S73 in one C-2742/VRC is operated momentarily,
ages of the improper polarity from energizing the
coil 29 of K71 in the other C-2742/VRC operates
preset channel relay.
and mechanically locks down contacts 6-8 and
b. Two C2742/VRC's in System. When two
5-3 thus removing power to the CONTROL indi-
C-2742/VRC's are used in the system, a cable
cater DS71 and CHAN SEL switch S71. Simul-
interconnects connector J72 of the first C-2742/
taneously, the same operated S73 operates coil
VRC with connector J71 of the second C-2742/
710 of its K71 to release the locking mechanism
VRC (fig. 2-1). The second C-2742/VRC can
and allow contacts 68 and 53 to close and apply
select high power through terminal P of connector
power to the CONTROL indicator and CHAN
J71. It cannot turn power off remotely since ter-
SEL switch. This operation causes control of the
minal N of connector J72 is open. The first C-
RT-246(*)/VRC to be transferred to the C-2742/
2742/VRC (connected direct to the RT-246 (*) /
VRC whose switch was last reported. At the other
VRC) functions as described in a above. Momen-
C-2742/VRC, diode CR72 insures that the ener-
tarily operating SW switch S73 at either C-
gizing voltage applied to relay K71 discharges
2742/VRC causes both latching relays K71 to op-
rapidly. This prevents both relays from being
energized at the same time.
erate. The circuit is so arranged that when switch
DIRECT SUPPORT MAINTENANCE
2-3. G e n e r a l
2-4. Test Equipment and Test Facilities
The C-2742/VRC is maintained at organizational
a. Test Equipment and Tools.
(TM 11-5820-401-12), direct support, and depot
(1) Multimeter TS-352B/U (FSN 6625-
553-0142 ; TM 11-6625-366-12).
(2) Toolkit, Electronic Equipment TK-
a. Repair parts for the C-2742/VRC are listed
in appendix B.
b. Test Facilities. Either of the test facilities
b. Facilities for testing the C-2742/VRC are
in (1) or (2) below may be used to check the
provided in paragraph 2-4.
performance of the C-2742/VRC.
(1) Radio set facility.
Items required to use the test box are listed below.
test box facility capable of replacing the RT-
The RT-524(*)/VRC and MT-1029/VRC with
246 (*)/VRC may be used to check the perform-
the CX-4720/VRC are required in order to apply
ante of the C-2742/VRC. It will also be capable
dc power through the control box to the C-2742/
of testing the C-2299/VRC, control boxes of the
VRC. The adapter cable assembly shown in figure
radio-intercom system of some vehicular com-
2-5 is not required to test the C-2742/VRC or
munication systems, and the RT-246(*)/VRC.