Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!ucsd!ucsdhub!hp-sdd!ncr-sd!serene!pnet12!gbell
From: gbell@pnet12.cts.com (Greg Bell)
Newsgroups: sci.electronics
Subject: Flourescent light communications
Message-ID: <1129@serene.UUCP>
Date: 29 Nov 89 20:15:46 GMT
Sender: root@serene.UUCP
Organization: People-Net [pnet12], Del Mar, CA
Lines: 27


I just read a great "Gee, I wish I'd thought of that" in the recent issue of
Photonics Spectra:

Apparently, the idea of making a store's price tags electronic has been held
up because of the high cost of IR or microwave transmitters needed to send the
data to all the tags (supermarkets would especially be candidates for this
kind of product).

Some ingenious Australian company came up with the idea of
modulating the store's flourescent lights with the tag data!  Obviously, the
lights are modulated at a frequency  high enough that the flicker isn't
visible to the customers.  An address, and a command are sent, and the
appropriate tag responds appropriately since they all can see the lights.  In
addition, the tags are all powered by solar cells (ie. off the same light
source that's carrying their data!).

The system transmits at 70b/sec.  For a large supermarket, with 5000 labels,
it would take about an hour to update everybody.

What a great idea!  If this particular idea doesn't have other applications,
this approach to problems certainly does!

    Greg Bell_________________________________________________________
      Hardware hacker          |
      Electronics hobbyist     | UUCP:  uunet!serene!pnet12!gbell
      EE major at UC San Diego |


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