Discrete Functions - Garmin GTX330 Installation Manual

4.4.4 Altimeter Selection Priority
The installer must be aware of the GTX 330 priority for selecting encoded altimeter interconnections.
The GTX 330 searches in this sequence for altitude, and stops when it finds a valid pressure altitude
input.
Only approved devices may provide altitude to the GTX 330 in accordance with 14 CFR 91.217. In
addition, all altitude reporting devices installed in the aircraft must meet certification requirements of
14 CFR 91.413. The installer must select an altitude reporting device that is a certified altitude source for
the particular aircraft.
Altitude reporting equipment order of precedence:
1) ARINC 429 Air Data Computer (label 203, if configured W/ALT) (25')
2) ARINC 429 EFIS (label 203, if configured W/ALT) (25')
3) RS-232 data from GNS 480 (CNX80) if so connected
4) RS-232 Fuel/Air Data Computer (if configured W/ALT.) (25')
5) Shadin Altitude Serializer/Encoder (if configured for 25')
6) Icarus Altitude Serializer/Encoder (if configured for 25')
7) Parallel wire Gray Code input (100')
8) Shadin Altitude Serializer/Encoder (if configured for 100')
9) Icarus Altitude Serializer/Encoder (if configured for 100')
It is the installing agency's responsibility to determine that the installed encoder is compatible with the
selected altitude reporting criteria, either 100' or 25'. Refer to Section 5.2.8 and 5.2.9 for the altitude data
reporting configuration.
For additional information, refer to GNS 480 (CNX80) Installation Manual 560-0982-01 for the altitude
data reporting configuration when connecting a GTX 330 to a GNS 480 (CNX80).
4.5

Discrete Functions

4.5.1 Discrete Outputs
External suppression should be connected if a DME is installed in the aircraft avionics system. The
GTX 330 suppression 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 port and can be damaged by the GTX 330 mutual suppression output. In this case, leave the
suppression pin open.
Table 4-6. Discrete Outputs Pin Assignments
ALTITUDE ALERT ANNUNCIATE*
EXTERNAL SUPPRESSION I/O
* This output is considered active if either the voltage to ground is < 1.9 V or the resistance
to ground is < 375 Ω. This output is considered inactive if the voltage to ground is 11-
33 Vdc.
GTX 330/GTX 330D Installation Manual
190-00207-02
Pin Name Pin Number I/O
19 Out
31 In/Out
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Revision R