Inductive Coupling to transfer power is used in the real world. I believe
that it is used to charge some electric vehicles like forklift trucks,
pallet handlers etc
I have had a quick look at likely sources but not come up with any reference
sites. I believe that the system is also proposed for electric cars. If I
remember correctly the efficiency is not good, particularly when compared to
plugging in a cable. However, you do not have to remember to unplug the
cable before driving off !!!

Regarding Signalling an On/Off instruction.

Precisely what do you mean by "a few feet", I'm sure we have all been caught
out be imprecise phrases such as this :-)    The speaker means 50 feet, the
listener assumes he means 2 feet. The result being a cock-up

Inductive Coupling is one method, but has very limited range, If you want to
rule out RF such as 433MHz then how about using 40kHz Ultrasonic Transducers

Regards
Chris

> > Dear all,
> >
> > I still didn't get any replies about inductive coupling. Forget the bit
> > about battery charging, if you like :-) - perhaps if I phrase it
> > differently - how would you transmit an on-off switch signal a few feet
> > without using RF? (no infra-red etc. please!).
> >
> > 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
> > Send subscribe/unsubscribe to listproc@info.curtin.edu.au
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