A landline telephone is a device with a physical line connection to a telecommunications network. Landline phones were developed in the late 19th century and became common around the world in the following decades. Cellular networks in the 2000s began to replace landlines as the dominant form of telephone connectivity.
Alexander Graham Bell invented the telephone in 1876. Bell's invention was based on the electric telegraph. Several different telephone designs appeared shortly after Bell's, but they were all landlines, connected through transmission wires. Once telephones became common, central operating switchboards appeared in which physical connections were made by operators so that telephone users could talk to one another.
Landline telephones, from Bell's onward, operated on the principle of electrical resistance. When a user speaks into a landline phone's handset, he activates a microphone that sends an electrical current through a pair of insulated wires. The current follows a physical course, passing through a telephone exchange, where it is re-transmitted to the listener on the other end of the connection and converted to sound. Even "wireless" phones using landline networks employ a physical connection, replacing the cord between the phone and the handset with a radio signal.
Digital telephone signals were introduced in the 1960s and began to replace analog signals. Cellular networks appeared in the 1970s, using a modem to transmit a telephone signal without the use of a wired network. Cell phones were approved by the Federal Communications Commission and became available to the public in the 1980s, though quality was generally poor and usage was expensive. In the late 1990s, a new generation of cell phones made use of new digital network technology, replacing many private landlines and bringing telephone service to parts of the world where landlines never were installed.
Even with cell-phone use on the rise and landline use declining, landline telephones do present advantages over cell phones. The biggest advantage is consistent fidelity of the telephone signal. Landlines don't suffer from the signal problems cell phones face during bad weather or in remote areas. Landline telephones do not require an electrical connection and are operational during power outages--whereas cell phones rely on relay towers that must be powered to receive or send a signal.
The biggest disadvantage to landline telephones is their immobility. While cell phones can be taken and used almost anywhere, landline phones can be used only in or near the home or office. The landline may represent a redundant service and an added cost for those with a cell phone, though most basic landline service packages cost less than basic cell-phone plans. Landline phones are quickly losing their quality advantage as cell phones' audio signals and reliability improve.