190-00734-11
GTX 33X and GTX 3X5 ADS-B Maintenance Manual
Rev. 6
Page 2-4
2.2 GTX 33/33D
GTX 33/33D units are remote mounted and require a display/control interface as provided by the
GTN 6XX/7XX or GNS 480 in order to be installed in accordance with this STC. Basic transponder
functions of the GTX 33/33D are identical to the GTX 330/330D.
GTX 33/33D units provide the following features.
Mode S transponder
ADS-B Out capability
Entry and display of squawk code and flight ID*
Display of pressure altitude*
Display of density altitude*
Display of outside air temp*
Display of flight timers*
Audio output
TIS-A traffic output to a compatible display
*Requires supported external control and display system.
The transponder annunciates when the unit has an ADS-B Out failure to alert the crew that the unit has a
degraded ADS-B system.
GTX 33/33D units communicate through the following interfaces.
ARINC 429
RS-232
Gray code
Discrete I/O
Power is provided by the aircraft’s existing avionics bus. Non-diversity GTX 33 units interface with a
transponder antenna mounted to the bottom of the fuselage. GTX 33D units interface to a transponder
antenna mounted to the top of the fuselage as well as an antenna mounted to the bottom.
Figure 2-2 provides a summary of the interfaces provided for the GTX 33 or GTX 33D. Refer to
GTX 3XX Part 23 AML STC Installation Manual
for interfaces allowed under this STC.
