(3) Store Button. This button, placarded
STO, allows up to six preset frequencies to be
selected and entered into the control unit's memory.
After presetting the frequency to be stored, push the
STO button. The upper window displays the channel
number of available memory (CHAN 1 through CHAN
6) while the lower window continues to display the
frequency to be stored. For approximately 5 seconds,
the MEM switch may be used to advance through the
channel numbers without changing the preset display.
Push the STO button a second time to commit the
preset frequency to memory in the selected location.
After approximately 5 seconds, the control will return
to normal operation.
(4) Frequency Select Knobs. Two concentric
tuning knobs control the preset or active frequency
displays. The larger knob changes the three digits to
the left of the decimal point in 1-MHz steps. The
smaller knob changes the three digits to the right of
the decimal point. The faster the kHz knob is turned,
the more channels will be skipped. A single click of
the kHz knob will either increase or decrease the
channel by a single channel.
(5) Active Button.
placarded ACT, enables the tuning knobs to directly
tune the VHF transceiver, when depressed and held
for 2 seconds. The bottom window will display dashes
and the upper window will continue to display the
active frequency. Pushing the ACT button a second
time will return the control unit to the normal two-
(6) Test Button. This button, placarded
TEST, initiates the transceiver self-test diagnostic
routine. Self-test is active only when the TEST button
(7) Light Sensor. This built-in light sensor
automatically controls display brightness.
(8) Volume Control. The volume control is
concentric with the power and mode switch.
(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 circuits.
(10) MEM TX Annunciators. The transceiver
control unit contains a memory (MEM) and a transmit
(TX) 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,
frequencies are being changed. The ACT 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 carrying
the same voice message, attempting to
listen to the received signals from both
simultaneously could result in a great
reduction in the actual audio volume.
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 of 136.9917 MHz. Table 3A-1 shows the
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
assessing the reasonableness of operation
as displayed on the associated transceiver
control unit and by the quality of received
signals and transmissions.
(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 preset frequencies that were present when the
equipment was last turned off.
If two short 800-Hz tones are heard, the
transceiver has detected an internal fault. Push the
TEST button on the transceiver control unit to initiate
self-test and display the fault code.