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Demystifying 999 calls on a mobile phone

Over the many years we have heard it all…….

I can always make a 999 call – even when there’s no signal

A mobile phone will make an emergency call without a SIM card

There is a special number which is pre-programmed into every SIM card that will dial 999 when there is no signal

and many more.

We’re big fans of myth busting so here are the FACTS about mobile phones:

Signal verses service

The most common myth is that you can make a 999 call when there is no signal. Well, depending on your definition of ‘signal’, this is partly true. For simplicity let’s say that a signal is the phone using small radio waves to communicate with a ‘cell’ (mobile phone network mast). Like all radio waves there must be a clear line-of-sight for the phone to connect to a cell which, if all is well and good, allows our phone to have some ‘service’.

If something blocks the signal, however (such as a mountain or large brick wall) the signal may not reach the cell. In many instances this is not a big problem as there are usually several cells in any given area which offers a greater probability of making a connection. However there are times when there is no signal and therefore no calls can be made – here in the mountains of Cumbria this is very typical!

MAKING A 999 CALL on another network

In 2009 all mobile phone network providers introduced the ability to make cross-network emergency calls. This allows anyone to make a 999 call on another network should their own network be unavailable. For example I subscribe to O2 but there is no network for O2 at the end of Patterdale in the Ullswater Valley however there is a Vodaphone network. In an emergency Vodaphone will allow me to make a 999 call using their network.

When A MOBILE PHONE cannot make a 999 call – part 1

Another common myth is that it is possible to make a 999 call on a phone without a SIM card. This would be handy however phones without a SIM card are blocked from making any calls to reduce the frequency of hoax calls.  This has often confused people as a SIM-less phone may display ‘Emergency Calls Only’, however that is just the phone’s software displaying the message when turned on. As the phone is not yet subscribed to any network it will not be possible to make a 999 call.

It is possible, however to make a 999 call on a Pay as you Go phone with no credit left – good to know!

When A MOBILE PHONE cannot make a 999 call – part 2

Going back to our original myth that it is possible to make a 999 call when there is no signal it is perhaps worth understanding each stage your phone goes through in it’s attempt to make a 999 call.

1.  To make a 999 call the phone needs to show some ‘signal bars’ or a message such as ‘emergency calls only’.  It must also have an active SIM card (with or without credit).

2. If your home network is available your phone will connect to the emergency services on this network. This also has the added advantage in that they can call you back should you break the connection  or if they require further details.

3. If your network is unavailable but a signal is available on another network your phone will use this alternative network to connect to the emergency services. This is technically called being camped-on, and is free in the UK (and many other countries).

4. If there is no other network available you will not be able to make a 999 call.

RECEIVING  CALLS in an emergency

In most circumstances making a 999 call will simply require a signal call and, once the emergency dispatcher has recorded all the necessary information, the ball starts rolling get that emergency help to come to your aid!

However it is useful to note that a phone that’s using another UK network (camped-on) for the purposes of placing a 999 call, cannot receive a call on that network, even if the inbound call is from the emergency services.

So if the emergency services needed to call you back (i.e. to update their progress or to gather further information about your location, for example) they will be unable to do so unless you are connected to your own network. This may not seem that vital if you are in an urban setting when an ambulance is only 20 minutes away (if you are lucky!) however this would be incredibly significant in a remote settings where the use of search & rescue teams may be the only option of rescue. In this case it is often typical for the rescue team to call you back to gather further information once they have arrived at their HQ or remote operating base – good to know! 


It’s possible to text the emergency services if you have poor signal, hard of hearing or need to make a ‘silent call’. More in this blog >>

You can make a 999 call from any phone that has a password lock. Simply dial 999 or look for the word ‘Emergency’ which will open a new screen to make the 999 call from.

Many smart phones now have a ‘Medical ID’ app which can allow a rescuer to gather further information should you be incapacitated. More in this blog >>

You can use a smart phone to pinpoint your location without any signal or data connection anywhere in the world. More in this blog >>

Written by Ross Wallace, Senior Trainer