A telephone line or telephone circuit (or just line or circuit within the industry) is a single-user circuit on a telephone communication system. Typically 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.
These wires were typically copper, although aluminium has also been used, and were carried in balanced pairs separated by about 25 cm (10") on poles above the ground, and later as twisted pair cables. Modern lines may run underground, and may carry analog or digital signals to the exchange, or may have a device that converts the analog signal to digital for transmission on a carrier system.
In most cases, two copper wires (tip and ring) for each telephone line run from a home or other small building to a local telephone exchange. There is a central junction box for the building where the wires that go to telephone jacks throughout the building and wires that go to the exchange meet and can be connected in different configurations depending upon the subscribed telephone service. The wires between the junction box and the exchange are known as the local loop, and the network of wires going to an exchange, the access network.
The vast majority of houses in the U.S. are wired with 6-position modular jacks with four conductors wired to the house's junction box with copper wires. Those wires may be connected back to two telephone lines at the local telephone exchange, thus making those jacks RJ14 jacks. More often, only two of the wires are connected to the exchange as one telephone line, and the others are unconnected. In that case, the jacks in the house are RJ11.
Famous quotes containing the words telephone and/or line:
“A woman spent all Christmas Day in a telephone box without ringing anyone. If someone comes to phone, she leaves the box, then resumes her place afterwards. No one calls her either, but from a window in the street, someone watched her all day, no doubt since they had nothing better to do. The Christmas syndrome.”
—Jean Baudrillard (b. 1929)
“The middle years of parenthood are characterized by ambiguity. Our kids are no longer helpless, but neither are they independent. We are still active parents but we have more time now to concentrate on our personal needs. Our children’s world has expanded. It is not enclosed within a kind of magic dotted line drawn by us. Although we are still the most important adults in their lives, we are no longer the only significant adults.”
—Ruth Davidson Bell. Ourselves and Our Children, by Boston Women’s Health Book Collective, ch. 3 (1978)