A SECURITY DEVICE

Abstract: There is described a security device for inhibiting unauthorised interference with electrical and/or electronic apparatus. The security device comprises: vibration detection means having a first sensitivity and a second sensitivity, the second sensitivity being higher than said first sensitivity; switching means operable to switch the vibration detection means between the first sensitivity and the second sensitivity in response to the state of the apparatus; and means for initiating an alarm signal, the means for initiating being connected to the vibration detection means and operable to initiate an alarm signal in response to an indication from the vibration detection means that a vibration has been detected. The security device may switch sensitivity automatically in response to the protected apparatus being switched off, or in response to external power supply to the device being interrupted. The first level of vibration sensitivity may be zero, and the device may also include an anti-tamper switch.

Description: A SECURITY DEVICE This invention relates to a security device, electrical and/or electronic apparatus, and a security system. Theft of electrical and/or electronic apparatus, in particular the theft of computers, their peripherals, or internal components, is a major problem. A wide variety of security devices exist and are well known, including mechanical locks and vibration detectors able to detect movement during attempted removal of, or disturbance to, the apparatus to which the security device is attached. Problems with mechanical locks are that secure attachment to the apparatus may be difficult to achieve, given sufficient time a thief may be able to defeat them, and no alarm is signalled during the thief's attempt to remove the apparatus. Security devices incorporating vibration or movement detectors are known for the protection of computers, and which transmit an alarm signal via a network link or a dedicated hardwired link to an alarm system when activated. Typically, these devices are set or switched on either by entering a code via a keypad, or by operating a key-switch. However, a problem with these kind of devices is that the necessary hardwired links may be expensive and/or inconvenient to install, and in any case may be broken. In addition, these devices have only one sensitivity as determined by the vibration detection element composition, may inadvertently be activated or triggered during the periods of normal use of the computer if switched on, and rely on users remembering to leave them switched on overnight or over any period during which their protection is desired. A user is also required to remember a code, or carry a key to operate the key-switch. Therefore, it is desirable to produce a security device incorporating a vibration detector which may be attached to a wide variety of electrical and/or electronic apparatus without the provision of wiring in addition to that required for the normal operation of the apparatus, transmits an alarm signal when activated, is less likely to be activated inadvertently, and yet provides sensitive protection for the apparatus outside its periods of use. According to a first aspect of the present invention there is provided a security device for inhibiting unauthorised interference with electrical and/or electronic apparatus, the security device comprising: vibration detection means having a first sensitivity and a second sensitivity, said second sensitivity being higher than said first sensitivity; switching means operable to switch said vibration detection means between said first sensitivity and said second sensitivity in response to the state of said apparatus; and means for initiating an alarm signal, said means for initiating being connected to said vibration detection means and operable to initiate an alarm signal in response to an indication from said vibration detection means that a vibration has been detected. Advantages of the first aspect of the present invention are that: 1) by having two levels of sensitivity, the device may be operated at a reduced, or zero, sensitivity during periods of normal operation of the protected apparatus, thereby reducing the frequency of inadvertent triggering of the vibration detector, and at higher sensitivity at other times; and 2) the switching means may automatically switch the device to high sensitivity according to the state of the apparatus, for example when it is switched off at night, thereby obviating the need for a user to remember to set the device outside the periods of normal use of the protected apparatus. It will be apparent that in the terms "first sensitivity" and "second sensitivity", "first" and "second" do not imply any necessary sequence or order in time, but merely indicate that the vibration detection means has two different levels of sensitivity. Advantageously, at least one of said first sensitivity and said second sensitivity may be adjustable. The first sensitivity may in fact be zero, such that at this sensitivity no vibration or movement may be detected by the vibration detection means. At the first sensitivity, therefore, the vibration detector may be disabled. The switching means may be operable to switch the vibration detection means to the higher sensitivity in response to the apparatus being