JP2951226B2 - Anti-theft system and anti-theft signal transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-theft device used to prevent theft of shoplifting and the like, and more particularly, to the operation of the tag device in an anti-theft device using a self-sounding tag device. -It relates to a signal transmission circuit for stopping.

[0002]

2. Description of the Related Art In recent years, in order to prevent shoplifting or theft of merchandise in stores and the like, a self-sounding tag device for preventing theft has been often attached to the merchandise. In this type of anti-theft device, for example, a gate device (antenna device) as a transmitting side that emits an electromagnetic wave using an electromagnetic induction coupling method is installed at an entrance of a store, and the product with a tag device as a receiving side is attached to the product. When passing through the gate device, the electromagnetic wave is detected, and the tag device emits a warning sound.

The tag device includes, for example, a wire, a pin,
It is attached to the product via an adhesive tape or the like, and is placed at the sales floor together with the product. And if the customer takes the product out of the store without completing the accounting process, the tag device will pass through the gate device attached to the product,
The tag device detects an electromagnetic wave of a specific frequency from the gate device and generates a warning sound. Further, when the customer forcibly removes the tag device from the product, the tag device detects that the wire has been removed, and also generates a warning sound.

[0004] On the other hand, in the case of normal shopping, the clerk removes the tag device from the product at the time of checkout, so that the warning sound does not sound even if the customer passes the gate device with the product. In this case, there is an antenna device that emits electromagnetic waves of a specific frequency at the checkout place so that a warning sound is not generated even if the wire is removed from the tag device. It does not emit.

Next, FIG. 6 shows a configuration of a signal transmission circuit in a conventional gate device. Reference numeral 1 denotes a signal generator, which generates a sine wave having a constant frequency from a rectangular wave oscillation source. Reference numeral 2 denotes a driver unit, and the driver unit 2 power-amplifies the sine wave signal output from the signal generator 1. Reference numeral 3 denotes an antenna, and the driver unit 2
And radiates a sine wave signal (hereinafter referred to as an alarm activation signal) amplified in power into the space.

The antenna device for emitting an electromagnetic wave so as not to generate a warning sound even when the tag device is removed has basically the same configuration as the signal transmission circuit shown in FIG. The only difference is the frequency of the sine wave signal (hereinafter referred to as an alarm stop signal) output from the antenna.

[0007]

As described above, the alarm activation signal or the alarm stop signal is output from the antenna. To amplify each signal to the required output power,
There is a problem that power consumption in the driver section is large and power loss (consumed as heat) is also large.

The alarm activation signal and the alarm stop signal include:
Since each is a continuous simple sine wave signal having a different constant frequency from each other, the tag device on the receiving side causes a disturbance signal (noise) other than the alarm activation signal or the alarm stop signal.
Therefore, there is a problem that a malfunction easily occurs.

[0009]

In order to solve the above-mentioned problems, according to the present invention, an operation signal or a stop signal is transmitted to a warning device which is configured to receive an external signal and start and stop the operation. In a signal transmission circuit of an anti-theft device, a signal transmission circuit of the anti-theft device in which the operation signal or the stop signal is an intermittent sine wave is provided.

According to the present invention, there is provided a signal transmission circuit of an anti-theft device for transmitting an operation signal or a stop signal to a warning device configured to receive an external signal to operate and stop the operation signal. And a signal transmission circuit of an anti-theft device in which the stop signal is an intermittent sine wave having the same carrier frequency and different periods.

[0011]

With the above construction, the activation signal or the stop signal is transmitted from the signal transmission circuit to the warning device as an intermittent sine wave signal.

Also, with the above configuration, the activation signal and the stop signal are transmitted from the signal transmission circuit to the warning device as intermittent sine wave signals having the same carrier frequency and different periods.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the configuration of the signal transmission circuit of the present invention, and FIG. 2 shows the waveform of the warning deactivation signal. In FIG. 1, reference numeral 5 denotes a signal generator. The signal generator 5 generates a sine wave having an intermittent cycle set by the timing control circuit 4 under the control of the timing control unit 4. 6
Is a driver unit, and the driver unit 6 power-amplifies the sine wave signal of the intermittent period output from the signal generator 5. The sine wave signal amplified by the driver section 6 is radiated from the antenna 7 to the space as an alarm actuation signal as a sine wave signal having an intermittent cycle as shown in FIG.

Then, when the average output power (effective power) of the driver unit 5 is obtained according to an equivalent circuit as shown in FIG.

