ISDN RJ11 to RJ45

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 Question by Jack Shugart posted 15 Aug 2006
 ISDN RJ11 to RJ45
I just got ISDN 128k service installed to my house, now I have to run the cable to the ISDN modem.

The phone company box has a RJ11 jack for the ISDN, but the incoming port on the ISDN Modem is a RJ45.

Can someone tell me the correct pinout for the jacks?
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 Answer by Dmitri Abaimov posted 15 Aug 2006
Dear Jack,

If you are in US or Canada, chances are you are getting an ISDN-U variety of service from the phone company which works over a single pair. The pair used is the two central conductors in both RJ11 and RJ45 interfaces. Actually, I believe that by RJ45 you mean simply an 8 pin 8 conductor plug/jack interface that is commonly referred to as RJ45. Actually RJ45 stands for a particular pin payout.

In any case you should be able to get away with simply plugging an RJ11-RJ11 cord into both devices. It should fit nicely inside the 8 pin jack as well.

Sincerely,
Dmitri Abaimov, RCDD

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