disconnected from a power source or being switched off. The security device may comprise electrical and/or electronic circuitry, and may further comprise a battery for supplying electrical power to operate this circuitry. This battery may of course be rechargeable. The means for initiating an alarm signal may comprise a transmitter including an aerial, the transmitter operable to transmit a signal for reception at a remote sensor. The device may further comprise means for connecting to an external supply of electrical power to operate the circuitry. By "external" it is meant that power is supplied from means outside the security device, i.e. not for example from any internal battery. The external supply may be from, or via, the protected apparatus. The electrical power may be used to operate the circuitry and/or charge a rechargeable battery. Advantageously the switching means may be operable to switch the vibration detector to its higher sensitivity when the device is disconnected from the external power supply. Thus, the higher sensitivity vibration detection may be enabled automatically according to the nature of the power supply powering the security device. The device may further comprise an encoder and memory means, the encoder operable to encode information stored in the memory means together with an output from the vibration detector and pass the encoded material to the transmitter for transmission. Advantageously the memory means may contain an address, which may be unique to the security device. The security device may also comprise a receiver connected to the switching means, and the switching means may be operable to switch the vibration detector between sensitivities in response to signals received by the receiver. The device may also include means for connecting it to the apparatus to receive electrical power from the apparatus. Power supply may be from an internal battery in the apparatus, or in the case of apparatus connected to an external supply, such as the mains, may alternatively be supplied to the device via the apparatus. The apparatus may be connected to the mains, and the device supplied with power by means of a transformer in the apparatus. Alternatively, where the security device does not receive electrical power via the protected apparatus, the security device may further comprise means for connecting it to the apparatus to supply electrical power to operate that apparatus. Thus, the security device may be in-line between the apparatus and a power supply. Advantageously, the security device may also comprise relative movement detection means connected to the means for initiating an alarm signal and arranged to detect relative movement of at least a portion of the apparatus with respect to at least a part of the device, the means for initiating an alarm signal being operable to initiate an alarm signal in response to an indication from the relative movement detection means that a relative movement has been detected. The relative movement detection means may comprise a switch arranged to be activated when the casing of the apparatus is opened or removed, completely or partially. The casing may also be referred to as the housing of the apparatus. The term "switch" is intended to encompass a wide variety of switching means for example electrical circuits and/or mechanical arrangements. The relative movement detection means may comprise a switch arranged to be activated when the security device is separated from the apparatus. Of course, the relative movement detection means could alternatively be arranged to detect attempted removal of a component or other part of the apparatus, for example a memory chip. The relative movement detection means may take the form of a case tamper switch which is activated when the casing of the protected apparatus is removed or partially opened. The case tamper switch may be a micro switch. Alternatively, the case tamper switch may comprise a light detecting element, such as a photodetector, and may switch in response to an opening of the casing which allowed entry of light into the apparatus. The relative movement detection means may comprise a resilient member which normally keeps part of the relative movement detection means in contact with the casing, or another part, of the apparatus. Relative movement may be detected when the resilient member is distorted or when the contact pressure with the apparatus changes. The resilient member may be electrically conductive and may be arranged to form an electrical contact with a conductive portion of the apparatus. The relative movement detection means may comprise circuit means arranged to detect changes in the resistance of the contact and accordingly indicate the detection of relative movement. The relative movement detection means may comprise an electrical circuit including an electrical connection between two conductive parts of the apparatus. The relative movement detection means may be arranged to indicate the detection of relative movement to the means for initiating an alarm signal when the electrical contact between the two parts is broken. Advantageously, the security device may also comprise means for mounting the device to the apparatus to be protected. The security device may be adapted to be mounted inside the expansion port of the computer, or an