Garmin GTX 320A - Manual (Page 4)

Function Selector Switch:
The function selector switch is a fi ve position rotary switch. The fi ve positions are:
OFF-Turns off all power to the GTX 320A (the unit should be turned off
before starting aircraft engine(s).
SBY-Turns the transponder on, but when in SBY the unit will not reply
to any interrogations.
ON-The transponder transmits the aircraft’s identifi cation code (Mode A)
but does not include altitude information.
ALT- The transponder transmits the aircraft’s identifi cation code, in Mode
A and pressure altitude (29.92 inches Hg) information in Mode C pro-
vided the aircraft is equipped with an optional altitude encoder. The unit
is normally operated in the ALT position at all times unless otherwise
directed by ATC.
TST-Moving the switch to the TST position tests the reply light. The
function selector is spring loaded and must be held in TST position.
When released, it automatically returns to the ALT position.
Any time the function switch is in the ON or ALT position the tran-
sponder becomes an active part of the Air Traffi c Control Radar Beacon
System (ATCRBS). The transponder also responds to interrogations from
TCAS equipped aircraft.
Function Selection Knob Code Selection Knobs
Ident Button Reply Light
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