Mark Castle

Last month BT announced that by 2025 they intend to have all customers migrated to an IP network before switching off their legacy PSTN and ISDN networks. Until now there has been no firm date for the switch off despite much deliberation within the industry.


The announcement from BT is the first step towards their vision of a single IP core network replacing all legacy networks and platforms. But what does that mean for the businesses that depend on the 3.2 million ISDN channels still being used in the UK?

The alternative – Voice over IP (VoIP)

First of all there’s no need to panic, BT have given themselves a decade to migrate customers off the ISDN network, so your phone lines aren’t going to just stop working next week. However, we think this announcement is a great opportunity for businesses to get ahead and unlock the benefits of VoIP by switching to SIP Trunking now.

The use of SIP Trunks to deliver VoIP is now the recognised alternative to traditional ISDN and PSTN lines, offering a great opportunity for businesses to unlock a number of key benefits including cost savings, mobility, scalability and more functionality.

In a VoIP solution, your traditional ISDN or PSTN lines – which form the expensive ‘line rental’ part of your phone bill – are replaced with SIP trunks; allowing the concurrent running of voice and data over your internet connection.

Benefits of SIP and VoIP:

  • Quicker and easier to provision new lines and port numbers
  • With voice and data on the same line, you’ll half line rental costs and save around 25% on call costs too
  • VoIP gives you flexibility, your phone number is tied to an IP address, not a geographic location
  • It’s a voice solution that has the ability to change with your business; scale lines up or down, quickly and easily to suit your businesses current requirements
  • SIP enables a comprehensive Disaster Recovery solution compared to ISDN which can only be forwarded to a single number

What to do now…

As you can see migrating to SIP and VoIP offers businesses a great many benefits. We would advise businesses to start thinking about migrating sooner rather than later, but there are two important questions every business should consider:

1. Can your internet connectivity handle VoIP?

The first question you need to ask yourself is ‘Can your office internet handle VoIP, in addition to everything else you do online?’ Because, without sufficient resources, the advantages of VoIP are lost—you’ll experience poor call quality and intermittent service.

You will need a baseline of 5Mbps down and 2Mbps up as the bare minimum for a smaller office of about 5-7 users on VoIP. You can check your current speeds using an online speed test.

2. What kind of phone system do you have?

Your phone system and handsets will also need to support VoIP.

If you have already invested in an IP enabled system, then you should have no problems using your existing hardware as long as it is compatible with the provider you are considering.

If your current phone system is not compatible you have 2 options – upgrade to an IP-enabled on-premise PBX or replace your phone system with a hosted telephony offering.

Unify (formerly Siemens Enterprise) offer a range of IP-enabled phone systems packed with customisable features including full Unified Communications for solutions to suit any size business. As an accredited partner, we are currently able to save you up to 50% on the price of an IP phone system.

The other option is a hosted telephony offering providing an extensive range of fixed and mobile telephony capabilities via an easy-to-use web portal, suitable for any size business. From a cost management perspective, this is a great option as it is priced on a per user/per month basis.

We’re keen to help businesses begin the process of migration and unlocking the benefits of VoIP now. If you would like more information about making the move to SIP don’t hesitate to get in touch.

We are happy to help, just get in touch.

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