The BT SwitchOff May Be Four Years Away But the Time to Act is Now

The BT SwitchOff May Be Four Years Away But the Time to Act is Now

The great switch-off is coming. By 31st December 2025, BT and Openreach will have deactivated all analogue and third-gen digital 'static' phone services (ISDN-PSTN) in the United Kingdom. No new ISDN packages, lines, or hubs will be sold or installed from September 2021. ISDN and PSTN renewals, and replacements will also cease from September 2023.

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What Will The Switch-Off Mean?

Ageing ISDN landlines, ISDN-PBX hubs, unpowered PSTN phones, and local switches using older protocols will all be rendered useless without upgrades. Existing SIP and VoIP systems will need no alterations, meaning, most business landlines should be fine. However, an estimated five million ISDN-only business and ISDN-brokered lines are still active in the UK. If your telecoms reseller business is one of the many still selling soon-to-be obsolete protocols, it's crucial to get your vital network replacements and modifications completed ahead of time.

Why Is BT Switching Off The ISDN Protocol?

BT added the Integrated Services Digital Network (ISDN) to the UK's original copper-wire analogue phone network (PSTN) in 1986. The ISDN-PSTN system used early kilobit-capable modems to deliver then cutting-edge services such as faxes, multi-conversation transmission, and dial-up Internet to clients.

The arrival of ISDN greatly extended the useable lifespan of the UK's analogue-only GPO network. Unfortunately, development of ISDN-PSTN froze solid in the Ceefax era. The invention of fibre-optic broadband, Voice Over Internet Protocol (VoIP) calls, SIP, virtual exchanges, digital phone automation, and ADSL modulation have all combined to eclipse ISDN in speed, usability, and functionality.

BT cites cutting their overall running costs, migrating customers to better tech, a changing world, commonplace fibre-optic lines, falling subscriptions, and improving basic quality of service as their main reasons for discontinuing ISDN-PSTN provision.

What Should I Do To Prepare In 2021?

As a reseller, if you've already migrated your services to SIP, VoIP-only (local or remote), or Internet-only tech - relax! It's the responsibility of your telecoms provider and broker to make sure their hardware is fully compatible with the online-only switchover. If you're still running managed-ISDN trunking hardware, you have several upgrade options to offer your customers between now and 2023.

You can either:

  • Install SIP-PBX trunking on an existing phone and computer network
  • Install a hybrid VoIP-ISDN router
  • Offer remote VoIP PBX management
  • Offer remote SIP-PBX management with VoIP (via Supported IT)
  • Install a local VoIP-Only Exchange Network as the PBX


SIP Trunking 'virtualises' your customer’s private business exchange (PBX) using server software. The virtual exchange then processes incoming and outgoing calls via dedicated software and a remote connection to your telecoms provider.

VoIP PBX systems can either be virtualised, be integrated to OS shell packages (e.g. Microsoft Teams) or built into a standalone physical system. Alternatively, you can also pay a third-party company to broker fully supported telecoms services to your business. It's up to you how you do your upgrades - so long as they're all Internet friendly (i.e. VoIP and SIP). You can add advanced features to both such as call routing, automated systems, and queues to enhance the strength and appeal of your offering.

Anything Else?

You'll need to arrange for any unique ISDN-PSTN UK phone numbers your customers want to keep after 2024 to migrate across to their new PBX. Your telecoms provider can talk you through how to set this in motion.

Don't worry about line replacement, either. ISDN-era lines will still be able to handle standard speed internet-protocol (IP) phone traffic. Additionally, all modem phoneline Internet traffic (legacy 56K and ADSL broadband) will remain unaffected. You should also make sure any PSTN emergency access phones can stay independently powered for one hour. Due to the VoIP switchover, this rule will be made a UK legal requirement from 2024.

Cloud PBX Migration From Sysconfig

Sysconfig specialises in scalable, robust SIP-PBX routing for white label telecoms resellers alongside our own, personalised, affordable telecoms packages. Get in touch today. We'll supply you with everything you need to migrate to the post-ISDN era.

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Tags: Hosted Telephony, SIP Trunking