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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
Figure B-1
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.
Pin
Connector
5
P2402
6
P2402
7
P2402
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.
Pin
Connector
16
P2401
29
P2401
13
P2402
19
P2402
30
P2402
*Denotes Active Low (Ground to activate)
190-00917-01
Rev. D
Table 4-5 Lighting Bus
LIGHTING BUS 14V LO/28V LO
LIGHTING BUS 14V HI/28V LO
LIGHTING BUS 14V HI/28V HI
Table 4-6 External Configuration Pins
Pin Name
Ground to disable Master Avionics Squelch circuitry. This will
cause alerts and selected radios to be heard at all times
MASQ
without needing to exceed the mute threshold. This causes
INHIBIT* IN
an increase in background noise from the inputs during quiet
output.
Ground to configure the unit for CREW ICS isolation. In this
configuration, the copilot headset jack should be wired in
CREW ISO*
parallel with the pilot headset output. The mics are wired as
IN
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.
PILOT ISO
Ground to allow Music audio to be heard by the pilot during
MUSIC* IN
pilot isolate mode.
BUTTON
PRESS
Ground to enable beep tone annunciation of button presses
TONE
ENABLE* IN
Ground to enable muting of other selected radios during mic
MUTE ON
selected COM transmission (mic-selected COM is still heard,
COM TX* IN
but not other selected radios)
Pin Name
Description
GMA 240 Installation Manual
I/O
--
IN
IN
Page 4-5
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