Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
X~i6
ANTI-TI~EFT P~ODU~r RACK AND MET~IOD
~EC~ICAL FIELD
The invention pertains to anti-theft devices
and methods for consurner product racks.
BACKGROUND OF T~E INVEN~ION
A fundamental requirement of product display
racks used in a retail enviroslment is that they present
the product in an aesthetically pleasing and readily
accessible manner in order to promote product sales.
10 However, in order to minimize loss of revenue due to
shoplifting, the rack should also provide some means of
indicating when products have been removed frorn the rack
for the purpose of theft rather than for purchase.
Approaches to the problem of shoplifting from
display racks include placing the product behind trans-
parent barriers with apertures that are large enough for
the human hand but too small to remove a product
displayed in the rack. When a consumer chooses a
product, he or she is required to request the aid of a
salesperson to unlock the transparent barrier allowing
removal of the product. The barrier may present an unac-
ceptable aesthetic impression of the product which will
result in lost sales. ~lso, requiring a customer to
request assistance in choosing a product will also result
in lost sales.
Often, transparent barriers are provided on
display racks which allow stacked products to be removed
one at a time from the bottom of the stack. The products
are removable only through a slot or the like in the
transparent barrier aligned with the bottom of the stack
o~ products. Requiring products to be removed only one
at a time clearly discourages multiple product purchases.
Other approaches display products on a rack
with the products being captured by a slidable retainer
or the like. If the slidable retainer is moved without
proper authorization, an electrical circuit is inter-
rupted and an alarm is sounded. Once again, this display
rack requires intervention of a salesperson in order to
deactivate the alarm system for legitimate product
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removal.
Therefore, product disp]ay racks which provide
protection against shoplifting either present an intimidating
display by enclosing -the product in a protective barrier, or
require the intervention of a salesperson to facilitate
legitimate removal of product, or both. These anti-theft
features combine to necessarily reduce product sales.
SUMMARY OF THE INVENTION
The present invention aims to avoid the above-
identified failings by providing improvements in and relating
to product unit racks and corresponding methods. The rack
may detect theft while providing absolutely no physical
barrier to product removal, ancl while requiring no sales-
person intervention for legitimate product removal.
In a representative aspect, the invention providesa method of indicating removal of product units from a
product unit rack including the steps of; monitoring a weight
of said rack; detecting a disturbance of said rack, according
to monitored weight; calculating a number of product units
removed from said rack corresponding to a difference in
monitored weights before and after said disturbance; and
providing an indication of unauthori2ed removal if said
number of product units removed from said rack is greater
than a limit. Similar methods may indicate theft of product
units or disturbance of the rack.
In another representative aspect, the invention
provides an anti-theft apparatus for use in a product unit
rack or the like. The apparatus includes means for measuring
a weight of a group of product units, means responsive to the
means for measuring for detecting disturbance of a group of
product units, means, responsive to said means for detecting
disturbance, for calculating a number of product units
removed from said group according to a difference between a
measured weight of said group before a detected disturbance
and a measured weight of said group after said detected
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disturbance; and means for indicating theft if said number of
product units removed from said group exceeds a limit. The
invention also provides an anti-theft product unit rack and
an apparatus for detecting theft of product units from a
group of product units~
According to a feature of the invention, the weight
of the display rack is monitored and an alarm is sounded if
the sensed weight indicates that more than a programmable
number of product units have been removed at one time. In
addition, an alarm is sounded if the sensed weight indicates
that more than a pro~rammable number of product units have
been removed from the display rack within a programmable time
period. Also, the present invention is capable of detecting
rack tampering such as "swapping" other products for product
units in the rack in an attempt to defeat the system. An
alarm will occur if the display rack is disturbed
continuously for a programmable amount of time, or if a
number of unstable episodes not associated with legitimate
product removal occur during a programmable time period.
The number of product units that must be removed in
order to sound either the instantaneous or periodic alarm is
variable, as are the time periods required for periodic
removal and for detection of disturbances. Therefore, the
present invention is applicable to retail environments having
high sales volume or low sales volume by simply reprogramming
the various alarm limits.
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The fact the rack of the present invention is
alarmed at all can be made completely transparent to the
consumer because no physical barriers appear between the
consumer and the product. In addition, the product is
S not restrained in any way from removal by a le~itimate
consumer. Also, intervention of a sales person is not
required for the removal of products.
