telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is i ...

, the local loop (also referred to as the local tail, subscriber line, or in the aggregate as the last mile) is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the

common carrier A common carrier in common law countries (corresponding to a public carrier in some civil law systems,Encyclopædia Britannica CD 2000 "Civil-law public carrier" from "carriage of goods" usually called simply a ''carrier'') is a person or compan ...

or telecommunications service provider's network. At the edge of the carrier access network in a traditional public telephone network, the local loop terminates in a circuit switch housed in an incumbent local exchange carrier or

telephone exchange telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syste ...

Infrastructure

Traditionally, the local loop was an

electrical circuit An electrical network is an interconnection of electrical components (e.g., batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e.g., voltage source ...

in the form of a single pair of conductors from the telephone on the customer's premises to the local

. Single-wire earth return lines had been used in some countries until the introduction of electric tramways from the 1900s made them unusable. Historically the first section was often an aerial open-wire line, with several conductors attached to porcelain insulators on cross-arms on "telegraph" poles. Hence party line service was often given to residential customers to minimise the number of local loops required. Usually all these circuits went into aerial or buried cables with a

twisted pair Twisted pair cabling is a type of wiring used for communications in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted b ...

for each local loop nearer the exchange, see

outside plant In telecommunication, the term outside plant has the following meanings: *In civilian telecommunications, outside plant refers to all of the physical cabling and supporting infrastructure (such as conduit, cabinets, tower or poles), and any asso ...

. Modern implementations may include a digital loop carrier system segment or fiber optic transmission system. The local loop may terminate at a circuit switch owned by a

competitive local exchange carrier A competitive local exchange carrier (CLEC), in the United States and Canada, is a telecommunications provider company (sometimes called a "carrier") competing with other, already established carriers, generally the incumbent local exchange carrier ...

and housed in a point of presence (POP), which typically is an incumbent local exchange carrier telephone exchange. A local loop supports voice and/or data communications applications in the following ways: * analog voice and signaling used in traditional POTS * Integrated Services Digital Network (ISDN) * variants of

digital subscriber line Digital subscriber line (DSL; originally digital subscriber loop) is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric dig ...

(DSL). The term "local loop" is sometimes used for any " last mile" connection to the customer, regardless of technology or intended purpose. Local loop interrelations in this sense include: *Electric power lines. *Cable connections used with television, internet and telephone. *Wireless signals or local loop (WLL): LMDS,

WiMAX Worldwide Interoperability for Microwave Access (WiMAX) is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide physical layer (PHY) and media access control (MAC) options. The WiMAX ...

GPRS General Packet Radio Service (GPRS) is a packet oriented mobile data standard on the 2G and 3G cellular communication network's global system for mobile communications (GSM). GPRS was established by European Telecommunications Standards Ins ...

, HSDPA, DECT *Satellite connections for beamed signal. *Optical or fiber optics services.

References

{{Authority control Telecommunications infrastructure

Infrastructure

See also

References