From: azur@netcom.com (Steve Schear)
Date: Sun, 5 Jan 1997 21:29:54 -0800 (PST)
To: Secret Squirrel <nobody@squirrel.owl.de>
Subject: Re: High-tech tracking by police raises legal outcry
Message-ID: <v02140b04aef63a3e801a@[10.0.2.15]>
MIME-Version: 1.0
Content-Type: text/plain


>>From The Orange County Register, Front Page, Sunday 1-5-97
>
>Police across the country secretly tail hundres of people each year by
>attaching high-tech
>transmitters to suspects' cars and tracking them on squadroom computer screens.
>
[snip]
>
>The technology, marketed by a company called Teletrac, is simple: A
>tramsmitter sends a
>radio signal to a computer, which pinpoints the car's street location.
>Police with the
>proper software can follow a transimitter-equipped vehicle in real time as
>it moves across a
>street map on a computer screen.
>

I'm quite familiar with Teletrac's technology.  It consist of a receiver,
very similar to a pager, tuned to about 930 MHz and a transmitter (up to a
50 Watt peak power) operating in the unlicensed 902-928 MHz band using
direct sequence spread spectrum coding.  The service acts by sending out
'ping' messages to mobile devices on the pager channel and triangulating
for the their return pulses via a rather dense chain of stations in each
city/area covered.  This is very similar to how aircraft transponders work.

There are at least three straightforward countermeasures to Teletrac.
First, look under your car.  Teletrac requires a relatively good antenna
placement.  The box should be visible.  Second, a sweep by any professional
surveillance service will surely find it.  Third, any competent RF person
(e.g, an amateur radio operator) can retune any number of narrow band 900
MHz RF comsumer electronic devices (e.g, cordless phone) to jam the
Teletrac paging receiver and disable all such devices in your proximity.
Please note this is not legal, but your unlikely to get caught.


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