Telephone line

Single-user circuit on a telephone communication system / From Wikipedia, the free encyclopedia

A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable.[1] It is 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. Telephone lines are used to deliver landline telephone service and Digital subscriber line (DSL) phone cable service to the premises. Telephone overhead lines are connected to the public switched telephone network. The voltage at a subscriber's network interface is typically 48 V between the ring and tip wires, with tip near ground and ring at –48 V.

Utility pole with electric lines (top) and telephone cables.
Fixed telephone lines per 100 inhabitants, 1997–2007.
Cross section of telephone cable of 1,800 twisted pairs, 1922.