System Description; Gtx 330/330D; Gtx 330/330D Transponder - Garmin GTX 330 System Maintenance Manual

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SYSTEM DESCRIPTION

Automatic Dependent Surveillance-Broadcast (ADS-B) technology improves situational awareness and
flight safety. A Garmin transponder with ADS-B capabilities will automatically transmit position,
velocity, and heading information to other aircraft and ground stations. The current air traffic control
system depends on a transponder request for pertinent aircraft information, whereas ADS-B provides
automatic transmission of aircraft information without a request.
All Garmin transponders have a radio transmitter/receiver that operates on radar frequencies, receiving
ground radar or TCAS interrogations at 1030 MHz and transmitting a coded response of pulses to ground-
based radar on a frequency of 1090 MHz. Each unit is equipped with IDENT capability and will reply to
ATCRBS Mode A, Mode C and Mode S All-Call interrogation.
The Garmin transponders approved by this STC are the GTX 330 and GTX 33 (Non-Diversity Mode S
Transponders) and the GTX 330D and GTX 33D (Diversity Mode S Transponders). The ES option of
any of the transponders provides ADS-B Extended Squitter functionality.
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GTX 330/330D

The GTX 330/330D transponders are panel mounted and contain an integrated display to inform the crew
of the current code, reply symbol and mode of operation. The GTX 330/330D screen also displays
pressure altitude, density altitude, temperature, and timer functions (depending on equipment connections
and configuration selection). The unit also features an altitude monitor, TIS traffic advisories and flight
timers. A voice or tone audio output announces altitude deviation, TIS traffic advisory and count down
timer expiration. Additionally, the GTX 330/330D display will annunciate when the unit is actively
transmitting ADS-B information.
The GTX 330/330D feature multiple transmit/receive ARINC 429 and RS-232 data ports. The units
concentrate data from three ARINC 429 inputs, gray code, RS-232 input data and discrete inputs to the
high-speed ARINC 429 output bus used by display systems such as the Garmin 400 Series/500 Series
units.
The Garmin GTX 330/330D panel mounted transponder(s) is a stand alone transponder that can operate
via the faceplate or can communicate with the on-side GTN 6XX/7XX or GNS 4XX/5XX through RS-
232 digital interface. This STC installation allows for installation of two GTX 330 non-diversity
transponders, two GTX 330D Diversity transponders, one of each type, or a single transponder.
Power is provided by the aircraft's existing Avionics Bus. Each non-diversity GTX 330 transponder
interfaces with a transponder antenna mounted to the bottom of the fuselage whereas each GTX 330D
diversity transponder interfaces to a transponder antenna mounted to the top of the fuselage as well as the
antenna mounted to the bottom.
Figure 2 provides a summary of the interfaces provided for the GTX 330 or GTX 330D.
Figure 1. GTX 330/330D Transponder
190-00734-11 GTX 330/33 with ADS-B Out
Rev. 1 Maintenance Manual with ICA
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