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Intelephony, thelocal loop (also referred to as thelocal tail,subscriber line, or in the aggregate as thelast mile) is the physical link or circuit that connects from thedemarcation point of thecustomer premises to the edge of thecommon carrier ortelecommunications service provider's network.[1]
At the edge of the carrieraccess network in a traditional public telephone network,[2] the local loop terminates in a circuit switch housed in an incumbentlocal exchange carrier ortelephone exchange.
Traditionally, the local loop was anelectrical circuit in the form of a single pair of conductors from the telephone on the customer's premises to the localtelephone exchange.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. Henceparty 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 atwisted pair for each local loop nearer the exchange, seeoutside plant.
Modern implementations may include adigital loop carrier system segment orfiber optic transmission system. The local loop may terminate at a circuit switch owned by acompetitive local exchange carrier and housed in apoint 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:
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:
