A landline or main line is a telephone line which travels through a solid medium, either metal wire or optical fibre. This is distinguished from a mobile cellular line, where the medium used is the airwaves. Landlines usually cost less than cellular lines and provide better voice quality, and are used when there is no need for mobility or where cellular service is unavailable. A land line is also used to increase the security of communications, as it cannot be intercepted by a receiver without physical access to the line. This does not, however, mean that a telephone company will not send the call over the air on some point in the journey. A telephone line (or just line) is a single-user circuit on a telephone communications system. ... This article or section does not adequately cite its references or sources. ... Fiber Optic strands An optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light. ... A telephone company (or telco) provides telecommunications services such as telephony and data communications. ...

In 2003, the CIA reported approximately 1263 million main telephone lines worldwide. China had more than any other country, at 350 million, and the United States was second with 268 million - this compared with 219.4 million cellular telephones, a number which is expected to exceed the main line number within a few years. 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... The Central Intelligence Agency (CIA) is an intelligence agency of the United States government. ... The telephone or phone is a telecommunications device which is used to transmit and receive sound (most commonly voice and speech) across distance. ...

A Land line Phone from Siemens

Image File history File linksMetadata Size of this preview: 800 × 576 pixel Image in higher resolution (1964 × 1413 pixel, file size: 690 KB, MIME type: image/jpeg) Picture of a Siemens Land Line Phone. ... Image File history File linksMetadata Size of this preview: 800 × 576 pixel Image in higher resolution (1964 × 1413 pixel, file size: 690 KB, MIME type: image/jpeg) Picture of a Siemens Land Line Phone. ...

Dedicated Lines

The term landline is also used to describe a connection between two points that consists of a dedicated physical cable, as opposed to an always-available private link that is actually implemented as a circuit in a wider switched system (usually the public switched telephone network). So-called leased lines are invariably of the latter type; the implication of a landline in this context is one of security and especially of survivability. For example, a military headquarters might be linked to front-line units "by landline" to ensure that communication remains possible even if the conventional telephone network is damaged or destroyed. This was the case in the Second World War, in which the RAF Fighter Command had its radar stations and aerodromes connected to headquarters by land lines; its opponent, the German Luftwaffe, used radio - and so its commands were deciphered by the British (see Ultra). It has been suggested that Office classification be merged into this article or section. ... A leased line is a symmetric telecommunications line connecting two locations together. ... Ultra (sometimes capitalized ULTRA) was the name used by the British for intelligence resulting from decryption of German communications in World War II. The term eventually became the standard designation in both Britain and the United States for all intelligence from high-level cryptanalytic sources. ...

This usage is (obviously) much older than the use of "landline" to indicate a non-mobile telephone, and older than its similar use in CB slang. Engineers and other telecommunications experts have at times seen the more popular use as a misuse of the word. As a consequence, in professional contexts "fixed line" or "wireline" are more commonly used words than "landline", although even in these contexts the use is becoming more common and "landline" will likely be the dominant word before too long . CB slang (commonly called CB Talk) are terms that those operating CB radio used mainly during the CB craze of the 1970s and 1980s. ...

See also Local loop In telecommunications, the local loop is the wiring between the central office (telephone exchange in British English) and the customers premises demarcation point. ...