BT Telephone Wiring

The Main BT Cable

The main BT cable coming into the property often has Orange, White, Green and Black wires.  Orange and White are usually the active pair which would connect to A and B or 5 and 2 on some older boxes.


Cct diagram

wiring disagram

These pairs supply -48v and 0v, its a good idea to test these as the polarity is important for some older modems and answering machines -48v is the B connection or J2 and 0v is the A connection or J5.