A. description of system interfaces, A.1. control port (db25 female) – Western Telematic CAS-81 User Manual
Page 11
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A. Description of System Interfaces
A.1. Control Port (DB25 Female)
The Control Port is a 25 pin female connector wired in a DCE (modem) configuration.
Pin
Signal
I/O
Not
Connected Connected
2
RXD
Input
-
To Serial Port Pin 3
3
TXD
Output
Low
Follows Serial Port
4
RTS
Input
-
To Serial Port Pin 7
5
CTS
Output
High
* Follows Serial Port
6
DSR
Output
High
Always High
7
GND
Signal Ground
8
DCD
Output
Low
* Follows Serial Port
20
DTR
Input
-
To Serial Port Pin 4
*
May be forced high by DIP Switches 9 and 10. Always high when all Serial Ports are
connected.
Apx-1
Figure A.1: Control Port / Serial Port Interface
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