BT ISDN Switch Off, the Full ISDN Switch off Guide for Businesses

Learn more about this landmark telephony event that’s due to take place in 2025.

All You Need To Know About the BT ISDN Switch Off

As our lives change and our requirements become greater and more immediate, the need for legacy technology, and outdated systems, to be replaced, in order to keep up with our demands, has become more vital than ever. From the technology we use in our personal lives, be it smartphones, wearable technology such as watches, or even household appliances that use the internet to offer customers new features, right the way through to businesses who use networks, reliable internet connections, and a host of other modern technology to function on a daily basis.

This shift and change are happening everywhere but, in particular, it is going to become prominent across the telephone networks of the UK. Known as the ‘BT ISDN Switch Off’, this huge shift in the way people make phone calls will happen in 2025 and it is vital that, for business continuity, companies learn about it and make the necessary changes now to avoid having to play catch-up in a few years.

This switch shouldn’t be seen as a bad thing, for businesses in particular this switch from traditional phone systems to new internet-based telephone lines is going to be transformative and ensure that outdated technologies are no longer needed. As a result, they’ll be able to enjoy the benefits of high-speed communication that utilises broadband and takes advantage of the flexibility it offers teams and users.

Here at Prestige Telecom Group, we are driven to ensure that, over the next few years, the millions of businesses that operate in the UK are made aware of these new VoIP-style systems and the urgent need for them to work with business telecoms experts now, so they are ready for when the big switch off happens in 2025.

BT ISDN switch off guide for businesses

This drive has led us to create this page on our site which is a comprehensive look at this topic and aims to cover absolutely everything you could ever wish to know about the 2025 ISDN Switch Off, also known as the ‘BT Switch Off’ or ‘Copper Turn Off’. On this page, which is split into sections, you’ll find all sorts of information, from the history of ISDNs, right the way through to the reasons behind it, and what you need to do now to make a success of the ISDN lines switch. Once you’ve gone through this content, you’ll feel confident about what to do next which, we hope, will be to pick up the phone to our expert sales team here at Prestige Telecom Group to talk about our business telecom solutions, business mobile broadband internet connections, virtual landlines, and VoIP systems – all of which can help you migrate to a fully-hosted cloud system. To learn more, get in touch with us today on 03303 200 222, or email us at to discover how we can help.


The Only ISDN Switch Off Summary You'll Need To Read...

This page goes into incredible detail about the ISDN switch off which, as we mentioned, is due to take place in 2025. From specific dates that you need to keep in your diary, right the way through to a history of ISDNs, how we came to use them, and why we need to replace them – we really will cover it all. But, to kick things off we thought we’d provide you with a summary of the ISDN switch off so that you have all the important information needed immediately to hand. As always, if you have more questions, feel free to get in touch with us and we’ll happily talk you through this pretty significant telephony event. Now though, let’s take a look at the plans.

The great BT Switch Off, as it is colloquially called, began way back in 2015 when this national institution made an announcement that they would be effectively turning off ISDN (Integrated Service Digital Network) and PSTN (Public Switched Telephone Network) lines and switching to digital lines, or internet lines. This means that from 2025 onwards, people won’t make calls using these analogue lines and instead switch networks to new IP technology, and SIP technologies, that are faster, clearer, and come with a host of new features.

Why Are BT Switching Off ISDN, Anyway?

The reason behind the switch off is simple, but fundamental to the smooth running of the nation’s telephony network. Essentially, it is happening because technology has become such a huge part of everyone’s lives that the traditional copper network that is used to make and receive phone calls can’t keep up with faster, slicker alternatives. ISDN and PSTN copper lines were introduced way back in 1986. To date, that is over three decades ago and, while regular maintenance and upgrades to the physical lines have been made by BT, the pace at which IP phone systems have become more developed, popular, and cost-effective has meant that no matter how much telephone system maintenance occurs, this outdated landline technology could never have kept up. The announcement in 2015 was BT acknowledging this and pledging to increase its investment in replacement products, such as VoIP services, which run on fibre optic connections and provide a greater experience for users, especially businesses.

