Local loop

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In telephony, the local loop (also referred to as a subscriber line) is the physical link or circuit, that connects from the demarcation point of the customer premises to the edge of the carrier, or telecommunications service provider, network. At the edge of the carrier network in a traditional PSTN (Public Switched Telephone Network) scenario, the local loop terminates in a circuit switch housed in an ILEC (Incumbent Local Exchange Carrier) CO (Central Office). Traditionally, the local loop was wireline in nature from customer to central office, specifically in the form of an electrical circuit (i.e., loop) provisioned as a single twisted pair in support of voice communications. However, modern implementations may include a digital loop carrier system segment or fiber optic transmission system known as fiber-in-the-loop.

The local loop may terminate at a circuit switch owned by a CLEC (Competitive LEC) and housed in a POP, which typically is either an ILEC CO or a carrier "hotel".

A local loop may be provisioned to support data communications applications, or combined voice and data such as digital subscriber line (DSL).

Local loop connections can be used to carry a range of services, including:

analog voice and signaling used in traditional POTS
Integrated Services Digital Network (ISDN)
variants of Digital Subscriber Line (DSL)

Making the local loop available, usually by law, to the owner's competitors, is referred to as local loop unbundling.

The term "local loop" is sometimes used for any "last mile" connection to the customer, regardless of technology or intended purpose. Hence the phrase "wireless local loop".

Local loop connections in this sense include:

Electric local loop: PLT and PLC
Optical local loop: Fiber Optics services such as FiOS
Satellite local loop: communications satellite and cosmos Internet connections of satellite television (DVB-S)
Cable local loop: Cablemodem
Wireless local loop (WLL): LMDS, WiMAX, GPRS, HSDPA