Page 4-24
GTN 725/750 TSO Installation Manual
Rev. A
190-01007-02
4.3.14 COM Discrete Inputs
Pin Name
Connector
Pin
I/O
COM MIC 1 KEY*
P1003
11
In
INTERCOM ENABLE* (function not currently implemented)
P1003
12
In
COM MIC 2 KEY* (function not currently implemented)
P1003
26
In
COM REMOTE TRANSFER*
P1003
27
In
COM REMOTE TUNE UP*
P1003
28
In
COM REMOTE TUNE DOWN*
P1003
29
In
An asterisk (*) following a signal name denotes that the signal is Active-Low, requiring a ground to
activate.
These inputs are considered active if either the voltage to ground is ≤3.5 VDC or the resistance to ground
is ≤375
Ω
. These inputs are considered inactive if the voltage to ground is 11-33 VDC or the resistance to
ground is >100kΩ.
4.3.14.1
COM MIC 1 KEY* (GTN 750 only)
The COM MIC 1 KEY discrete input, when pulled low, allows the audio that is present on the COM MIC
1 AUDIO IN HI (P1003-5) to be transmitted over the radio.
4.3.14.2
COM MIC 2 KEY* (GTN 750 only)
The COM MIC 2 KEY discrete input can be used in installations in which no audio panel is present.
When this input is pulled low, the audio that is present on the COM MIC 2 AUDIO IN HI (P1003-6) is
transmitted over the radio.
4.3.14.3
COM REMOTE TRANSFER* (GTN 750 only)
The COM REMOTE TRANSFER discrete input may be used to flip-flop between the active and standby
COM frequencies. A momentary low on this pin will load the standby COM frequency into the active
COM frequency field.
The COM REMOTE TRANSFER input may be used for emergency operation of the COM transmitter. If
the switch is depressed for two seconds, the active COM frequency changes to 121.500 MHz. Once the
emergency frequency is activated through COM REMOTE TRANSFER, the GTN transceiver ignores
inputs from the front panel controls for COM selections only. The pilot may exit this independent
mode—restoring COM selection control to the front panel knobs and buttons—by again depressing the
switch for two seconds.
4.3.14.4
COM REMOTE TUNE UP* (GTN 750 only)
The COM REMOTE TUNE UP discrete input may be used to scroll through a list of preset COM
frequencies. A momentary low on this pin will load the next preset frequency in the list into the standby
COM frequency field.
4.3.14.5
COM REMOTE TUNE DOWN* (GTN 750 only)
The COM REMOTE TUNE DOWN discrete input may be used to scroll through a list of preset COM
frequencies. A momentary low on this pin will load the previous preset frequency in the list into the
standby COM frequency field.
4.3.14.6
INTERCOM ENABLE* (GTN 750 only)
The INTERCOM ENABLE discrete input activates the intercom function in installations in which no
intercom is present.
Summary of Contents for GTN 725
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