DE1295424B - Device for detecting the unauthorized passage of objects at a control point - Google Patents

Description

device, such as a Geiger counter to be arranged. However, many merchandise do take through the presence of any type of radioactivity damage.

It was also proposed to emit radio frequency energy in the vicinity of a control point and to attach frequency-selective devices with energy absorption to the items to be guarded,

are generally so high that these precautionary 15 odd harmonics of the transmitter frequency are corrected when used effectively, at least one beam, then the amplitude will also be a just as expensive or even more expensive than the extremely low vibration and the actuation loss due to the theft itself. unreliable alarm device.

As possible solutions to this problem are all of these difficulties are with the help of the

already eliminated numerous electrical and mechanical inventions. This happens in directions that have been proposed, however, all of which use a device of the type mentioned at the outset, either too expensive, too dangerous or too impractical for the receiver to be reliable on a high-frequency wave for it to be input within a second wave in practice given friends. So a known security system is tuned to the frequency range, and that on or in the type mentioned (German Patent 25 to be monitored objects attachable over-819 566) to the monitoring of electrically conductive transmission devices with a limited to the frequency of the objects that interfere with the balanced receiver part and the switching arrangement of the antennas, which are sharply tuned to the transmitter. A suggestion was made that the radioactive material to be attached by the guarding articles should be provided on the transmitter section to be determined, and that the receiver section of a device should be monitored at each control point Wave within the first frequency range excites the transmitter part in its resonance frequency and causes it to generate and broadcast a high-frequency wave itself within the second frequency range, that this high-frequency wave after reception by the receiver located in the vicinity of the control point is connected to it Activate alarm means whenever a transmission device

which cause a sudden absorption of energy at the transmitter to cause objects to pass the control point, as soon as they pass the checkpoint. That is moved.

Response of the transmitter to such an energy absor- With this device is an automatic and

tion is then measured by measuring devices absolutely reliable monitoring unauthorized and thus the bypassing of each with one of the objects bypassing the control type Energy absorption device provided 45 point guaranteed, and there is no risk of that Trade item displayed. People are exposed to dangerous radiation.

The frequency-selective energy absorption is also used when using this device Procedure, however, no supervisory staff is required for practical application, and it is not Application not particularly suitable, since the energy once the presence of an easily visible amount required in a 5 ° device to be guarded on an item. Innocent buyers walk through attached device is absorbed, the use of the invention does not pose any risk, extremely small fraction of the total benefit of being falsely arrested as at Sender. In addition, such before a properly sold goods show the on each directions low frequency selectivity, and there is transmitted transmitted object to be guarded many commodities, their own structure also 55 device before their delivery to the buyer absorbs as much or more energy as can be removed from them by the personnel. attached devices. Therefore, in many ways, the training shown in the figures

In all cases, it is impossible to distinguish between guarded and unconditional forms of the invention, which will be observed in the following Differentiate articles. To be described in more detail, a transmitter is also already seen an arrangement for Si-60, which sends a continuous signal from a signal transmission known (German patent first transmits specified frequency. In addition, is 969 289), which, among other things, is also intended to protect against a sharply tuned receiver, the Theft or burglary. With only a second Fredieser that differs from the first Arrangement is a transmitter device with frequency responds and which is arranged so that it a piezoelectric crystal containing 65 upon the impingement of RF signals of the second Fre resonance circuit provided, which operates the sequence from the transmitter an alarm device. The ones in the absorbs radiated vibrations and this comparator shown with both embodiments Frequency and changed pulse duration or transmission device includes a first on the

first frequency tuned resonance circuit, a second resonance circuit tuned to the second frequency, as well as means which connect the two resonance circuits to one another in such a way that the resonance of the one circuit causes a resonance of the second circuit. Each resonance circuit contains one Coil that serves as a receiving antenna in the first resonance circuit and as a transmitting antenna in the second. The connecting means has a diode to convert the energy present in the first resonance circuit into a Convert bias; furthermore it contains an amplifier device, for example a transistor, which serves to maintain the oscillation of the second resonance circuit. In a first embodiment the energy taken from the first resonance circuit by means of the diode is transferred to the transistor fed, which it uses to maintain the oscillation of the second resonance circuit. In a second Embodiment, this energy is used to bias the transistor to bring this over its reverse voltage. This in turn is separated between a Battery, the transistor and a second resonance circuit closed a circuit, so that the The battery can now supply energy via the transistor to set the second resonance circuit in oscillation to keep.

