Gamma SIP Trunks

4Sight SIP Trunks

The cost-effective and flexible alternative to ISDN

As a Gamma Gold Partner, 4Sight provides SIP Services that offers a highly-flexible alternative to ISDN. With our SIP Trunks you get a service that is more robust and cost-effective than ISDN. Our service can support connections ranging from two channels for businesses with small PBXs, with no limit on the number of channels that can be supported for large enterprises and contact centres.

Compared to ISDN, SIP Trunks are cheaper on a per-channel basis and more flexible in terms of what telephone numbers you can have and the locations in which you can have them. In addition, they are quicker to install and offer a robust business continuity service that ensures your business never loses any calls.

Find out more, download our SIP Brochure

Benefits Snapshot

The benefits of moving to SIP trunking can transform business communications and the process of switching is simple and safe, even for the most risk averse of businesses.



IP connectivity costs less than ISDN with lower call costs, free internal calls between extensions and offices and lower line rental costs for multi-sites.


Additional SIP trunks can be added in less than a minute! Number flexibility ensures that if you are changing office completely, you can keep your existing numbers.


SIP trunking comes with in-built resilience features that ensure that if something goes awry, business continuity can be maintained.

Easy to Set up

SIP requires less physical infrastructure, implementation can be seamless and in most cases the impact on productivity is minimal, if at all.

Get in touch to see how we can help your business transition from ISDN to SIP

Why Choose 4Sight?

Our SIP trunks connect your site directly into the Gamma network via an IP connection to carry and terminate your inbound and outbound voice calls across the public telephone network. They are compatible with all the leading IP PBX brands in the UK market, giving you peace of mind that your PBX hardware works with the network service.

Switching to SIP Trunks with us provides many benefits including:

Free Local, National and UK Mobile Calls*

Fixed charge of £ PCM per Channel

Free analysis of your line and billing information

Free Project Migration Management and Setup

Free Setup

Competitive International Rates

SIP Trunk Call Manager - putting you in control with powerful business continuity and future-rich centralised call control, together with all the benefits from your existing SIP Trunks.

SIP Trunk Call Manager provides you with all the benefits of 4Sight Gamma SIP Trunks together with feature-rich, centralised call control. This includes our market-leading call bundles and the only fraud management tool that financially indemnifies you against loss.

If you are looking for a solution that offers powerful business continuity and the ability to fully manage your entire number estate directly via your SIP trunks, SIP Trunk Call Manager is the ideal solution.

Gamma Sip Trunk Call Manager

*This is a channel inclusive deal that offers inclusive UK calls to Local, National, Uk Mobile and 03xx Numbers. There are terms that apply to this offer that require a minimum term of 3 years commitment. There are some restrictions when migrating existing Gamma clients to 4Sight Gamma services which we will advise if applicable. There is also a fair usage policy that will apply and this will be advised as part of our line audit.

**This a special reserved rate for the clients that have their Mitel support contracts with 4Sight or are in the process of moving their support to 4Sight. It is a time restricted offer designed to bring support and line provision under one roof where we can offer a more effective converged service wrap and fault resolution. This is a new billing customer exclusive offer that has offer timescale limitations due to commercial constraints.