2
AUDIO PANEL DESCRIPTION
The GMA 347 is a horizontally oriented, panel‐mounted audio control panel and marker beacon
system. Microcontroller circuitry processes front panel key commands, controls annunciator
operation, and processes input/output and communication information. A prominent design
feature of the audio panel is MASQ™ (Master Avionics Squelch) processing. When no airplane
radio activity is detected by the GMA 347, the amount of ambient background noise is reduced
by MASQ™.
2.1 UNIT FEATURES
2.1.1 Intercom System
The audio panel features a six‐position intercom system (ICS) with electronic cabin noise de‐
emphasis, two stereo music inputs, and combined pilot, copilot, and passenger volume
controls. The intercom provides four selectable modes of isolation (All, Crew, Pilot, Copilot).
A pilot‐selectable cabin speaker output can be used to listen to the selected aircraft radios or to
broadcast PA announcements. The PA function is pilot selectable.
2.1.2 Digital Voice Recorder
The audio panel contains a digital voice recorder with playback capability providing up to two
and a half minutes of recording. The playback feature is controlled by pressing the PLAY button
or a remote mounted switch. Recording is automatic when a COM signal is received. The
recorder can be disabled using an external switch.
2.1.3 Marker Beacon Receiver
A marker beacon receiver with dual sensitivity, audio muting, and automatic re‐arming is
incorporated in the audio panel. Receiver operating voltage range is 14/28 VDC.
2.1.4 SmartMute™
The marker audio is selected initially by pressing the MKR/MUTE button. If no marker beacon
signal is being received, then pressing button 2 again will deselect the marker audio. This
operation is similar when selecting any other source on the GMA 347. However, if the second
button press occurs when a marker beacon signal is being received, then the marker audio is
muted muted but not deselected. The button's LED will remain lit to indicate that the source is
still selected. The GMA 347's SmartMute™ function monitors the marker signal and
automatically unmutes the audio when the current marker signal is no longer being received. In
all cases, the marker beacon lamps operate independently of any audio selection and cannot be
turned off.
GMA 347 Maintenance Manual Page 2‐1
190‐00325‐02 Rev. A