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Page 4-14 500 SERIES INSTALLATION MANUAL
Rev G P/N 190-00181-02
4.7 COM/VOR/ILS AUDIO (GNS 530 ONLY)
4.7.1 COM/VOR/ILS Audio Function
Activation of COM MIC KEY enables COM MIC AUDIO and causes the transceiver to transmit.
500Ω COM AUDIO and 500Ω VOR/ILS AUDIO are 100 mW audio outputs that are intended to drive a
headset or an audio panel.
Momentarily depressing the COM REMOTE TRANSFER button toggles the active and standby COM
frequencies. Momentarily depressing the VLOC REMOTE TRANSFER button toggles the active and
standby VLOC frequencies.
The COM REMOTE TRANSFER input may be used for EMERGENCY operation of the COM
transmitter. If the remote transfer switch is depressed for two seconds, the active COM frequency changes
to 121.50 MHz. Once the emergency frequency is activated through COM REMOTE TRANSFER, GNS
530 COM transceivers with Mod 2 incorporated, ignore 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 momentarily depressing the COM REMOTE TRANSFER switch.
When TRANSMIT INTERLOCK is active, the GNS 530 COM receiver sensitivity is decreased. This
input is intended to reduce interference from other transmitters in the aircraft. The TRANSMIT
INTERLOCK input should be connected to the PTT input of other transmitters in the aircraft. If connected
to multiple PTT inputs, these connections must include diode isolation or multiple radios transmit
simultaneously.
4.7.2 COM/VOR/ILS Audio Electrical Characteristics
4.7.2.1 COM MIC KEY
Pin Name Connector Pin I/O
COM MIC KEY P5002 4 In
This input is considered active if either the voltage to ground is <1.9 V or the resistance to ground
is <375 Ω. This input is considered inactive if the voltage to ground is 11-33 Vdc.
4.7.2.2 COM MIC AUDIO, INTERCOM MIC AUDIO
Pin Name Connector Pin I/O
COM MIC AUDIO HI P5002 6 In
COM MIC AUDIO LO P5002 18 In
INTERCOM MIC HI P5002 5 In
INTERCOM MIC LO P5002 17 In
COM MIC AUDIO and INTERCOM MIC each have a 520 Ω AC input impedance and supply the
microphone with a 9 V bias through 620 Ω.
COM MIC AUDIO is set in the factory so that 275 mVrms modulates the transmitter to 80% nominally.
The microphone gain adjustment is accessible through the top cover.
When a 125 mVrms signal at 1000 Hz is applied to the INTERCOM MIC input, the level on the COM
AUDIO output is not less than 7.07 Vrms.