Long distance telephone

In telecommunications, a long-distance call or trunk call is a telephone call made to a location outside a defined local calling area. Long-distance calls are typically charged a higher billing rate than local calls. The term is not necessarily synonymous with placing calls to another telephone area code.

Long-distance calls are classified into two categories: national calls which connect two points within the same country and international calls which connect two points in different countries.

Before direct distance dialing (DDD) all long-distance calls were established by special switchboard operators (long-distance operators) even in exchanges where calls within the local exchange were dialed directly. Completion of long-distance calls was time-consuming and costly as each call was handled by multiple operators in multiple cities. Record keeping was also more complex, as the duration of every toll call had to be manually recorded for billing purposes.

In some countries, such as Canada and the United States, long-distance rates were historically kept artificially high to subsidize unprofitable flat-rate local residential services. Intense competition between long-distance telephone companies narrowed these gaps significantly in most developed nations in the late 20th century, although international calls to some countries continue to carry artificially high tolls as governments in those nations use them as a lucrative source of tax revenue.

In 1892, AT&T built an interconnected long-distance telephone network, which reached from New York to Chicago, the technological limit for non-amplified wiring. Users often did not use their own phone for such connections, but made an appointment to use a special long-distance telephone booth or "silence cabinet" equipped with 4-wire telephones and other advanced technology. The invention of loading coils extended the range to Denver in 1911, again reaching a technological limit. A major research venture and contest led to the development of the audion—originally invented by Lee De Forest and greatly improved by others in the years between 1907 and 1914—which provided the means for telephone signals to reach from coast to coast. Such transcontinental calling was made possible in 1914 but was not showcased until early 1915, as a promotion for the upcoming Panama–Pacific International Exposition in San Francisco in the spring of the same year.

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