Security control system for electrical equipment

Abstract

 A circuit is included within electrical equipment to disable it in the event of its being tampered with. Typically, the circuit is arranged to sense an unauthorized action, such as movement of the equipment, or removal of its plug from the power point, to trigger an electronic lock which will prevent operation of an important part of the equipment, such as its power supply.

Description

[0001] This invention relates to a security control system for electrical equipment, and is particularly suited for controlling unauthorized use or theft of electrical equipment.

[0002] In the past, many different forms of security control have been used in an attempt to curb burglary of expensive electrical appliances, such as colour television sets, video recording and playing equipment, tape decks, hi-fi equipment, and microwave ovens. These include such schemes as placing marks on equipment with invisible inks (which become visible under ultra-violet light), and expensive alarm systems and security locks on the premises.

[0003] Burglaries are continuing at a high rate, however, both from shops or other commercial premises, or private homes, and the rewards for the successful burglar are high. Property crimes comprise at least 90% of all reported crime, and approximately two-thirds of all goods stolen in burglaries fall into the area of electronic and photographic equipment.

[0004] The advance of electronic technology means that the value of electronic goods will continue to rise, as new developments, such as personal computers, photocopying equipment and electronically operated photographic devices become widespread.

[0005] It is an object of the present invention to provide a control system capable of preventing or making difficult the unauthorized use of electrical equipment with the aim of thereby making it difficult for thieves to sell such equipment.

[0006] Alternatively, it is an object of the present invention to provide an alternative means of deterring the theft of expensive electrical equipment.

[0007] Accordingly, in a first aspect, the present invention broadly consists in a control system for electrical apparatus including disabling means for electrically disabling the electrical equipment, and lock means capable of controlling the disabling means.

[0008] In a second aspect, the present invention broadly consists in a control system for electrical equipment, including an electrically operated switch within the circuitry of the equipment, control means capable of controlling said electrically operated switch, and an electronic lock capable of operating said control means, whereby said electronic lock is accessed by keys or switches of the equipment.

[0009] The above gives a broad description of the present invention, a preferred form of which will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a block diagram illustrating the operation of this invention;

Figure 2 is a second block diagram illustrating a preferred circuit arrangement;

Figure 3 is a circuit diagram of part of an electrical apparatus incorporating the present invention; and

Figure 4 is a block diagram illustrating an alternative arrangement incorporating the present invention.

[0010] The present invention contemplates the provision of an electrically operated switch within the equipment, in a position that is not readily accessible, and is preferably not readily apparent to persons unfamiliar with the equipment.

[0011] Preferably, the control device of the present invention is included as part of the circuit of equipment such as a television set, and installed as a factory component, with the circuitry being incorporated alongside the existing circuitry and perhaps concealed in integrated circuit chips forming part of the control circuitry of the apparatus.

[0012] The electrically operated switch is preferably a relay which can be installed in any part of the circuit to disable the equipment either completely or partially. For example, with the control system installed in a television set, the relay could disable the main power supply to the television, or could disable the power supply to the television tube, or the preamplifier or some other significant part of the equipment.

[0013] This relay 10 is controlled by control means 11 which draws power when the equipment is connected to a power supply, e.g. the mains. When power is continuously supplied to the control means 11, the relay is held open and power is allowed to be supplied to the equipment 18 for normal operation. If, however, the power supply is interrupted, e.g. by the equipment's being unplugged from the mains, or for some other reason, the interruption of power to the control means will cause the relay 10 to be disconnected, thereby breaking the power supply circuit to the equipment or that part of the equipment controlled by the relay.

[0014] Preferably, the control means is controlled by an electronic lock 12 which is accessed by a plurality of keys or switches 13. These keys may be special keys or switches accessed from the exterior of the equipment, or may be the existing control switches on the equipment. For example, in the case of a television set, the channel selection switch could double as the switches operating the electronic lock. The channel selector is particularly suited to this function as it involves the selection of differently numbered channels. Other keys or switches could be used, however, as required.

