General Question

elbanditoroso's avatar

How does the cell phone know where the state line is?

Asked by elbanditoroso (30716points) April 17th, 2012

I was driving the other day between two states – Alabama and Georgia. The state line happens to be the demarcation point between the Eastern and the Central time zones.

I happened to have my cell phone in my hand, and just as I got to the state line – like, within 50 feet of it – the time on my cell phone changed from 3:00 to 2:00 (I was going west).

I know that most cell phones get their time set by signals from the cell towers; that makes sense. But how can the towers know that I was at the state line? Is there GPS working in here, too?

(of course the clock on the dashboard did not change – which is a pain)

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7 Answers

dabbler's avatar

The towers know where they are, what states they are in, and you got passed along from a cell on a tower in one state to a cell on a tower in the other state.

JLeslie's avatar

It doesn’t happen the second you cross the line always. It has to do with the towers as @dabbler said. As you lose the signal from the tower in GA and pick up the one in AL the time changes. People living near borders of some states probably have some problems with it.

wundayatta's avatar

Yes. GPS plays a role. However, even without GPS, the location of a cell phone can be pinpointed by triangulating the signal strength from 3 towers. There are several apps that take advantage of this fact to help you locate lost and stolen cell phones.

marinelife's avatar

The towers your cell phone is pining off know where your cell phone is.

CWOTUS's avatar

Zey haff zere vays…

… and it has to do with the coordination of the signal between the towers, as has been noted.

ETpro's avatar

The software triangulates your phone’s ping off all receiving towers, calculates the strength of each signal, and from that data calculates your location. It’s nowhere near as accurate as GPS, but it’s good enough for government work.

adr's avatar

Funny story: When on the Vancouver Island, sometimes the cellphone providers think you’re in the USA. This is annoying because Canadians can randomly get high phone bills due to supposed roaming charges even if they never left Canada. Silver lining? Some clever Canadians have figured out that when they do go to the US and make phone calls, they can lie and tell their phone company that they were really only on the Vancouver Island, and the charges will be dropped!

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