PSTN/ISDN BT Network Switch-Off

VoIP and the PSTN/ISDN landline phone switch-off:
What does it mean for your business?

You are probably aware of the planned BT analogue PSTN/ISDN switch-off now planned for early 2027 (originally planned for 2025!), most likely via the number of telesales calls you or your business are receiving or via the more recent media coverage.

In simple terms, BT will be switching off the traditional BT exchanges and replacing the services with 'digital voice', commonly also referred to as, 'cloud', 'hosted' and 'VoIP'. This means most existing businesses with a traditional telephone system with ISDN or PSTN lines will need to upgrade to Digital Voice.

It's arguably the biggest social project since analogue television was retired some 10 years ago: the UK's telephone network is also going digital. 

To learn more about the PSTN/ISDN switch-off and how our knowledgeable team at Avalon Telecoms can support your business, contact us on 01278 228228.

Frequently Asked Questions

Frequently Asked Questions

What do PSTN and ISDN mean? 

PSTN stands for public switched telephone network – it's the traditional copper phone network that delivers analogue landline phone services that include ISDN (Integrated Services Digital Network) for business users. The plan is for it to be switched off at the end of 2026/early 2027 and for all landline services and telephone numbers to be offered digitally via cloud-hosted VoIP.

What Does ‘Digital Voice’, ‘Cloud’, ‘Hosted’ and ‘VoIP’ mean?

Essentially all the above names are used to broadly describe the same service, telephone numbers and lines held in the cloud and delivered over a data connection, like broadband for example.

For business users, this means a local onsite telephone system is no longer required as each telephone extension (which has its own ‘line’) is hosted in the cloud and is commonly charged on a monthly subscription basis.

What’s happening with the PSTN switch-off?

BT are migrating the old analogue public switched telephone network (PSTN) to a fully digital network. BT has already started, and the plan is to move everyone over before Openreach stops the PSTN (and ISDN) service by early 2027. By then, every phone line in the UK will be digital, routing calls over IP (Internet Protocol) rather than the traditional PSTN.

Why are traditional PSTN phone services being taken away?

The basics of the UK phone network that has existed since the Victorian era is coming to the end of its life. While its physical infrastructure remains similar to when it was installed, our communication needs have changed immensely. Alongside this, broadband and data connections rely increasingly on fibre optic networks. These not only offer faster speeds than copper but are also more reliable, more resilient, and easier for BT to maintain. 

When BT say ‘everyone…’ do they mean it?

Yes. They mean everyone. Business and home. And it’s not just your phone services you need to think about. It’s everything else that currently uses the old phone network – all your non-voice services connected to PSTN or ISDN lines such as alarms, EPOS machines, door entry systems, faxes etc.

When will my traditional landline actually be switched off?

We can't be sure as it is down to BT to inform service providers of their intention to switch to your local exchange as BT is implementing a region-by-region rollout.

We will inform our business customers when we have a notification about how long the notification period will be, again we cannot be sure, but the estimate is only 6~8 weeks’ notice!

For business users with ISDN, there is a chance you may need to be migrated sooner if the BT infrastructure in your local area fails. 

Will I be able to have Full Fibre Broadband (FTTP) before the switch off?

Not necessarily. The demise of the PSTN is linked to the roll-out of full-fibre broadband in the UK, although the two aren't on the same timeline. While phone services will no longer use the copper network by the end of 2026, the aim is for full fibre coverage to reach 85% in the same year.

What are the benefits of the move to digital voice services?

The move to 'digital voice' phone services is mainly about infrastructure and should offer more robust connections due to the removal of the old copper cables. As business users, you will also benefit from the flexibility of cloud-hosted VoIP telephony.

Can my existing Telephone System be made ‘Digital Voice’ Compatible’?

There is a possibility that a newer telephone system can be upgraded to SIP trunks (Digital Voice Lines that are delivered over broadband). However, this will often incur costs for new hardware and licensing and with many major traditional PBX manufacturers no longer producing new systems maintenance will become increasingly difficult and therefore upgrading may not be the best long-term solution.