In addition to sounding a local alarm if
removal of product units is detected in excess of the
10 program~able limits, the present invention can also sound
a remote alarm by wire or radio link. The invention also
provides a local acknowledge tone when product units,
less in number than the alarm limit, are removed from the
rack. The local acknowledge tone notifies the customer
that the display is monitored further discouraging
theft. The acknowledge tone may be used in addition to
or replaced by a synthesized voice which repeats a suit-
able salutation upon product removal. The local alarm
and acknowledge tone or voice may be silenced so that
only the remote alarm sounds.
The display rack can be used with a key lock
switch which allows the theft prevention feature of the
invention to be disabled for restocking of the rack. The
key lock switch may also be used to place the display
rack i31 a lock-up mode in which the display rack will
cause an alarm if any disturbance of the rack is
sensed. This serves to reduce employee theft during
periods when a store is closed but employees are
present. Finally, the key lock switch may be used to
place the display rack in a normal operating mode.
- The key lock switch may be replaced by, or used
in addition to, a switch controllable by a real-time
clock. The real-time clock controls the switch to modify
the various programmable alarm limits, and to automatic-
ally place the system in the lock-up mode dependent upon
time of day.
The present invention is also applicable to
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warehouse racks, such as pal~ets and the like, upon which
products are stored. The present invention Mllo~s such
warehouse racks to be protected from product theft with-
out providing expensive anti-theft measures such as lock-
able cages, and the like.
It is therefore a prirrlary object of the presentinvention to provide a rack for conswmer product units
that reduces loss of revenue due to shoplifting or
employee theft, but that does not discourage legitimate
product purchases
It is another object of this invention to
prevent consumer product theft from a product rack by
monitoring the weight of the rack holding the consumer
products, and by providing an indication, such as an
alarm, that a number of product units, in excess of a
programmable number of units, have been removed from the
rack.
It is yet another object of the present
invention to provide a consumer product rack that
provides an indication, such as an alarm, that a number
of product units, in excess of a programmable number of
units, have been removed from the rack during a program-
mable time period~
It is also an object of the present invention
to deter "swapping" of other merchandise for product
units contained in a consumer product rack by providing
an indication, such as an alarm, that the rack has been
disturbed continuously for more than a programmable time
period, or that the rack has experienced A number of
30 disturbances, in excess of a program~able number of dis-
turba-nces, during a programmable time period.
These and other objects, features and
advantages of the present invention will be seen more
clearly by reference to the following detailed specifica-
tion and to the appended drawings.
BRIEF DESCRIPTION OF TH~ DRAWINGæ
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Fig. 1 is a~ isometric view of a consumer
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product rack according to the present invention.
Fig. 2 is a partial sectional view of the base
of the rack shown in Fig. 1, showing the mechanical
details of a weight sensor used in the present invention.
Fig. 3 is a block diagram of the electrical
schematic of the present invention.
Fig. 4A-4D are a flow chart detailing the
computational steps of the theft detection routine of the
present invention.
Fig. 5 is a flow chart of the computational
steps of the alarm routine of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Fig. 1, a consumer product rack 10
according to the present invention is shown. Rack 10
15 includes a number of individual compartments 11, each
compartment holding a plurality of consumer product units
12 such as, for example, cartons of cigarettes. While
rack 10 of the preferred embodiment is a display rack
intended for placement in a retail establis~ent, it will
20 be understood that the present invention is equally
applicable to other product racks, such as warehouse
pal~ets, and the like. Rack 10 resets on base 13 which is
supported by a plurality of feet as shown in detail in
Fig. 2.
Referring to Fig. 2, which is a sectional view
of a portion of base 13, the detail of the placement of
weight transducers used in the present invention is
disclosed. Each transducer 16 is placed between a foot
17 and bracket lS. Bracket 18, in turn, is connected to
30base 13 by appropriate attachment means 19 such as screws
or rivets.
In practice, a plurality of weight transducers
16 are placed at a plurality of points beneath base 13 so
that the entire weight of rack 10 (Fig. 1) can be
35accurately sensed by the plurality of weight trans-
ducers. Each weight transducer is connected to the
weight signal processing circuitry of the present inven-
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tion (shown in detail in Fig. 3) by conductor 21 and
connector 22.