[0015] The electronic lock can involve the selection of a predetermined code, either a plurality of coded keys operated in any sequence, or, more particularly, a plurality of coded of keys operated in a particular sequence.

[0016] For example, the code chosen may be 3986, there being nine keys available to choose from. Or the code could involve lettered keys, or the operation of certain unlabelled switches in a predetermined sequence.

[0017] In the arrangement shown in Figure 1 of the drawings, only the coded keys 3986 will operate the electronic lock, while the choice of any other key, or the choice of one of the code keys out of sequence, will cause the lock to reset.

[0018] The electronic lock may be provided with an automatic time delay such that the lock is reset after a predetermined period of time if the correct sequence is not chosen. For example, a time delay of, say, ten seconds may be incorporated into the electronic lock to make it difficult for unauthorized users to work out the sequence on a trial and error basis. Moreover, the electronic lock may also include a provision that if an incorrect code is selected more than, say, three times in succession, then the electronic lock will send a signal to an alarm device 14. This may, for example, be the amplifier of the device (such as the audio amplifier of he television set) in conjunction with a noise or audio signal generator. Alternatively, the alarm could involve a radio transmitter making detection and location of the stolen equipment possible.

[0019] In place of the electronic lock and switches 13, it is possible to use a key operated mechanical lock which provides power to the control means. This, however, is not as advantageous as the provision if an electronic lock in deterring theft of such equipment, as a thief, and a receiver are less likely to endeavour to tamper with an electronically locking system than, say, a key-operated mechanical lock.

[0020] Turning now to the circuit of Figure 2, an improved circuit is illustrated which enables the disabling mechanism to come into play when the item is unplugged from the mains supply, but will not be disabled in the event of the power supply's being switched off at the socket, or in the case of a power failure.

[0021] In this circuit arrangement, the wall socket is shown generally as of the three contact type, for use with a three-pin plug. This has a power contact 21, a neutral contact 22 and an earth contact 23. In the event of the invention's being used in countries where a two contact socket is standard, such as the United States of America, then it will be desirable to connect the neutral terminal to an earth by way of a strap 24, so that the neutral and earth connexions are at the same potential. A three-pin plug is shown at 25, having power lines 26 connected to an electrical appliance 27 such as a television set or the like. Within this appliance there is an electronic lock 28, as previously described, and an alarm 29.

[0022] The electronic lock controls the power supply to all or part of the electrical appliance, by leads 31, and is in turn controlled by the relay circuit 32. In its simplest form, the leads 31 can be part of the power supply, and have a switch (not shown) within the electronic lock, such as a further relay, controlled by the relay circuit 32.

[0023] The relay circuit has a battery 33 connected to a coil 34 of the relay, which may be connected in series with a switch 35, described below. Such a switch 35 is normally closed to complete the circuit between the central pin 38 and the earth pin 39 of the plug 25.

[0024] In addition, a power supply in the form of a transformer 40 and voltage regulator 41 can be provided to control the operation of the electronic lock, and/or provide a power supply to the alarm 29. The alarm circuit may include an optional switch 44.

[0025] The switch 35 may be a microswitch in the removable panel of the appliance, so that in the event that the panel is removed in an attempt to circumvent the electronic lock, the switch 35 will open, thereby causing the lock to operate and disable the power supply to the appliance. Appliance, or in addition to the microswitch, the switch 35 may take the form of a motion sensitive switch, such as a mercury switch, which will break the circuit 34 if the appliance is moved, such as by carrying it from the owner's premises. If such a switch is opened by motion, then once again the circuit 34 is broken, thereby activating the electronic c lock and causing it to disable the power supply to the appliance.

