User's Manual

TT21/TT22 Transponder Installation Manual 13 July 2009
00560-00 Issue AF
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Trig Avionics Limited Page 37
8.3 Mode Selector Knob
The left hand knob controls the power to the transponder and the operating
mode.
OFF
Power is removed from the transponder.
SBY
The transponder is on, but will not reply to any interrogations.
GND
The transponder will respond to Mode S ground interrogations from
surface movement radar.
ON
The transponder will respond to all interrogations, but altitude
reporting is suppressed.
ALT
The transponder will respond to all interrogations.
When airborne, the transponder should always be set to ALT unless otherwise
directed by Air Traffic Control. When you are taxiing on the ground, the
transponder should be set to GND unless your installation includes a gear squat
switch. Aircraft installations that include a gear squat switch will automatically
select GND on landing.
8.4 Push Buttons
IDT
Press the IDT button when ATC instructs you to “Ident” or
“Squawk Ident”. This activates the SPI pulse in the transponder
replies for 18 seconds. IDT will appear in the display.
FN
Pressing the FN button provides access to changing the Flight
ID.
VFR
Pressing the VFR button sets the transponder to the pre-
programmed conspicuity code. Pressing the button again
restores the previous squawk code.
ENT
The ENT button enters a digit in the code selector.