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UK and Overseas Telephone Connection

Some information on connection of telephones in the UK and Worldwide.

I have seen many questions along the lines of "how do I connect my UK phone/fax/modem to the phone network in xxxxx country?" or "How do I connect my US/German/French/… phone/fax/modem when I go to the UK?"

This Page aims to de-mystify what is a simple, if admittedly probably illegal, action and offer appropriate solutions to these problems.

What are the main differnces between the UK and other overseas networks?

In the majority of the world the analogue telephone network is a two-wire system where the speech, power and ring-signalling are passed down a pair of wires from the exchange to the customer and onto the phones.

The UK domestic phone network (as run by British Telecom in the main) is two-wire from exchange to customer and then a three-wire system from the initial terminal box to the rest of the phones.

How do I connect my UK equiptment when overseas?

In the above diagram, for a UK Master Socket, the exchange is connected to the terminals Line A and Line B. If you only intend to make outgoing calls, then simply connect terminals 2 and 5 of your equipment to the two wires available at the phone point.

What if I need to receive calls too?

C1 (approx. 1 to 2 F @ 250VAC) passes the AC ring signal to the phone/fax/modem ringer. In order to make the ringer work, we need to provide the circuit shown in the green outline. The easiest way being to get hold of a UK Master Socket (R.S., Maplin, Farnell, etc…) and add a length of wire with 2 crocodile clips on the end. This works wonders as a universal travel adapter.

I don't like the idea of croc-clips, what's the alternative?

The simple answer is to add a RJ11 connector (6P4C) to the end of the lead, connecting pins 2 and 5 of the BT socket to the centre two contacts of the RJ11. This will work directly in the USA plus there is nearly always a US to xxx country adapter available locally.

 

Copyright Jon Whiten 1997-1999 All Rights Reserved.

18/04/99