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The difference between ISDN and VoIP ISDN vs VoIP 2019

Apr 18, 2019

For businesses looking at implementing a new phone system, one of the most frequent questions we get asked, is ‘What is the difference between ISDN and VoIP?’. In this post we’re going to address the differences, and the pros and cons of each.

ISDN stands for Integrated Service Digital Network, and it’s been the go-to communication solution for businesses for a long time. It's made up of a series of physical lines connected by telephone exchanges globally.

VoIP stands for Voice over Internet Protocol, and rather than physical wires and telephone exchanges, it uses the internet to route call data.

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Are you thinking of migrating from ISDN to VoIP? We're highly experienced in business communications with over 15 years in the industry, working with companies of all sizes from small businesses to multi-site organisations.

For more information on VoIP, download our free guide The Small Business' Guide to VoIP: A complete communications service for your business >>

Small business guide to VoIP cover
Download: small business guide to Voip

The pros and cons of ISDN


  • ISDN is incredibly reliable, and has been the go-to solution for many years
  • High quality voice calls


  • It's not easy to change a system by expanding or contracting to meet business needs of growth or restructuring
  • As there is a physical system to implement, moving premises can be a challenge involving high costs and downtime
  • There are large costs associated with the equipment for an ISDN system, whether buying or leasing
  • If ISDN circuit becomes unavailable, there's difficulty associated with keeping calls in service
  • ISDN is being phased out in 2025

 Pros and cons of VoIP


  • VoIP systems are easily scalable,adding and removing users takes minutes and is low cost
  • There's no physical installation so it's easy to move office without downtime
  • It's flexible – with hosted VoIP you can route calls making it possible to work from anywhere. This is especially useful in a disaster recovery situation, if there is a power cut or internet failure, calls can be transferred to mobiles
  • Free internal calls
  • It's possible to choose phone numbers for any geographical location
  • Low-cost equipment: often VoIP providers include handsets within their pricing packages

5 Ways to Reduce Your Small Business Phone Bill with VoIP >>


  • VoIP is reliant on broadband quality, so for businesses struggling with connection issues this would need to be addressed before implementation of VoIP.
So which is best?

A glance over the list above makes VoIP seem like a no-brainer, especially considering there is already a date set for ISDN being phased out in 2025. With VoIP being so dependent on the quality of broadband available to a business, if it isn’t up-to-scratch and isn’t being made so, there is still a place for ISDN.

If you would like some more information about choosing the right telephone system for your business, please get in touch.




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