As the 2025 BT Switch Off looms ever closer; schools, academies and colleges are running out of time to prepare for the huge technological change. But how can these institutions fully begin to embrace the future of telephony? What VoIP solutions are best suited for schools? And what do they need to consider before making the migration? As one of the UK’s leading telecoms experts for the education sector, Clarion are here to help.

ISDN (Integrated Services Digital Network) offers voice and data over digital lines offering further services such as DDIs (direct dial in numbers) and Video Conferencing. And allows for multiple calls on different channels over the same line.

PSTN (Public Switched Telephone Network) is where analogue voice data travels across copper-based circuit-switched phone lines.

VoIP (Voice Over Internet Protocol) telephony allows you to manage calls, text, and video meetings using an internet connection rather than traditional telephone lines. Sometimes VoIP can be referred to as internet protocol, IP, telephony or cloud-hosted telephony.

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    BT Announced in 2015 that it will be switching off its PSTN and ISDN networks in 2025, transitioning fully to IP Voice services and phasing out older networks from 2023. This means that BT will cease accepting ISDN orders and that any Schools or Universities looking for new or increased voice services will have to look at IP-based options for their Phone Systems.

    Recent surveys suggest that many organisations are still not aware of the impending switch-off and the affects that it may have on their voice communications. If you use either PSTN or ISDN, we recommend looking into how you can migrate your own system onto an IP service.

    Fear not, there is a great deal of positivity. Firstly, using IP and Cloud Telephony has significant cost benefits, reducing or eradicating line and call costs. Provisioning is much quicker and more easily controllable and service can be accessed from anywhere on multiple devices, making your staff more agile and responsive. And there are a plethora of new features and functions available.


    PSTN and ISDN are legacy technologies that have been significantly upgraded over their life-time but have high maintenance and running costs. BT is looking to switch to a single IP Network, allowing for SIP and VoIP, which offer multiple benefits. Investment in PSTN and ISDN networks is ceasing while there is ongoing investment in the IP Network.


    SIP (Session Initiation Protocol) provides a phone line over a fibre internet connection.

    VoIP is cloud based telephony whereby your phone calls are sent over your internet connection and your phone system is moved ‘online’. You can access your system via multiple devices – deskphone, mobile and tablet and it offers many additional features such as call recording, voicemail to email and unified communication benefits.


    If you would like find out more about making the switch and the financial and operational benefits it can bring, contact our Team of expert Advisers on 0333 222 6633 or email us on

    Clarion Communication ManagementWHAT YOU NEED TO CONSIDER:

    Find out your current contractual obligations and think very carefully before renewing any ISDN or PSTN contracts.

    Look at the options available. Many newer Phone Systems support IP Telephony. If yours doesn’t, you will need to replace the system with a VoIP system or an IP-enabled on-premise PBX (phone system)

    When switching to SIP/VoIP based systems, you will need to make sure that you have sufficient bandwidth to deliver voice on top of the existing services that your office data line supports, otherwise you may experience poor voice quality or intermittent service.

    MAKE THE SWITCH TODAY – If you would like find out more about making the switch and the financial and operational benefits it can bring, contact our Team of expert Advisers on 0333 222 6633 or email us on

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    • London School of Science and Technology"The cost savings are just phenomenal and the Hosted System provided by Clarion is much easier to maintain, which means I have saved a significant amount of time, so I can spend my time on more strategic work that adds value to LSST."

      Waliul Islam London School of Science & Technology
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