PSTN and ISDN switch-off

BT’s plan to decommission PSTN and ISDN lines will come into effect in 2025. To get prepared and to future-proof your infrastructure we’ve pulled together some key information you will need to know.


What is the PSTN and ISDN switch-off?

In November 2017, BT Openreach announced their timescales to switch off analogue and ISDN lines in 2025, effecting PSTN-based services and some broadband services. Since ISDN’s (Integrated service digital network) first iteration in the 90’s, digital demands on networks for organisations and homes have vastly changed, and the underlying technology needs to reflect and support modern requirements.


What services will be affected?

If your organisation is using analogue phone lines, ISDN or broadband services running over analogue lines, at the end of December 2025 these will be switched off and become end of life.

These include:

  • Analogue phone lines (including dial up devices, fax, modem, and PDQ machines)
  • ISDN (ISDN2 and ISND30)
  • Some broadband services (ADSL, Max, 2+ and FTTC circuits)


Key dates within the ISDN/PSTN switch-off

Organisations can get prepared for the 2025 switch-off, BT Openreach are taking a phased stop sell approach at individual city locations taking place between December 2020 to August 2023. When a location has met its stop sell deadline, then analogue and ISDN lines cannot be purchased or have additional features or changes made to existing services.


How to prepare for the ISDN/PSTN switch-off

If you’re still in contract with a line that is coming to end of life, like ISDN and PSTN, you need to start looking at your current technology ecosystem and get prepared following the tips below:

  • If you’re renewing contracts, look to move to a future-proofed solution
  • When you’re opening a new site location, consider IP based connectivity options
  • Assess your existing telephony options, if you’re using an on-site PBX with analogue or digital inbound/outbound lines review the marketplace for suitable VoIP (Voice over Internet Protocol) options including IP telephony and Microsoft Teams.


What Redcentric are doing

We’re working closely with BT Openreach and our customers to plan ahead for the ISDN/PSTN switch-off.

Our advice to customers renewing connectivity or telephone contracts over the next 3 years is to speak to Redcentric and review different connectivity options including SOGEA circuits, to get your organisation IP-ready and future-proofed. Additionally, we’re asking customers to consider further than their connectivity, but their internet connected devices as well (including alarm systems and PDQ machines etc) to ensure they are IP enabled for their new connectivity options.


Your different options to ISDN and PSTN

If you are still using a traditional on-premises PBX or using analogue telephone lines your organisation will need to be aware that these legacy service offerings are going to be no longer available and switched off.

For customers that are currently using ISDN services to connect their on-premises PBX platforms, we can provide an IP based alternative service. Redcentric’s SIP Trunking service is a VoIP (Voice over IP) based service that can be used to replace the legacy ISDN service. The service comes with a number of key benefit, as standard, including HD quality voice, network resilience and service flexibility above and beyond what can be delivered with the traditional ISDN offering.

For customers that are using analogue lines we can also look at migrating your services into a cloud hosted offering, again utilising VoIP to deliver an equivalent service capability.


If you have sites connected with traditional copper broadband, eg. Max, 2+ or FTTC, the broadband is delivered over an analogue phone-line, these will need to be replaced by FTTP or SoGEA before switch-off in a couple of years. Typically customers with small offices, large estates of small branch offices (e.g. retailers) and staff working from home use these cost-effective broadband connections. Redcentric still recommends dedicated Ethernet circuits for predictable performance and high availability at larger offices where the circuits carry a combination of voice, video, inter-site data and internet access.


Get in touch about the PSTN and ISDN switch-off

If you have any questions about the PSTN and ISDN switch-off our network and telephony specialists are happy to discuss your current infrastructure and help create a personalised timeline to get your ready in time.


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