(2) Manual frequency selector/indicator
(tens). Selects and indicates tens digit of frequency (0
through 9) in MHz.
(3) Manual frequency selector/indicator
(units). Selects and indicates units digit of frequency
(0 through 9) in MHz.
(4) Preset channel indicator. Displays preset
(5) Manual frequency selector/indicator
(tenths). Selects and indicates tenths digit of fre-
quency (0 through 9) in MHz.
(6) Preset channel selector. Selects one of 20
preset channel frequencies.
(7) Manual frequency selector (hundredths
and thousandths). Selects hundredths and thou-
sandths digits of frequency (00, 25, 50, or 75) in
(8) Mode selector. Selects operating mode
and method of frequency selection.
(a) MANUAL. Enables the manual selec-
tion of any one of 7,000 frequencies.
(b) PRESET. Enables selection of any one
of 20 preset channels.
(c) GUARD. Selection automatically
tunes the main receiver and transmitter to the guard
frequency and the guard receiver is enabled.
(9) SQUELCH switch. Turns main receiver
squelch on or off.
(10) VOL control. Adjusts volume.
(11) TONE pushbutton. When pressed, trans-
nits a 1,020 Hz tone on the selected frequency.
(12) Function selector. Selects operating
(a) OFF. Turns set off.
(b) MAIN. Selects normal transmission
with reception on main receiver.
(c) BOTH. Selects normal transmission
with reception on both the main receiver and the
guard frequency receiver.
(d) ADF. Not used.
c. Normal Operation.
(1) Turn on procedure:
It is presumed aircraft power is on and
normally used avionic circuit breakers
1. Avionics master power switch - ON.
2. Function select switch - MAIN or
BOTH position, as required.
If function selector is at MAIN setting,
only the normal UHF communications
will be received. If selector is at BOTH
position, emergency communications on
the guard channel and normal UHF com-
munications will both be received.
(2) Receiver operating procedure:
1. Transmitter-interphone selector
switch - No. 3 position.
2. UHF audio monitor switch - ON, No.
3. Volume control - Mid position.
(3) To use preset frequency:
1. Mode selector switch - PRESET posi-
2. Preset channel selector switch -
Rotate to desired channel.
(4) To use non-preset frequency:
1. Mode selector switch - MANUAL
2. Manual frequency selectors (5) -
Rotate each knob to set desired fre-
The PRESET channel selector and manual
frequency selectors are inoperative when
the mode selector switch is set to the
3. Volume - Adjust.