What is PSTN and how does it work?

What is the PSTN network?

The PSTN network is something you'll hear a lot about if you work in communications, but what is PSTN in telecom terms? Is PSTN still relevant in a world where we rely so much on VoIP communications?

What does PSTN stand for?

PSTN stands for public switched telephone network. This is the traditional network copper telephone lines (and, today, other lines that are connected to the switching network) that were commonly used before the internet, and even in the early days of online communication when people connected to the internet by dialing up to a service provider.

How does the PSTN network work?

PSTN is relatively old technology. Copper telephone lines have been used since the late 1800s. When telephony first became commonplace, being able to communicate over long distances in real time was revolutionary, but PSTN has many limitations.

Copper telephone lines are capable of handling only a limited number of voice calls at a time and have limited bandwidth for transmitting data. When PSTN was invented, the intention was to transmit only voice data, and the inventors of the system probably didn't expect it to become a huge network of hundreds of millions (or even billions) of users.

When a user places a call using the PSTN system today, several things must happen:

  • The telephone converts voice data into signals and transmits them to a terminal
  • The terminal forwards those signals to a central office
  • The central office converts the signals into a format that can be transmitted over fiber-optic cables
  • The fiber-optic cables carry the data to the next step on the route, a tandem office
  • When the data arrives at this office, it looks at the destination and passes the information on to a hub or office, as required
  • Once the signal has reached the nearest hub or office, it's converted back into electrical form at a terminal, to be passed along copper wires
  • The terminal passes the signal to the receiving phone

Switching is an involved process, but it works, and it's quite affordable for a consumer to have a PSTN phone in their home. The system works well for single lines.

The problem arises when the system needs to be used at scale. The cost per line is high, and if a business needs dozens or hundreds of phone lines to be used all at once, PSTN is an inefficient and unwieldy way to do it.

PSTN vs. VoIP

Voice over Internet Protocol, or VoIP, uses the internet for voice calls. PSTN is falling out of favor, with many telephony providers decommissioning their copper telephone lines.

PSTN still has a few years of life left in it, but for many businesses, moving to VoIP makes sense for many reasons:

  • VoIP systems can handle dozens (or hundreds) of calls on one high-speed line
  • VoIP numbers are easily portable
  • Adding and removing extensions, numbers and users is easy
  • Many digital systems are backward compatible with PSTN
  • VoIP systems support multimedia communications, not just voice
  • VoIP offers significant potential cost savings for businesses

If your business needs a scalable and flexible communications system but you're currently relying on a PBX that connects to the legacy PSTN system, consider using cloud-based business phone solutions to future-proof your communications.

At 8x8, we offer business communications systems for companies of all sizes. Call us today to schedule a demo and request a free quote for your business.