Weight transducers 16 are preferably of the
highly accurate vibrating wire-type which produce a Yol-
tage signal h~ving a frequency which varies in proportionto the weight sensed by the transducer.
Referring to Fig. 3, the hardware embodiment of
the present invention is shown. The invention uses a
central processing unit (CPU~ 31 to perform the calcula-
10 tions and to control the various input/output operationsof the present invention. Processor 31 can be, for
example, a type 8031 microcomputer available from Intel
Corporation.
Connected to processor 31 are data bus 32 and
15 address bus 33. Buses 32 and 33 allow proeessor 31 to
communicate with the various other hardware components of
the present invention. Processor 31 communicates with
read only memory (ROM) 34 and random access memory (RAM)
36. ROM 34 is used to store the control program of the
20 present invention shown in Figs~ 4A-4D and 5, while RAM
36 is used as a scratch pad memory. ROM 34 can also
store the synthesized voice of the acknowledge
salutQtion. It should be noted that both ROM 34 and RAM
36 may be located within processor 31, such as, for
25 example, in ~ type 8051 microcomputer available from
Intel Corporation.
The individual weight sensors 16 are connected
by conductors 21 to respective frequency counters 37
which, in turn are connected to data bus 32 and address
30 bus 33. The individual frequency counters 37 count the
frequency of the voltage produced by respective weight
sensors 16, and produce a binary word indicative of
sensed weight which is placed on data bus 32 when inter-
rogated by processor 31 Vifl address bus 33. A $ypical
35 accumulation period for counters 37 is 0.25 seconds. At
the end of a particular accu~ulation period, counters 37
Are reset and a new count is begun. Although Fig. 3
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shows only three sets of frequency counters and weight
sensors, any number of sensors and counters can be used
in the presen$ invention. Frequency counters 37 can be,
for example, type ~253 frequency counters manufactured by
Intel Corporation.
Also connected to data bus 32 and address 33 is
input/output controller 38 which can be, for example, a
type 8155 controller available from Intel Corporation.
Controller 38 is connected to ~anged switches Sl and S2
10 which allow a user of the system to program the system
for a specific application. Details of this
programmability will be discussed below.
Also connected to controller 38 is amplifier 39
which powers alarm speaker 41. Speaker 41 produces both
15 a local acknowledge tone and a local alarm. Alterna-
tively, a synthesized voice signal may be stored in ROM
34 and may be played instead of, or in addition to~ the
acknowledge tone. The volume of the acknowledge tone or
voice is controlled by potentiometer 42, and the volume
20 of the local alarm signal is controlled by potentiometer
43.
The tone and duration of the acknowledge signal
and the local alarm are adjustable by use of potentio-
meters 45-48. One end of each potentiometers 45-48 is
25 connected to a voltage source + V, and the other ends are
grounded. The wiper of each potentiometer is connected
to analog-to-digital converter 49 which, in turn, is
connected to controller 38. Analog-to-digital converter
~9 can be, for example, a type ADC0844 converter manufac-
30 tured by National Semiconductor Corporation.
_ Three positon key lock switch 50 is alsoconnected to controller 38. When switch 50 is in a first
position, the display rack is in a normal mode with all
features active. In a second position, key lock switch
35 50 disables the theft prevention features of the present
invention to allow restocking. Switch 50 can also be
positioned in a third position which places the rack in a
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night lock-up mode. In the night lock-up mode, any
disturbance of the rack will cause an alarm.
Processor 31 is also connected to data output
bus 51 which can be used to drive a display or printer
5 (not shown) for the purpose of monitoring the weight of
the system or monitoring the disturbance activity or
purchase activity of the system. Processor 31 is also
connectable to remote alarms 52 through individual links
53. Alarms 52 can be located far from the product
10 display rack for remote monitoring of the system. If
desire, the local alarm can be reduced to zero volume and
the product display rack can be monitored using only
remote alarms 52. Once again, it will be understood that
while only two alarms 52 are shown in Fig. 39 this
15 disclosure is offered by way of example rather than
limitation and any number of remote alarms may be used.
Linl~s 53 are preferably wire or radio link. A
preferred radio link may use, for example, a type D-24A
.; ~ransmitter 54 and a type D-67 receiver manufactured by
~:` 20 ~inear ~lectronics of Carlsbad, California. Since this
preferred transmitter 54 is powered by an internal
battery and sends a signal when its control contact is
open, this allows an alarm signal to be sent to remote
alarms 52 when the display rack becomes unpowered or if
25 the connection between processor 31 and links 53 is
severed. Links 53 can also be used to actuate a video
camera which will record activity in the vicinity of the
protected rack.
