SIP (Session Initiation Protocol) trunking is the protocol used for VoIP (Voice over IP) which is used to carry in/outbound calls on a PBX (Private Branch Exchange).

In a nut shell the call is carried over the internet via IP instead of over copper wires using analogue signals and is able to router to all telephone subscribers both fixed and mobile across the globe. For your company to take advantage of this new and ever growing technology you will need a VOIP telephone system such as 3CX which is a low cost scalable solution and SIP compatible handsets such as Yealink, Grandstream and Snom.


Some advantages of VOIP

VOIP can integrate with your network – while some businesses choose to separate the VoIP traffic on its own network/VLAN this isn’t necessarily required. You can simple have your handsets plug into the same switch and be on the same subnet as your corporate network. Furthermore you can use a PoE (power over Ethernet) switch with PoE enabled handsets which will have the power to the handset provided via the Ethernet cable and thus not require a power brick for the handsets which keeps things neat and tidy.

With a VoIP system you are not tied down to a particular geographical location which means if you want to move office it’s as simple as picking up your PBX and handsets and plugging them back in the other end (assuming you have an internet connection provided). There is no need to lease with your telephone provider like before as the SIP trunks will simple re-connect once access to the internet is restore.


You can have external extensions which means you could have a phone registered at your home which will ring as if it was in the office. People can simply dial your internal extension to contact you and the phone will ring as per any groups it may be a member of as if it was in the office. This gives great flexibility for work from home individuals.

Using SIP trunks over ISDN30 is a lot cheaper on line rental and air time charges. A typical company with 20 handsets on an ISDN might typically save £700 to £1000 or more per quarter on their telephone bill which really makes the switch to VoIP a no brainer.

There is a large firm in London who can assist your business with the leap to VoIP. Sphere IT who are an IT Company in London are experts in the industry and at very little cost migrate you away from your old dying expensive phone system. With speed of internet connections getting faster and faster there is no reason as to why anyone should be paying for ISDN and most business will make the money back in the first year.