190-00734-11
GTX 330/33 with ADS-B Out
Rev. 1
Maintenance Manual with ICA
3-1
3
GTX CONTROL & OPERATION
All control and operation of GTX 330/330D transponder as normally used in flight occurs through the
front panel of the GTX. Control and operation of the remote mounted GTX 33/33D is handled through
the external interface provided via the GTN 6XX/7XX. Figure 6 and Figure 7 identify various interface
buttons for these units.
3.1 GTX
330/330D
Figure 5. GTX 330/330D Front Panel
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 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
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.
The document reference is online, please check the correspondence between the online documentation and the printed version.