associated peripheral device. Advantageously, the security device may comprise a microprocessor, and at least one of the first and second sensitivities of the vibration detection means may be programmable. According to a second aspect of the present invention there is provided electrical and/or electronic apparatus comprising: means for connecting a power source; vibration detection means having a low sensitivity and a high sensitivity; switching means operable to switch said vibration detection means between said low sensitivity and said high sensitivity in response to the state of said apparatus; and means for initiating an alarm signal, said means for initiating being connected to said vibration detection means and operable to initiate an alarm signal in response to an indication from said vibration detection means that a vibration has been detected. According to a third aspect of the present invention there is provided a security system for inhibiting unauthorised interference with a plurality of pieces of electrical and/or electronic apparatus, each piece of said apparatus being connected to a power source, the security system comprising: at least one remote sensor for receiving signals, the or each remote sensor connected to an alarm system operable to raise an alarm; and a plurality of security devices, each security device being associated with a respective piece of said apparatus, each security device comprising: vibration detection means having a low sensitivity and a high sensitivity; switching means operable to switch said vibration detection means between said low sensitivity and said high sensitivity in response to the state of the respective piece of said apparatus; and a transmitter including an aerial, said transmitter connected to said vibration detection means and operable to transmit a signal for reception by the or at least one of said remote sensors in response to an indication from said vibration detection means that a vibration has been detected. Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 shows a security device in accordance with a first embodiment of the present invention, attached to electronic apparatus; Fig. 2 is a block diagram of the first embodiment; Fig. 3 is a circuit diagram of the first embodiment; Fig. 4 shows a second embodiment; Fig. 5 shows a third embodiment; Fig. 6 shows a perspective view of a security device in accordance with an embodiment of the present invention; Fig. 7 shows a block diagram of a circuit for use in an embodiment of the present invention; Fig. 8 shows a circuit diagram of the circuit of Fig. 7; and Fig. 9 shows a diagram of part of the circuit of an embodiment of the present invention. Referring now to figure l, in a first embodiment of the present invention, the security device 50 contains a rechargeable battery, and is additionally provided with electrical power from a mains electricity supply 60 by means of an input cable 61. The security device 50 is attached, by means not shown, to the apparatus 40 to be protected and is connected in line with the mains electricity supply to the apparatus 40. Electrical power is thus supplied to the apparatus 50 via the security device 40 by means of a second cable 62. Any attempt to remove the apparatus would therefore necessitate either the disconnection of the cable between the security device 50 and the apparatus 40, or disconnection of the security device 50 from the mains supply 60. As will be described below, disconnection from the mains supply would result in the vibration device switching to high sensitivity, causing any further movement of the apparatus to trigger the alarm. The operation of the security device 50 in accordance with the first embodiment will now be described in detail, firstly by referring to figure 2. The security device 50 comprises a power supply and rechargeable backup battery A, a two-stage vibration detector B having two levels of sensitivity, switching means for switching the vibration detector B between its two sensitivities, a flip-flop C, an encoder circuit D, and a transmitter circuit E Connected to the transmitter circuit E is a transmitter aerial 90, and connected to the encoder circuit D are a code memory 100 and an address memory 110. When the device 50 is connected to a mains electricity supply 60 via input lead 61, the backup battery is trickle charged, and power to blocks B, C, D and E is provided from the mains supply 60. When the mains supply 60 is disconnected, power to these blocks is provided by the battery. The two-stage vibration detector B has two levels of sensitivity, and includes a vibration detection element which senses movement of the device 50. The switching means is operable to switch the vibration detector B between its two sensitivities, such that the more sensitive level is selected when the mains supply to the device 50 is disconnected (i.e. while power is being provided by the battery) or the apparatus 50 is switched off. If the mains supply is connected to the device 50 and the apparatus is connected to the device 50 (by the lead 62) and switched on, then the switching means ensures that the lower sensitivity is selected. When vibration or movement is detected a pulse is produced by the vibration detector which enables blocks C, D and E. The flip-flop circuit C, after being triggered by block