Garmin GTX 330 Installation Manual page 23

4.4 Altitude Function
Altitude inputs are considered active if either the voltage to ground is < 1.9 V or the resistance to ground is < 375 Ω.
These inputs are considered inactive if the voltage to ground is 11-33 VDC.
The GTX 330 contains internal altitude code line isolation diodes to prevent the
unit from pulling the encoder lines to ground when the transponder is turned off.
Pin Name
ALTITUDE D4
ALTITUDE A1
ALTITUDE A2
ALTITUDE A4
ALTITUDE B1
ALTITUDE B2
ALTITUDE B4
ALTITUDE C1
ALTITUDE C2
ALTITUDE C4
ALTITUDE COMMON
4.4.1 Altimeter Calibration and Checkout
Refer to section 5.2.13 for the gray code altitude checkout.
4.4.2 Altimeter Interconnect, Dual GTX 330 Units
Refer to Figure 4-2 on page 4-7 for Dual GTX 330 altimeter interconnect.
4.5 Discrete Inputs
Pin Name
EXTERNAL IDENT SELECT
EXTERNAL STANDBY SELECT*
SQUAT SWITCH IN
ALTITUDE ALERT ANNUNCIATE*
TIS CONNECT SELECT*
These inputs are considered active if either the voltage to ground is < 1.9 V or the resistance to ground
is < 375 Ω. These inputs are considered inactive if the voltage to ground is 11-33 VDC.
EXTERNAL IDENT SELECT (remote IDENT) is a momentary input. Refer to sections 5.2.10. and 5.2.14 for the
squat switch.
Page 4-4
Rev. 1
NOTE
CONNECTOR/PIN
Table 4-5. Encoded Altitude Pin Assignments
Connector
P3301
P3301
P3301
P3301
P3301
Table 4-6. Discrete Inputs Pin Assignments
I/O
P3301 11
P3301 2
P3301 4
P3301 5
P3301 7
P3301 9
P3301 10
P3301 8
P3301 3
P3301 6
P3301 50
Pin I/O
12 In
13 In
17 In
19 Out
46 In
In
In
In
In
In
In
In
In
In
In
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GTX 330 Installation Manual
190-00207-02