When most businesses think about the ISDN and PSTN Switch Off in January 2027, they immediately picture their office phone systems. It’s natural – telephony is the most visible part of the change. But what many SMEs across South London don’t realise is that a surprising number of everyday devices still rely on those same copper lines.
These “hidden dependencies” often sit quietly in the background, working away reliably for years – until the day they stop. When the Switch Off happens, those analogue connections will cease to function, potentially halting operations overnight.
The impact can range from missed payments to security failures, depending on which systems are affected. For small and medium-sized businesses, identifying and addressing these dependencies early is critical to avoid costly downtime.
Common devices still running on PSTN/ISDN
Our team at Palace Prime IT has carried out numerous audits across South London, and one theme is consistent – very few businesses have a complete picture of how many devices still depend on ISDN or PSTN.
Here are the most common examples we find:
- Alarm systems – Many fire and intruder alarms still use analogue lines to send alerts to monitoring centres. If these fail, you may not be covered by insurance and could even breach building safety regulations.
- Payment terminals – Older card machines frequently connect through PSTN lines. When those go offline, your business can’t process payments, leading to immediate revenue loss.
- Lifts and emergency call lines – These are critical safety features in many buildings. If their communication line is still analogue, you could be left non-compliant with health and safety laws.
- Fax machines – Still surprisingly common in sectors like healthcare, legal, and local government. While outdated, they often carry sensitive information that must remain accessible.
- CCTV and modem systems – Legacy surveillance systems or modems sometimes rely on PSTN for remote monitoring or data transfer.
Each of these represents a single point of potential failure once copper services are switched off.
The hidden costs of overlooking dependencies
Failing to identify analogue devices before the Switch Off can lead to serious operational, financial, and compliance risks. Let’s look at what’s at stake:
- Business disruption – If your alarm, card machine, or safety system stops working unexpectedly, the cost of lost trade or downtime can be significant.
- Financial loss – Even a few hours of payment failures could translate into thousands in missed revenue.
- Compliance exposure – Healthcare providers, charities, and financial institutions risk breaching GDPR or PCI standards if systems fail or data becomes inaccessible.
- Insurance issues – Insurers may reject claims if your alarm or safety system isn’t operational or up to current standards.
- Reputation damage – Customers quickly lose confidence if your systems go down or their payments fail.
What makes these risks particularly dangerous is that many business owners simply don’t realise these dependencies exist until they fail.
How to identify your hidden dependencies
The good news is that uncovering PSTN or ISDN-connected devices is relatively straightforward with a structured approach. Here’s how to start:
1. Conduct a full site audit
Walk through every part of your premises and list all devices that use a phone line. Include alarm systems, lifts, faxes, and card machines.
2. Check service contracts
Many third-party service providers (security, payments, facilities) still rely on PSTN. Review agreements and confirm their connectivity methods.
3. Speak to your staff
Long-serving employees often know where older systems are located or how they connect.
4. Consult your IT partner
A professional network audit can quickly identify active PSTN/ISDN lines and connected devices using diagnostic tools.
The benefits of acting early
Addressing hidden dependencies ahead of the Jan 2027 deadline doesn’t just eliminate risk – it can also unlock significant business benefits:
- Greater reliability and security – Modern digital systems are more stable and harder to compromise.
- Improved customer experience – Faster, digital payment terminals and reliable communications enhance service quality.
- Simplified vendor management – Consolidating analogue services into one digital solution streamlines billing and support.
- Future-proofing your infrastructure – Moving to all-digital systems ensures compatibility with future technology and compliance frameworks.
Proactive preparation gives SMEs more time to plan, budget, and phase upgrades without unnecessary pressure.
Palace Prime IT: Helping you find what’s hidden
At Palace Prime IT, we specialise in helping SMEs uncover these overlooked systems through our FREE PSTN/ISDN Audit. Our audit identifies every device, service, and line still dependent on analogue connectivity, then provides a clear plan to transition safely to digital alternatives.
We also review your broader IT and connectivity setup to ensure your network is secure, resilient, and ready for future growth.
Don’t wait until systems fail
The ISDN switch-off isn’t just about phones – it’s about every connected device that keeps your business running. Missing even one dependency could mean downtime, lost income, or compliance headaches.
Book your Free PSTN/ISDN Audit with Palace Prime IT today and uncover hidden risks before they cause disruption.