Cordless telephone

A cordless telephone or portable telephone replaces the handset cord with a radio link. The handset communicates with a base station connected to a fixed telephone line. The range is limited, usually to the same building or some short distance from the base station. The base station attaches to the telephone network the same way a corded telephone does.

The base station on subscriber premises is what differentiates a cordless telephone from a mobile telephone. Current cordless telephone standards, such as PHS and DECT, have blurred the once clear-cut line between cordless and mobile telephones by implementing cell handoff (handover); various advanced features, such as data-transfer; and even, on a limited scale, international roaming. In specialized models, base stations are maintained by a commercial mobile network operator and users subscribe to the service.

In 1994, digital cordless phones in the 900 MHz frequency range were introduced. Digital signals allowed the phones to be more secure and decreased eavesdropping—it was relatively easy to eavesdrop on analog cordless phone conversations. In 1995, digital spread spectrum (DSS) was introduced for cordless phones. This technology enabled the digital information to spread in pieces among multiple frequencies between the receiver and the base, thereby making it almost impossible to eavesdrop on the cordless conversations.

Unlike a corded telephone, a cordless telephone needs mains electricity to power the base station. The cordless handset is powered by a rechargeable battery, which is charged when the handset is stored in its cradle.

A jazz musician named Teri Pall invented a version of the cordless phone in 1965 but could not market her invention, as its 2-mile (3.2 km) range caused its radio signals to interfere with aircraft communications. In 1968, she sold her rights to the cordless phone to a manufacturer who modified it for practical use.

Bell Labs Lineless Telephone 1963-1967

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