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Re: Modem Caller-ID question (long-ish)


  • To: ukha_d@xxxxxxx
  • Subject: Re: Modem Caller-ID question (long-ish)
  • From: nigel@xxxxxxx
  • Date: Thu, 16 Nov 2000 07:27:02 -0000 (GMT)
  • Delivered-to: rich@xxxxxxx
  • Delivered-to: mailing list ukha_d@xxxxxxx
  • Mailing-list: list ukha_d@xxxxxxx; contact ukha_d-owner@xxxxxxx
  • Reply-to: ukha_d@xxxxxxx

>>Do you know wich two? - there are 4 connected pins in a line cord
>>aren't there?
> ISTR, US modems use the middle 2 of a RJ45, UK ones 2 and 6 of a BT
> jack.

I think you meant 2 and 5.  2 and 5 are the incoming pair from the
telephone exchange, the master socket derives a ring signal and puts
it on pin 3.  Pin 4 is designated earth, and is rarely used in
domestic installations (used for earth recall on some pabx's), and 1
and 6 are spare.

Note that some phones derive the ring signal internally from 2 and 5,
so if you put in an extension and some phones ring but others don't,
you've probably not connected pin 3!

Nigel

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