[0026] In use, the coil 34 is energized so long as the plug 25 is inserted in the wall socket 20. This is achieved by the circuit from the neutral pin 38 passing down through the switch 35 (closed) through the coil 34 and back via the earth line to the earth pin 39. As the neutral and earth pins are at the same potential, the relay is maintained in a closed position and no current flows from the battery 33. The relay is maintained in the closed position as long as the pin is plugged into the wall socket, irrespective of whether or not the power is interrupted by switching it off at the wall, or the mains supply to the premises, or through a power failure in the mains supply. The moment the plug is removed from the wall socket, however, the relay circuit is broken, and the relay circuit is broken, and the relay is de-energized, thereby causing the electronic lock to break the circuit in the power supply to the appliance 27, or to a specific part thereof. If an alarm 29 is provided, and the alarm switch 44 is in the closed position, the alarm will activate, once the relay opens.

[0027] The switch 44 is optional, as such a switch can be provided for the use of an authorized technician to enable him to disable the alarm when repairing such an appliance.

[0028] It will be appreciated that if the switch 35 is in the form of a mercury switch, then it will not be necessary to use the plug sensing circuit described with reference to Figure 2. Instead, the circuit can be simplified so that the electronic lock operates to disable the equipment in the event that the appliance is moved.

[0029] A similar effect could be achieved by providing a microswitch in the plug, which would be depressed when the plug is inserted into a wall socket, such as in the case of a two-pin plug, the plug could be provided with a small third pin capable of operating a microswitch. Such a pin would press against the housing of the wall socket without interfering with the power supply. It could be used to complete a circuit of the type described with reference to Figure 2, and function as the switch 35.

[0030] Figure 3 is a circuit diagram illustrating the present invention. The circuit relates to a conventional mains/battery operated portable radio to which additional circuitry has been added to effect the present invention.

[0031] The circuitry is arranged to disable the radio automatically when it is tilted from side to side approximately ten times in quick succession. More movement will be required if the movements are made slowly, less movement if the radio had just been moved in the preceding minute. The radio will also be disabled if the back is removed.

[0032] The radio is returned to its functioning state by entering the correct code via two push-button switches 50, 51, typically mounted on the back panel of the apparatus. If the first push button 50 is red and the second button 51 is blue, then, for the illustrated radio, the code is internally set to the sequence:- blue, red, red, blue, red, blue, red. When the correct code has been entered, further activation of the push-button switches will have no effect.

[0033] The correct code will be held if the radio is turned off or unplugged from the mains, but it will be lost and have to be re-entered if the battery 52 is removed or runs flat.

[0034] If the radio is moved and is disabled by the lock circuitry, the correct code may be entered immediately, but further movement at that point may not disable the radio. The lock circuitry requires approximately thirty seconds to reset after movement. After this time, further movement will disable the radio.

[0035] Movement of the mercury switch 53 will cause a square wave at the switching rate to appear on pin 3 of the 4070 quad exclusive-OR gate.

[0036] This waveform is delayed at pin 6. Pin 4 will present a positive pulse waveform for every positive and negative switch transition, the pulse width being determined by the time constant on pin 6. These pulses charge up the capacitor 54 through the diode 55 and 1 Kohm resistor 56. The size of the capacitor 54 determines the amount of movement required to cause the level to operate, but it may typically be a 47 microfarad tantalum capacitor. This capacitor is slowly discharged via the 1 megohm resistor 57. Positive feedback around gate 3 creates hysteresis, avoiding oscillations when the capacitor is discharging. When the radio has been moved sufficiently for the capacitor to have charged to the threshold voltage level of gate 3, a pulse is fed to the 4015 shift register holding the code. This resets the entered code and locks the radio.

[0037] If the back of the radio is opened the microswitch 58 is operated and this also resets the shift register.

[0038] If switch 50 (the red button) is pushed, a pulse will appear on pin 9, the clock input, of the 4015 four-stage shift register. A pulse will also appear at pin 6 of the 4093 Schmitt trigger input quad NAND gate. This resets the push button 51 output on pin 10 to logic 0.

[0039] If switch 51 is pushed the pin 10 is reset to logic 1.

