Garmin GI 275 Pilot's Manual page 200

Additional Features
When above 2,500' AGL, the Rad Alt indicator needle is removed. When descending below
2,500' AGL, the indicator needle will come alive and indicate radar height above ground level.
Digital Rad
Alt Indicator
DH Set
to 200'
Analog
Altitude
Scale
Setting the Radar Altimeter Decision Height (DH):
From the 'Rad Alt' Page, turn the Inner Knob to increase or decrease the DH.
Or:
1) From the 'Rad Alt' Page, touch the DH Button.
2) Enter the desired height using the numeric keypad.
3) Touch the Enter Button.
When the aircraft is airborne and descends through the set DH, an amber 'DH' annunciation
illuminates, the digital AGL altitude becomes amber, the DH bug becomes amber, and the aural
alert, "Minimums, Minimums" sounds.
178
Airborne Radar Altimeter
Garmin GI 275 Pilot's Guide
DH Bug
Indicator
Needle
190-02246-01 Rev. A