What are the main things I need to consider before moving to ‘Digital Voice’?

Probably the most important factor for a reliable VoIP service is the data connection (broadband) you have or can get.

Ideally, if you can have a ‘full fibre connection’ often known as ‘FTTP’ (Fibre to the Premises) then one connection should be robust enough for both telephones and IT.

If FTTP is not available then there are a few factors to consider, the number of telephones and how often they are used at any one time and the number of PC users and how often they are uploading and downloading from the internet.

Telephones and calls don’t take up much bandwidth so for a small business with a few telephones then a single fibre-based (Not ADSL) broadband, ‘Fibre To The Cabinet’ (FTTC) or SoGEA (broadband without a telephone number or voice line) should be okay.

If there are a large number of telephones and PC users then you may want to consider two broadband connections preferably from two separate service providers using different networks.

For cabling, see the FAQ below.

Will my existing telephone sockets and cabling work for VoIP telephones?

If your existing business phones plug into a traditional-looking telephone socket via a lead with a traditional white BT plug, then the simple answer is no.

VoIP telephones require an RJ45 outlet and CAT cabling to work, in simple terms this is the same as a PC. VoIP telephones need to be powered so you will need a POE (Power Over Ethernet) data switch or a local power supply unit or POE injector (one of each per phone).

In most cases, you only need one RJ45 wall socket for both a VoIP phone and a PC. This is because the phone can be plugged into the wall socket (via Ethernet lead) and has a separate socket allowing for a PC Ethernet cable to be plugged into it, so allow both devices to use one wall socket.

Some VoIP telephones have the option for Wi-Fi connectivity, which should be okay for smaller systems of just a few users, however, we always recommend a hardwired ethernet connection for a reliable service. 

What are the expected costs when moving from PSTN to ‘Digital Voice’?

We can't give exact costs as each customer has different requirements; however, the following should be considered

Migrating/porting existing telephone numbers to digital voice

Cabling as VoIP telephones requires an RJ45 ethernet connection (same as a PC).

Wi-Fi can be an option for smaller systems.

POE (Power over Ethernet) data switch to connect and drive (power) the physical VoIP telephones.

A local PSU (Power Supply Unit) can be used for each phone, but a POE switch is recommended. 

For physical VoIP Telephones, there may be upfront charges or the cost is included in the going rental.

Installation of the telephones and the setup of the system to suit your needs.

Beware some providers simply send you the phones in the post and you will have to physically install yourself and program the system via a web-based admin portal. We will do all this for you.

Ongoing rental charges per user (extension), cost depends on what features are included. 

Are telephone calls completely free on Digital Voice?

In a word no, not with our Digital Voice services, however, we can offer 'inclusive minute' deals for those who make a lot of calls or would like to fix their monthly telephone bills.

There is an exception for internal calls to other users/extensions on your system even if they are working in another office or at home, these calls will not be charged. 

What is the lead time to move to Digital Voice services?

This largely depends on the contract with your current Service Provider as you will need to confirm if you are in contact and what the 'notice period' is for you to transfer/migrate your services to another provider.

For existing Avalon customers then expect around a 3 - 4 week lead time to allow for number porting (around 10 working days) and an installation appointment to be booked.

What if my broadband goes down?

If you have a single broadband connection, then in short you will lose both your telephone and internet services. Calls can be diverted to another number as a means of providing temporary service,

You may consider taking precautions, examples are; having two separate broadband connections from two different service providers on separate networks. A 4 or 5G router with a DATA SIM, however, there are some drawbacks to this as connections are subject to location and signal strength and throughput on the local mast. 

Alternatively, you may consider installing a ‘lease line’ (a private broadband connection) with an SLA instead of a broadband connection, however, these are more expensive.

Need further assistance?

Have a question we haven't answered? Get in touch with us today.

Contact us