The main features of the invention have hereby been broadly outlined, so that the following is more detailed Description becomes easier to understand and the contribution to technology made is better appreciated can be. Of course, the invention also has additional features, which are shown below are carried out and form the subject of the claims.

For the purposes of illustration and description, two exemplary embodiments have been chosen, which are shown in FIG the drawings and which form a part of the specification.

F i g. 1 is a partial perspective view of a door frame and shows together with one Block diagram of the overall system, an embodiment of the invention;

F i g. 2 is an electrical circuit diagram of one embodiment the transmission device used in the present invention;

F i g. Fig. 3 is a plan view showing the construction of a transfer device used in the invention;

F i g. Figure 4 is a side view of the arrangement in Figure 3;

F i g. Fig. 5 is a perspective view showing the structure of the transfer device of Fig. 5. 3 in an expanded arrangement;

F i g. 6 is a partial view showing a manner of attaching the transfer device of FIG F i g. 3, and

F i g. 7 is an electrical circuit diagram of another embodiment of that in the present invention used transmission device.

F i g. Figure 1 shows a door frame, designated 10, which is equipped to act as a fixed control point according to the invention serves to prevent unauthorized passage of guarded articles at this point to monitor. In the case shown, there is such a guarded object in a jacket 12, carried by a man 14 stepping out through the door frame 10.

The jacket 12 is the size of a card with the aid of a small transfer device 16 "Guarded", which is either sewn into the jacket 12 or attached to it in some other way. In 5 or on this transmission device, as will be explained in more detail later, there is an electrical circuit provided, received the high frequency signals of a first frequency and then with a second frequency can emit again.

ίο There is a transmitter 18 near the door frame 10 arranged. This transmitter generates a continuous, unmodulated high frequency signal, which is in turn broadcast by a main and a secondary antenna 20 and 22, respectively.

The transmitter 18 can be of very simple construction. For example, it can simply be made from a quartz-controlled Resonant circuit exist, and a frequency doubler and a signal amplifier can between the oscillator and the antennas 20 and 22

ao be switched. In the case shown, an output frequency of the transmitter of 27.2 megahertz has been selected, while its output energy is around 20 watts.

Each of the two transmitting antennas 20 and 22 is made of a loop with a turn of elongated or elliptical shape. The antennas are for reasons that will appear later in the description become clear, arranged at right angles to each other. As shown in the picture, they are in a door jamb 24 or a door sill 26 of the door frame 10 is embedded. In practical application and for better fitting within the confines of the door frame assembly, the Loop of the main antenna 20 in the form of an ellipse of about 76 cm along its main axis and 45 cm be formed along their minor axis.

The two transmitting antennas 20 and 22 are at right angles to each other and around at different points the control point or door frame arranged to the transmission device 16 to a maximum Apply high frequency energy so it doesn't matter how the transmission device is oriented is when it passes the door frame and that it always encounters a source of transmission energy.

Since the transmission device itself continues to transmit essentially in all directions, that is sufficient single receiving antenna 28 to be used by the transmitting device regardless of its orientation Record signals.

A receiver 26 is also mounted near the door frame 10. This recipient is on matched the frequency emitted by the transmission device. These signals are the Receiver is supplied via a receiving antenna 28, which is located in the other door post 30 of the door frame 10 is embedded.

The receiver 26 can also be very simple Be construction. It just contains a multistage amplifier with band pass filters between each Amplifier stage. This arrangement causes the receiver to only respond to signals in a certain prescribed manner Frequency band responds. In the present case, this band is between 5.0 and 5.9 megahertz.

The receiving antenna 28 consists of a two-turn loop and is generally formed in an elliptical shape of 122 cm along the major axis and 61 cm along the minor axis.

5 6

The output of the receiver 26 is to an alarm-certain extent on the capacitor 144 an equalizing device, for example to generate a bell 32 or a voltage.

Flashing light 33 connected, which when recording The second resonance circuit 35 consists of a

of coil 48 lying in the range of 5.1 to 5.9 megahertz and a capacitor 50, which signals evenly is set in motion. 5 if connected in parallel. The coil 48, which is

The system works as follows: While the same serves as a transmitting antenna, consists of four wire normal business hours or anytime, if one winds, which is in the form of a loop with a Monitoring of the door frame 10 for unauthorized diameter of about 5 cm are formed. "Guarded" objects should be passed by. The amplifier contains a transistor 52 of the

is worth, the transmitter 18 is constantly in operation ίο pnp type. The collector and the emitter of the oil, and the transmitting antennas 20 and 22 in the sistor 52 are in series with the first three Windun areas of the door frame high frequency signals from gene of the coil 48 to the capacitor 144 at -27.2 Megahertz off. This energy is closed though it is.

