Landline

A landline is phone service provided to a subscriber via cable or wire (i.e. metal conductors or optical fiber). The term differentiates a phone service from the now ubiquitous wireless service. A landline allows multiple phones to operate simultaneously on the same phone number. It is also referred to as fixed-line, wireline, telephone line, twisted pair, plain old telephone service (POTS), or public switched telephone network (PSTN).

Landline services are traditionally provided via an analogue copper wire to a telephone exchange. Landline service is usually distinguished from newer services that use Internet Protocol over optical fiber (Fiber-to-the-x), or other broadband services (VDSL/Cable) using Voice over IP. However, sometimes modern services delivered over a wired internet connection are referred to as landline.

A subscriber's telephone connected to a landline can be hard-wired or cordless and typically refers to the operation of phones in relatively-fixed locations such as a home.

Landline service is typically provided through the outside plant of a telephone company's central office, or wire center. The outside plant comprises tiers of cabling between distribution points in the exchange area, so that a single pair of copper wire, or an optical fiber, reaches each subscriber location, such as a home or office, at the network interface. Customer premises wiring extends from the network interface ("NID") to the location of one or more telephones inside the premises. A landline can carry high-speed internet such as digital subscriber line (DSL) which links back to the digital subscriber line access multiplexer (DSLAM) within the central office, T-1/T-3, or ISDN.

In 2003, the CIA World Factbook 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 had 23.7 million residential fixed home phones.

A 2013 International Telecommunication Union report showed that the total number of fixed-telephone subscribers in the world was about 1.26 billion.

In many parts of the world, including Africa and India, the growth in mobile phone usage has outpaced that of landlines. In the United States, while 45.9 percent of households still had landlines as of 2017, more than half had only mobile phones. This trend is similar in Canada, where more than one in five households used mobile phones as their only source for telephone service in 2013. However, voice over IP (VoIP) services offer an alternative to traditional landlines, allowing numbers to remain in use without being tied to a physical location, making them more adaptable to modern ways of working. The FCC maintains both landline and Voice over IP subscriber numbers to monitor long term trends in usage.

By means of porting, voice over IP services can host landline numbers previously hosted on traditional fixed telephone networks. VoIP services can be used anywhere an internet connection is available on many devices including smartphones, giving great flexibility to where calls may be answered and thus facilitating remote, mobile and home working, for example. VoIP porting allows landline numbers to remain in use, whilst freeing them from actual landlines tied to one location. This is useful where landline numbers are believed to be preferred by callers, or where it is preferable that legacy landline numbers remain connected.