U.S. patent number 3,859,652 [Application Number 05/266,130] was granted by the patent office on 1975-01-07 for method and apparatus for detecting the theft of articles.
This patent grant is currently assigned to North American Systems Corporation. Invention is credited to Kenneth Clarkson, Roger L. Hall, Edward S. Wainwright.
United States Patent |
3,859,652 |
Hall , et al. |
January 7, 1975 |
METHOD AND APPARATUS FOR DETECTING THE THEFT OF ARTICLES
Abstract
The theft of articles or goods maintained in a vending place
such as a department store having at least one exit passageway is
prevented by affixing thereto a preferably small detection element
comprising a receiver of first predetermined frequency, a
transmitter of second predetermined frequency, and power supply
means coupled from said receiver and capable of disabling said
transmitter. At the authorized checkout area of the store there is
disposed a relatively high power transmitter of first predetermined
frequency capable of preferably permanently disabling the power
supply means and in turn said transmitter of second predetermined
frequency of the detection element. In one preferred embodiment the
power supply means includes a rectifier circuit which is destroyed
(burned out and thus opened) when the detection element comes
within predetermined proximity to the high power transmitter at the
checkout area. At the exitway there is disposed a transmitter of
first predetermined frequency and a receiver of second
predetermined frequency which only detects a signal when the power
supply means has not been disabled at the authorized checkout area
whereby an alarm signal is generated.
Inventors: |
Hall; Roger L. (Francestown,
NH), Wainwright; Edward S. (Nashua, NH), Clarkson;
Kenneth (Tonasket, WA) |
Assignee: |
North American Systems
Corporation (Londonderry, NH)
|
Family
ID: |
23013294 |
Appl.
No.: |
05/266,130 |
Filed: |
June 26, 1972 |
Current U.S.
Class: |
340/572.3;
342/42 |
Current CPC
Class: |
G08B
13/2434 (20130101); G08B 13/2414 (20130101) |
Current International
Class: |
G08B
13/24 (20060101); G08b 013/22 () |
Field of
Search: |
;340/258R,280,224
;325/16,21,185,186 ;343/6.8R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Swann, III; Glen R.
Attorney, Agent or Firm: Wolf, Greenfield & Sacks
Claims
What is claimed is:
1. A system for detecting the unauthorized removal of articles from
an enclosure having a checkout area and a passageway through which
said articles may be moved, said system comprising;
a transmitter of a signal of first signal characteristic disposed
at said passageway,
a receiver of a signal of second signal characteristic disposed at
said passageway and being non-responsive to a signal of first
signal characteristic,
means for establishing an alarm condition when said receiver
receives a signal of second signal characteristic,
a detection signal attached to the article and comprising a
receiver of a signal of first signal characteristic, a transmitter
of a signal of second signal characteristic, and means responsive
to a signal, of a level less than a predetermined threshold level,
from said receiver of a signal of first signal characteristic for
providing power to said transmitter of a signal of second signal
characteristic,
a power transmitter of a signal of first signal characteristic
disposed at said checkout area for establishing a signal of a level
greater than said predetermined threshold level from said receiver
of a signal of first signal characteristic to thereby inhibit the
providing of power to said transmitter of a signal of second signal
characteristic when said article is at said checkout area,
whereby said receiver of a signal of second signal characteristic
receives a signal to thereby establish an alarm condition when an
unauthorized removal of said article has occurred, and does not
receive a signal when an authorized removal has occurred,
said receiver of first characteristic comprising a tank circuit and
said transmitter of said second characteristic comprising a tank
circuit, said power providing means including a transistor having
an input electrode and an output electrode,
means for biasing the transistor including a resistor coupled to
the input electrode of the transistor, a diode coupling from the
output electrode of the transistor to one of the tank circuits and
capacitance means coupling from the output electrode of the
transistor to both tank circuits,
each said tank circuit including an inductor defining part of the
tank circuit and forming an antenna means for transmitting or
receiving signals.
2. The system of claim 1 comprising a demodulator associated with
said receiver of a signal of second signal characteristic.
3. The system of claim 2 comprising means positioned adjacent the
checkout area for registering a total count of each article passing
through the checkout area.
4. The system of claim 3 wherein said means for registering
includes an accumulator means.
5. The system of claim 1 wherein the anode of said diode couples to
the output electrode and the cathode of said diode connects to the
receiver tank circuit.
6. The system of claim 1 wherein said detection element comprises a
modulator coupling to said transmitter of a signal of second signal
characteristic and means for coupling power to said modulator from
said power providing means of said detection element.
Description
FIELD OF THE INVENTION
The present invention relates in general to an apparatus or system
and associated method of detecting the theft of articles from a
vending place such as a department store. More particularly, the
present invention is directed to the type of system that employs an
electronic detection element preferably of small integrated-circuit
size affixed to the article or goods.
