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@netbox.com PO Box 897 Oakland CA 94604