If links 53 are wire, elements 5~ in Fig. 3 can
30be appropriate line drivers.
_ Switch Sl, S2 are used by a system operator to
manually program various system par~meters as described
in detail below. The manual settings of switches Sl and
S2 may be overriden by contacts within switch S3. Switch
35S3 is controlled by real-time clock 55. Clock 55, in
combination with switch 53 allows one or more of the
various parameters to be automatically progral~nable
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dependent upon time o~ day. Clock 55 and switch S3 can
also be used to automatically place key-lock switch 50 in
the lock-up mode, for example, when a store is closed.
Referring to Figs. 4A-4D, the individual
processing steps of the present invention will be
described. After the routine is started, the states of
switches Sl and S2 are interrogated and parameters K0,
Kl, K2, K3 and K5 are set according to the following
Tables:
TABLE I
K0: Weight Limit For Instability
Sl-7 Limit tlOOths of Units)
closed 30
open 40
TABLE II
Kl: Instantaneous Removal Limit
Sl-l Sl-2 Sl-3 No. of Product Units
closed closed closed
open closed closed 2
closed open closed 3
open open closed 4
closed closed open 5
open closed open 6
closed open open 7
open open open 8
TABLE III
j K2: Unstable Episode Limit (C~ V~e cy'~e~)
Sl-8 Limit
closed lO
open 20
TABLE IV
K3: Periodic Removal Limit
Sl-4 Sl-5 Sl-6 No. of Product Units
closed closed closed 3
open closed closed 4
closed open closed 5
open open closed 6
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closed closed open 7
open closed open 8
closed open open g
open open open lO
TABLE V
K5: Time Period
S _ S2-5 S2-6 Time (min.)
closed closed closed
open closed closed 2
closed open closed 3
open open closed 4
closed closed open 5
open closed open 6
closed open open 7
open open open 8
In the present embodiment, parameter K4, which
is the periodic unstable episode limit is set equal to
5O However, this limit could also be programmable with
the addition of additional switches.
The remaining switches ~1-3 of S2) are used to
designate the number of weight transducers on a partic-
ular display rack. This allows the same theft detec$ion
hardware to be applied to various sizes of racks using
various numbers of weight transducers. Also, it allows
25 the system to detect if a weight transducer has been dis-
connected. The number of valid transducers is set
according to $he following Table.
TABLE Vl
Valid Transducers
S2-1 S2-2 S2-3 Valid Tranducers
_ closed closed closed tone test
open closed closed
closed open closed l, 2
open open closed l, 2, 3
closed closed open l, 2; 3, 4
open closed open l, 2, 3, 4, 5
closed open open l, 2, 3, 4, 5, 6
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open open open invalid setting
When switches S2-1, S2-2 and S2-3 are all
closed, the local alarm or voice is turned on thereby
allowing the tone and volume to be set as described
earlier. When switches S2-1, S2-2 and S2-3 are all open,
this state is ignored as an invalid setting. Therefore,
according to the pre~erred embodiment, at least one and
up to six weight transducers may be used. Once again,
this should not be considered a limitation of the present
10 invention. Additional transdlucers can be obviously
accommodated ~y adding additional switches.
-After the parameters are set by interrogation
of switches Sl and S2 in block 56, control is transferred
to block 57 where the first weight reading9 WTRDGl, is
15 taken. The weight is determined by interrogating the
individual weight sensors 16 via frequency counters 37
(both shown in Fig. 3), and by summing the individual
sensed weights. In this manner, the entire weight of the
display rack is sensed. The units of variable WTRDGl are
20 in 100ths of product units. Therefore the actual weight
sensed by sensors 16 must be multiplied by a predeter-
mined factor in order to convert the actual sensed weight
into a weight in 100ths of product units. If, when
taking ~eight reading WTGRDGI, the system detects weight
25 signals are being produced by less than the number of
transducers set by switches S2-1, ~2-2 and S2-3 according
to Table VI, an alarm is sounded.
Control is then transferred to block 58 where
variables WTRDG2, WTRDG3 and P~EWT are all set to ~TRDGl.
