Here’s everything you need to know about the PSTN/ISDN switch off

Long before the distinctive chime of iPhone’s iMessage, digital communication had an equally infamous soundtrack. You probably recall the sound of the dial-up modem, which connected servers via public telephone networks. It was a — noisy — icon of another era of technology. We’ll soon be saying farewell to another area of communication history — the public switched telephone network (PSTN). If your business’ phone calls are handled by a private automatic branch exchange (PABX) system, it’s probably connected to a telephone network using an integrated services digital network (ISDN). This is how you make phone calls, video calls, transmit data and other network services over the circuits of the traditional PSTN. But by 2027, BT is planning to switch off the ISDN network and the PSTN, as it moves to an entirely IP-based model of voice communication.

Why are we switching the PSTN off?

The PSTN dates back to 1875, and refers to a telecommunications network that allows subscribers at different sites to communicate by voice. It forms a large part of the UK’s telecoms infrastructure, and its functions include connecting voice calls using analogue voice data and supporting digital services such as the ISDN. Broadband products also rely on the service to work. The PSTN is deemed a legacy system. The equipment used to run it is aging and challenging to maintain, as many of the components used to build the infrastructure are becoming obsolete. The PSTN will be switched off in January 2027 and any services that are reliant on the network, including the ISDN, will no longer be operational. All ISDN/PSTN voice services will go to complete end-of-sale from September 2023, starting with a series of trial zones in the coming months. From now until 2027, infrastructure will be built to transfer all current systems over to an ALL-IP configuration. Those currently relying on the PSTN, and the ISDN, will have until 2027 to organise an alternative solution. However, with the range of alternatives already available, businesses will benefit from considering other options ahead of the switch off.

How do I prepare for the PSTN switch off?

To help prepare your business for the switch off, it’s important to know the modern telecoms solutions that can replace the ISDN/PSTN. With the right technology in place, you can future proof your business while improving current process performance. A voice over internet protocol (VoIP) system is a growing trend among businesses. VoIP allows you to make and receive calls through your existing internet, rather than the PSTN or an ISDN network. Not only will VoIP help businesses overcome the upcoming PSTN/ ISDN obsolescence, but it can also bring a number of other business benefits. When your calls are handled by a PABX system, you need to factor ongoing maintenance costs of on-premise hardware, storage and power requirements into your investment. With VoIP, all the system hardware is located offsite in a data centre, meaning there’s no direct maintenance costs. What’s more, because VoIP works independently from local power, network or systems availability, you don’t have to worry about business downtime should an unexpected event occur. If a flood, fire or power failure makes your office inaccessible, you can still work from any internet connection or mobile device. As more businesses choose to work flexibly, from home or anywhere else in the world, having business communications available on multiple devices will be key to remaining competitive. Other alternatives include Single Order Generic Ethernet Access (SOGEA). This offers similar connectivity to a fibre to the cabinet service, but without the need for an underlying PSTN product. SOGEA has wide availability across the UK, with coverage in over 28 million premises, and can deliver speeds of up to 80 Megabits per second (Mbps). At Crystaline, we work closely with our customers to recommend the best telecommunications service for their needs. Switching from a system we’ve relied on for so long can seem daunting, but our expert team is able to recommend the correct telephony and connectivity services for you. Like the dial-up internet tone, the PSTN and its associated systems will soon become a part of technology history. Before we say a final goodbye to the network, it’s time to start thinking about the alternative options that will keep your business switched on.


Want to learn more about ISDN/PSTN alternatives? Get in touch with our team today.