Garmin GTX 32 Maintenance Manual - Page 7

1 ABOUT THIS MANUAL This manual provides unit level troubleshooting and return to service procedures for the GTX 32/33 as installed with a Garmin GNS 480. Other configurations (e.g. as part of a Garmin G1000) are outside the scope of this manual. 2 DESCRIPTION The Garmin GTX 32/33 rack-mounted transponder is a radio transmitter and receiver that operates on radar frequencies. It receives ground radar or TCAS interrogations at 1030 MHz and transmits a coded response of pulses to ground-based radar on a frequency of 1090 MHz. The GTX 32/33 is equipped with IDENT capability that activates the Special Position Identification (SPI) pulse for 18 seconds. 2.1 GTX 32 The GTX 32 replies to Mode A and Mode C interrogation. Mode A replies consist of framing pulses and any one of the 4,096 codes, which differ in the position and number of pulses transmitted. Mode C replies include framing pulses and encoded altitude. By replying to ground transmissions or TCAS interrogations, the GTX 32 enables ATC to display aircraft identification, altitude and groundspeed on ATC radar screens or TCAS traffic indicators. The GTX 32 is configured to be turned on by the aircraft avionics master bus. Transponder code entry and functional control are accessed through keys on the GNS 480 (CNX80). The GTX 32 features transmit/receive RS-232 data parts. The unit concentrates data from gray code, RS-232 input data and discrete inputs to the high-speed RS-232 data ports that send and receive data to/from the GNS 480 (CNX80). 2.2 GTX 33 The GTX 33 replies to Mode A, Mode C, and Mode S interrogations. Mode A replies consist of framing pulses and any one of 4,096 codes, which differ in the position and number of pulses transmitted. Mode C replies include framing pulses and encoded altitude. Ground stations can interrogate Mode S Transponders individually using a 24-bit ICAO Mode S address, which is unique to the particular aircraft. In addition, ground stations may interrogate a GTX 33 for its transponder data capability on the aircraft's Flight ID, which is the registration number or other call sign. The GTX 33 makes the maximum airspeed capability (set during configuration setup) available to TCAS systems on-board nearby aircraft to aid in the determination of TCAS advisories. The unit features an altitude monitor and TIS traffic advisories. A voice or tone audio output announces altitude and traffic alerts. The GNS 480 (CNX80) screen displays the code, reply symbol, mode of operation and pressure altitude, depending on equipment connections and configurable selection. The GTX 33 features multiple transmit/receive ARINC 429 and RS-232 data ports. The unit concentrates data from ARINC 429 inputs, gray code, RS-232 input data and discrete inputs to the high-speed RS-232 data ports for display on the GNS 480 (CNX80). Although multiple output capability is available, the unit is designed to feed all outgoing data via RS-232 data ports. Two RS-232 data ports send and receive data to/from the GNS 480 (CNX80). GTX 32/33 MAINTENANCE MANUAL P/N 190-00304-60 Page 5 Rev. A