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PSTN - Public Switched Telephone NetworkWhat is PSTNPSTN is the abbreviation that stands for Public Switched Telephone Network. It is a collection of interconnected voice-oriented public telephone networks that may be owned both for commercial purposes and by government authorities. PSTN has evolved since the days of the inventor of telephone Alexander Graham Bell, and is an aggregation of circuit switching telephone networks. Though it is almost digital in technology, but there is a final link from the central (local) telephone office to the user that is not digital. More about PSTNIt is known as the earliest example of traffic engineering for delivering quality services. With the advent of Internet technology, it was foresighted that PSTN will lose some of its ground in terms of usage. But many observers still believe that the long-term future of the PSTN is to be just one application of the Internet; however, the Internet has some way to go before this transition can be made and there may be long gap in achieving that end. In voice over IP technology-latest technique of Internet to make cheaper calls-needs one improvement and that is in the field of Quality of Service guarantee, that is actually the field of PSTN.
Technical overview of PSTNPSTN involves a 64-kilobit-per-second digital channel, which is originally designed by Bell Labs. While making a call, the voice of one party is digitized to 8 kHz sample rate using 8-bit pulse code modulation. There is another term called routing strategy that is used to then transmit this signal from one end to another end. These digital channels are responsible for switching of telephone exchanges. These channels are also known as timeslots, as they are multiplexed together in a time-division fashion. These channels are conveyed from an initial multi-plexer to the telephone exchange through a set of equipments that are known as the access network. Within the access network, there are a number defined reference points and they are of more interest for ISDN. But a particular reference point, called V reference point, have some general interest, as it is the reference point between a primary multi-plexer and an exchange. Last words about PSTNThough due to advance electronic technology, there are other techniques that may be somehow better than PSTN, but it still is one of the most sought after technique and has a mass appeal. It would perhaps take much long to overpower completely the use of PSTN by any other technique! Read more..Phone cards and long distance plans
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