Gamma SIP Trunks

SIP trunking from the UK’s leading provider*


* Illume Report Dec 2016

Gamma SIP Trunks

SIP trunks offer a more flexible and lower cost alternative to ISDN for inbound and outbound voice calls.

SIP trunking is a standards-based replacement for traditional ISDN. It connects your PBX to the PSTN via broadband, ethernet or private circuit into our national network.

Compared to ISDN our SIP trunking service is less costly per channel and more flexible in how and where geographic telephone numbers can be used. It’s also quicker to install and provision and, as standard, it delivers extremely robust business continuity.

The service can support connections ranging from two channels for small PBX-equipped businesses to an unlimited number of channels for large enterprises and contact centres.

Our SIP trunks work seamlessly with each of the leading IP PBX brands in the UK market. View the PBX vendors we work with.

Any business with a PBX can switch to our SIP trunking service and immediately benefit from a more flexible, less expensive and more resilient phone service.

Try our SIP vs ISDN cost calculator right now and see for yourself.

Don’t have a PBX? Why not consider our hosted phone system – Horizon.

The benefits of Gamma SIP Trunks

Save money on call costs and line rental

SIP delivers less costly, more reliable connectivity than ISDN over an IP connection. It can save up to 50% on line rentals and 25% or more on call costs.

Free internal calls and great features

Perfect for medium or large organisations with multiple sites, not only will you save on your line rental and call costs, but you’ll get free internal calls within your organisation and a whole host of great features.

Scale up and down when you want

SIP trunks are ideal if you are moving, upsizing or downsizing and want to keep your existing numbers. Scale up lines during busy periods and back down again afterwards. You can add lines, take them away, split calls at any time. You are always in control.

Built-in Business Continuity

SIP trunks can handle emergencies easily. They are inherently disaster recovery / business continuity ready, letting you reroute calls to an alternative location quickly and easily.

Compatible with Skype® for Business

Our SIP trunks are integration tested and approved to interoperate with Microsoft Skype® for Business, allowing you to directly connect to the platform to make external calls.

Want to know more? Contact us directly via the form below, or learn about working with one of our platinum partners

Introduction to Gamma SIP Trunks

Savings Saves up to 50% on line rentals and 25% on calls Expensive
Flexibility You’re in control. Add lines, take them away, split calls – it’s up to you Sorry, can’t do flexible
Control Choose how and where you want calls delivered. Make changes instantly Changes take months. At the mercy of suppliers
Future Well mapped out and ready for Voice/Data convergence Going nowhere fast
Contingency Handles emergencies with ease. Reroute calls to backup sites in seconds Hope nothing bad happens

From the past to the future: How to make the move from ISDN to SIP

Gamma’s team of telecoms experts offer practical advice on the main steps you can take to successfully migrate to SIP trunking, with insights on how the Open University succeeded in making the transition.

SIP Trunks are resilient and offer maximum security

How resilient is SIP trunking?

SIP trunking is now a mature service enjoyed by thousands of UK organisations and this alone is testimony to the reliability of SIP. For added reassurance while you switch to us, SIP trunking can even be used with existing ISDN connections to ensure the transition goes smoothly.

Owning our own national network means we can identify and fix issues faster, through our advanced monitoring and diagnostic tools. It’s a combination which has helped us win many major UK Fixed Line Network awards in recent years and one of the reasons more and more businesses are specifying Gamma SIP Trunks.

SIP trunks offer a more flexible means of communication

What’s the quality like?

From the moment we connect your SIP trunking service, you will enjoy all the reliability, resilience and quality that comes from working with the UK’s leading SIP trunk provider. We proactively monitor and manage quality of service across our entire network – it’s the underlying network quality that makes a real difference to SIP trunking. And as a consequence we are able to support both G.729 or G.711 codecs.

Gamma SIP Trunking support is 24/7

What happens if our internet or power goes down?

Should disaster happen, you can use SIP trunking to minimise disruption to your business. For example, if your London branch has to close in an emergency, and you need the calls routed to Manchester immediately, Gamma SIP Trunks can do this and at no extra charge to you.

Getting SIP trunks from Gamma in your business is a pain free process

What if we’re moving office?

Number flexibility with SIP trunking means that you can keep your existing number, even when moving out of the area, saving you costs on printed company literature and stationery whilst maintaining the perception that you still have a presence in the area you’ve moved from. We can easily transfer your old or existing numbers too so that you can avoid expensive Remote Call Forwarding (RCF) or call diversion charges.

With CLI flexibility you can also decide which number you want to display on a call by call basis – great for contact centres.

What if we want to add or remove some of our lines?

SIP trunks are valuable for businesses with seasonal voice capacity requirements where more lines can be quickly and easily implemented with no long term commitments, for example when running sales campaigns.

Conversely, if your business has multiple sites with ISDN connections into each, using Gamma SIP Trunks you can reduce the number of ISDN connections that your business requires and also reduce the maintenance costs on all of your various PBXs. At the remote sites you are left with just the cost of an IP connection and the handsets that you need and you can then pull all the telephony traffic back into your centralised PBX.

Gamma SIP Trunks have a resilient network throughout the UK

Does SIP work with other business networks and applications?

Gamma SIP Trunks are integration tested and approved to interoperate with Skype® for Business, allowing you to directly connect to the platform to make external calls.

