Fixed line telephone

A landline telephone (also known as land line, land-line, main line, home phone, landline, fixed-line, and wireline) refers to a phone that uses a metal wire or fibre optic telephone line for transmission as distinguished from a mobile cellular line, which uses radio waves for transmission. In 2003, the CIA reported approximately 1.263 billion main telephone lines worldwide. China had more than any other country at 350 million and the United States was second with 268 million. The United Kingdom has 23.7 million residential fixed homephones. The 2013 statistics show that the total number of fixed-telephone subscribers in the world was about 1.16 billion. The number of landline subscribers continuously decreases due to upgrades in digital technology and the conveniences that come with switching to wireless (cellular) or Internet-based alternatives.

A fixed phone line (a line that is not a mobile phone line) can be hard-wired or cordless and typically refers to the operation of wireless devices or systems in fixed locations such as homes. Fixed wireless devices usually derive their electrical power from the utility mains electricity, unlike mobile wireless or portable wireless, which tend to be battery-powered. Although mobile and portable systems can be used in fixed locations, efficiency and bandwidth are compromised compared with fixed systems. Mobile or portable, battery-powered wireless systems can be used as emergency backups for fixed systems in case of a power blackout or natural disaster.

The term landline is also used to describe a connection between two or more 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 wired switched system (usually the public switched telephone network). So-called leased lines are invariably of the latter type; the implications of a land line in this context are security and 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. Another example of this is in airports. All air traffic control towers have dedicated lines connected to the police, fire department, hospitals, army, etc. Deployed as a precaution in case of emergency, these can be used at any time.

...
Wikipedia