30The program then enters the main loop of the
routine beginning with block 59 where, with operation
identical to that of block 57, the weight WTRDGl is again
sensed, and it is determined if the nunber of transducers
is less than that indicated by switches S2-1, S2-2 and
35 S2-3 according to Table Vl. Control is then transferred
to block 61 Yhere cycle counter CYCLCNT is incremented by
1 and counter OLDCYCL is set equal to counter CYCLCNT
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less K5.
Control is then transferred to motion detection
decision blocks 62-64. In these decision blocks, the
three stored weight readings WTRDGl, corresponding to the
S present weight, WTRDG2, corresponding to the last sensed
weight, and WTRDG3, corresponding to the penultimate
sensed weight, are each subtracted and the differences
are compared with parameter K0. If the difference
between any two of the sensed weights is greater than
10 parameter K0, flat MOTFLAGl is set equal to "l" in block
66. Otherwise, flag MOTFLAGl is set equal to "0" in
block 67. Control is then transferred to decision block
68 where the state of MOTFLAGl is detected. If flag
MOT~LAGl was set in block 66, counter MDTCNT is incre-
15 mented by l in block 69. Otherwise, counter MOTCNT isset to 0 in block 71. Counter MOTCNT keeps track of the
number of consecutive cycles wherein motion is
detected.
The value of counter MOTCNT is compared with
20 parameter K2 in decision block 72. If counter MDTCNT is
greater than parameter K2, indicating that the number of
consecutive unstable episodes is greater than the desired
limit, control is transferred to block 73 where variable
ALARM is set equal to "2", counter MOTCNT is reset in
25 block 74 and the alarm is sounded in block 76 (processing
steps described in detail with reference to Fig. 5).
This ends $he motion detection portion of the routine.
Control is then transferred to decision block
77 where detect;on of the nwnber of product units removed
30 is begun. In block 78, variable PR~WT is set equal to
the last sensed weigh~, WTRDG2, if M~TFLAGl is equal to
"1" and if flag MOTFLAG2 is equal to "0" as determined in
decision block 77. In other words, decision block 77
determines if motion is detected during the present cycle
35 when none was detected during the previous cycle.
Control is then transferred to decision block
79 where it is determined if no motion WAS detected
6~;
during the present cycle, but that motion was detected
during the previous cycle. This is accomplished in
decision bloek 79 which interrogates flags MOTFLAGl and
MOTFLAG2. If true, control is transferred to block 8l
where the integer number of product units removed is
determined by the rounding formula shown. Using this
formula, weights less than 0.49 units are rounded down,
weights between 0.50 and 1.49 units are rounded to l, and
so forth. Control is then transferred to decision block
10 82 where it is determined if any product units were
removed. If so, the local acknowledge tone is sounded,
or the stored synthesized voice is played back, in block
83 and control is transferred to block 84 to determine if
the number of product units removed is greater than
15 parameter Kl. In other words, block 84 determines if the
detected number of units removed from the rack is greater
than the instantaneous removal limit. If so, control is
transferred to block 86 where variable ALARM is set equal
to "l" and the alarm is sounded in block 87. This ends
20 the instantaneous removal detection portion of the
routine.
Control is then transferred to block 88 where
the routine for determining the number of unstable epi-
sodes occuring during time period K5 is determined. In
25 block 88, counter N is set equal to 1'0ll and control is
transferred to a loop beginning with block 89 where
counter N is incremented.
In decision block 9l, all entries in motion
vector MOTPER(N) are discarded if the entries are greater
30 than counter OLDCYCL. Motion vector MOTPER(N) is a time
stamp vector in which the individual entries record the
cycle number when motion was detected when that motion
was determined not to be a removal of an integer number
of product units.
By this means, only time stamps less than ~5
old are retained in vector M~TPER(N). Counter N is
incremented in block 93 and the checking loop is
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traversed until N equals 10. It should be emphasized
that although only 10 time stamps are retained in vector
MOTPER(N), this is once again by way of example only and
not by way of limitation.
Control is then transferred to decision block
94 where if there has been no motion detected during the
present cycle and if there was motion detected during the
past cycle, and if the number o;E product units removed is
less than 1, control is transferred to block 95 where
10 counter N is set equal to "0". In the loop beginning
with block 96, counter N is incremented and consecutive
entries of vector MOTPER(N) are interrogated and deter-
mined if equal to 0 in block 97. When the first 0
element is detected, control is transferred to block 98
15 where the individual element of MOTPER~N) is set equal to
the present cycle, CYCLCNT, in block 98 thereby recording
a time stamp of the detected motion. The loop including
block 97 is not exited unless a ~ero element is found in
vector MOTPER(N), or unless the end of the vector is
20 detected in decision block 99.
