1.2Pilot Controls

The GNC 255 controls have been designed to simplify operation of the system and minimize workload and the time required to access sophisticated functionality. Controls are comprised of dual concentric knobs for frequency tuning, Com volume/squelch knob, Nav volume/ID knob, and bezel keys.

1.2.1Power/Com Volume/Squelch Knob

The Power/Com Volume/Squelch knob located in the top left corner of the bezel controls audio volume for the Com radio. Rotating the knob clockwise past the detent turns power on and counter-clockwise turns power off. When the Com radio is active, press the Power/Com Volume/Squelch knob to toggle automatic squelch control On/Off for the Com radio.

Com Mode

Annunciator

Squelch, TX, or RX

 

 

 

 

Annunciator

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Active Frequency

 

 

 

 

 

Active Nav

 

 

 

 

Annunciator

 

 

 

 

 

Frequency

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Com Volume Bar

Graph

Standby Frequency

 

 

 

 

 

 

Annunciator

Figure 1-2 Com Volume and Squelch Display Description

The Com radio features an automatic squelch to reject many localized noise sources. You may override the squelch function by pressing the Power/Com Volume/Squelch knob. This facilitates listening to a distant station or setting the desired volume level.

To override the automatic squelch, press the Power/Com Volume/Squelch knob momentarily. Press the Power/Com Volume/Squelch knob again to return to automatic squelch operation. A “SQ” indication appears to the left of the active Com frequency window in the upper left corner of the display when automatic squelch is overridden.

1.2.2Nav Volume/ID Knob

The Nav Volume/ID knob located in the bottom left corner of the bezel controls audio volume for the Nav radio. Press the Nav Volume/ID knob and the Morse code tones will be heard. When Morse code tone is active, “ID” will appear to the left of the Nav active frequency.

1-2

Garmin GNC 255A/255B Pilot’s Guide

190-01182-01 Rev. A

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Image 14
Garmin 255A manual Pilot Controls, Power/Com Volume/Squelch Knob, Nav Volume/ID Knob