Who Is Set To Benefit From The Switch Off?

From a selfish point of view, BT now has an opportunity to save money over time because they only have to manage one platform that has advanced functionalities and will be used way into the future, which will help keep costs down as systems become more popular, and cheaper. They also don’t have to spend vast sums on maintenance or deal with the hassle of travelling the country fixing old landlines that aren’t up to scratch. For companies, this switch presents an opportunity to become a genuinely remote organisation that isn’t tied down to an on-premise telephony network. A key problem with these traditional phone lines is that they are fixed to certain areas meaning people had to use them to make phone calls. Now though, because of the explosion in internet usage, people no longer have to rely on physical phone lines and can use business mobiles to make mobile calls from wherever they are in the world. The switch means they can take advantage of VoIP, virtual landlines, and other fibre products that allow them to make telephone calls.

How Prestige Telecom Group's Solutions For Businesses Can Help

So, there is a relatively brief summary of the events that have taken place, however, for a more in-depth view, be sure to check out the rest of the page. Now, while knowing about the events is one thing, the other element that is just as important, if not more, is knowing what your business must do to avoid this switch becoming a problem.

After reading this page, the next logical step is to get in touch with Prestige Telecom Group. Operating in the business telecom world, offering business telecom solutions to companies of all sizes, we are ideally suited to offer you a hassle-free, no-nonsense approach that will ensure that your future business plans are secure when the switch off arrives. Our business connectivity experts can get under the skin of your business and discover which bespoke solutions would work best for you before going ahead and installing a selection of new services that mean you can make and receive phone calls, and access super-fast business broadband, no matter where you are. What follows is a brief description of our main services, those that relate most heavily to the 2025 BT Switch Off.


Standing for Voice over Internet Protocol, VoIP will soon be the default way people and businesses communicate. This type of phone system frees you from an on-premise phone system that restricts your ability to work outside of the same four walls. Rather than speaking to someone over a standard phone line, on public telephone networks, VoIP allows you to communicate verbally with people over an internet connection, on a cloud network. Virtual phone lines that are held over an internet protocol (IP) lead to clearer call quality regardless of geography, as well as a range of other features such as automatic call routing, and brand-specific on-hold music.

Virtual Landline

Another great solution, that frees you from the office, a virtual landline is a business telecoms solution that makes it look, to customers, like you have a normal landline. However, this ‘office number’, once dialled, automatically redirects to the mobile phone or internet-connected device of a person in the business who has been assigned to answer it. The great thing about a virtual landline is that it can be answered from anywhere in the world while still appearing as if you have an office number. With a virtual landline, you can rest easy knowing that your customers only ever have to dial, and/or remember, one number the next time they need to contact your business.

Business Mobiles

Supplying teams with business mobiles ensure they can always be reached by you or their colleagues no matter where they are during business hours. As we head toward the big switch in 2025, the reliance on business mobiles will become even greater as businesses move away from traditional channels of communication, such as regular landlines, to more disparate forms of communication – devices that can be found in your pocket, not your desk. It’s important to ensure business mobiles are prevalent so that employees aren’t relying on their own devices which may be old and feature out-of-date technology. Business mobiles ensure people are taking advantage of the latest tech and remaining professional when on the phone.

A Full History Of ISDN

So, we’ve established the main points surrounding the ISDN switch off but, because this is a comprehensive guide, we want to go beyond the basics and take a deep dive into this topic so that, as promised at the top of the page, this guide ends up covering “absolutely everything you could ever wish to know” about the big 2025 switch off! Therefore, this second section aims to look back at how the ISDN (standing for Integrated Services Digital Network) came to be across the world. We’ll examine when this communication network first came to the UK, how it helped companies with business communications and phone calls in general, and we’ll also look at what organisation runs it, as well as a wide range of other subtopics. 

