Definition of the Public Switched Telephone System
- Public Switched Telephone Network (PSTN)
- A domestic telecommunications network usually accessed by telephones, key telephone systems, private branch exchange trunks, and data arrangements. Note: Completion of the circuit between the call originator and call receiver in a PSTN requires network signaling in the form of dial pulses or multifrequency tones. (As defined in FS-1037-C)
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If you live in North America, you have access to the Public Switched Telephone System (PSTN). The term PSTN used to refer to the public communication system that provides local, extended local and long distance telephone service to the majority of the United States and North America. This system is made available to the public through a group of common communications carriers such as American and Canadian phone companies who have agreed to exchange calls and connections on behalf of their subscribers as mandated by international law and the laws of the country in which they do business and and provide telephone service. Anyone who subscribes to this public service may make calls to anyone else who has purchased access to the phone system through any other carrier.
The PSTN is composed of telephone exchanges networked together to form a nationwide (and worldwide) telephone communications system. It is public because (theoretically) the system is available to anyone who can afford the service. All calls are switched, that is, a caller's conversation is broken into pieces (the pieces are called packets) and these pieces are sent simultaneously over many connections to reach a receiver at the other end. The individual pieces are 'swtiched' from one telephone device to another until they reach their final destination at the receiving end. All phones in the PSTN are networked in that any phone can make a call to any other phone because all the local phone systems around the country are connected to each other. Connecting communications systems together is called networking. Thus, all phone systems in the country are part of a nationwide network.