PSTN has played a crucial role in connecting the world for centuries, and even with the emergence of modern communications methods, the traditional telephony PSTN system has not been fully replaced yet. Do you know why?

So, In this article, we will explore all the aspects of  PSTN. 

What is PSTN? 

What is PSTN

PSTN (Public Switched Telephone Network) is a traditional telephony system operated through the physical infrastructure like telephone poles and lines for voice-oriented communications since the late 1800s. 

It is also known as Plain Old Telephone Service (POTS) or landlines, which still operates through copper wire and landlines to connect to people worldwide. It lacks modern features like video calls, recording, or call routings as it is independent of an Internet connection and works smoothly during power cuts. It is still accepted as a standard and reliable means of communication but has been continuously declining over time. There has been a gradual replacement of outdated PSTN by modern IP-based communications channels as they come with advanced features and benefits. In general, both forms of communication have become reliable for interaction in households and businesses.

How does PSTN calling work?

PSTN is operated by combining multiple physical factors like telephone lines, underground wires, cellular networks, and switching centers for a smooth flow of calls from the destination to the recipient’s destination, connecting people worldwide. It lacks automated electronic switching, so instant transmission is not possible.

Here is an easy way to understand the workflow of PSTN:

First, the user dials the number that has the indication for callers to choose their route. Like each set of numbers represents unique information, the first 3-digit number indicates the area code, referred to as a regional switching station; the following 3-digit number is an exchange code, and the remaining four digits are a recipient’s unique and specific phone ID and address.

After choosing a route, the caller’s voice is converted into an electrical signal by telephone and transmitted to the terminal. Then, they are transmitted to the Central Office, and based on the caller’s location and the call route, the CO will direct the call to the CO ( in the same neighborhood as the recipient), tendon office (same city but a different town, a call travels to caller’s central office -> tandem office ->central office of the recipient -> Recipient), toll office (different city, a call route from tandem office -> toll office which is responsible for long-distance switching inside the nations), or International gateway (different country).

After the call reaches the right destination, the electrical signals are routed to the terminal and sent to the correct number. Once the recipient picks up the call, the electrical signals are converted back to sound waves for accessible two-way communication. 

PSTN Network Architecture

Switches are crucial aspects of carrying out communication between two phones. It creates switches to maintain a connection between two phones until the last moment. For instance, the international PSTN gateway will switch the call if you want to make an international call.

Here are the top four factors that cover the PSTN network Architecture, they are:

Central Office

It is also known as local exchange or telephone exchange that connects individual calls to an extensive phone network where each switch can connect upto 10,000 lines. Since all the phones are connected to the central office, they will determine the call’s destination and direct it so you can connect to the right person.

Tandem Office

It manages the switches of two different local exchanges. For example, if the caller dials the receipt who lives in the same country but in a different town, the call will be directed from the caller’s central office to the tandem office. Then, it will forward the signals to the recipient’s nearest central office.

Toll Office

It is responsible for switching long-distance national calls. 

International Gateway

The international PSTN gateway is liable for switching international calls to the desired nation.

How Much Does PSTN Access Cost?

Its cost varies depending on the size of the users. Telephone and PSTN service providers are needed to get PSTN access at home. They can buy unlimited local and international phone calls at around $50 monthly. It’s affordable and enough for a single family.

However,  the cost changes for business purposes, as a separate line is needed for the individual employee to access the PSTN phone system. Individual payment per individual connection per month, with a price of around 30$, is expensive. So, many businesses use VoIP.

Benefits of Public Switched Telephone Network

Benefits of Public Switched Telephone Network

Though PSTN is an outdated telephony system with limited features, they are still well known for all generations and do possess benefits like:


It is reliable as it does not depend on an Internet connection and can operate in extreme weather or outrage. It is reliable in crucial times of emergency where consistent communication is required. 


It offers excellent data security. The conversations shared over PSTN are less likely to be hacked since its physical architecture is primarily physical. Despite being a traditional telephony system, it provides high protection to its users’ data and interactions.


They are user-friendly. All the ages of generations can easily make a call due to its simplicity. Minimal understanding is enough to connect to the people around the world. 

Excellent Service

The system is independent of the Internet Network, so it is not interrupted by low connectivity or power outages and provides a seamless quality voice service that is significantly crucial in emergency cases.

Drawbacks of PSTN Phone

The drawbacks of PSTN Phones are:

Limited Features

It lacks advanced features like email, file sharing, video calling, and instant messaging. It has only basic functions like voice calls, voicemail, call waiting, and call forwarding, which do not meet the needs of growing trends.

Limited Call

PSTN lines are designed to manage a single call at a time. Its implications can be ineffective for medium and large-scale industries that handle multiple conversations daily.


