The PSTN, which stands for public switched telephone network, is an invaluable part of the telephone communications infrastructure.This network is a collection of the entire world’s circuit-switched telephone networks, and consists of telephone lines, cellular networks, communication satellites, fiber optic cables, microwave transmission links, and even undersea telephone cables.
A circuit-switched telephone network, which is the type of network that makes up the PSTN, is a telecommunications network used for telephone calls between two or more parties. This includes landlines (networks where the telephones are wired directly into the PSTN), wireless networks, and private networks, where closed groups of telephones communicate with each other and use a single gateway to communicate with telephones outside the group—this is used in call centers and companies, and is referred to as a PBX, or private branch exchange. The PSTN is a collection of circuit-switched telephone networks, which are operated by national, regional, and local telephony operations.
Changes in the PSTN
The public switched telephone network was once a network of exclusively fixed-line telephones, or landlines. It is now almost completely digital, and it includes mobile networks as well as the remaining fixed-line analog telephones. The PSTN has also had to evolve in its overall form over the years to adapt to huge influxes in wireless network users and connections to other countries.
Originally, the PSTN was based on a system of hierarchies—when a call was made, it would first be handled by a local branch of telephone operations. If the call could not be handled by that branch, the call would then be passed up the hierarchy to be routed. In this way, long-distance operation costs were reduced overall, as local systems were relied upon as often as possible. Within the modern PSTN, however, costs for long-distance transmissions are much lower, as is the cost of telephone transmission equipment. Due to this price-drop in transmissions, the hierarchy system that the PSTN previously operated on to keep prices down is not needed as much. There is still a similar hierarchy in place for routing calls, but it has been reduced to only two layers.
In addition to this change in the PSTN structure, most telephone exchanges are now digital, where they previously consisted of mechanical or analog switching.
Improvements in Quality
All of these changes to the PSTN have not only made the system more efficient, but have also greatly increased the quality of sound on telephone calls and allowed for telephone customers to communicate across the world with ease.