How to connect your UK BT telephone

Master and Extension sockets are identical except that the Master socket has additional components:
A gas-discharge voltage-surge suppressor.
A 4k7 resistor to "loop the line".
A 1µ5F capacitor to pass ringing current but not d.c.

Connect incoming line wires to terminals 2 and 5.

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Wire extension socket to master socket..

...by wiring terminals 2, 3 and 5 together.
2 and 5 should be a twisted pair since these carry the voice. 3 is used to disable ringing when the handset is lifted.

UK Cable colour convention:-

Red/blue/green/white is the standard for British line cords. The colours match up with the fixed wiring and jack terminals as follows:

2 = Red (or Blue with white tracer) <-----
3 = Blue (or Orange with White tracer)
4 = Green (or White with Orange tracer)
5 = White (or White with Blue tracer) <-----

Only 2 and 5 usually need be connected.

Fit socket so that plug clip fits on the right side. The sliding cover should slide upwards to open.

Plug has a spring clip to keep it in the socket. The clip is designed to break if someone pulls- or trips over- the cable.

A cord with plug can be fitted to the old fashioned "746" telephone as shown in the sketch.