In 2020 the PSTN network will become legacy, this means that if you move home or change provider after 2020, and your area is BT supplied, you will no longer be able to have a landline phone that runs off of the PSTN network, but you will be able to have a landline phone that operates over VoIP. The BT PSTN Network will be turned off in 2025

In this article we will look at

  1. Understanding Technology
  2. Understanding Ofcom Guidance in relation to technology
  3. Solutions you could consider away from how the Ofcom is guiding the industry

We also have a petition on which you can see on this link.

Video Version

We have a video version of this article you can watch below that covers the issue at a high level


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Below we look at this topic in more detail, on the following pages we look at some solutions that can be put in place.

Understanding Technology

What is VoIP?

For the purpose of this article, VoIP is simply a way of connecting your phone to a router instead of plugging it either directly into the BT Socket on the wall, or into a filter.

Your voice calls then work over your Router and on the internet.

What is PSTN?

Acronym aside, this is just the way landline phones in our homes work now, also called ‘Analogue’.

Your phone connects to the BT socket either directly or via a filter.

What are the drawbacks of PSTN over VoIP?

Cost, it is as simple as that. You won’t get a better service with VoIP over PSTN, you should see a reduction in line rental and call charges.

What are the benefits of PSTN over VoIP?

Now, this is where we get interesting.

The significant benefit of PSTN over VoIP is continuity.

PSTN will continue to operate in a power cut, VoIP may only operate for a limited time in a power cut (Potentially 1 hour, but likely less)

So, whether the power cut is caused by a blown fuse at your property, a local power cut on your street, a city wide power cut, in theory PSTN will continue to operate.

This is because the power for your phone is currently supplied from the local exchange, you plug a phone in and you hear a dial tone, you don’t need any mains power at your premises.

VoIP requires power at your premises for

  1. Your Router
  2. Your Analogue Gateway (How you connect a traditional telephone to a router)

By the time we get to the PSTN switch off in 2025, VoIP will require power at multiple points between your property and the local exchange, most notably your cabinet.

This is because it runs over the broadband service, Fibre services require power in the cabinet in order to operate

Now we also need to understand how power works with Mobile phones

There are a lot of myths around mobile phones, especially when dialling 999.

  1. You can dial 999 from a mobile handset that does not have a SIM – False, this was prevented over a decade ago due to miss use.
  2. Mobile phones use Satellite technology to call 999 or 112 – False, your mobile phone does not call over satellite technology for any circumstance. The exception to this is where you have a Satellite phone.
  3. Mobile phones continue to operate in a power cut – False

Your physical mobile device has a battery, so this will continue to operate.

However, it relies on the mobile masts around it to have a power supply.

The mobile masts currently only remain up for 1 hour in a power cut, (as far as regulation is concerned, but some may have been installed when the regulation was 4 hours)

Your mobile device will roam for emergency calls only, 999/112, so a Network provider at a mast in range requires power at the mast in order for you to dial 999.

When the back up batteries at the mobile mast expire in a power cut, you cannot dial out of your mobile phone to any number, emergency or otherwise.

What services and situations benefit most from PSTN technology and uninterrupted service?

For Residential Services, it is likely these

  1. Alarm Systems in the home
  2. Panic Lines
  3. Dalliers for vulnerable people
  4. People living in rural areas
  5. People who have fallen out of touch with technology
  6. Any type of monitoring system
  7. Vulnerable people in general

Are there any Traps with VoIP on these services?

Yes, unfortunately there is one quite significant trap with point 5 and 7

It is with the way the dial tone works, right now a dial tone pretty much means you can dial out. There are rare exceptions to this, but that is what a dial tone has always meant.

Going forward, a dial tone is simply presented for comfort and to prompt you to dial. You can hear a dial tone and if there is a fault in any part of the service you cannot dial out.

This is because the dial tone in the future comes from either the physical handset, or from the analogue gateway. If the router is disconnected, you may hear a dial tone but be unable to dial out.

If the local exchange is down, the same rules apply, you will hear a dial tone but be unable to dial out.

If the local cabinet on your street (Green Box) has lost power, you will hear a dial tone but be unable to dial out.

Why is that important in a residential situation?

We are conditioned to act certain ways in a crisis, these are the ones that pop into my head

  1. Never leave someone alone, unless absolutely necessary.
  2. Call for help

So if you are not aware that a dial tone doesn’t mean the phone works going forward, people could enter into a situation where they are trying to dial out of a line that will never connect, how much time is wasted is going to be an individual circumstance, I know instantly something that may take several attempts for you to conclude in a panic situation, dial, wait, hang up, try again. It is not an instant process, 20 seconds for each loop would be a fair estimate.

Every second is crucial, at least that is what we are told and educated on from a young age, so at what point do people stop trying to use a phone with a dial tone?

One thing that you cannot conclude is that the thought process in this situation will get more rational, if anything you start to panic and you get less rational.

Other bits we need to know for Technology in VoIP

The only thing we need to consider before moving on to the Ofcom Guidance is around a UPS

A UPS is an uninterrupted power supply, think of it like a car battery, the engine is off, but you can still listen to the radio or put the lights on.

So the power goes down in your home, your TV is off, computer is off, but your router and and phone retain power for you to be able to dial out.

Currently the Guidance is for 1 hour of service, so a 1 hour UPS. The current methodology implies that having a UPS for larger and longer would be a substantial investment, requiring yearly on site maintenance visits, we don’t agree with this which we look at on the coming pages.

However, having a UPS does not mean your landline will work, it all depends on the extent of the power cut and the area that the power cut impacts, this is because there are multiple points of power failure along the phone line going forward with a VoIP solution.

PSTN only has 1 point of failure in relation to power, which is the exchange losing power. They would usually have back up generators to cater for this and because the power comes from the exchange to power the phone in your home, your home doesn’t currently have any power requirements for you to be able to dial out in a power cut.

We will look at Ofcom Guidance on the next page in relation to the technology points we have raised here.

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