Seems trivial, but this is one of the more substantial changes coming that will catch people out, especially in an emergency situation.

The generic advice I recall for emergencies is as follows

  1. Where possible, do not leave someone alone
  2. Don’t move them (dependent on circumstance) as you may cause more damage
  3. Call for help

Pretty basic stuff, but from 2020 what a dial tone means will change, it no longer means that you can dial out, so let’s look at that and see how this impacts us.


PSTN – This is how your landline phone works today, also known as analogue

VoIP – This is how a landline will work going forward, calls go over your router, then over the internet.

Note: There is a link at the end of this article to a petition for the PSTN switch off and 999 calls in general.

Current (PSTN) Dial Tone

When you lift a receiver today and you hear a dial tone, what this means to you is that you can make a call.

What it means to technology is that there is 1 uninterrupted connection from your property to the exchange.

The sound of the dial tone comes from the Exchange, so if you hear one, you can assume your phone works and it would be rare at this point that you cannot dial out.

PSTN Power

New (VoIP) Dial Tone

Going forward, the dial tone you hear does not mean you can dial out and it does not mean that you have an uninterrupted connection to the exchange.

The dial tone will come from the Analogue Gateway OR it will come from the physical handset.

As far as technology is concerned, the dial tone is not necessary, it is simply there because we are used to hearing it and it will prompt us to call.

No dial tone simply means one of two things

  1. Your handset is broken
  2. Your analogue gateway is broken or disconnected from the mains

For the majority of people, the tone will come from the Analogue Gateway on the below diagram.

VoIP Power

So what is the big deal?

Well first off, most individuals have no way of knowing where the fault is.

Hearing a dial tone means nothing other than your analogue gateway is connected to the mains, and the handset is connected to the analogue gateway.

If you don’t hear a dial tone then you know the issue is with one of these.

If you do hear a dial tone but you cannot dial out, it could be a technical or physical fault with any of the steps in our change after and including the analogue gateway.

So what happens in an emergency?

What happens with you or what happens with me?

With Me

I would know if it is going to connect pretty much straight away, so I try a phone, VoIP or otherwise, I know what sounds mean.

Working in support and doing engineer roles for telecoms, you basically get used to working out where faults are by ‘sounds like’.

So I know based on the type of set up I am working on what sounds come from what equipment in the infrastructure. I know where the Dial Tone comes from, where the ringing sound comes from (the bit you hear on the receiver when you dial out), I know which bits mean the phone call is working and which bits are Kipper Rouge (red herrings).

So I call 999, I know based on the solution in place whether or not the service is going to connect based on what sounds I hear back.

With you

Well, if you don’t know the difference, you may be in a bit of a pickle.

Today it is very easy, ‘hear dial tone, can call’.

As an example, my granddad was a BT engineer on the PSTN network, if he picks up a phone and hears a dial tone, he has no reason to believe that the call will not connect.

If he follows this advice in an emergency

  1. Where possible, do not leave someone alone
  2. Don’t move them (dependent on circumstance) as you may cause more damage
  3. Call for help

He would try several times before giving up because a dial tone to him means it should connect, there is no reason to think otherwise, because if a line presents a dial tone, even one you cannot use for other phone calls, you can still call 999.

Most consumers would be of that expectation, if there is a dial tone, you can use the phone.

So without knowing otherwise, how many times do you try to call out before you consider alternatives? How long do you waste in an emergency where every second counts?

So what about other automated systems?

Without getting technical, automated systems in the home can often be considered ‘automated life savers’

So a tone on a line can be used to determine if the line is working and notify if it does not work.

Anything from an alarm line, to panic button, or even medical devices in the home can be connected to an analogue line and by virtue of a tone being present, this lets you know that it works.

So let’s say a medical device malfunctions or ceases to operate due to power loss or any other reason, these would often then send communication via analogue lines.

The methods in place for these need to be reconsidered.

What about power cuts?

Well, the current notion is for VoIP services to be provided with 1 hour battery units, so in a power cut, you can call people for 1 hour.

Mobiles Masts are the same, they have 1 hour of back up (some are more, but we don’t know which ones, so cannot bank on it)

The old PSTN technology was potentially an indefinite solution during a power cut, this is because Exchanges have back up generators.

However, while exchanges do have a back up generator, we don’t know how long a local BT street cabinet will last or if it will work in a power cut at all to meet our vulnerable person requirements. Fibre Broadband requires the local street cabinet to have power, VoIP works over the broadband, so in order to dial out the street cabinet must have power.

In any case, from the VoIP landline if the street cabinet loses power then you will hear a dial tone but not be able to dial out.

The consideration for vulnerable people is that they be given more than 1 hour in a power cut, so the router and analogue gateway in their premises should last longer. There has been no published detail as to how this would work if the cabinet loses power or how long the cabinet will retain power for, so for now we assume that the service will not work.

The only factual information we can find on the cabinets that is not opinion is from rural customers with back up generators who have moved to fibre services, they complain that unlike ADSL when there is a power cut, their fibre service stops working.

Everything else we can find is opinion, ‘Could be as long as 3-4 hours’, ‘a short time’, ‘enough time’, nothing we could base a solution on for vulnerable people or anyone who relies on their landline phones.


Education is always a requirement with technology, in a residential scenario personally I do not see the point in persisting with landline phones over a fixed line broadband, without the ability to operate in a power loss scenario, they offer no benefit over other solutions.

Satellite being the obvious choice for a robust solution during a power loss scenario.

Mobile being the obvious choice for any other scenario.

A combination of both can provide resilience likened to the services we have in place today, so would suggest that this combination provides vulnerable people with the service that they need.

For everyone else, we can replicate the ‘VoIP’ benefits via other methods for power loss and emergency scenarios using the mobile phones we have today, these can make voice calls over the broadband in our homes at no extra cost, so VoIP offers very little benefit to the vast majority of us even outside of an emergency situation.

Ofcom are currently stating “People can use mobiles in a power loss scenario” as the solution to VoIP not working at all in a power loss scenario.

People who are not comfortable with a mobile phone can get a GSM/3G Desk phone, it operates on a SIM, looks like a landline phone, but can make calls over the mobile networks and the broadband without paying for additional VoIP rental.

So all things considered, what is the point of a VoIP landline in our homes?

But not knowing about this change to the PSTN, even with something as trivial as a dial tone, when we are educated for emergencies to believe that every second counts, well what does that reality mean in that scenario? Can we argue that education is needed here as it can impact life and death situations?

You can read more about this upcoming change on the link below, looking at a wider perspective of what the PSTN switch off means and whether there is any benefit to a VoIP landline with the way we use technology today.

10 Reasons Why You Shouldn’t Get a VoIP Landline In Your Home

For further detail around the legislative side, technology side and solutions that can be put in place instead of a VoIP landline, you can see more detail here

PSTN switch off and what it means to you

In general we want MPs to consider the PSTN switch formally and review the mess that Ofcom are creating for us, we have started a petition on the link below, we also intend to engage with journalists and politicians directly.

Thanks for reading, please support us in supporting people with this changeover by sharing the petition on social media and other channels.