INTERCOMMUNICATION SET, AN/VIC 1(V). Continued

TM 11-5820-890-20-2 1-35 1.13. INTERCOMMUNICATION SET, AN/VIC 1(V). Continued (c) Intercom Keying. When a handset PTT generates a ground on pin H of J504, J505, J506, or J507 the AM 1780 energizes relays K501, K502, and K503 for the intercom mode. Due to the presence of CR521, only the commander can key relay K503. RELAY FUNCTION K501 Listen Relay K502 Crew Talk Relay K503 Commander's Talk Relay (d) Intercom Voice. The amplified audio from the control boxes enters the AM 1780 at pin K of J504, J505, J506, and J507. After being summed with the radio signals they are amplified again by the A250 amplifier and exit through the energized K501 relay. The commander is the only one who can talk on control box MONITOR position C. In position C his voice will enter at J504, pin V and then follow the above path. LISTEN PATH SETTING CONNECTORS J504-J507 ALL Pin L A Pin M B Pin B C Pin J (7) AM 1780 Radio Interface. See Figure 1-2. (a) Fixed Audio. When a RT receives a signal the audio is present at the RT system connector P1. It is called fixed audio because the RT volume knob will have no effect on the audio level. RT A or SRM fixed audio enters J501, pin K. RT B fixed audio enters J503, pin K. The combined audio is passed through the INT ACCENT switch. If the INT ACCENT switch is ON the audio level is reduced by passing through a resistor and then sent to the A250 amplifier. If the INT ACCENT switch is OFF the combined audio is sent directly to the A250 amplifier. After amplification and summing with intercom audio the fixed audio exits at J504 through J507, pin L. The control boxes must be set to ALL in order to hear this audio. (b) Variable Audio. Variable audio exits the RT AUD/DATA connector and the level can be controlled from the RT volume knob. RT A variable audio enters J501, pin H and exits at J504 through J507, pin M. The control boxes must be set to A in order to hear this audio. RT B variable audio enters J503, pin H and exits at J504 through J507, pin J. The control boxes must be set to C in order to hear this audio. (c) RT Keying. When a handset PTT generates a ground on J504, J505, J506, or J507, pin D it will key RT A or SRM. This ground passes from pin D through the RADIO TRANS and INSTALLATION switches and exits on J501, pin S. The control box settings are set to ALL or A for RT A, or A for the SRM.