The (PSTN) Public Switched Telephone Network is the nationwide communication web that is operated by national and regional telephony operators providing infrastructure and services for the public. Effectively it is the method of delivery. Today, both homes and businesses use the PSTN to call one another.
Since Alexander Graham Bell (1847-1922) made the first phone call in 1876, the phone has become a part of everyday life. Since then, continuous development has resulted in a worldwide network of telecommunications equipment.
Although the first phones required direct user to user wired connections, rapid developments created environments where calls could be passed from one user to another via a central location where all the lines terminated – the telephone exchange was created.
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These original exchanges were manual and relied on the operators plugging in the connection between the caller and the recipient of the call. This proved to be a drawback, as the connection between the exchanges could take a long time.
As the quantity of phone users increased, numbers were introduced to identify the telephone line involved rather than asking for a name.
This was still, however, processed by manual operators who switched the call, in the case of longer distances from one operator to another. It was not unusual for long distance phone calls to take as long as 15 minutes to actually get through to the receiver.
It was 1888 when the next revolution in telephones occurred. This was when re-directing calls were introduced. A patent was soon granted for the Automatic Telephone Exchange.
This new method of exchange automation effectively sounded the end for the manual operators, although it did take time for them to fully disappear. This was the start of the global implementation of telephony services. Further developments such as signalling methods have only gone on to refine and speed up the process and brought us to the point that we have been used to for years. These days you can pick up a phone and dial a number to speak to someone and it just happens.