While the benefits are clear, the transition brings many questions. What does the switch-off mean for businesses? How will it impact services like fax machines, alarm systems, and landlines? And, most importantly, what steps should you take to ensure a smooth transition?
In this blog post, we’ll answer the most frequently asked questions about the ISDN/PSTN switch-off, providing you with practical insights and guidance to navigate this major change.
1. What is the ISDN/PSTN switch-off?
2. Why is the ISDN/PSTN being switched off?
ISDN and PSTN infrastructure is outdated, costly to maintain, and lacks the flexibility and scalability of newer technologies. Switching to IP-based systems improves efficiency, scalability, and compatibility with modern communication tools.
3. When is the switch-off happening?
In the UK, the switch-off is scheduled to take place by the end of January 2027. Initially a target was set of December 2025 but this was extended to ‘allow any issues that arise with transferring vulnerable customers to be ironed out’. The extension shouldn’t be seen as a reason for businesses to keep legacy connections running for an additional year.
4. How will the switch-off impact businesses?
Businesses relying on ISDN/PSTN services for telephony, fax, alarm systems, door entry systems, CCTV or payment terminals will need to upgrade to IP-based solutions before January 2027 to avoid service disruption.
5. What do I need to do to prepare for the switch-off?
The first step in preparing for the switch-off is to audit all of your telecom infrastructure and work out which systems are reliant on legacy ISDN/PSTN and therefore will be impacted by the switch-off.
Once you have identified which systems will need to be updated to an IP based solution you can start to look at the options available to you, including VoIP and SIP Trunks and Lines. Here at CloudConnX we have a realm of experience in helping fellow businesses to navigate the switch-off so please get in touch if we can help.
6. What will replace ISDN/PSTN?
ISDN and PSTN are being replaced by modern, IP-based communication technologies, including Voice over Internet Protocol (VoIP) and Session initiation protocol (SIP) trunking.
7. Will I lose my phone number?
In the majority of cases, you shouldn’t lose your existing number(s) as they can be ported across onto the IP based system.
8. What happens to legacy systems like fax machines and alarms?
If you have a piece of equipment or system, such as an alarm system or fax machine, that you would like to continue using after the switch off Analogue Telephone Adapters (ATA’s) can be programmed to enable you to continue using a piece of equipment that functions over analogue networks on a digital network. Some providers (including CloudConnX) are able to offer premium routers with 2 ports on the back that can be programmed in the same way, enabling the continuation of legacy equipment. We recommend switching to IP ready equipment where possible but there are ways to enable legacy devices to function on IP networks.
Many new IP offerings provide email to fax and fax to email functionality, removing the need for a physical fax machine.
9. How much will the transition cost?
Costs associated with preparing for the switch-off vary depending on the size of your organisation, the complexity of your existing infrastructure, and the solutions you choose. While there may be upfront costs, many businesses benefit from long-term savings with IP-based systems.
10. Are there benefits to switching to IP-based systems?
Yes, there are many benefits that IP systems can offer to businesses. IP-based systems offer a range of benefits including lower operating costs, enhanced scalability and flexibility, improved call quality, advanced features (including video conferencing) and easier integration with other platforms and technologies.
11. What happens if I don’t make the switch?
After the switch-off, ISDN/PSTN services will no longer be supported, leading to service interruptions or total loss of communication. Transitioning early ensures continuity of service and avoids last-minute disruptions.
12. Will my internet connection affect VoIP call quality?
Yes, a stable and high-speed internet connection is essential for optimal VoIP performance. Poor internet quality can lead to issues like call drops, delays, or reduced audio clarity.
13. Are IP-based systems secure?
IP-based systems are secure, but they require proper security measures, such as firewalls, encryption, and regular updates, to protect against potential cyber threats like hacking or eavesdropping. Ask your telephony provider for more information about their security measures.
14. How long does the transition to IP systems take?
The timescale for transition to IP systems depends on the complexity of your setup. A simple migration might take just a few days, whilst larger systems may take a couple of months or more for full deployment and testing.
15. Will my business experience downtime during the switch?
Minimal downtime may occur during the transition, but careful planning and coordination with your provider can help mitigate interruptions.
16. How can I minimise disruption when my business makes the switch to IP systems?
Speak to your provider about disruption concerns and schedule the switch for non-peak hours. Test new systems in a controlled environment before full deployment. Work with experienced IT professionals to ensure a seamless switchover. Working with a business specific provider can help to minimise the disruption caused when making the switch as business-specific providers are geared towards minimising disruption for business customers, and are focused solely on business rather than residential customers.
17. Can I use my existing phones with IP-based systems?
It is possible to use an Analogue Telephone Adapter (ATA) to connect traditional phones to IP networks or upgrade your PBX system to support SIP trunking. A business specific provider should be able to advise you on the suitability of your existing phones.
18. Will the switch-off impact residential customers?
Yes, residential customers using PSTN or ISDN for broadband and/or telephony will need to migrate to an IP-based solution. If you haven’t already heard from your provider, you can ask them about their plans to transition your services to IP-based solutions ahead of the switch-off.
19. What happens during a power outage with IP systems?
Unlike traditional phone lines, IP systems require power to function. You may need a backup power source to ensure continuity in the event of a power outage if your phone lines are crucial to the daily operation of your business. Soe providers, including CloudConnX are able to provide mobile apps to ensure continuity during these periods.
20. How does the switch-off affect voicemail and call forwarding features?
Modern IP-based systems retain and often enhance these features, offering options like voicemail-to-email and advanced call routing.
The ISDN/PSTN switch-off is more than just a technical upgrade—it's a pivotal shift across the UK (and many other countries) to adopt more flexible, and scalable communication technologies. While the transition may seem daunting at first, proper planning, informed decision-making, and collaboration with your telecom provider can ensure a smooth journey.
By understanding how the switch-off impacts your current systems and exploring modern alternatives like VoIP, SIP trunking, and cloud-based communication platforms, you’ll not only maintain business continuity but also unlock new opportunities for growth and efficiency.
If you would like further information, you can download our full guide to the switch off here. If you have further questions or need personalised advice, please reach out to a member of the team on 0330 122 0550 or email