Subject:  Anti theft devices (Tegenfeldt)..
Date:     Thu, 4 May 2000 050320 -0500 (CDT)
From:     "Roy L. Beavers" 
To:       emfguru 
--------------------------------------------------


.......Clas is reminding us that the "Blue World" is more than
the "obvious" EMF sources we tend to focus our attention on.....

Roy Beavers (EMFguru)
roy@emfguru.com

.....It is better to light a single candle than to curse the darkness.....
                    NEW!!! Website... http://emfguru.com
...................People are more important than profits.................
                            
             DO YOU KNOW OF OTHERS WHO SHOULD BE ON THIS LIST???

---------- Forwarded message ----------
Date: Thu, 04 May 2000 07:01:25 +0200
From: Clas Tegenfeldt 
To: "Roy L. Beavers" 
Subject: Anti theft devices

Lately there has been a discussion about the bar code scanners
used to read the identity of packages to access their price. These
are mostly harmless. However, I believe the discussion is focused 
on the wrong source, the barcode readers are not an EMF exposure
to be especially catious about, but various anti-theft devices
give off immensively strong EMF!

First you have the anti-theft loops at exits in stores, often at
or very near the cashier/shop assistant. These are of two kinds
a low frequency and a high frequency type, each using a magnetic
field to induce current into a resonant circuit (LC) put onto/into
the goods to be alarmed. The low frequency type gives of tens of 
mikroteslas in the 5-2000 Hz band at up to 2 meters! The high 
frequency type gives very little in 5-2000 Hz but is registered 
some in 2-400 kHz, unfortunately I have no numbers at hand (in
the head) for these.

Second you have the device used to remove or activation of the 
tags themselves. On clothes etc. you physically remove the tag
but on books etc. you just deactivate it. This is done with a 
forcefull magnetic field, this is also why there are zones on the
cashiers desk where you shouldn´t put your credit card...
This magnetic field is very strong and very near the cashier.
Also, there are one more device, the one used in libraries where
the tags must be re-activated, these machines are notoriusly giving
off severe magnetic fields, also very close to the person handling
the process.

As I see it, there are lots of sources around a cashier in the
supermarket, shops, etc. but also in libraries. Among the strongest
and almost always dominating sources are the anti-theft devices...

Skip the barcode debate and concentrate on the big issues instead.


Clas Tegenfeldt

BEMI
Tornevalla Gamla Skola
S-590 62 LINGHEM, SWEDEN

tegen@bemi.se, http://www.bemi.se
Telephone +46 (0)13-74 000, telefax +46 (0)13-13 47 00




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Reprinted with permission of Roy Beavers, http://www.emfguru.com