Avionics Support Equipment; Audio Control Panel; Transmitter Selector Switch; Automatic Audio Selector Switch - Cessna SKYHAWK 172M 1976 Pilot Operating Handbook

d
l.
CESSNA
MODEL 172M
SECTION 7
AIRPLANE & SYSTEMS DESCRIPTIONS
is operative.
AVIONICS SUPPORT EQUIPMENT
The airplane ma y. at the owner's discretion, be equipped with vari-
ous types of avionics supJX)r t equipment such as an audio control panel,
microphone-headset , and static dischargers. The following paragraphs
discuss these items.
AUDIO CONTROL PANEL
Operation of radi o equipment is covered in Section 9 of this handbook.
When one or more rad·o are installed, a transmitter/audio switching sys-
tem is provided (se e f1..... re 7-10). The operation of this switching system
is described in the fo ll \\ing paragraphs.
TRANSMITTER SElECTOR SWITCH
A rotary type tran mitter selector s witch, labeled XMTR SEL, is
provided to connect the .icrophone to the transmitte r the pilot desires
to use. To select a transmitter , rotate the switch to the number corres-
ponding to that trans mitte r. The numbers 1, 2 and 3 above the switch cor-
respond to the top, sec ond and third transceivers in the avionics stack.
An audio amplifier is required for speaker operation, and is automati-
cally selected, along with the transmitter, by the transmitter selector
switch. As an example,
if
the number 1 transmitter is selected, the audio
amplifier in the ass ociated NAV / COM receiver is also selected, and func-
tions as the amplifie r for ALL speaker audio. In the event the audio am-
plifier in use fails, as evide nced by loss of all speaker audio, select
another transmitter. This should re-establish speaker audio. Headset
audio is not affected by audio amplifier operation.
AUTOMATIC AUDIO SElECTOR SWITCH
A toggle switch, labeled AUTO, can be used to automatically match
the appropriate NAV / COM receiver audio to the transmitter being select-
ed. To utilize this automatic feature, leave all NAV /COM receiver
switches in the OFF (center) position, and place the AUTO selector switch
in either the SPEAKE R or PHONE position, as desired. Once the AUTO
selector switch is positioned, the pilot may then select any transmitter
and its associated NAV / COM receiver audio simultaneously with the trans-
mitter selector switch.
If
automatic audio selection is not desired, the
AUTO selector switch should be placed in the OFF (center) position.
7-35