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What is SIP Trunking?

Posted by: Jo Love
Category: Blog, Hosted Phone System

With ISDN and analogue lines switching off in 2025, if you have not yet switched, now is the time to start planning. There are two main options – Cloud Telephony or an On-premises System. For businesses not moving to a Cloud Solution, they will need to move to an on-premise system that supports SIP Trunking. But what exactly is SIP? Here is a simple guide to explain more.

What is SIP?

SIP stands for Session Initiation Protocol, and is essentially a way to make and end connections for data and voice transfers over the internet. The ‘trunking’ element  refers to a virtual link between your PBX and the standard phone network (the PSTN), using an internet connection. A SIP trunk is effectively a virtual version of an analog phone line. Using SIP trunks, a SIP provider can connect one, two, or twenty channels to your PBX, allowing you to make local, long distance, and international calls over the Internet.

Business Continuity

SIP Trunking offers flexibility that is not available through traditional ISDN. Several possibilities can affect how resilient voice and data connections are, such as damage to lines, moving offices or being unable to redirect calls, all of which can damage a business. SIP Trunking minimises these problems.

Number Flexibility

Supports a business by allowing them to decide which number they want to display. SIP Trunking allows out-of-area geographic number ranges to be used, showing a business as local, despite being physically located elsewhere.

Save Money!

By discarding any unnecessary ISDN lines there will be an instant saving. In addition, SIP Trunking can typically save businesses up to 50% in line rental and up to 25% on calls. It also allows free calls between linked sites, even internationally and flexibility to reduce or increase lines depending on demand.

Contingency Plan

SIP Trunks come with a contingency plan. Often, things will happen beyond a business’s control. The system can automatically reroute calls, so there is no disruption for customers should an emergency occur.


To view more information on Cloud Telephony and On-Premises Systems click here: To discuss your requirements further, contact a member of the team on 01865 367111.


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