TM-9-2350-311-20-2
HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5
TECHNICAL MANUAL; UNIT MAINTENANCE MANUAL FOR CAB, ARMAMENT, SIGHTING AND FIRE CONTROL, ELEVATING AND TRAVERSING SYSTEMS AND ASSOCIATED COMPONENTS
DECEMBER 1993
TM-9-2350-311-20-2 - Page 213 of 828
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
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