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SIP Trunk

What is a SIP Trunk?

A SIP trunk, or Session Initiation Protocol trunk, is a virtual communication link that enables the delivery of voice and other unified communications services over the internet. It serves as a modern alternative to traditional telephone lines, allowing businesses to make and receive calls using the Internet Protocol (IP). SIP trunks facilitate the transmission of voice, video, and other multimedia sessions between an organisation’s private branch exchange (PBX) and the service provider’s network.

By adopting SIP trunks, businesses can modernise their communication infrastructure, achieve cost savings, and enjoy the benefits of enhanced flexibility and scalability. 

The business benefits of SIP Trunks

Session Initiation Protocol (SIP)

SIP, a signalling protocol, is used to initiate, manage, modify, and terminate real-time sessions that involve video, voice, messaging, and other communications applications and services.

Internet Telephony Service Provider (ITSP)

SIP trunks are typically provided by Internet Telephony Service Providers. These providers deliver the SIP trunk service, connecting the organisation’s PBX to the public switched telephone network (PSTN) or other communication networks.

IP Network Connectivity

SIP trunks use internet connectivity to establish communication links, eliminating the need for traditional physical phone lines. This enables more efficient and cost-effective communication.


SIP trunks can support multiple communication sessions concurrently, allowing for simultaneous inbound and outbound calls over a single trunk.

Flexibility and Scalability

One of the key advantages of SIP trunks is their flexibility. Organisations can easily scale up or down by adding or removing SIP trunks based on their communication needs.

Geographical Flexibility

SIP trunks enable geographical flexibility, allowing businesses to establish virtual local presence in different regions without the need for physical infrastructure in each location.

Cost Efficiency

SIP trunks often offer cost savings compared to traditional phone lines, especially for businesses with high call volumes. They eliminate the need for dedicated physical lines and associated maintenance costs.

Rich Communication Features

SIP trunks support a wide range of communication features, including voice calls, video calls, instant messaging, and more. They also integrate seamlessly with modern unified communications solutions.

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How Opus' telecoms consultants can assist you

Opus are the leading telecoms reseller in the UK. We have a dedicated consultancy team who are technology agnostic in their consultative approach to unified communications, design, deployment and ongoing telecoms support. 

Our specialist telecoms services include but are not limited to:

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