Garmin GTX 330 Installation Manual page 42

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
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transponder displaying the last active identification code.
STBY  Selects the standby mode. When in standby mode, the transponder does not
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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 squitters and replies to discretely addressed Mode S interrogations.
ON  Selects Mode A and Mode S. In this mode, the transponder replies to Mode A, Mode C and
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Mode S interrogations, as indicated by the Reply Symbol ("
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)
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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
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Configuration mode (Set to 1200 at the factory). Pressing the VFR key again restores the
previous identification code.
NOTE
The VFR button is on (functional) by default, but can be disabled in configuration mode
FUNC  Changes the page shown on the right side of the display. Display data includes
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Pressure Altitude, Flight Time, Altitude Monitor, Count Up and Count Down timers. In
the Configuration mode, steps through the function pages.
START/STOP  Starts and stops the Altitude Monitor, Count Up, Count Down and
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Flight timers. In Configuration mode, steps through functions in reverse.
CRSR  Initiates entry of the starting time for the Count Down timer and cancels
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transponder code entry. Selects changeable fields in Configuration mode.
CLR  Resets the Count Up, Count Down and Flight timers. Cancels the previous
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keypress during code selection and Count Down entry. Used in Configuration mode.
8  Reduces Contrast and Display Brightness when the respective fields are displayed
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and enters the number eight into the Count Down timer. Used in Configuration mode.
9  Increases Contrast and Display Brightness when the respective fields are displayed
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and enters the number nine into the Count Down timer. Used in Configuration mode.
GTX 330/330D Installation Manual
Page 5-2
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"), but the replies do not include
190-00207-02
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