to the receiving antenna 28 and the receiver 26. The feedback branch has a resistor

notices, unable to actuate the alarm 15 on which is between the base of transistor 52 and 54 bell 32 or the flashing light 33 to cause a point between the last turn of the coil the receiver is sharply tuned so that it is connected to only 48 and capacitor 50. A responds to signals between 5.1 and 5.9 mega-capacitor 56 is parallel to resistor 54 and hertz lie. If now a "guarded object" works together with the resistance to create a as the jacket 12 passes the door frame 10, 20 carries rectified bias at the base of the transie to maintain the transmission device 16 the size of a sistor.

Card with itself. This transfer device can, The operation of the transfer device is

As mentioned above, high frequency signals from a fre- as follows: Incident high frequency signals from record frequency and then cause it to another 27.2 megahertz that the first resonance frequency forward. In the present case, the 25 circle 34 oscillates at this frequency and thus Device 16 is tuned to extract energy from signals from these signals. This response Receives 27.2 megahertz and causes signals with a frequency, as stated above, that at the Kondenquence emits between 5.1 and 5.9 megahertz. In- sator 144 generates and consequently maintains a DC voltage speaks one with such an over- is received. This tension in turn is passed on to the Guarded counterpart collector and emitter connections of the transistor 52 provided with a carrying device "stood" as soon as he passed the door frame 10, to the signals via the three upper turns of the coil 48 of the transmitter 18 and transmits signals with laid. At the same time, some of that tension is over the frequency of the receiver 26 further, so that the lower turn of the coil 48 and the receiver reacts so that the alarm bell 32 stood 54 applied to the base of the transistor 52, or the flashing light 33 switches on. 35 These voltages bring the transistor across the

The construction and the wiring arrangement of a reverse voltage so that it becomes conductive first embodiment of the transmission arrangement begins. As soon as the transistor starts conducting tion 16 is shown in FIGS. 2 to 5 shown. At elek, existing non-linearities cause the Irish facilities contains the arrangement, such as generation of a frequency spectrum in the system, in the circuit diagram of FIG. 2, has a first 40, however, due to the parameters of the second Resonant circuit 34, which reacts to the frequency of resonant circuit 35 only that part of the frequency spectrum 27.2 Megahertz matched, as well as a second span, which is close to 5.5 megahertz, Resonant circuit 35, which on the frequency of a significant amplitude. This part is about 5.5 megahertz is tuned, further connecting the resistor 54 to the base of the transistor return means, which is connected to the first resonance circuit 45, where it is amplified again. To this are, an amplifier arrangement that acts between the ways the transistor 52 in conjunction with the Connection means and the second resonance circuit, the second resonance circuit as an oscillator, which with is connected and a feedback arrangement, oscillates at a frequency of 5.5 megahertz, which is connected in such a way that it forms part of the signal. It should be noted that the circuit described above

in the second resonance circuit, so that it is completely passive in the 50, i. H. he is merely using the ener booster is reinforced again. operated by the impinging high-frequency signals

The first resonance circuit 34 consists of a coil and therefore does not require any batteries or anything else and a capacitor 142, the parallel connected external energy sources. Also, the circle can are tet. The coil 40, which is also fully encapsulated as a reception, is likely to be unlimited The antenna is used, consists of one in the form of a 55 lifetime.

Loop formed wire turn with a like from the F i g. 3 to 5 can be seen, is the

Diameter of about 6 cm. Circle of the transmission device 16 in one

The output of the first resonant circuit 34 encapsulates a card-like plastic part 58 that holds a capacitor 144 and a diode 46, for example as a label for the items to be guarded which are connected in series and can be used in parallel with the Reso 60. As in FIG. 6th nanzkreis 34 lie. When high frequency signals are shown, the card-like arrangement 58 has no Schwieder Frequency of the first resonant circuit (i.e. roughness in the hem or lining of a clothing 27.2 Megahertz) hit it, the circle will be attached to the object, where it will be held by a Phase vibrate with these signals and they would go unnoticed by potential thieves. the Withdraw energy. The capacitor 144 and the card-like arrangement 58 include a bottom 60 Diode 46 now act so that the current flow to a and a cover 62, which is either by a only direction is limited and fluctuations glue or with the help of rivets 64 on the bottom be smoothed in this output so as to be captured in one. The receiving and transmitting coils

