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SIP Trunking

SIP Trunking

Multiple numbers, multiple benefits

You can’t be in several places at once - but with SIP Trunks, your business can. Allowing you to channel multiple numbers from different exchanges into one office, you can have London, Glasgow and Bristol numbers all answered in Birmingham.

And that’s just one of the advantages of moving your telephone lines to Spitfire SIP Trunking. You’ll also benefit from lower call costs, exceptional business call quality ensured by Voice Approved data circuits, and flexible cost effective business continuity options.

Business SIP Trunks – High Reliability UK SIP Trunking


From £4 per SIP Trunk per month

If you need the flexibility and control of your own phone system – and either already have a phone system or are happy to buy, run and manage the phone system yourself – SIP Trunks are the right choice for you.



Trust Spitfire for superior SIP Trunking

  • Business SIP Trunks from just £4 per month
  • Ensured call quality using Spitfire Ethernet or Voice Approved SDSLM
  • Keep your existing phone number
  • Service implemented on our own secure and resilient core network infrastructure
  • Flexible options for providing backup to ISDN lines
  • Award-winning support
  • Converged Voice & Data available using Fibre Ethernet

Cost Comparison Examples – Spitfire SIP trunks vs. BT ISDN30e


10 BT ISDN30e channels & 100 DDIs – Spitfire SIP Trunks are 63% less expensive:

  • BT ISDN30e with 10 channels and 100 DDIs plus CLIP – £212.31 per month
  • Spitfire SIP SDSLM 1:1 with 10 SIP trunks and 100 DDIs plus CLIP – £77.50 per month
  • Saving over £134 per month, with ensured ISDN30e equivalent call quality


30 BT ISDN30e channels & 200 DDIs – Spitfire SIP Trunks are 52% less expensive:

  • BT ISDN30e with 30 channels & 200 DDIs plus CLIP – £602.06 per month
  • Spitfire 20Mb FTTC Ethernet, 30 SIP trunks & 200 DDIs plus CLIP – £290 per month
  • Saving over £312 per month, with ensured ISDN30e equivalent call quality


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More About SIP Trunking


There are a three key elements to delivering ISDN30e quality SIP Trunking for businesses: A SIP compatible Phone System or Gateway, an Internet connection designed for Voice, and the ability to terminate SIP calls onto the standard phone network.


Spitfire are one of the few SIP Trunking providers able to offer a complete end-to-end SIP Trunking service.


Indeed, Spitfire SIP Trunks are a genuine alternative to ISDN30e – with us providing a managed service covering the IP connectivity, SIP Trunks and number management – exactly the same as with ISDN30e. We take responsibility from day one for delivering a robust, business-class SIP Trunking solution.


What’s more, we also provide SIP Trunks through another leading UK Wholesale Provider, Gamma Telecom. We use these wholesale SIP Trunks in situations where a customer wishes to use a non-Spitfire circuit, or where Spitfire SIP Trunks are not tested with a particular phone system or application. Effectively having access to two SIP networks allows you to have two separate SIP Trunk services all managed by Spitfire. These non-Spitfire SIP Trunks, provided by Gamma Telecom, are sometimes referred to as Off-Net SIP Trunks.


See a more detailed explanation of SIP Trunks here



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Spitfire SIP Trunks – more benefits and savings


  • Spitfire runs its own core network infrastructure to implement our SIP Trunk service.
  • We can provide telephone numbers from geographic areas all over the UK and route them to your SIP service, enabling you to have a virtual office anywhere.
  • Our SIP trunking has flexible options for providing backup to ISDN lines and vice-versa , and further options to forwarding to mobiles/home numbers.
  • Spitfire can provide all the components necessary to connect your telephone system via SIP Trunks including quality IP access and gateways, including on site engineering.
  • We take responsibility for delivering your SIP Trunking solution from the day you place your order, including the circuit, numbering, back up and engineering.
  • With our dedicated test facility we have tested our service with a wide range of manufacturers SIP devices.


Ready to make the switch to SIP Trunking? Make the call. Our expert consultants are available on 0800 319 6363.

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