To learn more, please read on and discover how we came to rely on ISDNs to make voice calls, or, if you wish to hear about how our cost-effective solutions can help you take advantage of VoIP features, for instance, so you’re ready for the big 2025 migration to digital transmission, then feel free to get in touch. Our team, based down south, as we mentioned, would be delighted to chat with you if you’re looking to the future, and are ready to harness new phone systems and technology. Get in touch with us today on 03303 200 222, or email us at

What Is An ISDN?

The Integrated Digital Services Network (ISDN) is a system of telephone lines that helps create networks of communication that deliver data transmissions and high-quality voice calls. While many people think that ISDNs relate solely to traditional phone lines, they are used in a variety of other applications, for example, their continuous data transmission capabilities make them perfect for EPOS (Electric Point of Sale) machines, and intelligent tills. ISDNs were brought in to help people move away from traditional analogue lines (referred to as landlines by most people) to more sophisticated digital lines that sped up communications and offered clearer services.

A good example of an ISDN is a typical office phone system. Imagine you have a reception desk on a business site that has four or five different receptionists on the desk, taking calls at any one time. ISDN allows them all to use separate business telephones at the same time because they are all connected to different lines. The negative thing about this is that you have to install/connect new lines each time. This means your business scalability is hampered because installation takes longer. Think of ISDN like TV, before 2012, when television wasn’t digitised. Before the switch to Freeview, most people only had access to a handful of channels. Now, however, users can purchase a set-top box for a small fee and enjoy hundreds of channels for free. The ISDN Switch Off is the phone network’s equivalent. 


In the 1960s, as trade spread throughout the world, the analogue phone network could not handle the long-distance calls made by, for example, advertising executives in New York, who wanted to call their counterparts in the London office. Globalisation was continuing at pace and the then-current phone network was not able to keep up. It was during this decade, over 60 years ago, that the entire phone network began to change to a digital switching system. 

You’d think that the rest would be history and that the analogue phone line would be consigned to the history books. However, it wasn’t until two decades later, in 1988, that things started to progress. In that same year, the International Telecommunications Union (ITU), which was founded by the United Nations (UN), started to formally recommend to companies that they should invest in, and switch to, ISDN to communicate and sell their products.

The take up of it was slow, to begin with, and it wasn’t until the 1990s when big corporations, such as Motorola, offered ISDN channels to companies and people. This brought down global prices and made the ISDN channel the go-to phone service.

When were they first introduced to the UK?

The history of this particular telephone service in the UK begins in 1985. The ISDN was launched as a replacement technology on June 25th 1985 and was originally named Integrated Digital Access (IDA). The IDA was an extension of the digital phone network and allowed for much faster data transfer for customers and businesses. The IDA/ISDN was the only one like it in the world and BP (British Petroleum) were the first customers on this new network. 

This telephony event signalled the end of analogue phone systems. Originally, when these digital exchanges started occurring, the ‘last mile’, as it was termed, was done over an analogue system, between the customer and their local exchange. This led to the IDA being changed to the ISDN (Integrated Services Digital Network) because that term more accurately described the system that facilitated this new switch from analogue phone lines. 

As testing across the country became more widespread, ISDN was soon able to offer plenty of 64kbit/sec (kilobit per second) channels that both commercial and domestic customers could use. Because these were binary systems, as opposed to analogue, they were named ISDN B Channels. As business activity exploded, due to the invention of the internet, companies and organisations began to use this new network. From it, they could get some of the fastest internet access around (which in hindsight was extremely slow).

Who runs the ISDN?

The British Telecom Group, or as they are more commonly known, BT, run the ISDN network in the UK. They were the first people to announce that they had plans to switch off the network, and the Public Switch Telephone Network which ran it. This began with the announcement that they would cease supply in 2020, with the aim of undergoing a full migration in 2025.

The reason for the long wait is to ensure that everyone in the UK can transfer over to the internet provided network in good time. For businesses, they must assess their ISDN usage now so that they are well prepared, and can look forward to, the switch. The best thing to do is to invest in VoIP, SIP Trunks, and other business telecom solutions today. These solutions are what our team here at Prestige Telecom Group do best. They would be happy to help you adopt a hosted VoIP (Voice over IP) solution and digital telephone systems in time for this key date in 2025.

