User's Manual

TT21/TT22 Transponder Installation Manual 13 July 2009
00560-00 Issue AF
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Page 36 Trig Avionics Limited
8. Normal Operation
8.1 Overview
On the front panel is a monochrome LCD display flanked by a rotary mode
selector knob (OFF, SBY, GND, ON, and ALT) and a continuously rotating
knob used for code and data entry.
8.2 Display
The display shows the operating mode of the transponder, the reported pressure
altitude, and the current squawk code and Flight ID. The reply indicator is
active when the transponder replies to interrogations.
The pressure altitude is displayed as a Flight Level, which is the pressure
altitude in hundreds of feet. When non-standard atmospheric conditions apply,
this may not match the altimeter indicated altitude, but will be correctly
displayed by the ATC radar.