JP2002099970A - Burglarproof system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems of the conventional systems, or that of generation and detection of an very precise alarm sound is required for distinguishing it from BGMs or noise in a store, because the conventional alarm sound uses single frequency, and an expensive quartz oscillator is necessary for enhancing the frequency precision in the generating circuit and receiving circuit of the alarm sound. SOLUTION: This burglarproof system comprises an alarm unit which is to be connected to an object of theft prevention and an alarm sound detector for detecting the alarm sound of the alarm unit and transmitting the alarm signal. The alarm unit generates the alarm sound, whose frequency is changed with the lapse of time, and the alarm sound detector measures the frequency of the sound detected by each prescribed time and judges the detected sound as being alarm sound, when the differential value with the adjacently measured frequency is within an allowable value of alarm sound frequency change preliminarily set in the alarm unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-theft system for protecting goods displayed in a store from shoplifting and other fraudulent activities, and more particularly to an alarm sound generated by an alarm unit attached to the goods. Related to an anti-theft system.

[0002]

2. Description of the Related Art Conventionally, at stores which display and sell products such as compact disk cassettes, magnetic tape cassettes, and apparel-related articles, as shown in FIG. Employs an anti-theft device.

The anti-theft device is located near the exit of the store (4
0) and the goods (5)
0) attached to the alarm unit (20). The circuit board (3) is connected to the anti-theft gate (30).
1) and a transmission antenna (not shown) are built in, and the circuit board (31) is provided with a transmission circuit (not shown) for generating an alarm activation signal for the alarm unit (20).

The alarm unit (20) is, as shown in FIG.
A buzzer (22), a circuit board (23), a battery (not shown) and the like are provided inside the casing (21). A plurality of sound holes (24) are opened on the surface of the casing (21), and an alarm is issued. An operation switch piece (25) is embedded. The operation of the buzzer (22) is controlled by the circuit board (23).
0) is removed or the alarm unit (2
0) is emitted when passing through the anti-theft gate (30). There is also a type in which an alarm unit is attached to a product by a wire instead of the alarm operation switch piece (25). In this case, the alarm unit issues an alarm by detecting that the wire has been removed, that the wire has been cut, or that the wire has passed through the anti-theft gate (30).

[0005] In a store, the product (50) is displayed on a display stand with the alarm unit (20) attached. When a clerk sells a product (50) to a customer, a specific reset signal is sent from the alarm ineffective device (not shown) to the circuit board (23) of the alarm unit (20), and the buzzer (22) is sent.
The alarm unit (2
0) is removed from the product (50), and the product (50) is handed to the customer in exchange for the price.

[0006] On the other hand, if the customer illegally removes the alarm unit (20) from the product (50), the alarm operation switch piece (2).
5) is turned off, and the buzzer (22) sounds. If the customer illegally takes the product (50) out of the store together with the alarm unit (20), the circuit board (23) of the alarm unit (20) is connected to the anti-theft gate (3).
In response to the alarm activation signal from the transmitting antenna of 0), the buzzer (22) sounds.

However, the accounting office where the clerk is located is located at the back of the store, and is often far from the exit (40) of the store where the anti-theft gate (30) is installed.
The buzzer (2
The alarm sound from 2) may be difficult to hear.

To solve this problem, as shown in FIG. 5, an alarm sound detecting device (10) having a microphone (11).
Is installed near the anti-theft gate (30), and the alarm sound (1) of the alarm unit (20) is detected by the alarm sound detection device (10).
2) Detect theft, generate a new alarm signal (13), and use a wired or wireless method to cause a clerk to generate an alarm using a speaker (15) and a lamp (16) installed at an accounting office (14). Prevention systems are used supplementarily.

[0009]

The frequency of the alarm sound (12) of the alarm unit (20) of the anti-theft system is as follows.
This is indicated by a solid line (33) or (34) in FIG. That is, what is indicated by the thick solid line portion (33) in FIG. 4 is a type in which the alarm sounds continuously at a single frequency (f6).
A thick solid line (34) indicates that a single frequency (f
The alarm sound of 7) continues to be emitted. The frequency of these alarm sounds is measured by the alarm sound detection device (10), and if the frequency of the alarm sounds, a new alarm signal is generated.