How Do ISDNs Work?

This broadband and phone service which, as we’ve mentioned, is being slowly phased out, can appear complicated and difficult to understand. So, to give you a better understanding of how this system works, and to emphasise how much better it will be when we are all using the new alternative solutions (i.e. the internet), we thought we’d explain how it operates.

In its most basic, fundamental form, an ISDN line is just a digital phone line. As a result, it’s not something you just plug into a telephone and expect to work. For it to operate, you need to connect it to devices that are ISDN-enabled – these are very often modems or telephones. The initial reason for using an ISDN channel was speed. A typical user could get either 64Kbps or 128Kbps from a Basic Rate ISDN. The reason for the two speeds was to allow for separate phone calls to be made and received at the same time. Several modems used Plain Old Telephone Service (POTS) lines that allowed you to plug into analogue devices and make several calls at once because each line could support this. 

Installing an ISDN channel is quite complicated and another reason why this classic product is being phased out. Once you had connected the modem to the computer, you would then have to programme it and tell it what phone numbers you want to use. Once that is done, you would then have to set it up to dial your internet service provider (ISP) which would give you a particular number that is configured for ISDN access. 

In summary, it’s all very complicated and it’s clear to see how VoIP solutions and other digital connections are preferred so heavily. With them, as we’ll explain in this guide, there is no complicated set-up or any process that involves ‘telling’ your modem which numbers to access. You simply download a piece of software and any device with a digital connection becomes a phone, with the ability to make a video call, as well as a broad range of other functions. This is one of the key benefits of VoIP, allowing business scalability to happen much faster and easier. 

What are the types of ISDNs?

Traditionally, there have been two types of ISDNs that have run on the Public Switch Telephone Network (PSTN). They are called the Basic Rate Interface (BRI), and the Primary Rate Interface (PRI). The BRI was the lower tier and provided users with an ISDN channel, and its basic features, for a low cost. PRI was the better ISDN channel and provided a much better, more reliable service, with faster speeds.

ISDN Switch Off: What Next?

When Does The Big Switch Off Happen?

BT has set the target date for the big switch off as 2025, with a forced migration phase between the months of April and December. From 2025, every phone line in the country will have switched from a PSTN/ISDN service to a fully digital service, routing calls over an IP (Internet Protocol). Whilst the 2025 date is considered the most significant, and a milestone in the switch off process, there are still dates to note beforehand. 

BT’s current plan is to cease the installation of ISDN lines nationally in 2023, but this may happen sooner in parts of the country that already have a high level of coverage thanks to gigabit-capable networks, which will be introduced from the summer of 2021 in certain areas. BT actually announced this switch in 2015, stating that from 2020, ISDN lines would no longer be available to purchase. They have since revised this date, and you can still purchase ISDN lines up until September 2023.

Whilst 2025 might seem like a while off yet, it’s important to be aware of the changes so that you can plan your move – there may be a lot that you need to do. For example, you’ll need to review everything that’s connected to your phone lines, such as alarms. If you haven’t already, it’s probably time to move to a digital-focused way of working, considering the cloud as an option for operating and communicating.

Why Is It Happening? What Are The Reasons?

When BT announced the switch off back in 2015, it acknowledged the evolution of technology and the need to move to digital. Technology is a huge part of our lives and the old copper network now struggles to keep up with this increased use of technology, as well as its evolution. Even since the announcement in 2015, technology has continued to evolve with the likes of Zoom, the cloud, and the numerous changes and improvements made to smartphones. This in itself exemplifies the need to switch to digital from ISDN.

The switch off isn’t happening just simply because the current phone system is old, although that is a key reason. The reasons extend far beyond the phone system to all digital communications in general. We now need more than these older technologies were designed to provide, and switching to IP provides the solution for individuals and businesses. It can also be incredibly cheaper to use, making it a no-brainer for businesses that want to get moving and make the switch before the 2025 deadline. 

