Page 4-16 400W Series Installation ManualRev. G 190-00356-024.7 COM/VOR/ILS Audio (GNC 420W and GNS 430W only)4.7.1 COM/VOR/ILS Audio FunctionActivation 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 aheadset or an audio panel.Momentarily depressing the COM REMOTE TRANSFER button toggles the active and standby COMfrequencies. Momentarily depressing the VLOC REMOTE TRANSFER button toggles the active andstandby VLOC frequencies.The COM REMOTE TRANSFER input may be used for EMERGENCY operation of the COMtransmitter. If the remote transfer switch is depressed for two seconds, the active COM frequencychanges to 121.50 MHz. Once the emergency frequency is activated through COM REMOTETRANSFER, GNS 430W and GNC 420W COM transceivers with COM software version 4.01 or laterignores inputs from the front panel controls for COM selections only. The pilot may exit this independentmode—restoring COM selection control to the front panel knobs and buttons—by momentarilydepressing the COM REMOTE TRANSFER switch.When TRANSMIT INTERLOCK is active, the GNC 420W or GNS 430W COM receiver sensitivity isdecreased. This input is intended to reduce interference from other transmitters in the aircraft. TheTRANSMIT INTERLOCK input should be connected to the PTT input of other transmitters in theaircraft. If connected to multiple PTT inputs, these connections must include diode isolation or multipleradios transmit simultaneously.4.7.2 COM/VOR/ILS Audio Electrical Characteristics4.7.2.1 COM MIC KeyPin Name Connector Pin I/OCOM MIC KEY P4002 4 InThis 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 AudioPin Name Connector Pin I/OCOM MIC AUDIO HI P4002 6 InCOM MIC AUDIO LO P4002 18 InINTERCOM MIC HI P4002 5 InINTERCOM MIC LO P4002 17 InCOM MIC AUDIO and INTERCOM MIC each have a 520 Ω AC input impedance and supply themicrophone with a 9 V bias through 620 Ω.COM MIC AUDIO is set in the factory for 275 mVRMS to modulate the transmitter at 80% nominally.The microphone gain adjustment is made through Configuration Mode.When a 125 mVRMS signal at 1000 Hz is applied to the INTERCOM MIC input, the level on the COMAUDIO output is not less than 7.07 VRMS.