BACKGROUND OF THE INVENTION
Many different means have been devised for preventing or deterring
the theft of articles or goods from a store or other vending place.
Some of these means include mirrors, security police, cameras,
television with video recording and gentian violet marking. None of
these means are completely effective, and once the thief has been
able to conceal the item these above devices cannot detect the
passage of the item through the exitway of the store.
The problem of stolen merchanidse is further complicated by the
possible legal rights of the individual against false accusations.
Thus, persons in authority at the store are hesitant to accuse any
potential thief, in the absence of effective detection means, for
fear of the possibility of a suit for defamation of character being
filed. Also, any false accusations may have a deleterious outcome
regarding the good-will of the store.
Accordingly, it is important that the detection means accurately
identify, preferably at the exitway of the store, articles that
have not passed through the checkout counter and been paid for. In
the past there have been both electrical and mechanical devices
designed. Generally, however, these devices are too costly, too
dangerous, or too unreliable. One technique, for example, shown in
U.S. Pat. No. 3,582,931 uses a radioactive material affixed to the
article. The problem with this technique is that the articles
carrying the material may be adversely affected by the presence of
any radioactive material. Another technique is to use a sensitive
reed switch (see U.S. Pat. No. 3,577,136) which is responsive to a
magnet disposed at the exitway. This type of a device has, inter
alia, the disadvantage that it can be too easily falsely triggered.
Still another prior art device is of the resonant frequency type
(see U.S. Pat. Nos. 3,493,955 and 3,500,373) wherein a resonant
circuit is affixed to the article and a receiver/transmitter
combination is used to monitor changes in the ambient energy level
due to the presence of the resonant circuit. This device also is
susceptible to false triggering because the frequency sensitivity
of the energy level monitoring equipment is quite low and metal
objects can cause false triggering.
OBJECTS OF THE INVENTION
Accordingly, it is an important object of the present invention to
provide an improved apparatus or system and associated method for
detecting the theft or articles or goods from a vending place such
as a department store. The apparatus of the present invention is of
the electromagnetic wave detection type.
Another object of the present invention is to provide a system for
preventing article thefts that is both safe and effective in
operation. With the apparatus of the present invention there is no
exposure to harmful radiation.
A further object of the present invention is to provide an
apparatus for monitoring the unauthorized passage of articles past
a predetermined checkpoint preferably adjacent an exitway of the
store wherein there is no need for additional security personnel
and wherein the apparatus is readily concealable from the view of
the ordinary purchaser.
Still another object of the present invention is to provide a
system for preventing article thefts that effectively distinguishes
between the authorized and unauthorized passage of articles past a
given checkpoint thereby alleviating the false alarm problem.
An additional object of the present invention is to provide a
detection element that readily impregnates or adheres to various
articles whether constructed of paper, cloth, wood, plastic, etc.
that is very small in size, and that may be easily disabled by even
non-skilled workers.
SUMMARY OF THE INVENTION
To accomplish the foregoing and other objects of the invention,
there is provided a system for detecting the unauthorized removal
of articles from an enclosure such as a department store having a
checkout area and a passageway through which the articles are
generally moved from the enclosure. The system comprises a
transmitter of a first frequency and a receiver of a second
frequency both being disposed at the exit passageway. The receiver
of second frequency is not responsive to a signal of first
frequency. A means is also provided for establishing an alarm
condition when the receiver at the passageway receives a signal of
second frequency.
A relatively small detection element is attached to the article and
comprises a receiver of first frequency, a transmitter of second
frequency and means responsive to a signal, of a level less than a
predetermined threshold level, from said receiver of a first
frequency for providing power to the transmitter of a signal of
second frequency.
If the article is properly taken from the enclosure it passes
through a checkout area where there is located a high power
transmitter of a first frequency for establishing a signal of a
level greater than the predetermined threshold level from the
receiver of the detection element to thereby disable the power
providing means, interrupting power to the transmitter of the
detection element. Thereafter, when the detection element passes
through the exit passageway the receiver of second frequency
disposed at the exit passageway does not receive a signal because
of the permanently disabled power providing means and therefore no
alarm condition is established. Alternatively, if the article does
not pass as it should through the checkout counter area and is not
subjected to the high power transmitter disposed thereat, the means
for providing power to the transmitter of the detection element is
not inhibited and thus as the article passes through the exit
passageway the receiver disposed at the passageway will receive a
signal of a second frequency and thus there will be an alarm
condition established.
In accordance with another aspect of the present invention the
transmitter of a second frequency which forms part of the detection
element has a modulation means associated therewith. Each of the
modulation means is different for each type of article being
protected. By using a first frequency transmitter and second
frequency receiver just before the checkout area, it is possible to
keep track of all articles passing to the checkout area for
purposes of inventory control. For this purpose it is also
necessary to have some type of accumulator for distinguishing each
article and providing a cumulative count of each article sold.
