If the COVID pandemic taught us anything, it is that effective communication is critical for schools to remain operational. The telecoms industry has entered a period of significant change in recent years, as we transition away from traditional phoneline-based telephone systems and toward a world where VoIP is the default. 

Liam Bonthron, Head of DB Comms, part of the Zenergi Family explains what you can do now to start preparing for this significant change.

Liam also ran a webinar on this subject which you can view by clicking here. 

Countdown to the Digital Switch Off

We will all be unable to purchase new or additional ISDN and PSTN telephone lines from September 2023. Then, in 2025, all Analogue and Digital Lines will be completely decommissioned and replaced with IP Telephony, which means we will make and receive calls over the internet. IP Telephony is not a new concept; it has been tried and tested. Personally, I’ve been using IP Telephony in some form for the last ten years, and I haven’t even had a phone on my desk for the last six.

This Digital Switch Off in 2025 will greatly benefit schools, allowing them to streamline services, reduce costs, and improve the solution they provide their users.

There are several IP Telephony options available, but three are the most common.

Like-for-Like Replacement:

SIP Trunking can act as a like-for-like replacement for ISDN. When you have an onsite phone system you can connect SIP to the system rather than the current ISDN Phone lines. If you are considering this option, you will need to evaluate the compatibility in the current system as well as the availability of a compatible broadband service. Why is this? SIP Trunking will use the internet to make and receive calls, therefore, you would need to make sure the bandwidth/stability of the line is compatible. 

Hosted Phone System:

In simple terms, a hosted telephone system sits in a network data centre, known as the cloud. This removes the phone system infrastructure from your office. A hosted telephone system is easily managed via a secure, web-based portal, therefore, you can make changes and additions remotely as you see fit. Alongside this, staff will be able to make and receive calls using a combination of handsets from Analogue, DECT, or IP. In addition to the physical handset, most hosted systems have an App that can be used via your PC or mobile device, meaning you can truly work from anywhere. Just like SIP, users make calls through their data connection rather than a physical line, so, the same considerations need to be made regarding connectivity.

Direct Routing:

Albeit a relatively new solution, direct routing is built on the trusted SIP network, rather than the SIP connecting to a phone system. It involves connecting to an application, the most common of which is Microsoft Teams. Adding the Telephone License to Teams might be a logical next step for some of its 75 million daily users since they are already using the app daily.

Prepare for the digital switch off now

Adopting an IP Telephony solution now prepares your school for the 2025 digital switch off while also allowing you to gain an operational advantage.

Zenergi’s DB Comms division is dedicated to making your ISDN transition as smooth as possible. We can assist you in reaping the benefits of incorporating technology into your school’s fixed and remote working strategies, transforming the way you communicate by combining voice, video, chat, collaboration, and contact centre functionality into a single platform.


ISDN –  ISDN, or Integrated Services Digital Network, is a circuit-switched telephone network system that uses a digital line to transmit both data and voice.

SIP – SIP, a well-known internet telephony protocol, serves as the foundation for all types of internet communication sessions, which are typically delivered via SIP trunks, which are a direct replacement for ISDN.

IP – IP is an abbreviation for “Internet Protocol,” which is a set of rules that governs the format of data sent over the internet or a local network.

VoIP – VoIP, also referred to as voice over internet protocol, is a technology that enables online voice communication.

Contact us at bepositive@zenergi.co.uk for any guidance regarding how the “ISDN Digital Switch Off” will affect your school and how to get ready for the change right now.

This blog was written by Liam Bonthron, Head of DB Comms, part of the Zenergi Family




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