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Single-wire earth return never used in France (for example) |
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== Infrastructure ==
Traditionally, the local loop was an [[electrical circuit]] in the form of a single pair of conductors from the telephone on the customer's premises to the local [[telephone 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. Hence [[party line (telephony)|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]].
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