[0015]

(Equation 1)

## EQU1 ## 3, 8 is a driver section (corresponding to the driver section 6 in FIG. 1), 9 is an equivalent resistor, 10 is a matching capacitor, and 11 is an antenna coil (corresponding to the antenna 7 in FIG. 1). Further, in the above equation, Rm represents an equivalent resistance, Ip represents a current (peak current) flowing through the equivalent circuit, T1 represents a signal period, and T2 represents a non-signal period (see the waveform in FIG. 2). As described above, since the alarm activation signal has the non-signal period T2 as compared with the simple continuous sine wave alarm activation signal, the power consumption is reduced.

The circuit shown in FIG. 1 is applied to an antenna device that emits an electromagnetic wave for stopping the tag device (to prevent generation of a warning sound). The alarm stop signal to be transmitted has a different time width from the signal period T1 and the non-signal period T2 of the alarm activation signal shown in FIG. That is, both signals are intermittent sinusoidal signals having the same carrier frequency and different periods, so that the tag device on the receiving side can distinguish between the two signals.

FIG. 4 shows a circuit configuration of the tag device.
In FIG. 1, reference numeral 12 denotes a receiving antenna, which receives an alarm activation signal or an alarm stop signal radiated into the space from the signal transmission circuit. Reference numeral 13 denotes a signal amplifier, which amplifies a signal received by the receiving antenna 12. Reference numeral 14 denotes a waveform shaping unit, which performs envelope detection on the signal amplified by the signal amplifying unit 13 as shown in FIG. Reference numeral 15 denotes a signal determination unit which continuously compares and determines the time width t1 and the time width t2 (see FIG. 5) of the intermittent signal detected by the envelope shaping unit 14 with the standard value a plurality of times. The alarm device 16 is operated according to the determination result.

As described above, since the signal period T1 and the non-signal period T2 are different between the alarm activation signal and the alarm stop signal, the signal period t1 and the non-signal period t2 of the received intermittent signal are also different. Therefore, it is easy to determine the alarm activation signal and the alarm stop signal. Further, when a disturbance signal is received, the time width of the signal period t1 and the non-signal period t2 are different from the normal alarm activation signal or the alarm stop signal, so that the alarm device 16 does not malfunction.

[0020]

As described above, according to the present invention, an anti-theft device for transmitting an operation signal or a stop signal to an alarm device which is configured to receive an external signal and operate and stop the signal. In the signal transmission circuit of the device, the operation signal or the stop signal is an intermittent sine wave, so that the alarm operation signal or the alarm stop signal for the warning device can be transmitted with low power consumption.

According to the present invention, there is provided a signal transmission circuit of an anti-theft device for transmitting an operation signal or a stop signal to a warning device configured to receive an external signal to operate and stop the signal, Since the operation signal and the stop signal are intermittent sine waves having the same carrier frequency and different periods, malfunctions in the warning device are reduced.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of a signal transmission circuit of the present invention.

FIG. 2 is a diagram showing a transmission signal waveform of the signal transmission circuit of the present invention.

FIG. 3 is a circuit block diagram showing an equivalent circuit of the signal transmission circuit of the present invention.

FIG. 4 is a circuit block diagram showing a circuit configuration of the tag device.

FIG. 5 is a diagram showing a received signal waveform after envelope detection of the tag device.

FIG. 6 is a circuit block diagram showing a configuration of a conventional signal transmission circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Signal generation part 2 Driver part 3 Antenna 4 Timing control part 5 Signal generation part 6 Driver part 7 Antenna 8 Driver part 9 Equivalent resistance 10 Matching capacitor 11 Antenna coil 12 Receiving antenna 13 Signal amplification part 14 Waveform shaping part 15 Signal judgment part 16 Alarm

Claims (6)

(57) [Claims] An alarm device having a function of receiving an operation signal from the outside and operating and receiving a stop signal to stop the operation, an operation signal transmitting device for transmitting an operation signal to the alarm device, An anti-theft system comprising: a stop signal transmitting device that transmits a stop signal to an alarm device; wherein the activation signal or the stop signal comprises an intermittent sine wave. 2. The anti-theft system according to claim 1, wherein the activation signal and the stop signal are intermittent sine waves having the same carrier frequency and different signal periods. 3. The anti-theft system according to claim 1, wherein the activation signal and the stop signal are intermittent sine waves having the same carrier frequency and different periods. 4. An anti-theft signal transmitting device for transmitting an operation signal or a stop signal to an alarm device having a function of receiving an external operation signal and operating and receiving a stop signal and stopping the operation, The anti-theft signal transmitting device according to claim 1, wherein the activation signal or the stop signal comprises an intermittent sine wave. 5. The anti-theft signal transmitting device according to claim 4, wherein the activation signal and the stop signal are intermittent sine waves having the same carrier frequency and different signal periods. 6. The anti-theft signal transmitting apparatus according to claim 4, wherein the activation signal and the stop signal are intermittent sine waves having the same carrier frequency and different periods.