I've had to document all of this to correct a customer site so here it is for everyone.
Serial port 3/4 RJ12 6 pin (tab down facing away left to right, this is how rj's are numbered)
Pinout
1 Pwr/RTS
2 GND
3 TX
4 RX
5 GND
6 CTS
1639-K401 RJ12 to rj45 adapter (personally I'd throw this away and make a new cord)
RJ12 pin RJ45 pin
1 No Connect
2 No Connect
3 3
4 2
5 5
6 8
Pin connections needed when fully wired inside a db25 (NOT using the 1639-K401)
RJ12 pin RJ45 Pin Db25 pin
1 2 5
2 3 7 (spliced inside connector)
3 4 3
4 5 2
5 6 7 (spliced inside connector)
6 7 4
If using the 1639-K401
RJ45 pin db25 pin
3 3
4 2
5 7
6 4
Serial port 3/4 RJ12 6 pin (tab down facing away left to right, this is how rj's are numbered)
Pinout
1 Pwr/RTS
2 GND
3 TX
4 RX
5 GND
6 CTS
1639-K401 RJ12 to rj45 adapter (personally I'd throw this away and make a new cord)
RJ12 pin RJ45 pin
1 No Connect
2 No Connect
3 3
4 2
5 5
6 8
Pin connections needed when fully wired inside a db25 (NOT using the 1639-K401)
RJ12 pin RJ45 Pin Db25 pin
1 2 5
2 3 7 (spliced inside connector)
3 4 3
4 5 2
5 6 7 (spliced inside connector)
6 7 4
If using the 1639-K401
RJ45 pin db25 pin
3 3
4 2
5 7
6 4
