External Sensors, Devices, And Interface Considerations; Table 3-6 Altitude Source Options; Mutual Suppression Bus; Altitude Source (Required) - Garmin GTX 335 w GPS Installation Guidance

3.8 External Sensors, Devices, and Interface Considerations

Install sensors in accordance with the sensor manufacturer's data. This manual does not give data for the
installation of any external sensors or devices. Refer to appendix C for a list of the permitted types of inputs
available. Refer to section 6 for possible GTX configuration selections.
The GTX accepts data from many sources. If more than one source is used, the GTX will accept data as
given in this section. The input priority of each external data source cannot be changed.
3.8.1

Mutual Suppression Bus

Other equipment on the aircraft can transmit and receive in the same frequency band as the GTX
transponder system, such as DME, TAS/TCAS system, or another transponder. Mutual Suppression is a
synchronous pulse which is sent to the other equipment to suppress transmission of a different transmitter/
receiver during the pulse train transmission. The GTX transmission can be suppressed by an external source
and other equipment on board can be suppressed by the GTX system. This feature is designed to reduce
mutual interference.
If a transponder, DME, TAS/TCAS system, or other equipment using the L-band is installed on the aircraft,
make sure a suppression line is connected between the GTX transponder system and the other equipment in
order to prevent mutual interference. For the GTX 335 series transponder system, and other equipment
I/O interconnect drawings, refer to appendix B.
I/O pulses may not be compatible with all models of DME. Known incompatible units include the Bendix/
King KN 62, KN 64, and KNS 80. These models have an output-only suppression and may damage the
GTX mutual suppression output. In this case, leave the suppression pin open.
3.8.2

Altitude Source (Required)

For ADS-B operation, an altitude encoder, air data computer, or other source that supplies uncorrected
pressure altitude information must be installed. The GTX 335 series transponders can acquire altitude
information from a GAE attached to the rear of the back plate. The GAE has a configuration module.
The GTX units accept altitude information from an altitude encoder, air data computer, EFIS, or encoding
altimeter. Refer to table 3-6 for more information.
Priority
1
2
3
4
5
6
7
8
190-00734-17
Rev. 1

Table 3-6 Altitude Source Options

Altitude Source
ARINC 429 Label 203 from an ADC
ARINC 429 Label 203 from an EFIS/ADC
RS-232 from an ADC
RS-232 from a 25ft-resolution altitude source
RS-232 from a remote control panel
GAE
Gray code altitude
RS-232 from a 100ft-resolution altitude source
GTX 335 w/GPS Installation Guidance
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