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Page 5-2 GTX 330 Installation Manual
Revision G 190-00207-02
5.1.1 Function Selector Switches
The function selection switches are:
• OFF Powers off the GTX 330. Pressing the STBY, ON or ALT key powers on the
transponder displaying the last active identification code.
• STBY Selects the standby mode. When in standby mode, the transponder does not reply
to any interrogations. Pressing and holding the STBY key selects ground (GND)
mode if Automated Airborne Determination is not otherwise selected from another
source. When GND is annunciated, the transponder does not respond to ATCRBS
interrogations but replies to All-Call interrogations.
• ON Selects Mode A and Mode S. In this mode, the transponder replies to Mode A,
Mode C and Mode S interrogations, as indicated by the Reply Symbol (“
®”), but
the replies do not include altitude information.
• ALT Selects Mode A, Mode C and Mode S. In ALT mode, the transponder replies to
identification, altitude and Mode S interrogations as indicated by the Reply Symbol
(“
®”). Replies to altitude interrogations include the standard pressure altitude
received from an external altitude source, which is not adjusted for barometric
pressure. The ALT mode may be selected in aircraft not equipped with an optional
altitude encoder; however, the reply signal
does not include altitude information.
NOTE
Any time the function switch is in the ON or ALT position the transponder
becomes an active part of the Air Traffic Control Radar Beacon System
(ATCRBS). The transponder also responds to interrogations from TCAS
equipped aircraft.
• IDENT Pressing the IDENT key activates the Special Position Identification (SPI) Pulse
for 18 seconds, identifying the transponder return from others on an air traffic
controller’s screen. During the IDENT period the word ‘IDENT’ appears in the
upper left corner of the display.
• VFR Sets the transponder code to the pre-programmed VFR code selected in
Configuration mode (Set to 1200 at the factory). Pressing the VFR key again
restores the previous identification code.
• FUNC Changes the page shown on the right side of the display. Display data includes
Pressure Altitude, Flight Time, Altitude Monitor, Count Up and Count Down
timers. In the Configuration mode, steps through the function pages.
• START/ Starts and stops the Altitude Monitor, Count Up, Count Down and Flight timers.
STOP In Configuration mode, steps through functions in reverse.