What is the big switch off? 


In 2015 BT Openreach announced that in 2025 both its PSTN and ISDN networks will be switch off in favour of IP voice services, with a gradual phase-out of the older systems happening across the next few years.


This is arguably the biggest change the telecoms industry has seen in the last 30 years and left many businesses wondering what to do next.


From September 2023 BT will stop the acceptance of new PSTN, ISDN2 and ISDN30 services. With the phase-out of ISDN already underway, now is the time for businesses to act.


In this article, we're revisiting the details of the switch-off and looking at what businesses need to be aware of when it comes to their current solutions and switching to new services.


direct case study graphics-03What is ISDN and PSTN? 


The Public Switched Telephone Network (PSTN) is what we all know as the landline telephone system. Set up originally for analogue voice communication. It works by sending analogue voice data over a circuit-switched phone line made of copper wires. Before the invention of digital transmission, PSTN handled voice calls and internet activity,


The Integrated Services Digital Network (ISDN) allows for the digital transmission of voice, video and other services simultaneously, using the traditional PSTN network. 


direct case study graphics-03Why are they being switched off? 


When you consider that ISDN and PSTN is essentially the same setup as the original phone lines of the 1800's it's no surprise it's not cut out for modern telecommunications.


BT recognises that IP telephony is the future of phone communications and with many businesses already having made the move to these new technologies the demand for legacy systems has decreased markedly over the last decade.


direct case study graphics-08Will it affect me? 


Ofcom reported that over two million businesses are still using ISDN connections. If you're one of these, then yes the switch off will affect you.


As the switch off is now underway and a gradual phasing out of these technologies is happening, now is a good time to look at the options available to you and assess the needs of your business.



direct case study graphics-04What options are available to me?


When moving to IP telephony there are a couple of options to choose from; SIP Trunking or a Hosted Phone System. Both of these enable you to make calls over the internet but differ slightly in set up and now they work.


Session Initiation Protocol (SIP) Trunking allows you to make calls through your on-site internet connection via your on-site PBX. SIP does away with the need for a physical phone line to make and receive calls. When making an outbound call, calls are routed from your PBX through your SIP Trunk over your internet connection. When receiving an inbound call these come via your SIP Trunk through the PBX to your phone.


A Hosted Phone System or Hosted PBX allows you to switch your telephony system to a completely cloud-based solution. Doing away with the need for any physical hardware to make and receive calls or manage your system. This is the perfect flexible solution for where remote working is required. Calls are made over VoIP (Voice over Internet Protocol) meaning all you need is an internet connection and you can call from anywhere.


direct case study graphics-07What do I need to consider?


Switching is straight forward but we recommend you consider the following before making a change. 


Your Existing System 


The number of users you currently have will have some impact on what the best solution for you is, along with any existing hardware you use.


If you're a small business such as a beauty salon or single-site retailer currently using one phone line then making the switch to a fully hosted solution is worth considering due to low costs, ease of management and scalability meaning it can grow as your business does.


If you are a larger business with an on-site PBX, you might want to keep your existing equipment and adapt it to make it suitable for after the switch-off. In that case, it’s important that if you’re considering a SIP solution that your PBX supports IP telephony, otherwise it might not be worth the cost of putting a new on-site system in place to be compatible. In that case, you might want to consider a hosted solution to avoid the high upfront costs. 


If you currently have an on-site PBX and are a larger business then keeping your existing equipment and adapting it for the switch-off may be an option you are considering. If you're considering a SIP solution it's important that your existing PBX can support IP telephony. If it doesn't a hosted solution is a more cost-effective solution.




If your new system is reliant on good connectivity speeds it's important that you have these in place. FTTP and SoGEA both provide exceptional levels of connectivity and guaranteed speeds making them ideal for modern telephony solutions for businesses of all sizes.


A reliable and robust connection is the backbone of your business, keeping you connected to your customers.


Number Porting 


When switching to a new system it's important to plan in your number porting particularly if you want to use existing numbers or location-specific phone numbers.

Depending on the amount of numbers you require porting this can take a few weeks so it's important you mention this to your provider so as to avoid any business disruption.




As we look to an increasingly remote work culture the flexibility of your system should be a consideration. The ability to easily transfer between locations and work seamlessly from home or wherever you choose is a key choice for many businesses.

A hosted phone system is the ideal choice for this. Providing the flexibility and agility needed for staff to use the phone system as normal from wherever they are working. 




Finally, the features you require on a phone system will also be something you need to consider.

You may have some new features you would like or existing ones you will still need. It's important to have a clear idea of what you're looking for and what features are available. Speak to your provider about these now, even if it's a feature you don't want just yet but will in the future. You don't want to choose a new solution and then find out some of the functionality you require is not available at a later date.





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