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PSTN – Public Switched Telephone Network

June 20, 2018

11:15 am

PSTN refers to a traditional fixed line phone network.

Commonly referred to as the Plain Old Telephone Service, PSTN represents the public and government-owned telephone system used by businesses and residents alike.

It’s international in scope, and comprises networks of circuit-switched wires that transfer analog voice data.

Among business telephone systems, one of PSTN’s main distinctions is that it’s not internet-based.

While it is mostly digital, relying on fiber optic cables and cellular networks in conjunction with local, non-digital connections, the system is operated and regulated by telephony providers that use dedicated wires, rather than data exclusively.

By contrast, VoIP (Voice Over IP) services use IP networks to make calls.

Benefits of PSTN over VoIP

  • Reliability
  • Call Quality
  • Emergency Calling


With PSTN, you rarely have to worry about an interruption to service due to a power outage (phone jacks don’t rely on electricity).

However, while some VoIP providers offer an emergency service recovery plan, service terminates when the internet goes down.

Call Quality

While VoIP has made leaps in service since its inception, some users still prefer the call quality of PSTN. An internet connection can become unstable from time to time, resulting in static or a dropped call.

Meanwhile, traditional phone lines are typically known for their always-consistent clarity.

Emergency Calling

PSTN services offer emergency calling features, and 911 calls can be traced to your location. By contrast, most VoIP providers have limited emergency calling.

Advantages of VoIP

  • Scalability
  • Cost
  • Adding features is easy


VoIP systems are known for their ability to scale up and down with ease. Adding extra lines with PSTN systems is a costly endeavor, and requires additional cables and hardware.

However, because VoIP is internet-based and can be accessed from anywhere with a connection, almost all VoIP providers allow businesses to adjust the number of lines without extra equipment or cost.


VoIP is cheaper than most PSTN systems, whose cost is determined by phone companies and telecom industry standards.

Most VoIP plans offer free VoIP to VoIP calling, and calls to cells and landlines are available for small fees.

A typical plan for small to medium-sized businesses costs around $14.99 per month, per extension, while enterprise companies might pay $34.99 per month, per extension for additional features and telecom integration.

Compare this to a typical PSTN plan, which starts at $35 per month and ranges up to $85 for advanced services.

Adding features is easy

VoIP packages come with standard features such as voicemail, caller ID, multiple devices linked with one extension, and more. But if you want to add, you just need software installation and possibly a bandwidth upgrade.

By contrast, adding features with a PSTN requires line provisioning and extra hardware.

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Connecting your VoIP system to the PSTN

If you want to take advantage of the best of both worlds, there is a solution.

You can maintain the predictable call quality of PSTN systems, while benefitting from VoIP’s low cost and advanced set of features by adding an FXO gateway.

FXO gateways act as a bridge linking your IP network and PSTN. It converts voice traffic into either an analog or digital signal, depending on where it’s headed.

For example, if voice traffic originates from a PSTN network that’s connected with a VoIP system, the FXO will transform the signal from analog to digital. From there, the signal is compressed into so-called packets and transferred across the IP network.

The gateway reverses the process for calls originating from the IP network.

FXO Gateway Suppliers

  • Sangoma Vega
  • AudioCodes
  • Patton

Sangoma Vega

Sangoma Vega FXO

Sangoma Vega’s 50 4 FXO gateway is a popular choice among those seeking to connect their PSTN and VoIP services.

It has 4 PSTN ports and provides a fail-safe during power outages, so you can always count on uninterrupted phone service. The model retails for $399.50.


AudioCodes MP114

The MP114 by AudioCodes promises a cutting edge, low-cost gateway to connect legacy telephones with IP-based systems. It’s available for $339.99.



Patton’s SmartNode SN4112 2-FXO has 2 analog ports, though it can support up to 8. Its flexible call integration allows you to assign telephone numbers to specific ports, and program distinctive ringing. The SmartNode retails for around $301.

What is the future for the POTS?

While POTS remains an option for businesses, its future is uncertain.

Trends in the telecom industry suggest that the traditional telephone service will eventually be surpassed by IP-based solutions, such as VoIP.

Presently, telecom heavyweights, Verizon and AT&T are lobbying for a full replacement of POTS in the U.S. Such a move would allow them to remove excess hardware and landlines, which are becoming increasingly obsolete anyway.
If you bundle your phone service with internet and cable services, you’re already placing calls through an IP network, rather than traditional copper wires.

Given the inevitable growth of internet-based phone services, it’s recommended that all businesses take out a contract with a VoIP supplier.

Compare leading suppliers to find the best phone system for your business.

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Jack is a senior writer at with over a decade's experience researching and writing about consumer technology, from security and privacy to product reviews and tech news.