Different countries have a three number emergency call (e.g. 911 in the US). When travelling, will the local three digit emergency number work on my US based cell phone?

Title says it all really.

If I am in London, 999 is the number to summon emergency services. There is also (I read) a pan-European emergency number…112.

If I am in a foreign country, using my American based cell phone, will dialing those emergency numbers work for me? Or, do I need to get a local person to call for me?

Also, is 112 the same as 999 in London?

Additionally, my phone will let anyone call 911 even if it is locked. Will it allow people to dial the local three-digit emergency number on my phone if locked?

Can’t speak for your phone/sim card but for mine:

Australia:
Triple Zero

So, if I am in Australia with my American based cell phone and dial 000 I will get emergency services same as anyone in Australia? (I didn’t expect 911 would work although it’d be kinda cool if it re-routed automatically…seems doable but I really do not know.)

Assuming your US provider has a “roaming” agreement with a local provider in whichever country you’re visiting, wouldn’t it connect to whatever local number you enter, i e., 911 wouldn’t work?

I’m used to my phone automatically telling me I’m connected to [local network X] whenever I cross (or sometimes go near) an international border in Europe (together with info on how much calls and texts will cost on the foreign network).

It appears that 112 is the recommended international standard:

From the Australian Communications and Media Centre:

Network coverage

You can call 000 even if your mobile provider does not have network coverage in the area.
Your call to 000 will be carried on any available mobile network.
You must be in the coverage area of one of the mobile providers in Australia to make emergency calls.

Years ago I asked about 112 in Australia and was told that it would work, but they really preferred if we didn’t use it. There were problems when GSM phones first came in with emergency calls and it took a while to settle down. The phones didn’t know 000 was supposed to be special. But 112 worked, partly because we used Ericsson base stations and infrastructure and that knew about 112. No idea if it still works.

There are all manner of under the covers questions with emergency calls. Where they get routed, and what location information is available to the call centre are big ones. This tends to be a mess of problems now. Landlines, mobile, even satellite phone, lots of carriers with different cell infrastructure, plus shared infrastructure. Somehow it has all got to work. So the locally defined number is likely to be the safest bet.

Interestingly, apparently the divide between 112 and 911 is due to the historically different architectures of exchanges between the US and Europe. The US exchanges saw the first digits reversed and needed to see three digits before realising it was an x11 number, whereas the European ones ran the numbers in serially and on the first digit could determine the number was special.

In the UK, 112 and 999 both work. As with Australia, there were some initial problems with 112, but I read that they are now all resolved.

Be aware though, that calling either will put you through to a call-handling agent in one of six call-handling centres, which will be nowhere near your location. You will be asked which service you require (Police, Ambulance, Fire and Rescue or Coastguard) and they will transfer you to the local emergency service control room. This depends on the system being able to “see” where you are geographically. If it can’t, you will need to be able to tell the operator where you are. “Somewhere in London” is not adequate.

I suggest that you get the brilliant free app what3words and use that to identify your location if you need to. It works for Uber as well.

There is also a non-emergency number - 101 - which you can use if there is a problem but it isn’t really an emergency.

I know this is FQ but as I’m reading discussions of which number to use, I can’t help but think of emergency number 0118 999 881 999 119 7253 on the IT Crowd.