[0040] The logic state present on pin 10 of the 4093 will be clocked into the 4015 shift register on the following positive transition of the clock pulse (caused by closing switch 50).

[0041] A time delay is introduced between pin 10 of the 4093 and the data input of the shift register to hold the data input steady as the clock transition occurs, since pin 10 is reset to logic 0 at the same instant.

[0042] Therefore, to shift a logic 1 into the register, switch 51 must first be pushed, setting the data input high. Switch 50 is then pushed to clock it into the register. In other words, a logic '1' is achieved by pressing the blue switch and then the red switch. To switch a zero into the register requires only the closing off of switch 50. The previous push of switch 50 will already have reset the data input to a zero, so that logic '0' is achieved by pushing red switch only.

[0043] If the lock code starts with an '0', switch 50 should be pushed twice at the start of the code sequence to ensure that a zero is present on the data input during the first clock pulse.

[0044] The code shifts down the register starting at pin 5 and proceeds to pin 4, 5 and 10 as the code progresses.

[0045] The 4063 4-bit magnitude comparator compares the code in the register with the code set up on its B inputs, which are hard wired at 59 to logic ones and zeroes on the printed circuit board.

[0046] When the code in the register matches this preset code the output on pin 6 goes high. This switches the radio off by removing the power supply connexion through the switching transistors BC548 and BC327. This will occur whether the radio is operated on the mains supply or on the batteries. The switch 60 shown on the diagram adjacent the 9 volt battery 52 is automatically operated when the mains plug is inserted into the back socket. This selects either battery or mains supply.

[0047] The capacitor 54 can be adjusted to permit normal movement of an appliance within the user's home, such as from one room to another, but to operate the lock if the movement is greater than that. Of course, the capacitor will slowly discharge through the resistor 57 once movement ceases, so that the appliance can be moved periodically by its owner, without fear that the movements will accumulate to disable the appliance. The resistor 57 could be set, for example, to permit the capacitor to be discharged ten minutes, say, after the appliance has been moved.

[0048] Although the invention is described above as involving the disabling the power supply of an electric circuit, it would be possible to disable some other part of an electric circuit. For example, many devices require a signal to be passed from one stage of a circuit to another. The locking device of the present invention could be arranged to prevent the passage of such a signal, by the use of an AND gate for example, which would be disabled when the lock is activated.

[0049] Figure 4 illustrates an apparatus 70 including a power supply 71, a lock circuit 72, a first stage 73 of the main circuit, and a second stage 74. The second stage drives an output device 75, such as a loudspeaker or a television tube.

[0050] The first and second stages 73, 74 are connected via an AND gate 76. If the lock circuit is supplying a signal to the gate, then the gate will pass on to the second stage 74 all signals received from the first stage 73. If, however, the lock circuit has been disabled, then the gate will not pass any signals from one stage to the other. The apparatus will effectively have been disabled.

[0051] Alternatively, the circuit element 76 could be a scrambling device, so that the signal is passed from one stage to the next in scrambled form, to render it unintelligible. Another alternative is for the circuit element 76 to replace the signal from the first stage with another signal of its own, such as a warning signal.

[0052] Any equipment with the control system installed therein can be suitably marked, and the equipment could, for example, include some form of display, such as a lamp, or a display on the screen in the case of a television set, that the lock is operative. A television set lends itself to the inclusion of prerecorded picture information which could display on the screen that the set has been stolen, if the lock is not operated correctly.

[0053] It will be appreciated that the present invention can be used as a control device to prevent unauthorized use of the equipment, such as for preventing children from watching television until the correct code sequence is entered into the electronic lock.

[0054] Various alterations or modifications may be made to the foregoing without departing from the spirit or scope of this invention as claimed. For example, in the arrangements described above as using a relay, an electronic switch may be used instead, typically within a microchip. The lock circuit may be located within a single microchip within the apparatus, or it may be spread across several chips, making it more difficult for a thief to bypass the lock.

