JP3374090B2 - Anti-theft system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antitheft system for protecting merchandise displayed in a store from shoplifting and other illegal acts, and more particularly to a theft device which issues an alarm on the gate device side as well as the tag device attached to the product. It concerns prevention systems.

[0002]

2. Description of the Related Art Conventionally, a store which displays and sells products such as compact disc cassettes and magnetic tape cassettes has an anti-theft system as shown in FIG. 4 in order to protect these products from illegal acts such as shoplifting. It is adopted.

The anti-theft system is provided at the outlet (40) of the store.
It is composed of an anti-theft gate (30) installed in the vicinity and an alarm unit (20) attached to the product (50).
The anti-theft gate (30) has a circuit board (31) and a transmitting antenna.
(Not shown) is built in, and the circuit board (31) is an alarm unit.
It is provided with a transmission circuit (not shown) for generating an alarm activation signal (notification signal) for (20).

As shown in FIG. 5, the alarm unit (20) includes a buzzer (22), a circuit board (23) and a battery inside a casing (21).
(Not shown) and the like, a plurality of sound output holes (24) are formed on the surface of the casing (21), and an alarm activating switch piece is provided.
(25) is projected. The operation of the buzzer (22) is controlled by the circuit board (23), and when the alarm unit (20) is removed from the product (50) or the alarm unit (20) operates the anti-theft gate (30). It sounds when passing.

At the store, the product is an alarm unit.
It will be displayed on the display stand with the (20) attached. When a store clerk sells a product to a customer, a disabling device (not shown) sends a specific signal to the circuit board (23) of the alarm unit (20) to set the buzzer (22) so that it does not sound. And the alarm unit
(20) is removed from the product (50) and the product is handed to the customer in exchange for the price.

[0006] A customer illegally sends an alarm unit (20) from a product (50).
When removed, the alarm activation switch piece (25) turns off and the buzzer (22) sounds. Also, when the customer illegally attempts to take the product (50) out of the store together with the alarm unit (20), the circuit board (23) of the alarm unit (20) will be removed from the transmitting antenna of the anti-theft gate (30). Upon receiving the alarm activation signal, the buzzer (22) sounds.

Further, in JP-A-8-279082, a signal generator is also provided on the side of the alarm unit (20) described above, and a response signal is sent in response to receiving an alarm activation signal from the anti-theft gate (30). There is described an anti-theft device that transmits a message and the anti-theft gate (30) receives the signal to sound a buzzer provided on the anti-theft gate (30) side.

In such a device, since the alarm is sounded from both the alarm unit (20) and the anti-theft gate (30), the reliability in crime prevention can be improved.

[0009]

However, in Japanese Patent Laid-Open No. 8-26
In the anti-theft device described in -2799082, since a circuit for generating and transmitting a signal is separately provided on the alarm unit (20) side, the circuit configuration of the alarm unit (20) becomes complicated and This causes a problem that the alarm unit (20) itself to be attached to the product becomes large and the appearance of the product is unsatisfactory when displayed.

In order to solve the above-mentioned problems, in the anti-theft system according to the present invention, the notification signal transmitting device for transmitting the notification signal and the anti-theft object are connected, and the connection state of the anti-theft object is separated. The alarm signal from the notification signal transmitting device is received, the first alarm unit that drives the electromagnetic buzzer with a square wave different from the waveform of the notification signal to emit a sound, and the electromagnetic buzzer. A second alarm unit is provided which, when sounding, simultaneously detects an electromagnetic wave generated from an electromagnetic buzzer and issues an alarm.

[0011]

[0012]

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit block diagram showing the configuration of the anti-theft system of the present invention, and FIG. 2 shows the signal waveform in each signal path.

In FIG. 1, reference numeral A denotes an anti-theft gate. In the anti-theft gate A, (1) is a signal generator for generating a SIN wave (sine wave) signal (see waveform 1 in FIG. 2). Is.

(2) is a burst control signal generator. The SIN wave signal generated by the signal generator (1) is turned on by a burst control signal (see waveform 2 in FIG. 2) to turn on the switch SW1.
A burst signal is generated by turning on / off (see waveform 3 in FIG. 2).

(3) is a transmission signal amplifier circuit, which includes a signal generator (1), a burst control signal generator (2), and a switch S.
The burst signal generated by W1 is amplified. Furthermore, (4) is a transmission antenna, and a transmission signal amplification circuit (3)
The burst signal (notification signal) amplified by is radiated into the air as an electromagnetic wave.

Reference numeral B shows the structure of the first alarm unit, which is connected to an antitheft object.

In the first alarm unit B, (5) is a receiving antenna, which is output from the transmitting antenna (4) of the anti-theft gate A when the first alarm unit B approaches the vicinity of the anti-theft gate A. Receive electromagnetic waves. And (6)
Is a reception signal amplification circuit, which amplifies the signal received by the reception antenna (5).

