cell phone anonymity

[Greg Broiles]

On Mon, Jan 08, 2001 at 02:14:43PM -0500, Ray Dillinger wrote:
> 
> This pretty much kiboshes the idea that they might be continuously 
> broadcasting; I'm more concerned about the idea that there may be 
> some signal they're passively listening for, to which they will 
> *respond* with a pulse signalling their location. 

Indeed, Motorola has done a good job building their pagers so that they'll
run a long time on a relatively small battery, because they've got internal
timers which shut down even the receive circuitry between transmission
cycles; they wake up every so often to listen for pages, then go back to 
sleep - if they go outside a coverage area, the battery life drops 
substantially because the receive circuitry is active full-time waiting
to find a familiar signal.

I have no information that this technique has been used in cellphones - or
will be - but it's already in consumer-grade technology that's been shipping
in volume for years now. So it's certainly not difficult to build a 
wireless device which remains active on very low power, waiting for a 
signal from its Real Owner to wake up and do something. 

--
Greg Broiles gbroiles at netbox.com
PO Box 897
Oakland CA 94604