So what happens when you call "112"?
When you call "112" you access the emergency services in the same way as "999".
"112" will work across Europe but not in every country world-wide but it does work in about 70 or so of them, so do always check when travelling how to access the emergency services.
When dialling "112" from a mobile it will over-ride the need to enter a PIN code, making it possible to use anyone’s phone. It will search other networks for a signal and prioritise the call if the network is busy.
You will find the video below quite informative and probably fascinating too, and it has some very useful advice about using "112" and calling the emergency services in remote areas.
It is also possible to register your phone for the eventual likely use of a
text service so that if needed you can
text the emergency services. This stands a much better chance of getting through if you are so remotely situated that the voice call just won't work.
Sometimes, you might just have a home medical problem and so you might just need to only dial "111".
Here is some more useful information about the differences between "999", "111" and "112"