We’re also a Janet-connected partner with an interconnect to provide voice services through Gamma SIP Trunks to the Janet community. Janet is the network dedicated to the needs of research and education in the UK, connecting institutions to each other, as well as to the rest of the world.

Some of the PBX vendors we work with

SIP solutions for your business

Number flexibility

Gamma SIP Trunks support business relocations by enabling a geographic number to be retained without call forwarding costs. This ensures business continuity and reduces the costs of having to change company stationery, listings and advertisements. As a leading UK communications provider we can also supply out-of-area geographic number ranges to make your organisation appear local, even without a physical presence.

Business-grade voice and internet convergence

With our SIP trunks delivered over Gamma Broadband or Gamma Ethernet, you’ll have a high-quality voice and data service from just one connection, making for significant cost savings.

Line and PBX estate rationalisation

For businesses with several locations, our SIP trunking service provides ISDN line rationalisation – the ideal way to reduce the number of PBXs requiring maintenance.

Business continuity

Businesses of all sizes need a business continuity plan for telephony. Combine our SIP trunks with our Inbound service and your callers will always get through. Set automated call plans or simply divert published numbers to backup locations or mobile devices – instantly and from anywhere.

Affordable resilience

If you’ve ever had to deal with a service outage you’ll know that speed of response is key. Our active/standby and load sharing designs are engineered to cope with any situation, so maintaining telephony uptime. Whether you need to keep your businesses running in an emergency without the high cost of call forwarding or simply need to balance call loadings between sites during peak, Gamma SIP Trunks will provide a business grade solution.

Free UK calls and fraud protection

Our SIP trunking service provides free call termination to UK fixed destinations, including 01, 02 and 03 number ranges. In addition, SIP provides free calls between connected sites, including international locations. CallGuard protection from unusual usage is also included free of charge with all of our SIP trunks.

Manage your entire inbound number estate through your SIP trunks

SIP Trunk Call Manager is a brand new solution to the market and encompasses all of the benefits of SIP combined with a unique web-based portal and app service that enables you to take full control of all aspects of your inbound calls.

PCI DSS compliance

The Payment Card Industry Data Security Standard (PCI DSS) is the proprietary information security standard defined by the major card companies to help combat fraud and protect consumer card data. Its members include Visa, MasterCard, American Express, Discover and JCB. PCI DSS applies to all organisations that store, process or transmit cardholder information, from any of these members’ cards. The type of annual assessment required varies according to “level”, which is defined according to the volume of payment transactions that are handled.

With 327 controls to consider in total, it is vital to ensure you have them all ticked. The effects of being non-compliant can be disastrous for a business due to the very real financial risk of opportunistic agent fraud and the associated reputational risks. Some of these include:

  • Compromising your customers’ payment data
  • Loss of customers, damage to your brand and reputation
  • Expensive lawsuits and insurance claims
  • Substantial payment card user and Government fines

We’ve partnered with Semafone to offer a flexible and cost-effective telephony solution to ensure your organisation remains compliant when taking Cardholder Not Present (CNP) payments over the phone. Combining our market leading Gamma SIP Trunks with Semafone’s award winning solution to protect your business from risk.

It’s quick to install, helps to improve agent productivity by reducing Average Handling Times and supports connections ranging from two channels to an unlimited number.

Protect your business from costly phone hacking and misuse

Hacking and abuse of business telephony is becoming as big as credit card fraud. With this type of abuse, the cost of the calls falls to your business. But with our CallGuard service your business is protected from such activity.

  • Your calls protected from unusual usage
  • Low cost for peace of mind knowing your calls are protected
  • Avoid any unwanted expensive bills
  • Can be applied to all of your existing numbers
  • Tailor your protection – opt numbers in and out as required

Flow Energy and Semafone turn up the heat for payment card frausters

How Gamma’s close partnership with Semafone enabled a secure payment system fully integrated into Flow Energy’s telephony platform

Flow Energy PCI solution

Quickfire SIP Q&A


PCI Compliance: Gamma SIP with Semafone


SIP vs ISDN cost calculator

See for yourself the savings that can be made when migrating over from legacy ISDN to SIP trunks. Try our simple ‘ready reckoner’ where we have factored in the current market prices for both ISDN and SIP; you just have to input your current ISDN capacity and we’ll calculate the potential savings with SIP… and if you like the result, let us know – we’d be happy to provide the detail.

Use our SIP Trunks calculator to figure out of SIP trunking is the right financial move for your business

Using ISDN30

(60 channels maximum)

Using ISDN2

(30 channels maximum)

Your data

Please Note:

  • Savings calculated in this model are indicative only and do not constitute any contractual obligation on behalf of Gamma.
  • The calculation includes Gamma’s Assured Broadband and Ethernet access as appropriate.
  • Other practical assumptions have been made in order to ensure the model reflects the most common environments.

Have you seen our other products?

SIP Trunk Call Manager provides you with all the benefits of Gamma SIP Trunks together with a centralised inbound call management service with many business features via an easy-to-use web portal and handy app.

Horizon is a cloud-based phone service that provides an extensive range of fixed and mobile telephony capabilities via an easy-to-use web portal.



Ensuring PCI DSS Compliance, with Gamma SIP Trunks and Semafone.



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