Telephone Cabling using Cat5 or UTP. Nowadays, Cat5 cable is commonly used instead of station wire for telephony. In which case, start with the blue pairs and use the orange pairs for the second line. Nowadays, Cat5 cable is commonly used instead of station wire for telephony. A telephone line or telephone circuit (or just line or circuit within the industry) is a single-user circuit on a telephone communication system. A telephone plug is a type of connector used to connect a telephone set to the telephone wiring inside a building, establishing a connection to a telephone network. It is inserted into its counterpart, a telephone jack, commonly affixed to a wall or baseboard.
Different telephone connections are generally compatible with the use of an adapter: the physical connector and its wiring is the primary incompatibility.