Telephone exchange

A system that connects telephone calls between users by routing signals between telephone lines or network endpoints. Exchanges may operate manually or use automatic switching equipment.

Circuit switching: A communication method that reserves a dedicated path between endpoints for the duration of a connection. Traditional exchanges establish a circuit that remains assigned to a call until it ends.
Telephone: A communication device that transmits and receives speech over electrical or digital networks. Telephone exchanges arose to connect the growing number of telephones into a usable network.
Telephone line: A wired connection that carries telephone signals between a subscriber’s equipment and a network. An exchange receives and routes calls from the subscriber lines attached to it.
Public switched telephone network: The global collection of interconnected public telephone networks that provides switched voice communication. Telephone exchanges are the switching nodes that make this public network function.
Automatic telephone exchange: A telephone exchange that establishes calls through switching equipment rather than manual operator connections. Automatic exchanges made routine call setup faster and less dependent on human staffing.
Telephone switch: A device that connects selected telephone lines or network channels under manual or automatic control. The switch is the exchange’s core component for selecting a path between callers.
George W. Coy: An American inventor associated with opening the first commercial telephone exchange in New Haven, Connecticut, in 1878. Coy’s New Haven exchange demonstrated centralized call connection for multiple subscribers.
Subscriber loop: The local circuit connecting a telephone subscriber’s premises to the serving telephone exchange. This last-mile connection gives an exchange access to each subscriber’s telephone.
Private branch exchange: A telephone switching system serving an organization’s internal extensions and connections to outside networks. It applies exchange functions within a business, campus, or institution.
Telephone exchange strike of 1919: A major Boston telephone workers’ strike in 1919 involving operators and other telephone-company employees. The strike exposed the labor conditions behind the human operation of telephone exchanges.

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