like there should be a workaround/hack that then let’s you place any kinda call for free.
In: 3640
I gotchu and I can answer with authority because I’ve actually written the embedded software that makes emergency phone calls.
Disclaimer: this is not an advice on what you should do during an emergency. Do what your local government authority recommends and figure out the right number to call.
[My top voted comment](https://www.reddit.com/r/explainlikeimfive/comments/7mb35n/-/drsxmdn) is an answer to a similar question. Feel free to look it up.
As others have said a SIM card is there to identify your phone to the network and to optimize how your phone searchs for service.
So if you are a T-Mobile customer, an AT&T cell tower won’t let you use their service/tower.
Also, say T-Mobile only uses radio frequency bands 1, 2 and 3 (I’m simplifying it here) and AT&T uses bands 4 and 5 in your region. If you are a T-Mobile customer, there’s no point in having your cellphone jump onto Band 5 and say “hey, I’m here! Can any cell tower hear me?”. It’s a waste of time and more importantly your battery.
But when you don’t have a SIM card or you have a T-Mobile one and your phone searches bands 1, 2 and 3 and finds no T-Mobile service, it starts searching other bands (in case you’ll need to make an emergency phone call in the future) and registers with whatever cell tower has the best signal and can actually support voice calls (for example some cell towers or bands mught be only for data).
And when you make an emergency call, the number doesn’t even matter really. In the protocol for making calls (think cool handshake between phone and cell tower) there’s a signal to say it’s an emergency call. The tower sees it is an emergency call, prioritizes you over Karen calling wanting to talk to the manager, disconnects her and puts you through (I gotchu buddy).
It doesn’t even care what number you called because it’ll have to route you to a different 911 call center based on your location anyway. IIRC (it’s been a long while) I don’t think we even send out the phone number you called when it’s an emergency call. Phones have a common list of emergency numbers and it’ll connect you to emergency services even if you dial 911 in Europe even though the actual emergency call number in Europe is 112.
Depending on your phone’s capabilities (most phones these days) it’ll even automatically start doing a GPS fix and then send it out when it has your location.
So yeah, you aren’t going to be able to hack anything in the emergency call protocol to make free calls.
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