Comment by usr1106
2 years ago
At least 2 decades ago when I worked with phones the phone as a list of emergency numbers which could be updated to country-spefic values. Often 000, 112, and 911 were always present.
Once the software notices one of these numbers dialled call handling will go a completely different code path than normal calls.
I have no idea how things work in Android, where you obviously must have VoIP hooks?
>I have no idea how things work in Android, where you obviously must have VoIP hooks?
Yes, there's emergency IMS (basically volte/vonr version of SIP) profiles the phone is supposed to register to and all the carriers towers advertise emergency numbers in their signaling.