TELECOM Digest OnLine - Sorted: Re: I Have a Telephony Mystery

Re: I Have a Telephony Mystery

Paul Coxwell (
Wed, 4 Jul 2007 09:33:06 -0700 (PDT)

> I'm in the UK. We have a master phone socket downstairs, and an
> upstairs extension that taps into the main socket by the use of a
> splitter plugged into the main socket. The extension plug is an RJ14,
> but the splitter's socket is an RJ11 (2 pins instead of 4).

> On the downstairs socket, we can use a phone, yet on the upstairs one,
> we can't -- we just get no dialtone. But here's the weird thing --
> the ADSL connection works fine when the modem's plugged into the
> upstairs socket. Any ideas why that might be? I thought the extra
> two pins on the RJ14 were superfluous when you only have one phone
> line.

I'm not excatly clear about your reference to the extension plug being
RJ14. Do you mean the plug which fits into the master jack to feed the
splitter and extension? That's not an RJ-anything configuration.

The standard British BT431 plug is 4-conductor with the line on the
OUTER pair of contacts. One of the inner contacts is also the bell
feed (capacitor in the jack), which may or may not be used by the
telephone depending upon its design/origin.

Are you sure you have the wiring connected correctly at the extension
jack? Standard coding for a basic line is blue/white on 2,
orange/white on 3, white/blue on 5. The DSL modem could be getting
enough signal to operate by capacitive coupling in the cable run, or if
the connections are incorrect you might even have it connected to the
line via the 1.8uF ringing capacitor in the master jack.


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