Maze of wires in Pratt, Kansas, 1900. A telephone line or telephone circuit is a single-user circuit on a telephone communication system. This refers to the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, and usually also implies a single telephone number for billing purposes reserved for that user. In 1878, the Bell Telephone Company began to use two-wire circuits (called the local loop) from each user's telephone to end offices which performed any necessary electrical switching to allow voice signals to be transmitted to more distant telephones.