Garmin GMA 240 - Manual (Page 6)

190-00917-00 Rev. A Garmin GMA 240 Pilot’s Guide 6
GMA 240 Audio Panel
FeATUres ANd OPerATION
The Garmin GMA 240 is a headphones only audio control panel. Pushbutton
keys control audio selection of COM, NAV, telephone (TEL), and intercom.
Two AUX inputs are available for additional avionics or audio devices.
LED annunciators indicate when a key function is selected. Annunciator
brightness is adjusted automatically by photocell dimming. LED-illuminated
key brightness is adjusted by the radio dimming bus control.
In case power is interrupted or the unit is turned off, a fail-safe circuit
connects the Pilot’s headset, microphone, and PTT directly to COM 1 and the
fail-safe alert audio, such as an autopilot disconnect tone.
In addition to radio squelch circuitry, MASQ TM (Master Avionics Squelch)
processing further reduces ambient noise from the avionics inputs.
Upon installation, the unit may be configured in various ways depending
on the aircraft type and the needs of the Pilot. See the configuration list at the
end of this manual. Contact a Garmin-authorized service center for details
and assistance in altering the configuration settings.
MICrOPhONes
The GMA 240 Audio Panel can accept up to four (4) microphone inputs,
allowing for a two-person crew and up to two (2) passenger intercom
stations in the aircraft. A push-to-talk (PTT) switch must be pressed to
transmit on a selected Transceiver. The passengers cannot transmit over the
active COM radio, even if equipped with a PTT switch.
Each microphone input has a dedicated VOX circuit to ensure that only
the active microphone is heard when squelch is broken.