Watching movies i get this question a lot
If a person throws his phone away , how does the police know who is the owner of the phone?
In: 8
Here’s a simplified explanation of how a cell phone works:
Your phone has a radio antenna inside that it can use to “shout” messages out around it. When you turn your phone on from a cold start, it will immediately “shout” a message in all directions to the effect of, “Is anyone there?”
The world around you is dotted with radio towers that listen for messages like this. They can usually be identified by their [distinct triangular platforms with tall, vertical slats on the edges](https://upload.wikimedia.org/wikipedia/commons/8/85/Cell-Tower.jpg). They can hear your phone shouting up to a dozen or so miles away in optimal conditions. When these towers hear your phone, they shout back, “Hello, I am Tower #####, I belong to XYZ company, I support this list of protocols…”
Your phone contains a tiny little ID card indicating who you pay for phone service and your account number. This is what your SIM card is. If your phone finds a tower it thinks it is compatible with, it will respond to that tower by presenting the information on the SIM card.
The tower phones up home base at the company who owns the tower and runs a few checks. Verifies if you’re a valid customer, whether you’re up to date on payments and are elligible for service, etc. If all the checks pass, the tower says, “ok, if you want to do data stuff, just let me know”. At this point, the signal bars pop up on your phone indicating you have service. The number of bars tell you how good the connection to the chosen tower is.
Where this becomes important to your question is that the towers keep logs of everyone who tries to connect. If you connect to a tower to get service, it’s known that some device with a SIM card connected to your account must be within a relatively small radius of that tower. If there are many towers in range, some fancy math can be done to triangulate a more precise position of the device. The phone company has access to all of this information.
For the police to get it, they have to ask the phone company to cooperate. They usually do.
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