Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!sun-barr!newstop!central!letni!rwsys!sneaky!gordon
From: gordon@sneaky.lonestar.org (Gordon Burditt)
Newsgroups: comp.society.futures
Subject: Re: Tracking and security
Keywords: phones, etc
Message-ID: <56991@sneaky.lonestar.org>
Date: 18 May 91 01:04:42 GMT
References: <1991May15.215007.26679@sugar.hackercorp.com>
Organization: Gordon Burditt
Lines: 30

>>P.S. Cellular phones may not be very *GOOD* tracking devices, but they
>>can be located within a few miles.
> 
>Cellular phones can be located only when they are transmitting.  The

Cellular phones can be made to transmit any time they are turned on by
transmitting a "poll" for the specific registered phone number / serial
number of the cellular phone, and getting that phone to respond.  This
locates the phone to what cell it is in.  This operation may be done as 
part of setting up an incoming call, but it can be done silently 
without continuing to the point of ringing the phone.  

This would work even if the phone is in a "standby" mode in which it can
still receive calls.

(When I say the cellular phone transmits, I do NOT mean that sounds near 
the phone are transmitted over the air.  What's being transmitted is
protocol information and negotiation between the phone and the cell site.
It would not be difficult to design an "open mike" mode into a cellular
phone.  If it was used too much, the user would notice the batteries
don't last long.)

Directional antennas at the cell site, and measures of signal strength
(the cell site can set the transmitting power of the phone) can locate 
the phone more closely.  This equipment may already be in use at the
cell site for better handling of handoffs and reducing spillover into
adjacent cells.

					Gordon L. Burditt
					sneaky.lonestar.org!gordon