Garmin GMA 240 Pilot's Guide - Page 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, MASQTM (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. 6 Garmin GMA 240 Pilot's Guide 190-00917-00 Rev. A