Telephone line
A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user
In the United States
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
Often the customer end of that wire pair is connected to a data access arrangement; the telephone company end of that wire pair is connected to a telephone hybrid.
In most cases, two
The vast majority of houses in the U.S. are wired with 6-position
Older houses often have 4-conductor telephone station cable in the walls color coded with Bell System colors: red, green, yellow, black as 2-pairs of 22 AWG (0.33 mm2) solid copper; "line 1" uses the red/green pair and "line 2" uses the yellow/black pair. Inside the walls of the house—between the house's outside junction box and the interior
Inside large buildings, and in the outdoor cables that run to the telephone company POP, many telephone lines are bundled together in a single cable using the 25-pair color code.[3]
Outside plant cables can have up to 3,600 pairs, used at the entrance of telephone exchanges.[4]
References
- ^ "Telephone Circuits". ScienceDirect. Retrieved 2022-12-12.
- ^ Public Service Commission of Wisconsin. "Testing, Repairing & Installing Home Telephone Wiring" Archived 2018-03-28 at the Wayback Machine.
- OCLC 26632919.
- S2CID 39098621.
External links
- Media related to Telephone lines at Wikimedia Commons