ISDN Phase Out: Five Alternative Options

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Updated: 25 May 2024

As the ISDN phase-out looms in the UK by 2025, businesses face a critical decision regarding their telecommunications infrastructure. This article presents 5 alternative options to navigate this transition effectively to ensure seamless communication and operational continuity.

From SIP Trunks to Hybrid, Hosted, and IP Phone Systems, each option offers distinct features, benefits, and considerations to meet the diverse needs of your business. Read on to explore the pros and cons of each solution to make an informed decision and safeguard your business's communication future.

Only have a few minutes? Here are the highlights:

  • All ISDN Phone Lines will be switched off by 2025 (or sooner.)
  • You have 5 alternative options; SIP, Hybrid Phone System, Hosted Phone System, IP Phone System and keeping your ISDN lines.
  • SIP is typically the best alternative because of flexibility, resilience and cost per line.
  • Hybrid Phone System means your can utilise your existing infrastructure but gain the benefits of IP technology.
  • Hosted Phone system is the most affordable alternative as everything is cloud based and you are effectively renting the phone system for your use.
  • IP Phone system means that you can utilise IP technology but purchase your own dedicated phone system which you have to choose where to host.
  • Keep your ISDN Lines – for now, it is risky but if you purchase your additional lines, now you can properly extend your phone system’s life for a few more years.

What is Replacing ISDN?

There are 5 options available to businesses to replace ISDN and PSTN:

Option 1 - SIP Trunks (SIP Lines)

SIP and SIP trunks offer an on-premise or hosted solution for a telephone system that will use virtual phone lines rather than physical wires.

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 is quicker to install.

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:

  • Save Money on call costs and line rental – IP connectivity costs less than ISDN so you’ll benefit from lower call costs; free internal calls between sites and free calls to UK local/national and mobiles. Typically, you are looking for saving of up to 50% on line rental and 25% or more on call costs.
  • Flexibility with phone numbers – SIP trunking enables you to reduce the number of PBX’s you need to maintain whilst retaining 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.

Option 2 - Hybrid Phone System

A Hybrid Phone System combines the different types of connection technology (ISDN, Analogue, Digital and IP) into a single modern and flexible phone system.

Most businesses opt for a Hybrid Phone System when they have ISDN, Analogue or Digital infrastructure but want the advantages that IP brings to the table.

Benefits of a Hybrid Phone System?

  • Hybrid Phone Systems can connect Analogue, Digital and IP extensions.
  • Hybrid Phone Systems can connect Analogue, ISDN and SIP lines.
  • Easy migration to an IP service without huge changes to your existing infrastructure and hardware.
  • Smooth migration for traditional phones to feature-rich IP phones.
  • Benefit from the cost-saving VoIP without needing to invest in an IP infrastructure and protecting your original infrastructure investment.
  • You have your own in-house communications service which you can distribute as you see fit. For example, your PBX would be hosted at Head Office and you can offer a cloud service to your other offices or remote workers; but only to your own staff.
  • Go Cloud and Save by deciding what features to stay on-premise, or offered hosted in the cloud to other locations.
  • Stay on top of Security by maintaining control over the network. Since the hosted service is still running off of your organization’s own hardware, the business can maintain control over the network, and therefore the network’s security.
  • Operate internationally, cheaper because if you have sites located across the world, long-distance call charges don’t apply.
  • Cost as you won’t need to pay a monthly subscription once you have paid for your hardware which means long term, you could save money.

Limitations of a Hybrid Phone System?

  • Unlike an IP Phone System, it cannot be put onto an industry standard server or be cloud-based; it needs its own dedicated PBX box
  • The PBX box needs to be on-premise which means you will need a secure environment for it to be located.
  • Cost because the initial capital outlay for the hardware can be significant, although it can be spread with a finance or leasing option.

Option 3 - Hosted Phone System

The 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.

A Hosted Phone system is a low-cost alternative to an IP / Hybrid Phone System because you don’t have significant upfront capital costs.

Benefits of a Hosted Phone System

  • Flexibility even if you are on the road (because you can make calls from your mobile using your phone system) or if you need to move to another office because your phone system will simply plug-in.
  • Scalability as adding and removing users is simple.
  • Variety of Features such as video conferencing, call routing, voicemail recording sent to email etc.
  • Automatic upgrades are distributed to all users.
  • Phone system Management is in your hands as you have access to change any settings such as opening times or we can do that for you.
  • Business continuity is covered with hosted telephony, as your calls can be instantly rerouted in the event of an outage – meaning you won’t be missing out on business.
  • Minimal set-up costs as there is no hardware except if you want a phone handset.
  • Low monthly cost per user.
  • No physical hardware to host on-site or remotely.
  • Speedy installation as it’s unlikely that you’ll need physical cabling because most places have internet connectivity.
  • Maintenance is included within your monthly subscription.

Limitations of a Hosted Phone System

  • There is only one caveat; it is IP technology which 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.

Option 4 - IP Phone System

An IP Phone System uses Internet Protocol (IP) technology and the handsets are connected via an Ethernet connection either on a Local Area Network (LAN) or a Wide Area Network (WAN.)

When you choose an IP Phone System, you purchase the phone system for your own use and you choose where to host it.

Benefits of an IP Phone System

  • You own the system.
  • You can choose where to host it, whether that be on your own server/ on-premise/ hosted in your own private cloud via a data centre; it gives you ownership on the maintenance of the system.
  • No long-term contracts (unless you purchase using finance.)
  • Flexibility even if you work remotely because you can make calls from your mobile using your phone system.
  • Scalability as adding and removing users is simple.
  • Variety of Features such as video conferencing, call routing, voicemail recording sent to email etc.
  • Phone system Management is in your hands as you have access to change any settings such as opening times.
  • Business continuity is covered as your calls can be instantly rerouted in the event of an outage – meaning you won’t be missing out on business.

Negatives of an IP Phone System

  • You will have up-front costs to purchase however, it can be financed or leased.
  • You will need to choose somewhere to host it, whether it be on-premise or hosted externally which may incur additional costs.
  • You will also need to be in charge of maintenance unless you outsource this aspect or it can be included in the lease.
  • You need to have a reliable Internet connection because if you lose internet, you lose access to your phone system (depending on where the system is located).
  • Your voice quality is determined by internet connection so again, you need to have a strong, reliable internet connection if you are using SIP Trunks or remote workers.)
  • Any upgrades are at your expense.

Option 5 – Keep your existing ISDN Lines

Yes, this is an option, at least until BT switch them off. It is a little riskier option but it is still an option.

You could purchase the additional lines that you think you may need to carry you through for the next few years and utilise one of the other options at a later date.

This could be a good option if you are struggling with budget for a new phone system solution or the one you want to purchase rather than a “make do”; it would certainly buy you the time you needed.

Do you really have until 2025?

At a recent partner event, we heard rumours that Openreach are, in effect, buying time to provide their own solution and as soon as they do, they will pull the rug out from under our feet and switch it off sooner to force our hand. This is why we’re recommending that all of our business customers switch over sooner rather than later.

Your Digital Switchover, Made Simple

If your business is ready to make the switch from ISDN, we can help. At BTT Comms, we provide a range of telecom solutions, making your ISDN to digital switchover simple. Get in touch with us to learn more.

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​Help with Migration

Would you like help choosing the right option for your business?

From planning, auditing, installing, testing to making the system "live", we can help. We have migrated hundreds of businesses across from ISDN to Hosted phone systems, IP Phone Systems, SIP lines or Hybrid phone systems.

Use our experience, get in touch.

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