When it comes to subscribing to a telephony service, people now have a choice between PSTN, cellular telephony, and VoIP. PSTN is the standard telephone, as we?ve always known it. The principle of operation relies on establishing an electrical circuit between two telephones. At the dawn of the telephone era, this connection was established by human operators manually connecting the two phone lines. Soon, automated switchboards came to be used, which were in turn replaced by digital exchanges. But the basics have remained the same

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