40 and 48 are arranged side by side on the bottom part 60, while the various others Circuit elements are distributed around these two coils and either through each other Wires or printed circuit boards are connected. The overall unit can be made very small The only limitation is that the receiving and transmitting coils operate simultaneously serve as antennas, are large enough to absorb and to absorb a sufficient amount of energy send. If desired, these antenna coils can be separated from the card-like arrangement 58, but be attachable to this and its associated circuit. This would of course have the consequence that a very large restriction on the size of the card-like arrangement 58 is made possible because therein then only the relatively small remaining circuit elements, i.e. resistors, capacitors, the diode and the transistor would have to be accommodated. The separate antenna coils could consist of loops of very thin wire, which are permanently attached to the merchandise to which the transmission device is attached.

For certain purposes, for example when the guarded items are loaned and not to be sold, it may be desirable to have the transfer device permanently attached to the To attach objects, although there is still the possibility of using them as a legitimate Borrower in possession of the item is to be put out of service. Such an arrangement is for example an advantage in the case of a lending library, where the books are stuck to their covers or Cover-mounted transmission devices can be guarded and the device cannot can be put out of operation without further ado, except with the help of a special device, which from Librarian controlled when a prospective borrower has been satisfactorily identified Has. According to the present invention, this can be done by means of a small, non-conductive, but magnetizable Elements, such as B. a ferrite 66 can be achieved on or very close to one of the two antenna coils is arranged in the transmission device. Usually this ferrite is in his non-magnetic state and has no effect on the operation of the device. However, if it does it is desirable to put the device out of operation, so that the guarded object without triggering an alarm can pass a control point, the ferrite will go into the magnetic state offset. This causes a disruptive influence on the electromagnetic field in the Proximity of the antenna coils existing waves and thus effectively prevents the operation of the transmission device. The ferrite 66 can be made with the help of a large, controlled by the librarian or supervisor Electromagnets are brought from the non-magnetic to the magnetic state in order to achieve the To put the transmission device in or out of operation.

Another embodiment of the transmission device 16 is shown schematically in FIG. 7 shown. This arrangement in turn provides a first resonance circuit 134, which consists of a coil 140 and a Capacitor 142 exists and is tuned to a first frequency. There is also a second resonance circuit 135 is provided, which is composed of a coil 148 and a capacitor 150, which together are tuned to a second frequency. In this particular arrangement, the coil is 140 equipped with two turns, while the coil 148 is provided with five turns. The resonance circles are connected to a diode 146 and a transistor 152 in a manner described below. A battery 76 is with the upper three and a half turns of the coil 148 between the collector and emitter of transistor 152 switched. A resistor 78 is between the emitter and base of transistor 152 is placed, and a feedback capacitor 80 is between the base and a point between the last one and a half turns of the coil 148 and the capacitor 150 switched. The first resonance circuit 134 is in series with diode 146 between the terminals of the base and the emitter of the Transistor.

In this switching arrangement, the emitter and base of transistor 152 are usually on the same Potential so that the transistor is below the reverse voltage or in its non-conductive state remain. As a result, that is from battery 76, the top three and a half turns of coil 148 and the emitter-collector path of the transistor 152 existing circuit open. Accordingly, flows into There is no power to this circuit and no power is drawn from the battery 76 until the unit is in operation is working. However, as soon as signals of the resonance frequency at the first resonance circuit 134 of the transmission device occur, the first resonance circuit begins to oscillate in phase with these signals and to take energy from them. This oscillation, in conjunction with diode 146, causes a Voltage drop across the base resistor 78 so that a base-emitter bias occurs. Through this the transistor 152 is brought over its reverse voltage, so that a conductive connection begins to occur between the emitter and the collector, thereby reducing the output of the coil 148 and the battery 76 existing circuit is closed. When the transistor begins to conduct, in effect This system existing non-linearities that a frequency spectrum is generated. Due to the Frequency selectivity of the second resonance circuit, however, will only be in the vicinity of its resonance frequency lying frequencies to the feedback capacitor 80 to be passed in the transistor 152 to be reinforced again. So as long as there is a bias on the base resistor 78 to the Keeping transistor 152 above its reverse voltage leaves the transistor and the second resonant circuit in vibration. However, when incident signals of the resonance frequency of the first resonance circuit fail and the circuit no longer maintains the output voltage at the base resistor 78, so transistor 152 reverts to reverse bias or a non-conductive state and can so no longer maintain the vibration.