BRIEF DESCRIPTION OF THE DRAWINGS
Numerous other objects, features and advantages of the invention
should now become apparent upon a reading of the following detailed
description taken in conjunction with the accompanying drawings in
which:
FIG. 1 is a schematic diagram showing the different areas of the
store and the components of the present invention associated
therewith;
FIG. 2A shows a block diagram of the detection element of the
present invention;
FIG. 2B shows a block diagram of the means provided at the checkout
area of the store;
FIG. 2C is a block diagram of the means provided at the exitway
area of the store;
FIG. 3 is a circuit diagram of a preferred embodiment of the
detection element shown in FIG. 2A;
FIG. 4 shows a block diagram of an alternate embodiment for the
detection element; and
FIG. 5 is a block diagram of the inventory monitoring means of the
present invention used in conjunction with the detection element of
FIG. 4.
DETAILED DESCRIPTION
FIG. 1 shows the three basic areas of a store that are of interest
in discussing the concepts of the present invention. Various
articles are disposed in storage or display area 10 in any known
manner and preferably each article A has a detection element
affixed thereto. FIG. 2A which is discussed in more detail
hereinafter shows a block diagram of one detection element of this
invention. If the article is being properly purchased it passes
from area 10 to checkout area 12 where there is usually disposed a
checkout counter 14 and associated cash register 16 or the like.
The high power transmitter of the present invention is disposed at
the checkout area 12 for disabling the detection element and
permitting passage of the article through the exitway area 14
without providing an alarm. This high power transmitter may be
disposed beneath the recess 18 provided in counter-top 20 of
checkout counter 14. A pair of doors 21 is shown in FIG. 1 for
providing final access to the outside of store or enclosure 22.
If the article A has not passed through the checkout area 12 and
has not been subjected to the high power transmitter thereat, when
the article does pass through the doors 21 means are provided
adjacent thereto as discussed with reference to FIG. 2C for
providing an alarm.
Referring now to FIG. 2A there is shown a block diagram of the
detection element 24 which is affixed to article A in an
appropriate manner. This detection element 24 is preferably
constructed by integrated circuit technology and may be no larger
than 0.025 sq. in. The detection element 24 includes an input
antenna 26 which couples to receiver R1. Receiver R1 is preferably
a fixed frequency receiver of frequency F1 which may be on the
order of 460 megacycles. The detection element 24 also includes a
transmitter T2 (and associated antenna 27), and a power supply 30
coupled from receiver R1 for delivering power to both receiver R1
and transmitter T2 when an input signal of frequency F1 is received
on antenna 26. Transmitter T2 may be of conventional design. Power
supply 30 which is discussed later with reference to FIG. 3
preferably includes a rectifier that is preselected so that if a
power greater than a predetermined threshold is received by
receiver R1 the rectifier of the power supply 30 is burned out
(opened) and thus when any future signal is received by receiver R1
the power supply 30 blocks power to transmitter T2 and prevents any
transmission of its associated frequency F2. Frequency F2 may be on
the order of 430 megacycles.
FIG. 2B shows the checkout area 12 and the transmitter 32 which is
a high power transmitter capable of generating sufficient energy
when the article is passed over the transmitter to cause the
rectifier of power supply 30 to be opened.
In FIG. 2C there is shown the exitway area 14 including a
transmitter T1 (with associated antenna 28) of first frequency F1
and a receiver R2 (with associated antenna 29) of second frequency
F2 having an alarm 34 associated therewith for generating an alarm
signal when a signal of frequency F2 is received by receiver R2. If
the article has been appropriately passed through checkout area 12
and passes as shown in FIG. 2C between transmitter T1 and receiver
R2 the signal from transmitter T1 is blocked because the rectifier
of power supply 30 has prevented transmission of any F2 frequency,
and thus receiver R2 does not trigger alarm 34.
Referring now to FIG. 3, there is shown a circuit diagram for one
embodiment of the detection element 24 shown in a block diagram in
FIG. 2A. The detection element 24 comprises a receiver R1, a
transmitter T2, and power supply 30. The receiver R1 includes a
tank circuit comprised of capacitor C1 and an inductor L1.
Similarly, transmitter T2 includes a tank circuit comprised of
capacitor C2 and inductor L2. The inductors of these tank circuits
function as the antennas of each tank circuit.
The power supply means 30 comprises transistor Q1, diode D1,
capacitors C3 and C4 and ressistor R. The collector of transistor
Q1 couples to transmitter T2 and the emitter of transistor Q1
couples by way of a diode D1 to receiver R1. Capacitor C3 also
couples from the emitter of transistor Q1 to both receiver R1 and
transmitter T2. Resistor R and capacitor C4 are coupled, in
parallel, from the base of transistor Q1 to transmitter T2.
