(9) Power and Mode Switch. The power
and mode switch contains three detented positions.
The ON and OFF positions switch system power.
The SQ OFF position disables the receiver squelch
(10) Annunciators. The transceiver control
unit contains a MEM (memory) and a TX (transmit)
annunciator. The MEM annunciator illuminates
whenever a preset frequency is being displayed in
the lower window. The TX annunciator illuminates
whenever the transceiver is transmitting.
(11) Preset Frequency Display. Displays
the pre-set (inactive) frequency and diagnostic
messages in the lower window.
(12) Compare Annunciator. An annunciator,
placarded ACT, momentarily illuminates when
annunciator flashes if the actual radio frequency to
which the transceiver is tuned is not identical to the
frequency shown in the active frequency display.
If two communications transceivers in
the same aircraft are tuned to stations
attempting to listen to the received
signals from both simultaneously could
result in a great reduction in the actual
c. Operating Procedures. The 8.33 kHz capable
CTL -22C shows the VHF COM frequency as a channel
frequency using all six digits of the display. There are no
8.33 kHz channels above 136.992 MHz. The last
channel name is 136.990, which is an actual frequency
channel/frequency scheme for the 180.000 to 136.992
MHz range. While the CTL is in the frequency range of
137.000 to 151.975 MHz, the unit behaves the same as
a 25 kHz only unit.
It is possible that erroneous operation could
occur without a fault indication. It is the
responsibility of the pilot to detect such an
occurrence by continually assessing the
reasonableness of operation as displayed on
the associated transceiver control unit and
by the quality of received signals and
(1) Equipment Startup. The transceiver and
the control unit are turned on by rotating the power and
mode switch on the transceiver control unit to the ON
position. When the transceiver is first turned on, it
sounds a brief tone while the microprocessor checks its
own memory. If there is a memory defect the tone
continues, indicating that the transceiver can neither
receive nor transmit. After the memory check, the
transceiver control unit will display the same active and
equipment was last turned off.
Table 3C-2. VHF Communications Transceiver Control Unit Channel/Frequency Scheme
(118.000 To 136.992 MHz Range)