[0055] If desired, there may be a means of disabling the equipment directly, such as a switch on the outside of the equipment, one or more micro-switches located within the appliance, (thereby making it difficult to tamper with the inner workings of the appliance without activating the disabling mechanism) or a remote disabling device, (operable through the equipment's antenna, for example). Once the equipment is disabled, it cannot be reenabled without entering the correct code sequence. Once the appliance is installed, in the user's home for example, and the code sequence has been selected, the appliance will operate as normal.

[0056] The remote disabling arrangement could be used on equipment that belongs to a rental company, so that the company can disable by remote control any equipment on which rental payments are not kept up.

[0057] It will be appreciated that the general idea of the invention involves the use of means to disable part of the electric circuitry of an appliance upon the occurrence of certain events, and, in particular, the removal of the appliance from the owner's premises, such as by unplugging the appliance from a wall socket, or by carrying the appliance. When such an event occurs, the power supply circuit or some other vital circuit is broken in the appliance, and it can be reset only by utilizing an unlocking device, which typically takes the form of an electronic lock which can be incorporated into the circuit board, integrated circuit chip, or other componentry of the appliance. Indeed, the electronic mechanism 28 described with reference to Figure 2 and the equivalent mechanism 12 described with reference to Figure 1 are essentially unlocking devices, rather than locking devices. Thus, the mechanism could either be part of an appliance or it could be separate from the appliance. For example, the unlocking device could involve the use of a remote control device of the type presently used with domestic television sets. As such a device can be made in a relatively compact form, and could readily be hidden, it will be appreciated that such an arrangement would facilitate the control of a device such as a television set, allowing parents to hide the device to prevent children from watching programmes without their permission. More particularly, it would enable an owner to hide the control device, making the theft of such a television set less likely.

[0058] It is envisaged that the present invention could be used to modify electrical equipment in the factory so that the electronic lock and control means are incorporated as an integral part of the electronics of the equipment. It is particularly desirable that the relay or other device which interrupts the operation of the equipment be concealed within the equipment or be installed in such a way that it is difficult to bypass the device.

[0059] It is believed that the installation of a control system in accordance with the present invention as part of the original equipment will make that equipment less likely to be stolen than equipment which is not provided with such a control system. Even if it is stolen, it will be difficult to dispose of, as receivers are unlikely to want to acquire inoperative equipment. It will be appreciated that once the equipment is unplugged from the wall during the course of a burglary or other theft, the electronic lock will be actuated, making it difficult for a thief or receiver to operate the equipment thereafter.

Claims

1. A control system for electrical apparatus including disabling means for electrically disabling the electrical equipment, and lock means capable of controlling the disabling means.

2. A control system as claimed in claim 1, wherein the disabling means is arranged to disable the power to at least part of the apparatus.

3. A control system as claimed in claim 1, wherein the disabling means is arranged to prevent the transmission of a signal from one stage of the apparatus to another.

4. A control system as claimed in claim 1,2 or 3, wherein the disabling means is arranged to disable the apparatus upon its being unplugged from a mains socket.

5. A control system as claimed in claim 1,2 or 3, wherein the disabling means is arranged to disable the apparatus upon its being moved more than a predetermined amount.

6. A control system as claimed in any preceding claim, wherein the lock means is arranged to be released by manipulation of control switches on the apparatus in a predetermined sequence.

7. A control system as claimed in any one of claims 1 to 5, wherein the lock means is arranged to be released by operation of a remote transmitter arranged to transmit a predetermined code sequence to a receiver within the apparatus.

8. A control system for electrical equipment, including an electrically operated switch within the circuitry of the equipment, control means capable of controlling sai-d electrically operated switch, and an electronic lock capable of operating said control means, whereby said electronic lock is accessed by keys or switches of the equipment.

9. A control system as claimed in claim 8, wherein the keys or switches include the main control switches for the equipment.

10. An electrical appliance including a control system as claimed in any preceding claim.

Drawing