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DB25 to RJ45 Cables

These notes are mostly for myself but others might be interested. For some time, I've been using RJ45 cables to run my serial connections (remember serial). I still have a number of serial devices such as X10 controls, UPS stats, various hardware monitoring, etc..

db9 plug db25 plug

So the RJ45 cables I use are all straight through. They plug into RJ45 to DB9 (left) or DB25 (right) connectors. If you need a straight-through cable (modems) then you should use a Non-swapped connector on both sides (or 2 swaps if that is all you have). For a swapped cable (terminals), then one of the sides should have a swapped connector and the other a non-swapped.

DB25 Pinouts

(N)on-Swapped (S)wapped
Pin Sig   Pin Sig  
2 TXD Red 2 RXD Green
3 RXD Green 3 TXD Red
4 RTS Orange 4 CTS Brown
5 CTS Brown 5 RTS Orange
6 DSR Black 6 DTR White
7 COM Yellow 7 COM Yellow
8 DCD Blue 8 DCD Blue
20 DTR White 20 DSR Black

DB9 Pinouts

(N)on-Swapped (S)wapped
Pin Sig   Pin Sig  
1 DCD Blue 1 DCD Blue
2 Rxd Green 2 Txd Red
3 Txd Red 3 Rxd Green
4 DTR White 4 DSR Black
5 COM Yellow 5 COM Yellow
6 DSR Black 6 DTR White
7 RTS Orange 7 CTS Brown
8 CTS Brown 8 RTS Orange
9 Unused 9 Unused

DB9 APC Unit (WARNING NOT TYPICAL)

(N)on-Swapped (S)wapped
Pin Sig   Pin Sig  
1 Rxd Green 1 Txd Red
2 Txd Red 2 Rxd Green
3 Unused 3 Unused
4 COM Yellow 4 COM Yellow
5 Unused 5 Unused
6 Unused 6 Unused
7 Unused 7 Unused
8 Unused 8 Unused
9 Unused 9 Unused

Labeling Notes

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