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.1
November 21, 2008
APPENDIX A
INTERFACE INFORMATION, GLSSU AIRCRAFT CONNECTOR SIDE (J1, J3)
1. DISCRETE SIGNAL INTERFACES
1.1 Discrete Inputs
The GLSSU recognizes seventeen input discrete signals (discretes):
- 2 Source/Destination Identification (SDI)
- 1 Data Loader
- 1 Air/Ground
- 1 Tune/Guidance Test Inhibit
- 1 DADS 429/419 Select
- 4 APD Select
- 1 APD Select Parity
- 1 ILS/GLS Source Select
- 1 Functional/Guidance Test
- 1 Frequency/Function Data Source Select
- 1 429 HS/LS Select
- 2 Spare discretes
Nine input discretes (DADS 419/429 Select, 429 HS/LS Select, the two SDI’s, the APD and APD Select
Parity) are intended to be grounded via the input discrete return on the navigation connector J1 or the
approach connector J3 (the "Local Discretes"). The eight remaining input discretes are intended to be
grounded to the aircraft frame via remote switches (the "Remote Discretes").
These discrete inputs have the following characteristics (measured between the discrete pins and the
Input Discrete Return pin J1-8 or J3-17):
Ground: DC resistance < 10 Ohms 100 mADC maximum
Open: DC resistance > 100 k Ohms (local discretes) or > 10 k Ohms (remote discretes)
WARNING: These discrete inputs must NEVER be connected to a conventional 28 VDC power line,
since the lightning protection circuits in the GLSSU will turn-on beyond approximately
+9 VDC.
The GLSSU determines the state of the remote discretes every second, while the state of the local
discretes is determined only once during the self-test mode (at the power-up or in an initiated test).
Digital filtering ensures that noise glitches will not cause false indications.
A remote discrete input may be grounded locally using a short loop of wire, but grounding a local
discrete input using a long loop of wire or a remote switch should be avoided due to the lower noise
immunity of these circuits.
A remote discrete input will reliably detect a ground state even in the presence of a ground voltage
mismatch of up to 3.5 volts in magnitude measured as the difference in the ground potential between
the GLSSU ground (either Chassis Ground or Input Discrete Return at pins J1-38, J1-8, J3-17) and the
remote grounding point of the discrete input.
The configuration of these discrete inputs is detailed below.
The document reference is online, please check the correspondence between the online documentation and the printed version.
To Next Page
Loading...
Need help?
General
