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IIRC, it's not exactly like the device detects you're in an emergency call, finds its GPS coordinates, and then sends the GPS coordinates along with the call initiation. You want to initiate the call, regardless of the status of finding the GPS location. I'm greatly simplifying, but you can think of it like I'm making any phone call, it's just I dial 911. This does set some special in-band signalling, that I'm dialling sos, and set's bits that say this is an emergency connection, so retain it over non-emergency calls. There is then some special routing that takes place, so that based on general location, you get routed to the correct 911 center. Then, the network has a sort of API, that lets the 911 center make an API call, requesting the current GPS coordinates. This can take time, as you might not be able to pick up satellites, or use other sources. then think of something like a kidnapping, you might need to be able to track a moving target, so this process can be repeated and updated or more accurate coordinates can be received. |