190-00917-01
GMA 240 Installation Manual
Rev. D
Page 4-5
4.3.2 Lighting Bus
The GMA 240 can be configured to track a 14 or 28 Vdc lighting bus using these inputs. These inputs
must be connected to a supply voltage (in the appropriate voltage range) for the backlighting to function.
Refer to
for lighting interconnections.
Backlighting refers only to the lighting of the text labels on the front panel and is controlled by the inputs
in the below table. The brightness of the LED annunciators that illuminate each key when selected is
controlled by a photocell that operates independently of the backlight input.
4.4 Configuration Pins
4.4.1 External Configuration Pins
The following pins may be used to change the configuration of the installation as described.
Table 4-5 Lighting Bus
Pin
Connector
Pin Name
I/O
5
P2402
LIGHTING BUS 14V LO/28V LO
--
6
P2402
LIGHTING BUS 14V HI/28V LO
IN
7
P2402
LIGHTING BUS 14V HI/28V HI
IN
Table 4-6 External Configuration Pins
Pin
Connector
Pin Name
Description
16
P2401
MASQ
INHIBIT* IN
Ground to disable Master Avionics Squelch circuitry. This will
cause alerts and selected radios to be heard at all times
without needing to exceed the mute threshold. This causes
an increase in background noise from the inputs during quiet
output.
29
P2401
CREW ISO*
IN
Ground to configure the unit for CREW ICS isolation. In this
configuration, the copilot headset jack should be wired in
parallel with the pilot headset output. The mics are wired as
normal. In this mode, when the PILOT ISO button is selected,
the pilot and copilot will hear each other, but will be intercom
isolated from the passengers.
13
P2402
PILOT ISO
MUSIC* IN
Ground to allow Music audio to be heard by the pilot during
pilot isolate mode.
19
P2402
BUTTON
PRESS
TONE
ENABLE* IN
Ground to enable beep tone annunciation of button presses
30
P2402
MUTE ON
COM TX* IN
Ground to enable muting of other selected radios during mic
selected COM transmission (mic-selected COM is still heard,
but not other selected radios)
*Denotes Active Low (Ground to activate)
