Garmin GTX 320 Pilot’s Guide
GTX 320
TRANSPONDER
Pilot’s
Guide
Operating The GTX 320
CODE SELECTION KNOBS
IDENT BUTTON
FUNCTION SELECTION KNOB
REPLY LIGHT
NOTES
The GTX 320 owner accepts all responsibility for obtaining the proper license before
using the transponder.
The coverage you can expect from the GTX 320 is limited to “line of sight”. Low altitude
or aircraft antenna shielding by the aircraft itself may result in reduced range. Range can
be improved by climbing to a higher altitude. It may be possible to minimize antenna
shielding by locating the antenna where dead spots are only noticed during abnormal
flight attitudes.
Function Selector Switch
The function selector switch is a five position rotary switch. The five positions are:
• OFF—Turns off all power to the GTX 320 (the GTX 320 should be turned off before starting
aircraft engine(s).
• SBY—Turns the transponder on, but when in SBY the GTX 320 will not reply to any interrogations from the ground radar system.
• ON—Places the transponder in Mode A, the identification mode. In addition to the aircraft’s
identification code, the GTX 320 will also reply to altitude interrogations (Mode C) with signals that do not contain altitude information.
• ALT—Activates all of the necessary circuitry (transponder to optional altitude digitizer and
return) to respond to ATC altitude interrogations and aircraft identification interrogations with
standard pressure altitude (29.92 inches Hg). The ALT position may be used in aircraft that
are not equipped with the optional altitude digitizer, however, the only response will be discreet signals that do not contain altitude information.
• TST—Turning the switch to the TST position tests the reply indicator. The TST position is
spring loaded and must be held momentarily. When released, it will automatically return to
the ALT position.
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