Discrete Functions - Garmin GTX 33 Installation Manual

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 the GNS 480 (CNX80) Installation Manual
or the appropriate GTN 6XX/7XX Installation Manual for the altitude data reporting configuration.

4.5 Discrete Functions

Discrete functions with pin assignments are shown for reference since the functions are available in the
GTX 33. External suppression should be connected if another transponder or DME is installed in the
aircraft avionics system. Depending on system configuration, the Garmin Integrated Flight Deck may not
use these inputs, as many functions are received from the GIA 63 in RS-232 format.
4.5.1 Discrete Outputs
External suppression should be connected if a DME is installed in the aircraft avionics system. The
GTX 33 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 33 mutual suppression output. In this case, leave the suppression pin
open.
Pin Name
ALTITUDE ALERT ANNUNCIATE*
EXTERNAL SUPPRESSION I/O (TXP/DME)
SIGNAL GROUND
SIGNAL GROUND
*
INACTIVE: 10 ≤ Vin ≤ 33VDC or Rin ≥100kΩ
ACTIVE: Vin ≤ 1.9VDC with ≥ 75 uA sink current, or Rin ≤ 375Ω
Sink current is internally limited to 200 uA max for a grounded input
4.5.2 DISCRETE INPUTS
Pin Name
EXTERNAL IDENT SELECT*
EXTERNAL STANDBY SELECT*
SQUAT SWITCH IN
TIS CONNECT SELECT*
AUDIO MUTE SELECT*
*
INACTIVE: 10 ≤ Vin ≤ 33VDC or Rin ≥100kΩ
ACTIVE: Vin ≤ 1.9VDC with ≥ 75 uA sink current, or Rin ≤ 375Ω
Sink current is internally limited to 200 uA max for a grounded input
190-00906-00
Rev. F
Table 4-5. Discrete Outputs
Table 4-6. Discrete Inputs
Connector Pin
P3301 19
P3301 31
P3301 51
P3301 58
Connector Pin
P3301 12
P3301 13
P3301 17
P3301 46
P3301 47
GTX 33 Installation Manual
I/O
Out
I/O
--
--
I/O
In
In
In
In
In
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