SIP Trunks

Most UK business telephone systems still connect via ISDN lines.

In 2019, it was announced that the Integrated Service Digital Network (ISDN) and Public Switched Telephone Network (PSTN) would be switched off in December 2025.

With 6 years until that date, there was no major rush from businesses to change. Fast forward 4 years, and the more forward-thinking businesses are now starting to make their contingency plans – because as of 2023 – customers will no longer be able to purchase new lines, with the complete switch off taking place in 2025.

Prepare your business for the BT ISDN & PTSN switch off | Anglia Tech (

SIP Trunks are the alternative. Standing for Session Initiation Protocol, SIP directs calls over your internet connection, reducing or removing the need for ISDN circuits. This means a number of benefits:

  • Cheaper connectivity. Internet connectivity prices have come right down recently, whilst ISDN prices have stayed broadly unchanged. So if you rent ISDN lines, you’re probably paying more than you need to.
  • Cheaper call rates. ISDN calls are very often more expensive than SIP calls, which place lower demands on the call carrier.
  • Only pay for what you need. With ISDN2 you buy two channels at a time. With ISDN30 you buy a minimum of eight channels. SIP can provide any number of channels, in increments of one, only limited by your bandwidth.
  • No additional hardware costs. With ISDN, if you need to add a circuit, you may need an extra ISDN line card for your phone system. The cost (if your system can accommodate it) can set you back a substantial amount. Not so with SIP.
  • Disaster Recovery ready. SIP Trunking can increase your phone system’s resilience, by eliminating its dependency on individual circuits.

Convinced?  We are. At Anglia Technology we have been using SIP trunks within our own operations for over 10 years, and we would be delighted to advise you on whether your current system can be adapted to become SIP compatible. Alternatively, our new Yeastar P Series offer will open the door to this and a whole host of advanced business benefits.

Contact Our Team

Contact Anglia Technology to discuss your VOIP telephone system requirements and we’ll guide you to a solution that suits you and your business.