Phone Wire Diagram. They are used in pairs for each phone line you have. In a typical home the telephone cables connecting your phones within you home contain four wires.
The a leg 6 whitegreen broadband wire. Terminals are marked a and b and can be screw type terminals or idc inserter type as shown in the photo. It is important that this size of wire is used or a good electrical connection cannot be guaranteed and there could be problems in the future with the system.
Most cable nowadays is utp unshielded twisted pair.
House telephone wiring uses cable containing six 05mm diameter solid conductors. The earth 5 whiteblue dialing wire. Repairmen in fact refer to the wires in terms of pairs so technically a standard four wire telephone line has two pairs. White with blue mark goes with blue with white mark for one phone line etc.