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A telephone line is a single-user circuit on a telephone communications system. Typically this refers to the physical wire or other signalling medium connecting the user's telephone aparatus to the telecommunications network, and usually also implies a single telephone number for billing purposes reserved for that user.

In 1876 the earliest lines were single electrically conducting metal wires directly connecting one telephone to another with the Earth forming the return circuit, later in 1878 the Bell Telephone Company ran lines from each user's telephone to end offices which performed any necessary electrical switching to allow voice signals to be transmitted to more distant telephones.

These wires were typically copper, although aluminium has also been used, and were carried in pairs separated by about 25 cm on poles above the ground, and later as twisted pair cables. Modern lines may run underground to a device that converts the analogue signal to digital for transmission on optical fiber.

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image of telephone lines on a pole

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