[0010] In the alarm sound of the anti-theft system, an extremely accurate frequency is generated and detected in order to distinguish it from disturbance noise similar to the alarm sound generated from BGM, noise, and the like in the store. This corresponds to the spots (6
As shown in 3), when the detection range of the frequency determined to be the alarm sound is expanded, as shown by the dashed line in FIG. 4, for example, steady-state harmonic noise (65), BGM, noise, etc. This is because a complex irregular disturbance noise (66) causes frequent malfunctions and becomes impractical.

Therefore, an inexpensive oscillating circuit with a low frequency accuracy such as a CR oscillating circuit cannot be used in the oscillating circuit of the alarm unit and the detecting circuit of the audible alarm detecting device. A vibrator had to be used. In particular, in the anti-theft system, since an alarm unit is attached to each product, the use of an expensive crystal oscillator for the alarm sound generating circuit has led to an increase in the cost of the entire system.

Accordingly, an object of the present invention is to provide an anti-theft system capable of judging an alarm sound with an inexpensive device without using a quartz oscillator.

[0013]

SUMMARY OF THE INVENTION The present invention relates to an anti-theft system having an alarm unit coupled to an object to be stolen and an alarm sound detecting device for detecting an alarm sound of the alarm unit and transmitting an alarm signal. In the above, the alarm unit generates an alarm sound whose frequency changes with time, and the alarm sound detection device measures the frequency of the sound detected every predetermined time, and calculates the difference between the frequency and the adjacent measured frequency. When the value is an allowable value of the frequency change of the alarm sound preset by the alarm unit, the detected sound is determined to be the alarm sound.

Further, in order to determine that the detected sound is an alarm sound, two or more of the difference values are used.

[0015] Further, a sum of two or more of the difference values is used to determine that the detected sound is an alarm sound.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an embodiment using a step waveform used for an alarm sound according to the present invention. FIG. 2 is a diagram illustrating a method for determining an alarm sound.

An embodiment using a step waveform will be described below. As shown by the thick solid line in FIG. 1, the step waveform of the alarm sound is one cycle (t2: 250 milliseconds) and has five steps, and each step is equally spaced (t
1:50 milliseconds) and the frequency (f1 to f5) is 2.6.
From 0 kHz to 3.00 kHz, 0.1 as a design standard
Set the waveform to rise by 0 kHz. (F1: 2.6
0 kHz, f2: 2.70 kHz, f3: 2.80 kHz
z, f4: 2.90 kHz, f5: 3.00 kHz)
However, the present invention uses an inexpensive ceramic oscillator (accuracy of about 0.5
%, 0.015 kHz for the reference frequency of 3.0 kHz
), The frequency is set to 0.01 kHz to 0.02 even if it is set to generate the frequency set above.
The error occurs at about kHz, and the error further increases due to variations in the assembly of the alarm unit. Therefore, the frequency (F1: 2.60 kHz ±) emitted from the actual alarm unit is used.
0.05 kHz, F2: 2.70 kHz ± 0.05 kHz
z, F3: 2.80 kHz ± 0.05 kHz, F4:
2.90 kHz ± 0.05 kHz, F5: 3.00 kHz
z ± 0.05 kHz), taking into account the error range, the allowable value of the frequency detection is set to ± 0 .0 of each frequency set value (f1 to f5).
05 kHz.

On the other hand, in the alarm sound detecting device, the frequency difference between the adjacent alarm sounds is 0.10 kHz which is the design standard and the error ±
A value including 0.05 kHz is determined as a judgment value (δf) 0.10.
For example, ± 0.05 kHz is stored in a memory (not shown).

In the following, the judgment operation will be described. In case of theft, as shown by the hatched portion in FIG. 1, the warning unit outputs an error including 2.55 kHz to 2.65 kHz.
The frequency (F1) sounds in the range of. Thereafter, every 50 milliseconds, the frequency (t1) increases by 0.10 kHz. On the other hand, the alarm sound detector measures the frequency of F2 to F5 measured every t1 (50 milliseconds) from the measurement of the frequency (F1) of the first alarm sound, and calculates the difference between adjacent frequencies indicated by black circles in FIG. (ΔF1, δF2, δF3, δF4) are calculated, and an allowable value (δf) for judging whether or not each is an alarm
If the value is within the range of 0.10 kHz ± 0.05 kHz, it is determined that the alarm is issued.

