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| part of a communication system that con-
bleeder resistor R1806 and terminals 10
sists of Receiver-Transmitter Group OA-
and 12 of P1801. Resistive networks with-
2648/VRC-24 and Radio Set AN/GRC-5,
in the RT-441/TRC-68 form a voltage di-
radio interphone switch S1504 functions
vider circuit that provides +125 volts from
as follows:
terminal 10 of P1801 to ground and -30
(1) On the RAD INT position, the radio
volts from terminal 12 of P1801 to ground.
interphone switch connects AN/
This circuit is protected by fuse F1807.
VRC-24 and AN/GRC-5 headset
Filtering is provided by reactors L1803
(through contacts 4 and 1 of S1504B
and L1804 and capacitors C1804 and C1805.
rear) and speaker (through con-
Capacitor C1803 and coil L1803, connected
tacts 8 and 5 of S1504B rear) audio
in parallel, present a high impedance to the
to terminal A and L on AUDIO jacks
120-cps components of the full-wave recti-
J1502 and J1503. In this position,
fier output, for improved filtering action.
push-to-talk transmission is per-
mitted on Radio Set AN/VRC-24
and the AF Amplifier AM-65/GRC
(part of the AN/GRC3-8 series)
interphone amplifier through con-
Radio Set Control C-1439/U permits
tacts 9 and 12 of S1504B rear and
remote control and operation of Receiver-
contacts 4 and 1 of S1504A.
Transmitter Group OA-2648/VRC-24 or
(2) On the INT position, switch S1504
OA-2649/TRC-68. The push-to-talk cir-
applies RT-323/VRC-24 and AN/
cuits of associated communication equip-
GRC-5 headset and speaker audio
ment such as Radio Set AN/GRC-3 through
to AUDIO jacks J1502 and J1503
-8 can also be controlled from this unit.
in the manner described in (1)
a. The C-1439/U contains controls that
above (except that contacts 3, 7,
duplicate the function of similar controls
and 11 of S1504B rear make con-
on the front panel of the rt unit. The func-
tact). In this position, the switch
tion of CHANNEL selector switch, S1503
permits push-to-talk transmission
is covered in paragraph 84. The functions
on Radio Set AN/GRC-5 interphone
of SQUELCH control R1501, SQUELCH
only.
DISABLE PUSH switch S1501, SQUELCH
OFF switch S1502, and CALL LIGHT lamp
(3) In the RAD position, switch S1504
I1501, are covered in paragraph 42. The
applies only RT-323/VRC-24 audio
function of POWER control S1505 is
output to AUDIO jacks J1502 and
covered in paragraphs 80 and 81. The
J1503. The headset and speaker
PHONE VOLUME and the SPEAKER VOL-
audio input terminals to the rt unit
UME controls, which consist of resistors
are terminals J and F of J1501.
R1502 and R1506, and resistors R1503 and
Microphone audio and push-to-talk
R1504, control the headset and speaker
control circuits are switched to
audio levels at terminals A and L, respec-
ouput terminals a and U of J1501,
tively, of AUDIO jacks J1502 and J1503.
and transmission on Radio Set
Both volume control circuits are similar
AN/VRC-24 only is permitted.
to the front panel volume control circuits
d. When the C-1439/U is used with Re-
(para 45).
ceiver-Transmitter Group OA-2649/TRC-
b. When the C-1439/U is used with
68, or when the retransmit cable used with
Receiver-Transmitter Group OA-2648/
Radio Set AN/VRC-24, Special Purpose
VRC-24, a pilot lamp I1502 is connected
Cable Assembly CX-4498/U, is not con-
as shown in figure 24. When the C-1439/
nected to the AN/GRC-5 equipment, radio
U is used with Receiver-Transmitter
interphone switch S1504 functions as fol-
Group OA-2649/TRC-68, the pilot lamp is
lows:
connected through rt case wiring to
(1) On the RAD INT position, radio
POWER indicator lamp I1801 (fig. 29).
interphone switch S1504 switches
c. When control C-1439/U is used as
the headset and speaker output
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