PSTN stands for "Public Switched Telephone Network", and it refers to the world's oldest collection of interconnected communication solutions.
Some people also refer to this communications option as the "Plain Old Telephone Service" or POTS.
Today, we know the PSTN as the evolution of the circuit-switching networks that have evolved progressively since the days of Alexander Graham Bell.
What started as single lines connected from one phone to another is now almost entirely digital in structure.
Moreover, the PSTN also furnishes much of the long-distance infrastructure of the internet.
Internet service providers (ISPs) pay other providers with connections across long distances to access their infrastructure.
Internet users can avoid paying excess usage tolls to anyone but their ISPs.
The History of PSTN
The Public Switched Telephone Network is the accumulation of global circuit-switched networks for telephone communication.
It is operated on various levels, such as local, regional, and national.
PSTN provides the infrastructure for public communication, consisting of fibre optic cables, telephone lines, microwave transmissions, communication satellites, cellular transmissions, and under-sea cables.
The very first telephones had no network connections. Instead, they were private-use solutions for communication wired together in pairs.
This meant that it was impossible to call more than one location.
Users who wanted to talk to a range of people had to have several different telephones - each with its own purpose.
By the 1960s, voice calls started to be digitised, with manual solutions for switching replaced by automated electronic switching.
Digital voice signals could share the same wire with other phone calls, and the communication abilities of the masses grew.
Over time, the PSTN transformed from fixed-line telephone analogue systems to an almost entirely digital solution.
The development of fibre optic cables now means thousands of calls can share the same line.
Despite technological developments, high-bandwidth and fibre optic cables have not changed the fundamental nature of circuit switching.
This method of communication still requires a circuit or connection to remain open throughout a phone call.
The technical operation of the PSTN adheres to standards that were initially created by the ITU-T or the International Telegraph Union Telecommunication sector.
These standards allow for different networks to connect seamlessly across countries.
The E.164 and E.163 standards of the ITU-T allow for a single address space for telephone numbers across the globe.
The nature of PSTN today means that we have never been freer to connect with people worldwide.
The Digital World of PSTN
Most automated solutions for telephone exchanges now utilise digital methods for switching rather than analogue or mechanical switching.
