Garmin GNC 420AW Installation Manual - page 64
Page 4-6
400W Series Installation Manual
Rev. F
190-00356-02
4.3
41B
Altitude Gray Code
Altitude input is useful for advisory vertical navigation (VNAV) calculations.
Pin Name
Connector
Pin
I/O
ALTITUDE D4
P4001
70
In
ALTITUDE A1
P4001
69
In
ALTITUDE A2
P4001
68
In
ALTITUDE A4
P4001
67
In
ALTITUDE B1
P4001
66
In
ALTITUDE B2
P4001
65
In
ALTITUDE B4
P4001
64
In
ALTITUDE C1
P4001
63
In
ALTITUDE C2
P4001
62
In
ALTITUDE C4
P4001
61
In
ALTITUDE COMMON
P4001
60
In
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.
NOTE
Some transponders and other altitude encoder receivers do not have internal isolation
diodes to prevent the unit from pulling the encoder lines to ground when the unit is off.
These units require a diode added to the installation harness for each encoder line. The
anode should be connected on the receiving unit’s side and the cathode should be
connected on the encoder side. A set of diodes is required for each unit without internal
diodes. The 400W Series unit includes internal diodes for isolation of the encoder lines.
Refer to Section
384H
5.3.9 for the gray code altitude checkout.
Refer to
385H
Figure H-6 for the gray code altitude interconnect.