TM 55-1510-221-10
3-4. DESCRIPTION.
The communications equipment group consists
of an interphone system connected to individual
audio control panels for the pilot and copilot which
interface with VHF, UHF, BU VOW, VHF AM-FM
and HF communication units.
3-5. MICROPHONES, SWITCHES AND JACKS.
Boom and oxygen mask microphones can be uti-
lized in the aircraft.
a.
Microphone Switches. The pilot and copilot
are provided with individual microphone control
switches, placarded INTPH-XMIT-MIC, attached to
respective control wheels. A foot-actuated micro-
phone switch is also positioned on the floorboards
forward of each pilot’s seat.
b. Controls and Functions.
(1.) Microphone control wheel switches
(fig. 2-17). Keys selected facility.
(a.) INTPH (depressed to first
detent). Keys interphone facility, disregards position
of transmitter selector switch.
(b.) XMIT (depressed full down).
Keys facility selected by transmitter select switch.
(2.)
Floorboard microphone switches. Con-
trols connection of selected microphone to audio
system.
(a.) Held
depressed.
Connects
selected microphone to audio system.
(b.) Released. Disconnects selected
microphone from audio system.
c. Microphone jack selector switches. T wo
switches, placarded MIC HEADSET - OXYGEN
MASK, are located on the extreme left and extreme
right of the instrument panel (fig. 2-29). These
switches provide a means of selecting whether the
headset microphone jack or the oxygen mask micro-
phone jack is connected to the audio system.
d. Controls and Functions.
(I.) MIC HEADSET - OXYGEN MASK
switch. Selects microphone jack to connect to audio
system.
(a.)
MIC HEADSET. Connects head-
set microphone to audio system.
3-2
Section II. COMMUNICATIONS
(b.) OXYGEN MASK. Connects
microphone in oxygen mask to audio system.
3-6. AUDIO CONTROL PANELS.
a.
Description. Separate but identical audio
control panels (fig. 3-1), serve the pilot and copilot.
The controls and switches of each panel provide the
user with a means of selecting desired reception and
transmission sources, and also a means to control
the volume of audio signals received for interphone,
communication and navigation systems. The user
selects between the UHF, VHF, BU VOW, VHF
AM-FM and HF transceivers. The audio control
panels are protected by respective 2-ampere AUDIO
PILOT and AUDIO COPILOT circuit breakers
located on the overhead circuit breaker panel (fig.
2-26).
b. Controls and Functions.
(I.) Master VOL control. Controls side-
tone volume to headset. Also serves as final volume
adjustment for received audio from any source
before admission to headset.
(2.) Radios audio monitor controls. Each
is combination rotary control and on-off push-pull
switch, permitting both receiver selection and vol-
ume adjustment.
(a.)
No. 1. On connects user’s headset
to audio from VHF-AM transceiver No. 1.
(b.)
No.2. On connects user’s headset
to audio from the VHF/AM/FM transceiver.
(c.)
No.3. On connects user’s headset
to audio from No. 1 UHF transceiver in use.
(d.)
No.4. On connects user’s headset
to audio from HF or VOW transceivers.
(e.)
No.5 On connects user’s headset
to audio from No. 2 UHF (BU VOW) transceiver.
(3.) NAV receiver audio monitor controls.
Combination volume control and “ON-OFF“
switches for NAV receivers.
(a.)
NAV-A. On connects user’s head-
set to audio from VOR-1, VOR-2 or marker beacon
set in use.
(b.) NAV-B. On connects user’s head-
set to audio from TACAN or ADF set in use.
(4.) Microphone impedence select switch.
Two-position, thumb-actuated switch. Enables selec-