Control is then transferred to block 101 where
counters Q and N are both set equal to "0" and another
ehecking loop is entered. In this loop, counter N is
incremented in block 102 and individual entries of vector
25 MOTPER(N) are interrogated by decision block 103. If any
entry is greater than 0, counter Q is incremented by 1 in
block 104. The loop is retraced until the end of vector
MOTPER(N) is detected in decision block 106. Thus,
counter Q is set equal $o the number of non-zero entries
30 in motion vector MOTP~R(N~.
- Control is then transferred to decision block
107 where it is determined if counter Q is greater than
parameter K4. If so, control is transferred to block 108
where variable ALARM is set equal to "4" and the alarm is
35 sounded in block 109. In other words, the alarm is
sounded if counter Q indicates th~t there has been a
number of unstable episodes greater than parameter K4
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during a period set b~ parameter I~5. This ends the peri-
odic unstable episode detection portion of the routine.
Control is then transferred to block 111 where
counter N is set equal to 0. Block 111 begins a routine
which detects the number of product units removed during
a time period set by parameter K5.
In block 112, counter N is incremented and a
loop is started in which the individual entries of
counter vector CNTREM(N) that are greater than counter
10 OLDCYCL (as determined by decision block 113), are set
equal to 0 in block 114. Count vector CNTREM(N), similar
in format to motion vector MOTPER(N), is a time stamp
vector in which the individual entries record the cycle
number when each product unit was removed. The loop is
15 retraced until all entries of vector CNTREM(N) have been
interrogated as determined by decision block 116. After
this loop, all entries of counter vector CNTREM(N) will
be set to 0 if the counts are equal to counter OLDCYCL
(i.e., older than time period K5). In decision block 117
20 it is determined if any product units have been removed
by interrogation of counter CNTREM. If not, no further
action is taken and control is transferred to block 118
(Fig. 4D). If true, control is transferred to block 119
where counter N is set equal to "0" and a loop is begun
25 with block 121 where counter N is incremented.
In the loop beginning with block 121, count
vector CNTREM(N) is interrogated for 0 entries in block
122, and counter CNTREM is compared with "0". If a zero
entry is detected and if CNTREM is greater than zero,
30 control is transferred to block 123 where the vector
entry detected as 0 in block 122 is set equal to counter
CYCL~NT, and counter CNTREM is decremented by 1. The
interrogation loop is continued until decision block 1~4
determines that the last entry in count vector CNTREM(N)
35 has been interrogated. As a result of this loop, time
stamps equal to the present cycle count are entered into
vector CNTREM(N~ for each product unit removedO It
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should be noted that'if more than one product unit is
detected as being removed during a single cycle, several
of the entries in count vector CNTREM(N) will have the
same value.
Control is then transferred to block 126 where
counter Q and N are both reset. In block 127, counter N
is incremented and a loop is begun wherein the individual
entries of counter vector CNTREM(N) are interrogated in
decision block 128. For each non-zero entry in vector
10 CNTREM(N), counter Q is incremented by 1 in block 129.
The loop is retraced until decision block 131 determines
that each element of vector CNTREM(N) has been inter-
rogated. As a result of this loop, counter Q indicates
the number of non-zero entries in count vector CNTREM(N).
In decision block 132, counter Q is compared
with parameter K3 to determine if the periodic unit
removal limit has been exceeded. If so, variable ALARM
is set equal to "3" in block 133 and the alarm is sounded
in block 134. Control is then transferred to block 118
20 where the flag MOTFLAG2 is updated as are weight readings
WTRDG3 and WTRDG2. Control is then transferred back to
block 136 (Fig. 4A) where the loop is once again begun.
Referring back to Fig. 4A, in block 136J which
operates identically to block 56, the states of switches
25 Sl and S2 are again sensed. This is in order to detect
any changes in the states of switches 51 and 52 under
action of switch 53 (Eig. 3).
