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This means that when you dial a number and it reaches your local exchange, your call is immediately linked to the subscriber without the need for any further routing. The first three digits of a phone number represent the exchange (the local switch), while the last four digits identify the individual subscriber within that exchange. The exchange then identifies the number dialed so it can route the call towards the correct end destination. Interestingly, if you were to dial the number of your supplier located in the building next to yours, the call won't leave your local exchange and will be routed to the supplier as soon as it reaches the exchange. Also known as a central office or a switching exchange, a telephone exchange may have as many as 10,000 lines.Īll telephones are connected to the local exchange in a specific area. The Local ExchangeĪ local exchange - which may consist of one or more exchanges - hooks up subscribers to a PSTN line. Now, let’s have a look at each of the four types of switching which take place at different levels. When a call is made, switches create a wire circuit between two telephones, with this particular connection lasting as long as the duration of the call. You could say that PSTNs are all about switching, which forms the backbone of traditional phone networks. PSTN - Understanding The Art of Switching Related: Ready for VoIP? Advantages and Disadvantages to Make the Right Choice This process is facilitated by using fiber optic cables and a global network of switching centers. This may sound complicated, but the thing to remember is that it takes a few seconds for your call to reach its destination. Upon receiving the call, the telephone set converts the electrical signals back to sound waves. Step #6 - The terminal routes the call to the appropriate telephone number. Step #5 - When your call reaches the right office, the signal is converted back to an electrical signal and is then routed to a terminal. Step #4 - Your call is routed to a tandem office (a regional hub responsible for transmitting calls to distant central offices) or a central office (for local calls). The fiber optic conduit then carries these signals in the form of light pulses to their final destination. Step #3 - The central office routes the calls in the form of electrical signals through fiber optic cable.
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Step #2 - The terminal collects the electrical signals and transmits these to the central office (CO). These signals are then transmitted to a terminal via a cable. Step #1 - Your telephone set converts sound waves into electrical signals. To fully understand how a POTS actually works, consider what happens when you dial a number from your own phone. Put simply, when you dial a phone number your call moves through the network to reach its destination – and two phones get connected. These help telephones communicate with each other. Think of a Public Switched Telephone Network (PSTN) as a combination of telephone networks used worldwide, including telephone lines, fiber optic cables, switching centers, cellular networks, as well as satellites and cable systems. In fact, there are currently just 972 million fixed-line telephone subscriptionsin use worldwide, the lowest tally this century so far. However, they have seen a steady decline over the last decade. PSTN phones are widely used and generally still accepted as a standard form of communication. The phones themselves are known by several names, such as PSTN, landlines, Plain Old Telephone Service (POTS), or fixed-line telephones. Using underground copper wires, this legacy platform has provided businesses and households alike with a reliable means to communicate with anyone around the world for generations. This is the system that has been in general use since the late 1800s. PSTN stands for Public Switched Telephone Network, or the traditional circuit-switched telephone network. So, What is PSTN? (Public Switched Telephone Network) In this article, we will look at PSTN telephone networks in detail, covering all aspects, from basic setup and how the technology works to some of the reasons for the global decline in usage, along with an overview of some modern alternatives to PSTN.