Branch : Computer Science and Engineering
Subject : Wireless Communication
PSTN
- The PSTN is a highly integrated communications network that connects over 70% of the world's inhabitants.
- Every telephone in the world is given calling access over the PSTN.
- Each country is responsible for the regulation of the PSTN within its borders
- In the PSTN, each city or a geographic grouping of towns is called a local access and transport area (LATA).
- Surrounding LATAS are connected by a company called a local exchange carrier (LEC).
- A LEC is a company that provides intralata telephone service, and may be a local telephone company, or may be a telephone company that is regional in scope.
- A long distance telephone company collects toll fees to provide connections between different LATAs over its long distance network.
- These companies are referred to as interexchange carriers (DCC), and own and operate large fiber optic and microwave radio networks which are connected to LECs throughout a country or continent.
- Each local exchange consists of a central office (CO) which provides PSTN connection to the customer premises equipment (CPE) which may be an individual phone at a residence or a private branch exchange (PBX) at a place of business.
- The CO is connected to a tandem switch which in turn connects the local exchange to the PSTN
- The tandem switch physically connects the local telephone network to the point of presence (POP) of trunked long distance lines provided by one or more JXCs.
- Sometimes I XCs connect directly to the CO switch to avoid local transport charges levied by the LEC
- The phone connections within a PBX are maintained by the private owner, whereas connection of the PBX tothe CO is provided