(7) is a control circuit, which is a received signal amplification circuit (6)
It is determined whether or not the received signal amplified by is a specified burst signal (notification signal), and if it is a specified burst signal, the buzzer drive circuit (8) in the subsequent stage is operated and the electromagnetic buzzer (9) is activated. Generate a warning sound. Also, the control circuit (7)
Detects that the first alarm unit A has been separated from the antitheft object (not shown), operates the buzzer drive circuit (8), and causes the electromagnetic buzzer (9) to generate a warning sound. .

Here, the buzzer drive circuit (8) drives the electromagnetic buzzer (9) with a square wave as shown in FIG. In this embodiment, the driving frequency is 2.7 kHz and the duty is 25 to
A 35% square wave is used. At this time, the electromagnetic buzzer
From (9), the frequency is n times (n = 2, 3, ...) together with the same 2.7 kHz electromagnetic wave (fundamental wave) as the driving frequency.
・) Nth harmonic is generated at the same time.

On the other hand, C shows the structure of the second alarm unit. In the second alarm unit C, (10) is a receiving antenna, (11) is a received signal amplifying circuit, and the receiving antenna is
The signal received at (10) is amplified by the received signal amplification circuit (11).

(12) is a bandpass filter, and in this embodiment, a filter which transmits a frequency of 5.4 kHz is used. That is, in the present embodiment, the second harmonic generated from the electromagnetic buzzer (9) when the warning sound is emitted from the first alarm unit B is transmitted through the bandpass filter (12).

(13) is a control circuit, which is a bandpass filter
A signal (second harmonic) that has passed through (12) is detected, and an alarm generation circuit (14) in the subsequent stage is driven to generate an alarm (not shown) such as sound or light.

However, in this embodiment, the first alarm unit B coupled to the anti-theft object has approached the anti-theft gate A (that is, the notification signal from the anti-theft gate A has been received). ) Alternatively, the second alarm unit C sounds an electromagnetic buzzer by detecting the disconnection from the anti-theft object, and the second alarm unit C also outputs an alarm by receiving the harmonic generated from the electromagnetic buzzer of the first alarm unit B. It will be.

Here, the second alarm unit C may be built in the antitheft gate A, or may be installed separately.

Further, in the present embodiment, an example of detecting the second harmonic is shown. However, compared with the frequency band of the fundamental wave which is usually used for driving the electromagnetic buzzer, the higher harmonics have a transmission range. This is because the second harmonic has a relatively large output among the harmonics. Of course, the transmission frequency of the bandpass filter (12) may be changed to set so as to detect the fundamental wave or the third or higher harmonics. For example, when detecting the third harmonic, the transmission frequency of the bandpass filter (12) may be set to 8.1 kHz. At this time, the electromagnetic buzzer
If the duty of the square wave signal that drives (9) is set to 50%, only odd-numbered harmonics are generated as harmonics, so that the output becomes large and detection becomes easy.

[0028]

According to the present invention, the alarm is generated even in the anti-theft gate or the second alarm unit separately installed without providing a circuit for generating and transmitting a signal in the first alarm unit attached to the product. Therefore, the circuit configuration of the first alarm unit can be simplified, and the first alarm unit to be attached to the product does not become large.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a configuration of an anti-theft system of the present invention.

FIG. 2 is a diagram showing a notification signal waveform in the antitheft system of the present invention.

FIG. 3 is a diagram showing an electromagnetic buzzer drive waveform in the antitheft system of the present invention.

FIG. 4 is a perspective view showing an anti-theft gate installed near an exit of a store.

FIG. 5 is a perspective view showing an alarm unit attached to a product.

[Explanation of symbols]

1 signal generator 2 Burst control signal generator 3 Transmission signal amplifier circuit 4 transmitting antenna 5 receiving antenna 6 Received signal amplification circuit 7 control circuit 8 Buzzer drive circuit 9 Electromagnetic buzzer 10 receiving antenna 11 Received signal amplification circuit 12 band pass filter 13 Control circuit 14 Alarm generation circuit

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G08B 13/00-15/02

Claims (3)

(57) [Claims] 1. A notification signal transmitting device for transmitting a notification signal and an object for theft prevention, which is combined with the object for theft prevention and is disconnected from the object for theft prevention, or a notification signal from the information signal transmitter is received. The first alarm unit, which detects that the electromagnetic buzzer is activated and sounds the electromagnetic buzzer with a square wave different from the waveform of the notification signal, and the electromagnetic wave generated from the electromagnetic buzzer is received at the same time when the electromagnetic buzzer sounds. A theft prevention system, comprising: a second alarm unit that detects the fact and issues an alarm. 2. The electromagnetic wave detected by the second alarm unit is
The anti-theft system according to claim 1, wherein the second alarm is a second harmonic generated from the electromagnetic buzzer of the first alarm unit. 3. The square wave for driving the electromagnetic buzzer has a duty of 25% to 35%.
Anti-theft system described in.