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The GNC 300’s automatic squelch and volume controls are located at the bot-
tom left of the unit, near the NavData card slot.
To adjust the radio volume:
1. Rotate the
B
knob.
Whenever the GNC 300 is powered up, the automatic squelch will be in the ‘on’
position, allowing only transmissions which are powerful enough for clear broadcast
to be received. Manual squelch control is not available.
To override the automatic squelch control:
1. Press the
Q
key. Press
Q
again to return to automatic squelch.
Whenever the GNC 300 is transmitting, a ‘tx’ icon will appear between the active
and standby frequency fields. If the microphone is stuck or accidentally left in the
keyed position, or if the headsets continue to transmit after the key is released, the
radio will timeout after 35 seconds of continuous broadcasting. You’ll also receive a
‘Stuck mic/Tx disabled’ message as long as the stuck condition exists.
The GNC 300’s emergency channel select feature provides a quick method of
selecting the 121.5 MHz frequency as the active frequency in the event of an in-flight
emergency. The emergency channel select is available whenever the unit is on, regard-
less of GPS or cursor status, or loss of the display.
To automatically tune for emergency transmission:
1. Press and hold the
@
key for more than two seconds.
31
REFERENCE
Airport
Information
‘TX’ indicating radio transmission.
SECTION
2
COMM FEATURES
Squelch & Volume/
Emergency Channel
The emergency channel will appear in the active
field.
300 7/14/98 8:49 AM Page 31