public switched telephone network (PSTN)
A 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 multi-frequency tones.
The worldwide network of public switched (circuit) telephone networks is based on ITU-T Recommendation E.164 (The international public telecommunication numbering plan). This document is available at:
http://www. itu. int/rec/T-REC-E.164/en
As defined in ITU-T Rec. G.100, The term “Public Switched Telephone Network” or, for short, “Public Network” is used for any network (without any relation to the legal status of the network operator) providing transmission and switching functions as well as features which are available to the general public, not restricted to a specific user group. The PSTN provides access points to other networks or terminals only within a specific geographical area. From the point of view of an end-to-end connection, a public network can function either as a “Transit Network” (a link between two other networks) or as a combination of “Transit and Terminating Network” in cases where the public network provides connections to terminal equipment such as telephone sets, or PBXs.