INSTALLATION MANUAL
CMA-5024 GLSSU
This document includes Proprietary Information and shall not be reproduced or communicated to third party
without prior written permission by CMC Electronics Inc.
Page A.4
November 21, 2008
(pin J3-15 grounded and pins J3-14, 45 and 66 left opened) and SDI = Center Unit (pins
J1-5 and 36 grounded), J3-16 must be left opened.
1.1.2.5 Aircraft Personality Data (APD) Select Discrete inputs
The GLSSU reads the four APD Select Discrete input pins and determine their states as defined below:
- Discrete pin open indicates a logical 0
- Discrete pin at Ground indicates a logical 1
The most significant bit of the APD Selection is the APD Select discrete #4 and the least significant bit
is the APD Select discrete #1. The resulting binary number (0...15) determines which of the 16 APD
Configurations is active.
The state of the APD Select input discretes is only be determined during Self-Test mode; later state
changes will not be detected.
1.1.2.6 Spare Discrete Inputs
Reserved. Leave unconnected.
1.1.2.7 Input Discrete Return pins
These pins (J1-8, J3-17) are connected internally to the GLSSU case and to the chassis ground pins,
J1-33 and J3-3. They may be used to provide a return current path to the discrete inputs.
1.1.3 DISCRETE OUTPUTS
There are 6 discrete output signals, operating as contact closures to ground, and capable of sinking
280 mA through a resistive load, a suppressed inductive loads or a lamp load wherein the hot filament
current is 280 mA.
The leakage current in the Open state is less than 150 uA. The output voltage in the closed state is
less than 2.0 Volts referenced to the return pin.
The output circuits are self-protected for short-circuits to ground or to voltage sources up to 36 VDC in
either state, opened or closed.
1.1.3.1 GPS Fault Discrete output
The GLSSU provides one high level Fault output discrete signal accessible via the aircraft connector J1
as defined in ARINC 743A-4. The return current is through the +28 Volt Return pin J1-34. This contact
is opened during normal operation, and is closed to ground when the GLSSU is in Fault mode (non
operational). The state may toggle during Self-Test mode.
1.1.3.2 ILS Select Discrete output
This contact is closed to ground when the ILS/GLS Source Select Discrete input is set to "ILS", and is
opened otherwise. The return current path is through the chassis ground. This output is intended for
activating an external indicator and reacts within one second.
The document reference is online, please check the correspondence between the online documentation and the printed version.
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