Hello:

There is already a government mandate (Emergency 911 or E911) that the location
of all phones calling 911 will be known to allow emergency response teams to go
to the caller.  This is now easily done with wired phones, but cell phones are
more difficult.

There are two approaches, one is to use GPS in the phone and the other uses Time
Of Arrival.  In the TOA case remember that there are typically 3 (and sometimes
more) cell sites that can "hear" a cell phone so it's position within that
triangle can be determined.  Note that this does not require that the phone is
in use, only that it is turned on.  The phone and the cell sites are always
having a conversation about signal strengths (a coarse measure of location) and
deciding if the phone should be handed off to an adjacent cell site.

This also applies to two way pagers.  That's why the WTC & pentagon rescue
workers are asking for cell phone numbers and pager numbers of missing persons.
If the cell or pager is turned on, it may be located.

73,

Brooke Clarke
http://www.prc68.com

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