This system lacks flexibility. It restricts businesses from adding and deleting lines during its necessity. 

Slow data transmission

There is slow data transmission in traditional telephony systems while making an international call, which causes disturbance and brings a negative impact on the customer.

PSTN for business

Despite its many advantages—such as superior data security, dependability, and usability—PSTN is not the best choice for commercial use. Since PSTN lines can only handle one call at a time, they are not appropriate for enterprises that handle several calls. For medium-sized and large-scale enterprises, its adoption may be ineffective. It lacks advanced capabilities like video calling, file sharing, email, and instant messaging and only supports essential services like call waiting and voicemail. As a result, its feature set is limited. It isn’t flexible enough to add or remove lines to suit changing company requirements. These characteristics are essential to a thriving company. A separate line is needed for the employee to access the PSTN phone system. Individual payment per connection per month, with a price of around 30$, is expensive. So, it is more reliable for single-house interaction than business. 

Alternatives to the PSTN


PSTN is a traditional voice-oriented telephony system operated through physical infrastructure like telephone poles and cables. VoIP phones are cloud-based telephony systems where communication takes place over the Internet. Let’s study their difference.

FlexibilityLow flexibilityHigh flexibility
FeaturesIntroductory phone calls are fit for a small business that has around ten employees.It has extensive features that support both medium and large-scale businesses.
PortabilityFixed locationCloud-based so that it can be accessed from around the world with an Internet  connection
CostIt is expensive because a separate line is needed for the individual employee to access the PSTN phone system. The cost is relatively lower.

PSTN vs. hosted PBX

Hosted PBX ( Private Branch Exchange) is a modern telephony system that operates via the Internet. The third-party service provider handles them, so it does not require physical hardware on-premises. It has features like call forwarding, conferencing, do-not-disturb mode, on-hold options, and more. PSTN is a traditional telephony system operated through the physical infrastructure like telephone poles and lines for voice-oriented communications. Here, let’s discuss PSTN and its alternatives- hosted PBX and the comparison between them.

InfrastructureIt operates through physical lines and optic-fiber cables.It is a cloud-based operating system.
FeaturesCover basic features like call waiting and voicemailHas advanced features for quality communication.
ScalabilityIt needs more scalability.It has comparatively high scalability.
FlexibilityLow flexibility since the setup is fixedIt is highly adaptable and has increased accessibility

Upgrade to VoIP from PSTN seamlessly through Dialaxy

Dialaxy is a cloud-based call center solution that provides an international virtual phone number of 100+ countries to connect to a global audience remotely. It has comprehensive features that benefit businesses seamlessly. Let’s discuss its features;

Call Features

One can buy unlimited calls that enable global calling, which enhances uninterrupted calls and customer interactions. It’s an ideal option for contact center operations. It facilitates putting the calls on hold for more extended client support without the risk of losing them, call recordings, and checking and accessing call history smoothly within seconds.

SMS Features

It has features like a Character Limit Indicator that manages and ensures precise and effective communication.

Voicemail Features

These features help clients and agents stay connected and support smooth communication by enabling leave and receiving voicemail services.

Contact Features

It enables one to connect with many contacts as needed quickly and enjoy uninterrupted communication.

Agent Features

This feature allows an extended team for better teamwork and assigns specific numbers to members for seamless communication that enhances accessibility and, inversely, increases productivity.

Cross Platform

You can access this cloud-based call center solution across applications like Windows, Mac, Linux, and Android devices.

It offers numerous advanced benefits that align with modern businesses’ needs.


How does the PSTN work?

The recipient dials the number where each set of numbers specifies the area, exchange, and recipient codes. The caller’s voice is converted into an electrical signal by telephone and transmitted to the Central Office, and based on the caller’s location and the call route, the CO will direct the call to the neighborhood CO, tandem office, toll office, or international gateway. Then, the electrical signals are routed to the recipient terminal, and the signal is converted into a sound wave upon receiving a call.

What is the PSTN number example?

The PSTN numbers follow a standard format, such as country code, area code, exchange code, and subscriber number. For Example: The PSTN number for the US is: +1(555) 122 -8763


+1: The country code

555: Area Code

122: Exchange code

8763: Subscriber number

What are the main elements of PSTN?

The main elements of PSTN include telephone lines, fiber-optic cables, circuit-switching, subscriber numbers, central offices, tandem offices, toll offices, and international gateways.

What is the difference between PSTN and cellular?

PSTN uses physical infrastructure like landlines and fiber-optic cables to communicate across a wired network. It is primarily dependent on circuit-switching technology. It has limited mobility and flexibility. Meanwhile, Cellular networks are wireless and provide data services like mobile communication and multimedia messaging. It often uses circuit-switching for voice calls and packet-switching for data services. It has greater mobility and high flexibility.

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