Dear Andy/Russell/Roman/Graham,

I thought those anti-shoplifting tags that you describe WERE RFID tags?
Are they different? How do they work? It sounds like exactly what I
want.

I think it's clear that I need to seperate the two functions of receiver
proximity detection and battery charging - the latter is obviously going
to need a very short range inductive link. I'd still like to know about
this as well, by the way - how many turns for each coil and what
frequencycurrent etc to use.

AS far as the data link is concerned, can I stress again that this is
not the major telemetry channel - that goes via a conventional RF
transmitter. All I need is someting to tell me that I am withink range.
I could arrange for coils in the carpet (the device is in the person's
shoe) but I'd rather have it based on the base-station PC if possible.
What about tramsmitting something via the AC power lines in the house -
would that work?

Chris
--
Dr. Chris Kirtley MD PhD
Associate Professor
HomeCare Technologies for the 21st Century (Whitaker Foundation)
NIDRR Rehabilitation Engineering Research Center on TeleRehabilitation
Dept. of Biomedical Engineering, Pangborn 105B
Catholic University of America
620 Michigan Ave NE
Washington, DC 20064
Tel. 202-319-6247,  fax 202-319-4287
Email: kirtley@cua.edu
http://engineering.cua.edu/biomedical

Clinical Gait Analysis: http://guardian.curtin.edu.au/cga
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