11 Public switched telephone networks – 11 Public switched telephone networks (PSTN) The Public Switched Telephone Network (PSTN) The term Public | Course Hero

11 Public switched telephone networks (PSTN

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The Public Switched Telephone Network (PSTN)

The term Public Switched Telephone Network (PSTN) describes the various equipment and

interconnecting facilities that provide phone service to the public. The network continues to

evolve with the introduction of new technologies. The PSTN began in the United States in

1878 with a manual mechanical switchboard that connected different parties and allowed

them to carry on a conversation. Today, the PSTN is a network of computers and other

electronic equipment that converts speech into digital data and provides a multitude of

sophisticated phone features, data services, and mobile wireless access.

PSTN voice facilities transport speech or voice-band data (such as fax/modems and digital

data), which is data that has been modulated to voice frequencies.

At the core of the PSTN are digital switches. The term “switch” describes the ability to cross-

connect a phone line with many other phone lines and switching from one connection to

another. The PSTN is well known for providing reliable communications to its subscribers.

11.1 Draw the simplified circuit diagram of a basic telephone instrument.

11.2 Recognise that telephone networks rely mainly on digital techniques for long distance

and, increasingly, short distance working

BASIC TELECOMMUNICATION SYSTEM

In an electrical communication system, at the transmitting side, a transducer converts the

real-life information into an electrical signal. At the receiving side, a transducer converts the

electrical signal back into real-life information.

But we still have a problem. The transmission medium introduces noise. The noise cannot be

eliminated at all. So, in the above case, we amplify the signal, but at the same time, we also

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