PSTN Calling 101 - Fundamentals & Benefits

What is PSTN Calling?

The PSTN (public switched telephone network) is the circuit-switched telephone network used worldwide. It is no longer a purely analog, fixed-line network; today it is almost entirely digital and includes mobile telephone lines as well as fixed telephones. These networks provide the infrastructure and services for public telecommunications.

For generations, PSTN calling has been the way businesses, households, and everyone else communicated. Think of the good old rotary-dial phones of the last century. PSTN calling was traditionally used to connect homes and businesses by phone. According to an article published by The National Interest, approximately 90% of US households had a working landline (PSTN) phone in 2004. Today that number has dropped to 40%. Although usage has decreased, some people still use PSTN calling. In this article, we will look at what PSTN calling means, how it works, and its history. We will also look at the differences between VoIP and PSTN calling and the benefits of PSTN.

How does PSTN work?

The PSTN allows its users to make landline phone calls. It consists of switches on a network that act as nodes, enabling communication between two points in the network. These switches are located at central points, and a call is routed through multiple switches before it is connected. A PSTN telephone line can also be used with traditional dial-up modems to connect a computer to the internet.

This method used to be common for internet access, but that changed with the introduction of broadband internet services. In short, the PSTN is a combination of the telephone networks used worldwide. When a call is made, a circuit is formed between the two phones and lasts for the duration of the call. To make this clearer, let’s go through the process step by step.

• Step 1 – First, your telephone converts sound waves into electrical signals. These signals are transmitted to a terminal via a cable.
• Step 2 – The terminal collects the electrical signals and forwards them to the central office (CO).
• Step 3 – Calls are routed in the form of electrical signals via fiber optic cable. The fiber optic channel carries these signals to their destination in the form of light pulses.
• Step 4 – Your call is forwarded either to a regional center responsible for forwarding calls to remote central offices, or to a central office (for local calls).
• Step 5 – Finally, the terminal forwards the call to the appropriate phone number.

With PSTN calling, your call is routed differently depending on where you are and where the call is going. Let’s examine step 4 in more detail.

• CO: If you are in the same neighborhood as your recipient, your call goes to the local central office.
• Tandem Office: If you are in the same city as your recipient but in a different part of the city, your call goes to your central office and is then forwarded to a tandem office. From there, it is directed to the recipient’s central office.
• Toll Office: If you are in a different city or state from your recipient, the tandem office connects to a toll office (national long-distance switching).
• International Gateway: If you are in a different country, your call is forwarded here to connect your long-distance call.

History of PSTN Calling

This system has been in general use since the late 1800s, with underground copper wires carrying analog audio. The history of the PSTN begins in 1875, when Alexander Graham Bell founded the American Bell Telephone Company. In 1876, private use of telephones increased. At first, a caller alerted the other party to an incoming call by whistling loudly into the transmitter until the other party heard it. That changed later, when bells were added for signaling, making the operator’s job easier.

Then telephone exchanges appeared, and each telephone was connected to an exchange set up for a town or region. Connections between exchanges were established for different regions, and the networks eventually spanned cities, countries, continents, and oceans. Over time, people could call others connected to the same exchange directly, but calls to other regions still required manual connection.

By the end of the 20th century, the Signaling System 7 (SS7) network had emerged and controlled calls between most exchanges. At the turn of the 21st century, the oldest parts of the telephone network still used analog technology for the last-mile loop to the end user. (In telephony, a local loop is the physical link or circuit that connects the demarcation point of the customer’s premises to the edge of the carrier’s or telecommunications service provider’s network.)

What is the difference between VoIP and PSTN?

VoIP (Voice over Internet Protocol) transmits real-time voice signals from one IP address to another. These audio signals are transmitted in digital format over the internet. A VoIP call can take place between two phones or between a computer and a phone. PSTN calling uses circuit-switched telephony between two points. It is a traditional method that uses copper wires and is separate from internet traffic. It also includes cellular networks, switching centers, cable systems, and fiber optic cables.

Companies already use Voice over Internet Protocol (VoIP) calling on devices of their choice. However, VoIP calling here works like an intercom: it connects voice calls within the company, not over the PSTN. VoIP uses the internet to connect, while PSTN uses a landline. Both have their own connection advantages. VoIP is customizable, while PSTN is built on copper wires. VoIP offers many additional services, such as call forwarding and voicemail, whereas PSTN calling is for making calls only.

Major Benefits of Using PSTN

Although more modern methods exist, let’s examine why PSTN calling can still be a good idea and what its advantages are. First, PSTN is purpose-built: it was designed for calling, and it does this job well. Most telecom operators offer extremely high voice clarity. And at a time when security issues are so sensitive, PSTN calling has an advantage in this regard.

The PSTN continues to operate during a power outage, which supports business continuity. This is due to its analog nature. It is easy to install and use, and the infrastructure is installed by telecom companies, who also take care of you if you run into a problem. You can also fall back on PSTN calling when you have an internet or VoIP problem.

Conclusion

Advances in internet technology have not made the PSTN redundant or ineffective. Some companies still use and even trust this system, and PSTN calling has many advantages. The largely analog nature of the PSTN means that it is not vulnerable to attack, which is one reason people prefer it. You can choose the option that suits the needs and operations of your business.

Resource:

• https://en.wikipedia.org/wiki/Public_switched_telephone_network