€ [17] ELECTRONICS (9:1992/111) €€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€ ELECTRONICS €
 Msg  : 20 of 167 - 18 + 24                                                     
 From : David Hinerman                      1:226/120       Thu 11 Mar 93 08:10 
 To   : Roger Kowalchyk                                                         
 Subj : Theft sensor                                                            
€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€

RK>I'm curious if anybody here knows how those anti-shoplifiting sensors
RK>work. They are used often in the electronics section at various
RK>department stores. I cut one apart that was on the box of a CD I
RK>bought. There were two thin pieces of metal inside. One was cut
RK>diagonally, if I remember correctly.

Roger,

Some of them have a piece of magnetic material inside, and magnetometers at the
doors. They use a special degaussing "pad" on the checksout counter to "erase"
the magnetic tag. The pad usually says "Do not lay bank cards, credit cards, or
ATM cards on this pad."

The people at the local Woolworth store have laid my American Express card on it
twice. It doesn;t take more than about a second to wipe the magnetic stripe
clean :-(

RK>Now just the other day I bought a 4 in 1 remote control. It had a 1.5"
RK>square sticker on the package. On this sticker there are 8 square
RK>concentric traces. It also looks like the inside and outside trace, or
RK>maybe all, are connected in one corner. There are some other small
RK>details too. What is this? I would guess some kind of tuned antenna.
RK>(That resonates a certain freq. when in the presence of a certain
RK>freq.) A wild guess anyway. :)

I think you're right about this one. It's probably a resonant circuit, and they
have the equivalent of a grid-dip meter at the exit. Our local library uses
these.

Dave

 * OLX 2.1 TD * Bird owners have a cheep on their shoulder!


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 * Origin: Colossus - The Columbus Computer Society - Columbus, OH (1:226/120)

€ [17] ELECTRONICS (9:1992/111) €€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€ ELECTRONICS €
 Msg  : 24 of 167 - 20 + 160                                                    
 From : Tony Rothrock                       1:288/2         Fri 12 Mar 93 01:52 
 To   : Roger Kowalchyk                                                         
 Subj : Theft Sensor                                                            
€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€

RK>I'm curious if anybody here knows how those anti-shoplifiting sensors
  >work. They are used often in the electronics section at various
  >department stores. I cut one apart that was on the box of a CD I
  >bought. There were two thin pieces of metal inside. One was cut
  >diagonally, if I remember correctly.

RK>Now just the other day I bought a 4 in 1 remote control. It had a 1.5"
  >square sticker on the package. On this sticker there are 8 square
  >concentric traces. It also looks like the inside and outside trace, or
  >maybe all, are connected in one corner. There are some other small
  >details too. What is this? I would guess some kind of tuned antenna.
  >(That resonates a certain freq. when in the presence of a certain
  >freq.) A wild guess anyway. :)

Your on the right track for both.  The store probably has stantions that
you walk between to leave the area or store.  These are transcievers.
they send out an RF signal that the metal strips or concentric traces
pick up and either reflect or resonate back at a different freq.  In the
simple systems it's likened to a metal detector.  All hte tags are the
same and the sensors pick them up, used a lot in video rental stores.
The good systems work this way.  The strip or concentric sends back a
unique signal that the system interpets a a code for that specific item.
When you buy the thing they sometimes say they are "deactivating" the
tag. NOT!  what they are doing when they hold it over the plate or pass
it in front of some device is picking up the signal, and telling the
system not to go into alarm when it senses this code.

A major conpany in this arena is Central Point Software.

Tony
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