Beechcraft C-12C Operator And Technical Reference Manual page 251

d. Emergency Operation.
Transmission on emergency frequency,
121.500 MHz, will
emergencies only.
frequency of 243.000 MHz, guard channel,
is also available on the UHF command
radio set.
1. Transmitter selector switch – VHF 1 or
VHF 2.
2. Frequency selector, VHF control panel
–
frequency.
3. Microphone switch – Press.
3A-10. VHF COMMUNICATIONS TRANSCEIVERS
(VHF-22D).
a. Introduction.
transceivers are an 8.33 kHz channel spacing cable
system. The operation between the 25 kHz and
8.33 kHz modes is seamless.
occupied by each 25 kHz frequency exist three
8.33 kHz channels. The 8.33 kHz "frequency" is
referred to as a "channel," not the actual frequency
tuned. The channel scheme avoids possible confusion
associated with shared 25 kHz and 8.33 kHz
frequencies. This method ensures that the equipment
will always be operating in the proper spacing mode
and occurs automatically as the user tunes the
Figure 3A-5. VHF Communications Transceiver Control Unit – CTL-22C
NOTE
be restricted
An emergency
121.500 MHz, emergency
The VHF communications
Within the space
controller. Provides airborne VHF communications
from 118.000 through 151.975 MHz and is operated by
two CTL-22C transceiver control units. Refer to Figure
3A-5.
to
The solid-state transceiver includes capture-
effect automatic squelch to help prevent missed radio
calls, plus audio leveling and response shaping to
ensure audio quality.
from detected transmitter signal, and is therefore a
reliable check of transmission quality.
transceiver is powered through its respective circuit
breaker, placarded VHF # 1 or VHF # 2, located on the
circuit breaker panel.
b. Operating Controls. All operating controls
for the transceivers are located on the CTL-22C
transceiver control units. Refer to Figure 3A-5.
(1) Active Frequency Display. Displays the
active frequency (frequency to which the transceiver is
tuned) and diagnostic messages.
(2) Transfer / Memory Switch. This switch is
a three-position spring-loaded toggle switch placarded
XF / MEM, which, when held to the XF position,
causes the preset frequency to be transferred up to
the active display and the transceiver to be returned.
The previously active frequency will become the new
preset frequency and will be displayed in the lower
window. When this switch is held to the MEM position,
one of the six stacked memory frequencies will be
loaded into the preset display. Successive pushes will
cycle the six memory frequencies through the display
(...2, 3, 4, 5, 6, 1, 2, 3...).
1. Active Frequency Display
2. Transfer/Memory Switch
3. Store Button
4. Frequency Select Knobs
5. Active Button
6. Test Button
7. Light Sensor
8. Volume Control
9. Power and Mode Switch
10. MEM TX Annunciators
11. Preset Frequency Display
12. Compare Annunciator
TM 1-1510-218-10
Transmitter sidetone comes
Each VHF
3A-9