what is a sip trunk

      What Is A SIP Trunk? Understanding The Advantages Over PSTN

      The IT world can be full of acronyms. When discussing telephony, have you ever wondered what a SIP trunk is? Here we explain SIP trunking, how it works and outline the advantages of SIP vs PSTN and ISDN.

      What is a SIP trunk?

      SIP stands for Session Initiation Protocol. The technology enables you to use a data connection to make calls. It’s how VoIP (voice over IP) telephony and calls are achieved.

      It’s becoming extremely popular for organisations, especially those with a significant call volume who may have multiple calls ongoing simultaneously.

      How does it work?

      A SIP trunk works in the same way as an analogue phone line, but virtually. A provider can use a SIP trunk to connect one, two or even 50 channels to a PBX telephone system, such as 3CX as well as solutions such as Microsoft Teams Calling. Trunking provides businesses with the capability to make local calls, long-distance calls as well as international calls, all via the internet.

      SIP vs PSTN: What are the benefits of SIP trunking?

      Saving Costs

      One of the most significant advantages of SIP vs PTSN is that it can save organisations money. When using traditional telephony over PSTN or ISDN lines, you end up paying for capacity that doesn’t get used. A SIP trunk can be tailored to suit the usage needs of your organisation, and all calls and line rentals are significantly less pricey. This is a huge advantage if you have high call volumes.

      Geographic Flexibility

      Traditional phone services can make growing your business in new locations, or even just expanding your current one, very costly. With traditional phone services, you’d need to buy PSTNs and PRIs. In contrast, SIP consolidates your data and voice services into a single network, so all your users, no matter their location, can also be combined.


      In 2025, BT are switching off all ISDN and PSTN lines across the country. At this point, VoIP phones will need to become the norm as all calls will be sent across the internet instead. For more information on the switch-off, we have prepared a blog detailing the key points.

      Unified Communications

      SIP trunks are a great way for organisations to unify all of their communication methods, including calls, texts, conferencing, emails and instant messaging. And, as they’re virtual, getting them set up and all channels unified is a quick and efficient process.

      Akita is a leading provider of internet phone solutions. For more about SIP trunks and VoIP telephony please, get in touch:

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