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CRS-311 1:1 Redundancy Switch
Appendix B
B.2.8
CRS-351 – Overhead Module Connector (DB-25M)
Table B‐11 indicates pinout for the DB‐25M Overhead "User Interface" connector: "P1" on the
CRS‐351 Overhead Module. This connector allows for connection of EIA‐422, EIA‐485 and EIA‐232
data interfaces for use with Overhead Framing. It also supports signaling for tactical applications.
Pin #
Signal Function
1
EIA-422 Transmit Data "A", Input
14 EIA-422 Transmit Data "B", Input
2
EIA-422 Transmit Clock "A", Output
15 EIA-422 Transmit Clock "B", Output
3
EIA-422 Transmit Byte Sync "A", Output
16 EIA-422 Transmit Byte Sync "B", Output
4
EIA-422 Receive Data "A", Output
17 EIA-422 Receive Data "B", Output
5
EIA-422 Receive Clock "A", Output
18 EIA-422 Receive Clock "B", Output
6
EIA-422 Receive Byte Sync "A", Output
19 EIA-422 Receive Byte Sync "B", Output
7
Shield
20 EIA-485 Transmit Data "-"
8
EIA-485 Transmit Data "+"
21 EIA-422 Transmit Handover Sync "A", Input
9
EIA-485 Receive Data "-"
22 EIA-485 Receive Data "+"
10
EIA-422 Transmit Handover Sync "B", Input
23 EIA-232 Clear to Send
11
EIA-232 Receive Data
24 EIA-232 Request to Send
12
EIA-232 Transmit Data
25 EIA-422 Transmit Handover Control "A", Input
13
EIA-422 Transmit Handover Control "B", Input
*For EIA‐485 2‐Wire Operation:
•
•
•
Table B-11. "P1" Overhead User Data Connector
Only two wires are required.
Tie pins 8 and 22 together (both +).
Tie pins 9 and 20 together (both ‐).
Name
Tx Data A
Tx Data B
Tx Clk A
Tx Clk B
Tx Sync A
Tx Sync B
Rx Data A
Rx Data B
Rx Clk A
Rx Clk B
Rx Sync A
Rx Sync B
Ground
485 Tx Data -
485 Tx Data +
THS A
485 Rx Data -
485 Rx Data +
THS B
232 CTS
232 Rx Data
232 RTS
232 Tx Data
THC A
THC B
B–11
Revision 7
MN/CRS311.IOM
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