The switch off of ISDN (Integrated Services Digital Network) and PSTN (Public Switched Telephone Network) will commence in 2025. This won’t come as a surprise to many people as BT first announced the plans back in 2015. The switch off will be the biggest change to the telecoms landscape for over 30 years and will significantly influence how we communicate. The reason for the switch-off is that the systems have become outdated. First introduced in the 1980s, and with the large amounts of traffic that come through them nowadays, they have come overwhelmed and unreliable. The change in direction from BT represents a universal move away from old fashioned communication methods in the UK. A more digital focused network is the future plans for BT. 

What does the IDSN and PSTN switch off mean for me?

Once the switch off happens, all services that utilise traditional copper phone lines will be affected. The 100-year-old Copper lines have been declining in use for a while now having become dated. As a result, this shouldn’t affect many companies. Once the switch off happens ISDN based systems in offices will become obsolete. As well as this PTSN supports other services such as FTTC (Fibre to the cabinet) broadband meaning companies may need to upgrade their broadband strategy. FTTC is the most common type of broadband in the UK, consisting of Fibre and Copper cables. BT deliver the service through existing copper telephone wires. By 2025 all organisations using PSTN and ISDN technology will need to switch to the latest IP technology. IP technologies are a set or specifications that standardise how things work in devices connected to the internet. BT are working hard to get this implemented by working on delivering a fully fibre network to the whole of the UK. 

What can I replace my ISDN and PSTN set ups with?

There are two potential replacements for companies to choose from these are VoIP and SIP. 

  • VoIP (Voice over Internet Protocol): A group of technologies which enables the delivery of multimedia and voice communications through IP networks. Instead of the data passing through PSTN copper lines, the public internet and/or private IP networks are used. VoIP assists with peer-to-peer calls through channels such as Teams for example. 
  • SIP (Session Initiation Protocol): A set of rules used in multimedia communications to manage and initiate data transfer between users. SIP creates, modifies, and terminates sessions with one or more parties in a network. SIP makes external calls and cross application possible in Teams. 

What steps can I take to prepare?  

  • Audit your telephony set up: What areas of your business use PSTN or ISDN? It is important to identify which areas of your business use what system, especially if you work on more than one site. By performing an audit of your infrastructure, you will get the bigger picture of what areas of your business use what systems. An audit will also allow you to consider whether your systems need to be adapted or completely replaced. 
  • Check your internet speed: Fast fibre broadband is the method of choice for most businesses. This is due to the volume of traffic it can cope with as well as its speed. Investing in the latest technology is essential to keep up with your competitors. The cost of fibre networks is becoming more competitive as demand grows. As a result, you can implement the network and benefit from better performance for nearly the same rate as your old set-up. 
  • Create a plan: Having a plan ready for 2025 when these changes come in can help you avoid any surprises. Make sure to be flexible with the plan though, don’t have everything set in stone as things may change from now until 2025. To accommodate this, make sure to keep up to date with developments and adapt your plan accordingly. 
  • Make use of the market: There are a range of providers who can support your organisation through this transition. Providers are useful in helping you select the best solution to your business’s unique requirements. The process of researching into providers can take some time. Therefore, it is a good idea to be proactive and start exploring the market as soon as you can, this will prevent any unnecessary business disruption. Selecting an experienced fibre network specialist can help you make informed decisions.  


It’s important for businesses to be aware of the planned switch offs of ISDN and PSTN. This is a major change that will benefit businesses in the long run due to the new systems being able to handle the large amounts of data, and work at a faster rate. It is important to prepare your business for the change. Having a plan in place can help you to avoid any surprises or barriers when the change does go through. The final result of these changes will be networks that can work faster than ever, leading to more efficiency in businesses. 

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