Local loop

In telephony, 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 or telecommunications service provider's network.

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 for each local loop nearer the exchange, see outside plant.