What's better than SIP?

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In the market for a new business telephone system? When first considering a new technology for your business, there are a number of variables you need to consider.


ISDN (Integrated Service Digital Network) has been the main solution for businesses for many years when it comes to their communications. It is a set of digital communication standards for the transmission of voice & data. It consists of physical copper and fibre lines connected via telephone exchanges across the world.

Session Initiation Protocol (SIP) is the set of rules that allows you to initiate and terminate a communication session, whether it’s a voice call between two people using an IP link. SIP trunking is the service that allows you to put this protocol into use. Essentially, SIP and SIP trunks are an on-premise solution for a telephone system that will use virtual phone lines rather than physical wires; delivered over a broadband link.

SIP Trunking is fast becoming the best alternative to ISDN as it is cheaper on a per line basis, it offers flexibility and control over your phone numbers and quicker to install.

The first ISDN deadline is looming; you’ll no longer be able to purchase additional ISDN lines from September 2023.

It makes sense to review your options before any of this becomes an issue.

What are the benefits of SIP and SIP Trunking?

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

Our top five benefits for upgrading your phone system to SIP:

  • Cost-effective – For businesses that rely on ten or more channels of ISDN, switching to SIP can deliver immediate cost savings. SIP channel rentals and calls are typically up to 40% cheaper than traditional ISDNs, and businesses have the extra benefit of consolidating their voice and data services into one single line for further savings.
  • No physical lines - Because SIP trunking uses virtual lines rather than physical wires, businesses have greater control over their telephony infrastructure. This means having the power to consolidate voice and data over a single network, increase resilience, and put in place flexible inbound call routing (i.e. to mobiles or alternate office sites) so that calls are never missed.
  • Flexibility with phone numbers – SIP trunking enables you to reduce the number of PBX’s you need to maintain whilst maintain your existing phone number(s) regardless if you move office.
  • Scalability – SIP Trunks are perfect if you are growing (or even downsizing) and you want to retain your phone numbers. You are always in control because you can add lines, remove lines and split calls at any time.
  • High Quality – We proactively monitor and manage the quality of service across the entire network – it’s their underlying network quality that makes a real difference to SIP trunking. This means we are able to support both G.729 or G.711 codecs.
  • Business Continuity – Should your office need to be temporarily relocated, SIP trunking allows you to take your phone lines with you quickly and cost-effectively.

Make the Move from ISDN to SIP

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All well and good, you say.

We believe SIP is the way forward, especially due to the timely demise of ISDN. However, if you don't want phone lines, your other option is:

A Hosted Phone System

A Hosted Phone system is cloud-based which means you connect to it using an internet connection (IP technology) but effectively you are renting the system rather than purchasing your own dedicated system. It is a low-cost alternative to an IP or Hybrid PBX Phone System because you don’t have significant capital costs.

Limitations of a Hosted Phone System

As it is IP technology, this means you need a reliable internet connection since the phone system runs across the internet; the connection determines the voice quality. A good connection is paramount.

Is switching to SIP too much hassle?

Historically, replacing any system with a newer version can be time and resource intensive. There are also concerns that the time taken to realise any cost savings will not be worth the effort to change. So logically, many businesses wrongly assume that the switch to SIP trunking will be exactly the same. But the switch to SIP trunking is surprisingly easy.

The Business Case for SIP

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Is switching to SIP going to cost a lot?

Many people assume that new technology commands premium prices.

However with SIP trunking this is not the case and, for the majority of businesses, moving to a SIP trunking solution can help make significant cost-savings on telephony. With SIP you no longer need expensive ISDN lines so you’re not paying for lines you don’t use. SIP trunking can even be used alongside your existing ISDN connections to ensure a smooth transition. Your business may be able to realise additional cost-saving benefits like reduced or free calls to fixed landlines - depending on the SIP trunk provider and services used.

More common concerns regarding a potential switchover to SIP can be found here.

  • No new lines required – SIP trunks can use your existing broadband connection or can run over a dedicated voice circuit with attached service level agreements

  • As SIP is a direct replacement for ISDN, doing away with your existing ISDN lines will create spare bandwidth

  • No new PBX hardware – Your VoIP supplier should be able to modify your existing PBX system to make use of SIP trunks.

ISDN is dead, long live SIP!

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So, what's better than SIP?

And, should I choose to move to SIP Trunks?

If you don’t have ISDN in place, a hosted solution rather than SIP might be the best choice but that depends on the business and existing infrastructure.

For modern businesses, there is no longer a good reason to continue working with an ISDN-based telecommunications solution, especially bearing in mind the phasing out of ISDN from 2020 with a switch off date goal of 2025 (see Phasing out of ISDN blog.)

With the cost saving potential of SIP trunking, as well as its resilience and reliability, it is the common sense option for any organisation looking to be truly always on, and to provide customers with a first class experience.

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.

As always, if you need some advice on this topic, please don't hesitate to get in touch.

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Explore your Options

SIP is just one option for your phone system, there are others that might suit your business.

For bespoke advice, get in touch.

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