[@simpsonpg]

@simpsonpg asked the Naked Scientists:
   @NakedScientists When someone phones my mobile, how dose it know where I am?


What do you think?

[Bored chemist]

Because your 'phone continually broadcasts it's identity and the cellular network knows which tower picked up that broadcast.

[RD]

When your mobile phone is on it transmits* a signal even when you are not making a call.
This signal, which identifies you, tells the network where you are.

[* every few minutes ]

[BrushJohn]

There are some service you need to activate or enter some number then you are able to know where your phone are.

[graham.d]

It is possible to triangulate an approximate position by noting signal strengths at more than one cell-site. This is not recorded routinely though and is not always reliable (you may only "see" one cell-site for example) but is a facility that can be invoked if required by security forces (for example). In fact there are quite a few systems available (and sold as separate software options) that the general public are unaware of, including things like remote phone tapping and recording.