Resistor R establishes the proper bias for the base of transistor
Q1 and capacitor C4 is an AC bypass capacitor. It is the diode D1
that is destroyed when receiver R1 receives a signal of strength
greater than a predetermined threshold level. This level is a
function of the type diode selected. When diode D1 is burned out
transistor Q1 can no longer supply power to either receiver R1 or
transmitter T2.
Because the receiving and transmitting antennas (inductors L1 and
L2, respectively) are much smaller than a half wave, an optimum
inpedance match has been calculated at the terminals of the
antenna, of approximately 73 ohms. By chosing a five microfarad
capacitor for capacitor C1 and assuming a resonant frequency of 460
MHZ for receiver R1, an inductance of approximately 6,000 .mu..mu.
henries can be calculated for inductor L1. A loop of wire whose
radius is 1/50 inch and whose thickness is 4 .times. 10.sup..sup.-4
inch can be used for inductor L. Using the same value of
capacitance for capacitor C2 the inductance in the transmitter can
be calculated to be approximately 5,800 .mu..mu. henries, assuming
that the transmitter T2 has a resonant frequency on the order of
430 MHZ.
Thus, when the receiver R1 is receiving a signal of frequency F1,
diode D1 rectifies the output from the tank circuit of receiver R1
and transistor Q1 provides power by way of capacitor C3 to both
receiver R1 and transmitter T2. A feedback line 36 couples from
transmitter T2 to capacitor C4 for providing regenerative feedback
to the power supply means 30. When the circuit shown in FIG. 3 is
passed adjacent the transmitter 32 shown in FIG. 2, the power from
the transmitter 32 which is received by receiver R1 is sufficient
to burn out diode D1, thereby inhibiting the power supply means 30
and the transmitter T2 shown in FIG. 3. When the article is
subsequently passed through the exitway area 14 shown in FIG. 2C
the transmitter T2 is not capable of sending any signal to receiver
R2 at the exitway area and thus no alarm condition is generated. If
the circuit of FIG. 3 is not subjected to the high power
transmitter 32 the diode D1 is not burned out and thus transmitter
T2 is capable of generating a signal received by receiver R2 at the
exitway area 14 for generating an alarm condition by means of alarm
34.
Referring now to FIG. 4 there is shown a block diagram of another
embodiment of a detection element of 24. The block diagram of FIG.
4 is similar to the previous block diagram of FIG. 2A with the
addition of a modulator 40 which receives an input from power
supply 30 and has an output connected to transmitter T2. Modulator
40 may be of conventional design. When receiver R1 receives a
signal of frequency F1, power supply 30 provides power to receiver
R1, transmitter T2 and modulator 40, and the output signal from the
antenna associated with transmitter T2 is a modulated frequency
signal. A known type of amplitude modulation can be provided by
modulator 40. With the use of the detection element of FIG. 4 the
exitway detection circuitry may be similar to that shown in FIG. 2C
with the addition of a demodulator associated with receiver R2.
FIG. 5 shows a block diagram of an inventory monitoring means which
may be disposed before or after the checkout area 12 (see FIG. 1).
The inventory monitoring means may be used in conjunction with the
high power transmitter 32 at the checkout area 12. The purpose of
this inventory control means is to provide a running total of the
number of total articles of each type that have been passed through
the checkout area 12. By determining the total amount sold the
total inventory on hand can be easily calculated.
The block diagram of FIG. 5 is similar to the one shown in FIG. 2C
and comprises a tranmitter T1, a receiver R2, a demodulator 42, and
an accumulator 44. As the article A passes between the transmitter
T1 and receiver R2, a modulated signal from transmitter T2 of the
detection element shown in FIG. 4 is coupled to receiver R2. The
demodulator 42 demodulates this signal, thereby in effect
identifying the particular article being sold, and an accumulator
44 provides a total of the particular article that has been sold
over a part predetermined time period. The modulator 42 and
accumulator 44 may both be of conventional design and would include
various electronics components. Accumulator 44 may even be a
general purpose digital computer. Also, the apparatus shown in FIG.
5 may replace the detection circuitry of FIG. 2C in one particular
system.
In accordance with another aspect of this invention the transmitter
T1 may have a modulator associated therewith (see FIG. 2C), in
which case receiver R1 would have a demodulator associated
therewith for enabling operation of power supply 30 (see FIG.
2A).
Having described some embodiments of the present invention, it
should now become obvious that there are numerous other embodiments
and modifications thereof all of which should fall within the
spirit and scope of the present invention as defined by the
appended claims.
* * * * *