Therefore, according to the present invention, as shown by the hatched portion in FIG. 1, even if the frequency (F1 to F5) of the alarm sound actually generated includes an error with respect to the set value (f1 to f5). ,
If the difference between the relative frequency and the adjacent frequency sequentially changes within a range of a preset allowable value (δf), it is determined that the alarm sound is generated.

On the other hand, as shown by the one-dot chain line (5) in FIG. 1, the frequency near 2.60 kHz, which is the frequency component of the alarm sound, is initially regarded as disturbance noise due to, for example, harmonics and resonance of the air conditioner in the store. Is detected when measuring
Since the difference from the adjacent frequency is close to 0 as shown by the black triangle in FIG. 2, after the measurement of the first frequency (F1),
Since the frequency does not rise every t2 (50 msec), it is not determined that the alarm sound is issued. In addition, BG which tends to occur in the store
M, the disturbance noise due to noise is as shown by the dashed line (6) in FIG. 1, but the change over time in the frequency is determined by the number of determinations (N1, N2, N3) as shown by the black circles in FIG. ,
For each N4), an irregular value is often taken, so it can be determined that this is not an alarm.

Further, in the mass production assembly of the alarm unit, although parts such as a circuit and a buzzer are the same,
Although an error occurred in the frequency when assembling including the outer case, in the present invention, by determining the difference value of the frequency, it is possible to determine the characteristics of the alarm sound over time,
Even if the frequency of the alarm sound contains some error, expensive parts such as a crystal oscillator are not required for the oscillation circuit of the alarm unit, and an inexpensive oscillation circuit such as a ceramic oscillator can be used. Frequency value errors can be tolerated and no adjustment is required.

FIG. 3 shows another embodiment in which the alarm sound has a sweep waveform. In this case, the frequency can be determined in exactly the same manner as the step waveform.

Although the step waveform and the sweep waveform of the embodiment have a gradually higher frequency, they are not particularly limited, and it goes without saying that the same applies even if the frequency gradually decreases.

Further, in the above-described embodiment, the determination is made for each time frequency difference value. However, it is needless to say that a new sum total of the difference values may be used as a determination reference.

[0026]

According to the present invention, there is no need to use expensive components such as a crystal oscillator in an oscillation circuit, and even if a ceramic oscillator is used, an inexpensive antitheft system with few malfunctions can be provided. it can.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of an alarm sound of the present invention.

FIG. 2 is an explanatory diagram of an alarm judgment according to the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram of a conventional alarm sound.

FIG. 5 is a diagram of the anti-theft system.

FIG. 6 is a diagram of a conventional anti-theft system.

FIG. 7 is a detailed view of an alarm unit.

[Explanation of symbols]

 f1 to f5. Design reference value of alarm sound F1 to F5. 4. Alarm frequency 5. Temporal change of disturbance noise over time Temporal change of unsteady disturbance noise t1. One step time of alarm sound t2. One cycle time of alarm sound δf. Alarm sound determination value δF1 to δF4. Difference values from adjacent frequencies N1 to N4. Number of judgments 10. Alarm sound detector 11. Microphone 12. 12. Alarm signal from alarm unit 13. Alarm signal by alarm sound detection device Accounting office 20. Alarm unit 23. Circuit board 33. Conventional alarm sound 34. Conventional alarm sound 63. Judgment range of alarm sound 65. 66. Schematic diagram of the frequency of a stationary disturbance in a store Schematic diagram of the frequency of irregular disturbance in the store

Claims (3)

[Claims] 1. An anti-theft system comprising: an alarm unit coupled to an object to be stolen; and an alarm sound detection device for detecting an alarm sound of the alarm unit and transmitting an alarm signal. In addition to generating a warning sound whose frequency changes, the warning sound detection device measures the frequency of the sound detected every predetermined time, and the difference value between the adjacent measured frequency is determined in advance by the warning unit. The anti-theft system characterized in that the detected sound is determined to be an alarm sound when the set value is a permissible value of the frequency change of the alarm sound. 2. The anti-theft system according to claim 1, wherein two or more of the difference values are used to determine that the detected sound is an alarm sound. 3. The anti-theft system according to claim 2, wherein a sum of two or more of the difference values is used to determine that the detected sound is an alarm sound.