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TM 11-5820-890-20-2
1-43
1.13.
INTERCOMMUNICATION SET, AN/VIC 1(V). Continued
RT A is keyed when a ground is applied at pin C of J902 by the handset or helmet. The ground is
passed to pin D of J904. The mic audio is applied to pin D of J902 or J903 and then to the A80
amplifier. The unamplified audio is applied to the MONITOR switch. The audio passes through the
MONITOR switch to J904 pin K.
When used with a single radio mount, the •ALL" position will be the only setting that the RT can be
heard from. The variable audio lines are not connected in the power supply adapter.
(b) •A" Position. RT A variable audio is applied to J904, pin M, then to the MONITOR switch. The
audio passes through the switch, through the VOLUME control, to connectors J902 and J903. RT
A is keyed in the same manner as in the •ALL" position. The mic circuits are the same as for the
•ALL" position.
(c) •INT ONLY" Position. When the MONITOR switch is in the •INT ONLY" position, the driver can key
only the intercom. However, when the intercom is keyed both intercom and radio audio can be
heard. The audio is applied to J904, pin E, and then through the MONITOR switch to J902 and
J903 as in the •ALL" and •A" positions. To key the intercom, the ground from the handset PTT at
connector J902 is applied to the MONITOR switch and J904, pin H. Other keying contacts of the
MONITOR switch are open therefore RT is not keyed. The mic circuits are the same as for the •ALL"
position.
(d) •B" Position. Not used with SINCGARS RADIOS.
(e) •C" Position. RT B variable audio is applied to J904, pin J, and then through the MONITOR switch
to connectors J902 and J903. RT B is keyed when a ground is applied to pin C of J902. From pin
C, the ground is applied through the MONITOR switch to J904 pin F. The mic audio signal is
applied to the amplifier A80 and then through the MONITOR switch to J904, pin V. In some tracked
vehicles, this position is NOT operational due to limited circuits in the cable CX 7060 and the slip
ring assembly. When the intercom is activated by another crew member, the intercom audio will
not be heard if the MONITOR switch is in the •C" position, or if the crew box is connected to the
commander's port (J504) on the AM 1780.
(3) Functions of the SIG EXT OFF Switch. In the •OFF" position, the MONITOR switch acts as
described above. Dc voltage is furnished by the main junction box and applied to J904 pin C. From
pin C, the dc is applied to the audio amplifier. •EXT" Position is not used. •SIG" Position is not used.
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