The switch off then makes way for more efficient and effective products that will replace ISDN. This includes VoIP services which use a fibre optic connection and provides a greater user experience. Along with the announcement of the switch off, BT also announced it would increase the availability of these products to replace ISDN and, of course, many other providers will be following suit.

What Is It Being Replaced With?

When ISDN lines are switched off in 2025, they’ll be replaced with IP technology, which can be used in various forms. The most common forms of IP technology are VoIP (Voice over Internet Protocol) and SIP (Session Interface Protocol), but ultimately it’s down to you to decide what to replace your business ISDN lines with. 

There are several options available, all of which have their pros and cons – there will be a different ‘best option’ for every business, depending on your needs. Here are some of the replacement options:


These systems allow users to make normal calls to anyone, anywhere around the world, for a very low cost. VoIP stands for ‘Voice over Internet Protocol’, which essentially means that the user communicates with their voice over a broadband connection (this is the ‘IP’ part of the term, which means Internet Protocol). As such, a reliable internet connection is vital for VoIP to work. With no internet connection, there’s simply no phone system. If you choose to use this type of system, you’ll own the phone system and will decide where you host it.

However, with a stable internet connection, VoIP can offer numerous benefits to the businesses that make the switch. This includes greater flexibility and scalability – you can add and remove users as necessary and with ease, and you can work from anywhere because you’ll have the ability to make calls from your mobile using the system.

VoIP also offers a great degree of portability and is a cost-effective solution – VoIP is usually considerably cheaper than using ISDN lines. Better still, because the solution is often cloud-based, you won’t need to worry about maintenance costs. It’s worth noting though that you will also need to consider where to host your phone system- if this isn’t on-premise you may face additional costs and these should be factored into your considerations.


If your company has a compatible PBX (Public Branch Exchange), you may want to consider switching to SIP trunks, or SIP lines. This type of service is much more flexible and affordable compared to ISDN. SIP offers great flexibility when it comes to scalability – if you have a growing business or even plan on downsizing, SIP allows you to add and remove lines as necessary. As well as this, using a SIP trunking service allows you to reduce the amount of PBXs you need. Instead, you can keep your existing phone number, regardless of your location, meaning that if you decide to relocate, SIP will provide business continuity.

SIP also provides a high quality service for a lower price. SIP trunking has an underlying network quality that brings real benefits and value, yet this form of IP connectivity typically costs much less than using ISDN lines. 

Has It Been Done Elsewhere?

The move towards digital connectivity and communication isn’t exclusive to the UK – this shift is happening globally. Some countries have already switched off their ISDN and PSTN networks, with Estonia taking the lead, along with The Netherlands. Other countries have soon followed suit, with Germany, Japan and Sweden vowing to make the move away from ISDN and towards digital options – these countries are ahead of us and will make the switch before the UK.

Globally, telecommunications companies are realising that ISDN must now be replaced with more reliable options that can keep up with technological advancements and the customer behaviours that feed the demand for digital. As such, businesses across the globe are switching to digital, from analogue.

The Future: What Will Life After The Great BT ISDN Switch Off Look Like?

Even though the move might feel daunting, especially if you need to prepare for the switch, it should be a straightforward process and simply a case of changing your plan, package or provider. Once the switch off has happened and businesses have adapted to their replacement systems, they should soon start to reap the benefits of all-digital communications.

Following the switch off, no data will be carried through ISDN and PSTNs and phone lines will no longer require maintenance or recovery. Furthermore, IP and similar options can often be more cost-effective than ISDN, providing businesses with a much cheaper way of working. 

Not only this, but these systems can provide a greater degree of flexibility and scalability. With most of the digital systems, you can take and make calls from anywhere, on any device. You can also seamlessly integrate your business systems and apps with calls and video chat for collaboration and communication. With cloud-based systems, you can also access company work at any time, from any place. 


What Does My Business Need To Do?

Things To Consider Before The Switch Off

Before the big ISDN switch off, there are a few things you’ll need to consider, to ensure that it doesn’t affect the way your business operates. 

