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The end is nigh for PSTN and ISDN in the UK and Europe

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The end is nigh for PSTN and ISDN in the UK and Europe

Written by Modality Newsroom on 30, May 2019

Did you know that ISDN is on its way out? Head of Consulting Iain Smith explains what this means for your business and how to prepare for the future of telephony.

Iain-Smith_Circle-Image5 years and counting…

UK and European telecoms providers have announced that by 2025 PSTN (Public Switched Telephone Network) and ISDN (Integrated Services Digital Network) will be switched off. But what does this mean for your business?

Understanding PSTN and ISDN

PSTN is a network of connected copper cables owned by the likes of BT. These cables run the length and breadth of the United Kingdom to transport analogue voice and data into most offices. Each office will have  a copper cable known as a bearer. These are connected to a green cabinet at the end of a street, which is then connected to a BT exchange building. From here the analogue voice traffic hits the ageing super highway of the PSTN network. This technology is now very old. Remember Alexander Bell, the inventor of the telephone system? He created and patented PSTN circuitry in the 1800s.

Of course, there have been updates along the way. In the 1950s, pulses dialling was created and could be sent down the PSTN connection. By the 1970s, basic data was being transported. Finally, in the 1980s the digital element of the PSTN circuits were created. These are called ISDN - the de facto circuit used by most companies worldwide today.


What does 5 years and counting really mean?

In the UK, BT has announced that ISDN and copper connectivity will be no more from 2025, which means the circuitry backbone of the network will cease to exist at this point. All the meshed copper cabling used today will be decommissioned, and voice and data traffic will be migrated over to the latest technology in telephony communications - SIP (Session Initiation Protocol: signalling protocol used for initiating, maintaining and terminating real-time sessions that include voice, video and messaging applications).


What does this mean for ISDN in 2019?

From 2020, new ISDN connections will no longer be available to your business. If you are using a plethora of ISDN connections today, by 2020 you will be forced to take up SIP connections for any new locations or offices. This means you will need to cater for a mixed estate of ageing and modern telephone technologies.


Some key questions to ask yourself are:

  • Does your PBX (Private Branch Exchange) i.e. your current telephone system have the ability to accept a SIP connection?
  • Is your hardware up-to-date?
  • Will you need a new daughter board for the circuit connectivity?


ISDN video infographic



Do you need to act now?

Absolutely. As with all new technologies, particularly SIP connectivity, there is planning, networking and cabling needed. SIP runs over an online network connection, making pre-planning and bandwidth testing essential before you order any SIP trunks from a SIP carrier.


What are the benefits of switching to SIP?

SIP is more cost effective. The earlier you can make the transition, the more money you will save. You will also benefit from:

  • High availability of the SIP telephone circuit with multi destination failover routing.
  • The ability to centralise DDI ranges into one core datacentre or split them between datacentres (even in different countries).
  • Faster, internet-based telephony via a dedicated MPLS link.
  • Encrypted calls.
  • Secure back-up in case of power outages.
  • Lower line rental costs per channel.


How can Modality Systems help?

Having worked in the telephony industry for over 15 years in a business with 300 years’ worth of combined experience (some of my colleagues have been working with SIP trunking since the start of its existence in 1999!), we are brilliantly placed to help companies migrate from ISDN to SIP. This includes PBX scenarios and businesses using Microsoft Skype for Business or Microsoft Teams.

Within the Modality Systems consulting team, we have integrated into all PBX vendors and newer Microsoft technologies for ISDN, SIP and old DASS2 connections. With our deep experience in telephony, we can guide and provide your business with an effective migration path.


Iain Smith | Head of Consulting

Modality Systems

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Looking to move your business from ISDN to SIP? Find out how our migration service will remove the hassle.

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