TM-9-2350-311-20-2 Maintenance Manual Volume 2 for M109 Cab Download
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TM 9–2350–311–20–2 3–101 i. INTERCOMMUNICATION SYSTEM The intercommunication system provides voice communication between crewmembers of the M109 howitzer. The system consists of amplifier AM 1780/VRC and control boxes for the driver, commander, and gunner. Amplifier AM 1780/VRC provides control of the dc power to the associated crewmember control boxes and to the radio system that may be connected to amplifier AM 1780/VRC. Amplifier AM 1780/VRC also amplifies and controls the audio signals in the intercommunication and radio circuits. The control box allows crewmembers, by means of the MONITOR switch, to communicate on the intercom circuit with other crewmembers, and on the radio(s) connected to the amplifier AM 1780/VRC. The MONITOR switch is located on the front panel of the control box and the VOLUME control is located on the bottom of the control box. Jacks, J804 and J801, on each side of the control box provide connection to the amplifier AM 1780/VRC. Jacks, J802 and J803, on the bottom of the control box, provide connection to the audio accessories. CONTACT ARM ASSEMBLIES GUNNER’S SELECTOR SWITCH BOX ASSEMBLY COMMANDER’S CONTROL BOX AMPLIFIER AM1780/VRC POWER RELAY BOX ASSEMBLY PICTORIAL VIEW CX4723