Here are a few points to consider:

  • When are you going to switch? If you’re coming to the end of a contract for ISDN, now would be a good time to consider the alternatives, such as Prestige Telecom Group, to futureproof your business and prepare for the switch off. Even if you have some time left on your contract, it’s worth talking to a provider about how you can migrate to a different system.
  • How are you going to move forward with VoIP? Here, you need to consider your plans for the future and how your chosen solution needs to fit in with this. For example, if you have staff working remotely, or future plans to expand across multiple sites, then this can affect the package and the solution that you select. When you contact us here at Prestige about making the switch, we can ensure that the solution fits in with your plans.
  • Will your chosen solution work well into the future? The ISDN switch off is taking place because of newer, better technologies that can withstand demand. That’s a big sign that technology is always evolving as our demands increase. As such, you must ensure that your chosen replacement will be suitable for years to come, with high levels of flexibility and adaptability.

What You Need To Do To Prepare

To prepare for the ISDN switch off, you need to consider which replacement is best for your business, using the information that has been provided on this page regarding the various options and the things to think about. However, what’s just as important is when you prepare for the switch off. Because it’s expected to happen in 2025, putting alternative technologies in place might not feel urgent but, in reality, 2025 will be here sooner than you think. 

Aside from the switch off, there’s really no need to wait until 2025 to make a change – if you are using ISDN/PSTN lines within your business, you should consider your alternatives as soon as possible. Not only does this ensure that you’re prepared, but it means you can start benefiting from IP as soon as possible.

The process of switching will usually take a couple of weeks, but this can differ business to business depending on the infrastructure that’s currently in place. If you have multiple sites for example, the switch may take longer. By acting now, you avoid leaving things until the last minute and can take advantage of the solutions much sooner than 2025.

Does Your Current Business Telecoms Support This Change?

Because ISDN will be replaced with IP, you need to look at whether your phone system is IP compatible and can therefore support the change to IP from ISDN. If it isn’t compatible, then you need to invest in a newer model that is IP compatible. If it is compatible, then you may wish to consider replacing your existing ISDN service with SIP trunking, which is a flexible and cost-effective solution.

Regardless of compatibility, you may also want to think about using a cloud-based system for your business telecommunications – this is easy to implement for all businesses. As a software based solution, you can save money as you won’t need to purchase hardware or pay for the maintenance of the system and its servers. Instead, a cloud system is always up-to-date and provides all the useful features you’d have access to with a phone system that’s on-premise.

Because a switch to IP relies so heavily on the internet, you’ll also need to assess whether your internet connection is stable enough to support IP telecoms technology. If your internet connection needs upgrading, it might be time to switch to a fibre optic connection or ethernet-based leased lines, in the case of larger offices.

Should I Talk To A Business Telecoms Expert?

If you’re still unsure about what the ISDN switch off entails, what it means for your business, and what you need to do to ensure business continuity, then we’d definitely recommend speaking to one of our business telecoms experts here at Prestige Telecoms. 

Not only can we provide support and advice, but we can take you through the alternatives to ISDN/PSTN lines to find the best solution for your business. It’s important that you select a solution that isn’t just effective now, but also far into the future as technology continues to evolve at pace – our experts are best placed to help you make these key decisions. Then, once we’ve established the best course of action, we can handle everything including the porting process, to ensure that you experience minimal disruption to your day-to-day business operations.

To migrate to a better, more modern system than ISDN, get in touch with the team here at Prestige Telecom Group to ensure that you’re fully-prepared for the switch off. Call us on 03303 200 222, or email us at

Benefits: How Will It Affect Your Business?