Next decision blocks 137, 139 and 140 are used
to detect the positon of key-lock switch 50 (Fig. 3~. If
30 key-lock switch 50 is in the lock-up mode (or if switch
53 has placed key-lock switch 50 in the lock-up mode),
block 137 directs control to block 138 where appropriate
parameters are minimized in order to place the rack at
its highest theft prevention sensitivity. Control is
35 then transferred to block 59 where the entire loop is
retraced.
If block 139 does not detect lock-up, control
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2~,~
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is transferred to block 138 where normal mode is
detected. If key lock switch 50 is in the normal mode
positon, control is transferred to block 59, and the loop
is retraced.
If block 139 decides key lock switch 50 is not
in the normal mode, control is transferred to decision
block 140 where, if key lock switch 50 is in the restock
mode, block 136 is again reentered without retracing the
main loop. Otherwise, the rnain loop is retraced by
entering block 59.
Referring now to Fig. 5, the alarm routine will
be described. In block 141, it is determined if variable
ALAR~ is equal to "3" or "4". If not, control is trans-
ferred immediately to block 146. If so, counter N is
reset in block 142, and a loop comprising blocks 143-145
is traversed a sufficient number of times to reset all
entries of vectors CNT~EM(N) and M~TPER(N). Then the
alarm is sounded in block 146.
In summary, switches S2-1, S2-2 and S2-3 are
positioned by the user of the system as shown in Table VI
to accom~odate the number of weight transducers in the
rack in use. Parameter Kl, the instantaneous removal
limit, is set by positioning switches Sl-l, Sl-2 and Sl-3
as shown in Table II, and is variable from 1 to 8 product
~5 units.
Switches Sl-4, Sl-5 and Sl-6 are used to set
the number of product units which must be removed over a
time period to cause an alarm. This is called the perio-
dic removal limit, K3, and is adjustable from 3 to 10
product units as shown in Table IV. The time period, K5,
for-the periodic removal limit is set by positioning
switches S2-4, S2-5 and S2-6, as shown in Table V. In
addition, an alarm will sound if the display rack is
disturbed continuously for a number of cycles settable by
switch Sl-8 (parameter K2) as shown in Table III.
Finally, rack tampering or "swapping" of other ~erch~nd-
ise ~or product units contained In the rack is dete~ted
` ' ~
: .
- 18 -
if five unstable episodes (parameter K~) occur within the
time period set by parameter K5.
The product rack will acknowledge removal of
product units (when not in excess of an alarm limit) by
S an adjustable local tone or synthesized voice which can
be set to %ero volume. The separately adjustable local
alarm tone can also be set to zero volume if local alarm
is not desired. The alarm signal can be transmitted to a
remote receiver, over wire or radio link, which will
sound an alarm at a remote location. The local tones are
both adjustable in volume, tone and duration.
A principal factor in determining how
restrictive the various programmable alarm criteria for
periodic removal should be is the extent to which legiti-
mate purchases cause false alarms. This would of courseoccur during peak $raffic hours. The following is a
table displaying the results of a computer simulation
which was based on the following assumptions:
1. During peak traffic hours, ten customers
remove one product unit and five customers remove two
product units for total sales of 20 product units during
a peak hour.
2. The purchases occur at random times.
3. The predicted false alarm rate is the num-
ber of false alarms which would occur during 200 suchpeak hours.
TABLE VII
Predicted False Alarms Per 200 Peak Hours
Alarm Limit Time Period K5
Kl 1 2 3 4 5 6 7 8
- 3 S 13 17
4 5 12 1~ 29
S 1 1 1 6 8 10 12 16
6 1 1 3 5 8 10 12 16
7 0 0 0 0 2 4 5 6
8 0 0 0 0 2 4 5 6
9 0 0 0 0 1 2 3 3
...
:
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., " .
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7~6~;
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'O O O O 1 2 3 3
It should be noted that odd numbered settings
for the product unit alarm limit permit more restrictive
settings without significantly higher incidence of false
alarms. ~hen time period and alarm limit settings are
restricted to the lowest values which do not cause intol-
erable false alarm activity, the maximum protection
against shoplifting is afforded. While theft of very few
product units over an extended period of time may go
undetected because this mimics plausible normal activity,
the monetary loss of this type of theft is minimal.
While the present invention has been described
with reference to a particular preferred embodiment, the
invention is not limited to the specific example given,
and other embodiments and modifications can be made by
those skilled in the art without departing from the
spirit and scope of the invention.
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