Due to the fact that most of the energy sent is supplied by the battery 76, it is not necessary in this embodiment of the transmission device that the coils of both resonance circuits are made as large as in the previously described embodiment. For example has been found that the coils at

909 520/285

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this version only need to have a diameter of about 2 cm, while the diameter of the coils in the previous example is about 6 cm. Therefore, although in this second form of training, additional a battery is required, the overall size can be considerably limited.

Claims (10)

Patent claims: 1. Device for discovering the unauthorized passage of objects to a Control post containing a transmitter for emitting a high frequency wave inside a first predetermined frequency range in a zone enclosing the control point, further a high-frequency receiver, also located near the control point, to the Switching means for triggering an alarm are connected, characterized in that that the receiver (26) on a high-frequency wave within a second predetermined Frequency range is matched, and that on or in the objects to be monitored attachable transmission devices (16 or 58) with a frequency of the Transmitter (18) sharply tuned receiver part (34 or 134) and one on the frequency of the Receiver (26) sharply tuned transmitter part (35 or 135) are provided that the receiver part a device (16 or 58) each absorbed energy of the wave within the first frequency range the transmitter part (35 or 135) excited in its resonance frequency and him causes itself to generate a high frequency wave within the second frequency range and broadcast that high frequency wave upon receipt by the one near the control point located receiver (26) actuate the alarm means (32,33) connected to it, whenever an object provided with a transmission device (16 or 58) is moved past the control point. 2. Apparatus according to claim 1, characterized by a pair of transmitting antennas (20, 22) which are connected to the transmitter (18), are substantially perpendicular to one another and are directed so that they radiate to the control point. 3. Device according to one of the preceding claims, characterized in that the Transmission device (58) consists of a flat, card-like part (60) on which two Loop antennas (40, 48) lying flat on it are arranged, the resonance circuits for transmission of high frequency waves. 4. Device according to one of the preceding claims, characterized in that several Transmission devices (58) are provided. 5. Device according to one of the preceding claims, characterized in that the Transmission device (58) consists of a first (34) and a second (35) resonance circuit, which are tuned to different frequencies, from a rectifier (46), the provides an output current from the resonant circuit (34) from one between that output and the other resonance circuit (35) connected transistor (52) and feedback means (54,56), which are connected in such a way that they feed part of the signal into the second resonance circuit (35) feed back in phase so that it is amplified in the transistor (52). 6. Apparatus according to claim 3 and 5, characterized in that in the part (60) a Diode (46) is arranged and connected so that it has a DC voltage proportional to the Amplitude of the resonance oscillation of the tuned to the frequency sent by the transmitter (18) Circle (34) generated that in the part (60) a transistor (52) is arranged and so connected is that it forms a feedback oscillator with the other resonance circuit (35), and that a circuit with the resistor (54) and the capacitor (56) is also arranged in the part (60) is, which supplies the feedback oscillator with energy when the diode (46) has a DC voltage occurs. 7. The device according to claim 6, characterized by a magnetizable element (66) which is arranged on one of the loop antennas (40 or 48) and prevents the occurrence of resonance vibrations. 8. Device according to one of claims 5 to 7, characterized by means for supplying energy, which contain the rectifier circuit and are arranged so that they the transistor Supply (52) with electrical energy to excite the oscillator. 9. Apparatus according to claim 6, characterized in that the second resonance circuit (35) a loop antenna (48) and a capacitor (50) that contains the collector and the Emitter of transistor (52) in series with capacitor (144) and the greater part of the Loop antenna (48) are connected, and that the feedback branch (56,54) has a connection between the end facing away from the larger part of the loop antenna (48) and the base of the transistor (52). 10. The device according to claim 9, characterized in that the resistor (78) for generating the base bias and the diode (146) are connected in series and are parallel to the first resonant circuit (134), that the collector and the emitter of the transistor (152) are in series with a battery (76) and the larger part of the transmission loop antenna (148) that the feedback circuit with the feedback capacitor (80) between the end of the loop antenna (148) facing away from the larger part of the loop antenna (148) and the base of the transistor (152) and that the resistor (78) for generating the base bias voltage is connected between the emitter and the base of the transistor (152) so that the transistor (152) normally, when no signal occurs, below the reverse voltage remains and the circuit containing the battery (76) remains open, but that when signals of the appropriate frequency appear at the bias resistor (78) a voltage is generated , which is above the reverse voltage and closes the circuit containing the battery (76) so that the second resonant circuit (135) oscillates at its natural frequency. For this purpose 2 sheets of drawings