Whilst making the initial switch from ISDN to VoIP might feel stressful because of the considerations that you need to make, it doesn’t have to be. With our support, we’ll help you to switch to a better solution. Then, you can start reaping the benefits of IP. Here are just some of the advantages that IP offers:

  • It’s cost effective – VoIP is a low cost solution when compared to a traditional phone system. By eliminating the need for phone lines, this can reduce your costs.
  • It offers high quality – VoIP offers better audio quality and clarity, providing that you have a stable internet connection.
  • It’s flexible and scalable – VoIP can be tailored to your business requirements and can be adjusted if you downsize or grow in the future.
  • It’s portable – VoIP allows businesses to be as mobile as they need. Both desk-based and mobile users can connect to the phone system, regardless of where they’re based.
  • It’s futureproof – Investing in VoIP means investing in a modern phone system that doesn’t risk becoming quickly outdated. VoIP will be one of the main solutions for the foreseeable future.

Contact Us To Learn More

As you’ll see on this page, we’re better equipped than most to help you take advantage of the upcoming changes to the way the country makes phone calls. There is still plenty of time to make the correct decision for your business and we would urge you not to rush into investing in equipment that may itself become obsolete in a year or two. The key to succeeding is a steady, well-thought-out plan, aided by the help of a business communication solutions team such as Prestige Telecom Group. Operating in Hampshire, we’ve had the pleasure of helping countless businesses with their telecom solutions in areas such as BournemouthSouthampton, and Portsmouth, as well as further afield in CardiffBirmingham, and Bristol. No matter where you, and no matter what your relationship is with your communication solutions, we can help. Get in touch with us today on 03303 200 222, or email us at

Have Questions?


Narrowband ISDN was an attempt to modernise the existing ISDN system by making it more digital, as opposed to its current analogue system. While well-intentioned, Narrowband Integrated Switch Digital Network (shortened to N-ISDN) did ultimately fail and become obsolete. It became so because it took far too long to agree upon a standardisation process, and, by the time it had been agreed, the technology that was initially put forward had become obsolete – a reminder of just how quick telephony solutions can change, improve, and adapt. The ‘narrowband’ refers to the use of communications, connections, and telecommunication tools across a narrower band of frequencies in any given communication channel, and is commonly used to carry voice data over a frequency set.

Known as an ISDN terminal adapter, it is a piece of technology that is used to stop a dial-up Integrated Services Digital Network line and instead connect it to a computer or LAN (Local Area Network). An ISDN adapter would be used by a business or consumer when they don’t have a dedicated ISDN telephone connection or sufficient computing equipment, they can sometimes be referred to as ISDN modems. The adapter transmits digital data directly from the computer to the specific ISDN line without having to switch between analogue and digital signals. This kind of equipment plugs directly into the serial port of your computer and acts like a modem.

Even in today’s world of superfast broadband, ISDN is still pretty quick. A typical line will run anything between 144 and 192 kbps (Kilobits Per Second), this can be increased by integers of 64kbps. It’s not that ISDN isn’t fast, it’s just the fact that broadband suppliers have advanced their technology to offer even quicker products, hence the ISDN Switch-off taking place in 2025. When it was first introduced, ISDN was the fastest connection solution out there and allowed businesses to take advantage of fast broadband, it surpassed dial-up and the more analogue rivals in no time at all.

An ISDN is an Integrated Services Digital Network that carries internet connectivity over specialist lines. A Digital Subscriber Line (DSL) is a connection that is ‘always-on’ and does not need to dial over the lines that it uses. The main difference between these two is that, with a DSL, a user can make calls while connected to the internet because the DSL does not need to dial out. This is unlike an ISDN, which does have to in order to create a connection and allow the data to flow through it. Another key difference is that DSLs use existing telephone lines and modems, whereas ISDN lines have to be installed and require adapters at both ends of the line. ISDNs must also be directly placed into the home business where it is being used.

Yes, ISDN, while being phased out and switched off in 2025, is still used today by plenty of people and businesses. ISDN is predominately used where broadband internet isn’t an option. Further, there are plenty of reasons why people choose to still use ISDN. For instance, it offers multiple digital services that operate through just one copper wire, it can connect devices and allow them to operate over one wire, and provides a higher data transfer rate. While plenty of providers and teams use it, time is ultimately going to see the use of ISDN end.

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