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SIP Trunks

Focus Group's UK SIP trunks offer a solution to BT Openreach’s legacy voice service withdrawal which can help you optimise your data connectivity whilst retaining all your existing services.

Upgrade your ISDN today! Call us now on 0330 024 2222.

Brighton, Sussex, UK SIP trunks - Focus Group
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Get in touch

Discuss your needs with our specialised team on 0330 024 2222.

A cost-effective alternative to legacy telephony that provides flexibility and continuity

SIP trunking is rapidly replacing ISDN services and Focus partners with the UK's leading SIP trunks providers. Our SIP trunks connect your site directly into the Focus Group network via an IP connection to carry and terminate your inbound and outbound voice calls across the public telephone network.

Focus Group's UK SIP Trunks provide a highly-flexible alternative to ISDN and are compatible with all the leading IP PBX brands in the UK market, giving you peace of mind that your PBX hardware works with the network service.

Call us today for a tailored quote on 0330 024 2222 or email isdnisdead@focusgroup.co.uk

Focus' UK SIP Trunks are suitable for any size of business from small businesses to large enterprises and government organisations that currently have a PBX, unified communications solution or key system.


UK SIP trunk solutions from Focus Group

What is Focus SIP Trunks?

SIP trunking is a standards-based replacement for traditional ISDN in the UK. It connects your PBX to the PSTN via broadband, ethernet or private circuit into our national network.

Compared to ISDN our SIP trunking service is less costly per channel and more flexible in how and where geographic telephone numbers can be used in the UK. It's also quicker to install and provision and delivers extremely robust business continuity as standard.

The service can support connections ranging from two channels for small PBX-equipped businesses to an unlimited number of channels for large enterprises and contact centres.

Focus Group's SIP trunks work seamlessly with each of the leading IP PBX brands in the UK market. We work with the following PBX vendors:





Any business with a PBX can switch to our SIP trunking service and immediately benefit from a more flexible, less expensive and more resilient phone service.

Don't have a PBX? Why not consider our hosted phone system - Horizon.


Why upgrade?

  • Save money on call costs and line rental
    Including free calls between your users, the ability to optimise your existing data bandwidth and create a far more resilient solution than traditional telephony can provide without the overheads.
  • Great additional features
    Including the ability to manage your Inbound number estate, advanced statistics and reporting, one click business continuity, the ability to route calls in different ways depending on the time of day or week along with many other ways to optimise your call handling.
  • Scale up and down when you want
    SIP trunks are ideal if you are moving, upsizing or downsizing and want to keep your existing numbers. Scale up lines during busy periods and back down again afterwards. You are always in control.
  • Built-in Business Continuity
    SIP trunks can handle emergencies easily. They are inherently disaster recovery / business continuity ready, letting you reroute calls to an alternative location quickly and easily. We can split calls across multiple sites, have active and standby solutions and also automatically fail these over in a business continuity scenario.
  • Compatible with Skype® for Business and Microsoft Teams
    Our SIP trunks are integration tested and approved to interoperate with Microsoft Skype® for Business, allowing you to directly connect to the platform to make external calls. We can also help utilise your Microsoft licencing and provide connectivity to the PSTN using the Teams application.
  • Serve International Offices Focus Group's SIP providers can provide in country SIP services with local numbering and breakout, call us for further details if you have an International requirement.


Why choose SIP Trunks?



UK SIP trunking solutions | Focus Group

How resilient is SIP trunking?

Focus Group SIP trunking is now a mature service used successfully by thousands of UK organisations, which is testimony to the reliability of SIP. For added reassurance when you switch to Focus Group, SIP trunking can be used alongside existing ISDN connections to ensure the transition goes smoothly.

By partnering with the UK's leading SIP trunk provider their national network means we can identify and fix issues faster, through our advanced monitoring and diagnostic tools. It's a combination which has helped us win many major UK Fixed Line Network awards in recent years and one of the reasons more and more businesses are specifying SIP Trunks.

UK SIP trunk telecoms | Focus Group

What happens if our internet or power goes down?

Should disaster happen, you can use SIP trunking to minimise disruption to your business. For example, if your London branch has to close in an emergency, and you need the calls routed to Brighton immediately, SIP Trunks can do this and at no extra charge to you.

SIP trunking and ISDN | Focus Group

What if we want to add or remove some of our lines?

SIP trunks are valuable for UK businesses with seasonal voice capacity requirements where more lines can be quickly and easily implemented with no long term commitments, for example when running sales campaigns.

Conversely, if your business has multiple sites with ISDN connections into each, using Focus Group SIP Trunks you can reduce the number of ISDN connections that your business requires and also reduce the maintenance costs on all of your various PBXs. At the remote sites you are left with just the cost of an IP connection and the handsets that you need and you can then pull all the telephony traffic back into your centralised PBX, either at a key premise or within a data centre environment.

UK's leading SIP trunk providers | Focus Group

What's the quality like?

From the moment we connect your SIP trunking service, you will enjoy all the reliability, resilience and quality that comes from working with the UK's leading SIP trunk provider. Focus Group proactively monitor and manage quality of service across our entire network - it's the underlying network quality that makes a real difference to SIP trunking. And as a consequence we are able to support both G.729 or G.711 codecs.

Moving offices with SIP trunks | Focus Group

What if we're moving office?

Number flexibility with SIP trunking means that you can keep your existing number, even when moving out of the area. You can host multiple number ranges and area codes as your business requires. Focus Group can easily transfer your old or existing numbers too so your customers can keep in touch on the numbers they have always contacted you on.

With CLI flexibility you can also decide which number you want to display on a call by call basis - great for contact centres.

UK SIP trunk networks and applications | Focus Group

Does SIP work with other business networks and applications?

SIP Trunks are integration tested and approved to interoperate with Skype® for Business, allowing you to directly connect to the platform to make external calls. We can also integrate with Microsoft Teams.

Focus Group are also a Janet-connected partner with an interconnect to provide voice services through SIP Trunks to the Janet community. Janet is the network dedicated to the needs of research and education in the UK, connecting institutions to each other, as well as to the rest of the world.

Focus Horizon

Why not upgrade to a hosted solution?

Horizon VoIP is a hosted business telephone service that resides in the cloud rather than your office. It provides an extensive range of fixed and mobile telephony capabilities accessed through an easy-to-use web portal. The service allows you, the administrator, to easily manage your environment whilst enabling your employees to maximise their productivity.

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