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PSTN and ISDN Switch Off 2025

Updated: Nov 9, 2021

Back in 2017 BT announced that the current PSTN and ISDN services will reach end of life in December 2025. But what is PSTN and ISDN and how will it affect you?

What is PSTN & ISDN?


Image of telephone operators in 1910
Telephone Switch Board 1920's

stands for Public Switched Telephone Network, more commonly known as a standard or 'traditional' telephone line. Traditionally, this was the most widely used technology which supported one channel, one phone, one number, and one conversation. This type of telephone line was also used during the early period of the internet for dial-up internet services. The system utilises copper cable telephone lines that carry an analogue signal. The copper telephone line infrastructure dates back to the 1800's.

ISDN stands for Integrated Digital Services Network, this is a more advanced technology that offers the digital transmission of voice and data services. The advantage of this technology is that it allows multiple channels to be used. This allowed businesses to utilise a PBX (Private Branch Exchange) a private telephone network, which gives the ability to manage multiple incoming and outgoing calls and offers individual extensions and other call management features.

Why are the PSTN and ISDN networks being withdrawn?

The PSTN & ISDN network carries services over ageing copper cabling. The demand for broadband services has increased the volume of digital traffic. Copper lines are able to carry digital information but are not as effective as fibre, which offers an almost lossless connection. Due to the age of the copper network and the ever increasing maintenance costs, the system is being retired. In short, the level of digital traffic and the demand for faster broadband connections has exceeded the capabilities of the traditional copper lines.

What is replacing the current cooper lines?

Openreach as well as a number of other companies have been undergoing the mammoth task of upgrading the countries network, by installing fibre connections directly to properties known as FTTP (Fibre To The Property) to replace the outdated copper cabling.

What does this mean for businesses?

Many businesses across the UK are aware that the PSTN / ISDN service is coming to an end and have been moving broadband services over to fibre connections and phones services over to VoIP systems (Voice over Internet Protocol). VoIP technology is far more advanced and allows calls to be made over the internet using physical handsets, computers, and smart devices.

While businesses have been preparing for the fast approaching 2025 deadline, many residential users have been blissfully unaware of the changes that will take effect in December 2025.

What is replacing PSTN & ISDN?

BT has begun to roll out Digital Voice, a service that utilises the homes fibre network connection via the router. This is essentially a VoIP system for the home. Customers can upgrade to Digital Voice as well as upgrading their handsets to take advantage of new features such as:

  • HD Voice sound quality

  • Call divert

  • Multi Call (two people can make calls at once)

  • Call Waiting

  • One Touch Alexa Button

For those wanting to continue to use their current handset, the BT Hub 2 has a telephone port on the rear for Digital Voice customers.

How will the switch off affect you?

For most people the switch to Digital Voice will be fairly straightforward, customers can upgrade both their router and handset when switching to an FTTP connection. Customers will also be able to use their existing phone by plugging it into the phone port on the BT Hub 2 or by using an adaptor that can be used in any standard mains socket.

However, there are a small number of people that may find the switch a little more problematic. Unlike a standard copper phone line, which is able to run independently of the home's mains power supply. The new Digital Voice service requires the router (Hub 2) to be powered on and connected, for customers to continue to make calls. In the event of a power cut, BT Digital Voice customers will be unable to make calls using this service. To overcome this issue BT suggests using an alternative method such as a mobile phone, this could be an issue for those customers in poor mobile coverage areas. If you live in a poor mobile coverage area and you are prone to power cuts, BT offers a BBU (Battery Back-up Unit) to continue to power the Hub 2 for up to an hour.

**At the time of writing this article BT shop shows this product as no longer available.

Is your home security ready for the switch off?

Any devices that rely on the copper phone line connection need to be upgraded. Many older home alarm systems rely on a hardwired connection to the phone line, enabling the alarm to communicate any emergency to homeowners and monitoring stations. Some alarms can be upgraded by adding a GSM module (Global System for Mobile communication), which utilises the mobile phone network as a line of communication. Others may offer a data module allowing the alarm to connect to the router.

If you would like to know more about upgrading your alarm system, please visit or call 01473 875975.

Unable to get connected?

For those who are unable to get a fibre connection, 4G broadband could be a good alternative. Even if you are in a poor mobile signal area, it may be possible to get a good 4G broadband connection using a dedicated antenna and 4G router. We have already helped a number of customers get a faster broadband connection using the 4G network. To find out more please visit or call 01473 875975.

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