Hypothetically speaking, if someone is living in New York and they call 911, how does the call not go through a hospital in Los Angeles or other city from another state? How does the call automatically transfer to a local hospital in the area one lives in?
In: Technology
To make the reasoning short and non-technical,
Your phone operator is at all times aware of where you are. When your phone is on, it talks to the cellphone towers.
To make it possible to call you, it’s required that the cellphone tower that you are currently communicating with knows that you are supposed to be there. For any of it to work, the tower ALSO needs to share that information with a centralised control system.
The first thing the phone system does when it tries to forward a call to you, is that it asks the centralised system “alright, who is it that talks to that phone right now?” so that the actual phonecall can be forwarded specifically to that cell tower that is tasked with maintaining the phonecall.
There are some more fiddling that occurs when a phone moves out of convenient reach of a cell-tower, and hooks up to another instead in a fashion that appears seamless. But those are not relevant for this explanation, besides that you need to know that when the phone moves, the centralised system gets an updated summary of where you are instead.
When you make a 911 call, the phone operator is forced by law to look at this information and make a sensible assumption on which emergency call centre to forward the call to. Generally speaking, this is a manually assigned decision on each and every cell tower, when it’s erected.
To top it off, many cell towers are “divided” into several cells. One antenna in each direction, so to speak. And that also offers an ability for the cell-tower to distinguish your rough direction relative to the cell-tower. And that information is also passed along to the call centre, together with the cell towers physical location. (It still gives a lot of guesswork since the information is something like “I am at 2200 Main Street, and my westward pointing antenna can hear this phone. It ought to be somewhere within a mile or so in that general direction.” But at least it’s something.)
In some places, regulations are pushing for cell towers to be able to force phones to activate their GPS and track themselves. In some places, cell towers already force phones to activate their GPS occasionally. But there are still phones on the market that has absolutely no GPS in them, and the technical information from the cell tower always works, which makes it a convenient start.
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