A simple 999 trick lets you contact the police via text message in an emergency.
In situations where it is unsafe to speak aloud, you can contact the police by texting 999.
However, the trick only works if you register first.
Twitter user Portia Pan drew attention to the service suggesting that people register now so that they can use it in an emergency.
"I’ve already said about this a million times but for people who don’t know - everybody with a mobile in Britain should text “register” to 999," she posted.
"It takes seconds, and will mean that, in an emergency where you are unable to speak, you can text 999 instead of calling."
Her tweet has been shared more than 1,400 times with people flocking to the comments section to thank her for the advice.
One replied: "Just done this. Thanks! Being autistic I find phonecalls draining overall and sometimes in high emotional distress I actually cannot speak."
Another said: "Thank you for this!!!! I had no idea it even existed... have registered and will be telling all I know."
The system was set up so that people with hearing loss or difficulty with speech have a way of contacting the police in an emergency.
But anyone can use for the Emergency SMS service by sending a text message saying 'register' to 999.
Anyone who is registered can then text 999 in an emergency to ask for help.
The message should clearly state which service - police, ambulance, fire and rescue or coastguard - is needed, a brief description of what is happening and the location of the incident.
You will then receive a message back either asking for more information or stating that help is on the way.
The service should only be used in an emergency - for example if someone's life is in danger, if a crime is happening, if people are trapped in a fire or if someone needs an ambulance urgently.
The service works throughout the UK on all mobile networks, but it cannot be used from abroad.