B, is set for approximately two seconds and then resets. Whilst set it enables the encoder D and transmitter E circuits. The encoder circuit D receives and processes an input from the flip-flop C, and encodes the code stored in the code memory 100 and the address stored in the address memory 110. It then emits a code to the transmitter circuit E. The transmitter circuit E receives the encoded information from the encoder E, processes the information, and then transmits it from the aerial 90 with appropriate modulation. The operation of the first embodiment will now be described in yet more detail, with reference to fig.3. When the mains supply 60 is connected to the device 50, 240VAC is applied to the transformer Tl, the secondary providing 15VAC. The diodes D10, Dll, D1 2 and D13 form a bridge rectifier with capacitor CI smoothing the output and resulting in 21VDC being applied to the voltage regulator IC3. IC3 regulates the voltage to 12VDC. This is fed through diode Dl and current limiting resistor R2 , The 12V input is also fed through D2 and Rl to charge the backup battery Bl. When the power is turned off, Bl, the backup battery, supplies power through D3. D14 is a reverse polarity protection diode. Vibration detection is achieved in the following manner. Components R3, R4 , R5, the relay RLA1, the vibration detecting element VI, C4 , Cll and D8 form a two-stage pulse shaping circuit for the flip flop IC1. The contacts of relay RLA1 are closed when the unit has mains voltage applied and when the protected apparatus 40 is connected to the power output terminals 140 and is switched on. This has the effect of connecting R4 and Cll into the vibration detection circuit so that its sensitivity is reduced during the periods of operation of the apparatus 40 (typically during the day-time) . The component values are chosen so that this reduced sensitivity is sufficiently low to allow small disturbances resulting from normal operation of the apparatus 40 to pass without triggering the vibration detector. When the mains power supply to the device 50 is disconnected, or the apparatus 40 switched off, R4 and Cll are removed from the vibration detection circuit, thereby increasing sensitivity. The relay RLA1 and power output terminals 140 thus provide means for switching the vibration detector between its two levels of sensitivity, where the switching means is responsive to the state of the apparatus 40 (i.e. in this case whether it is on or off) and to the power supply to the security device 50. The sensitivity of the vibration detector is switched automatically according to the state of the apparatus and the power supply to the device 50. When movement is detected, VI momentarily closes and charges C4 through R3. This puts a voltage on pin 3 of ICl. When this voltage exceeds 2/3 of the supply to ICl, pin 1 goes high, turning on transistor TR1 through R7/R8. After approximately two seconds the voltage on C5 which has been charging through R6 exceeds 2/3 supply voltage and causes the flip-flop to reset, discharging C5 through D5 in the process. When pin 1 of ICl goes high, TR1 is turned on, and in turn the base of transistor TR2 is pulled low causing TR2 to supply power to IC2, code memory SW1 100, address memory SW2 110, and transmitter module TXM1. In this embodiment the address memory is in the form of a DIP switch. In alternative embodiments comprising microprocessors, the memory may be programmable. The oscillator circuit in IC2 is activated. IC2 encodes the code set by SW1 and address set by SW2. This is fed through R16 to the transmitter module TXM1. Transmitter module TXM1 operates at 400 to 450 Mhz with either AM or FM modulation. Other frequencies can be catered for by substituting TXM1 for the appropriate part. In this first embodiment, the security device 50 is connected in line such that the protected apparatus 40 receives its electrical power via the device 50. An advantage of this embodiment is that any attempt to remove the protected apparatus necessitates the disconnection of the power supply to the apparatus 40 or to the security device 50, and so results in the vibration detector switching to the more sensitive mode. Thus, even if a user forgets to switch the apparatus 40 off at night, or after use, high sensitivity anti-movement protection will automatically be provided should any attempt to remove the apparatus be made. A second advantage is that the security device may be attached quickly and easily, for example by using adhesive pads, to a wide range of electronic and/or electrical apparatus, requiring the provision of no other services in addition to mains electricity supply. This apparatus may include computers, monitors, printers, fax machines and photocopiers. Installation of the security device is further facilitated by the fact that its attachment to the apparatus need not be strong, as any attempted separation of the two should result in triggering of the vibration detector switched to either sensitivity. Advantageously, the security device may be provided with means for attaching it to the apparatus. For example, attachment may be achieved by means of complementary Velcro strips glued to the apparatus and device. Advantageously, the casing of the security device may be designed so as to be highly distinctive and easily visible so as to provide a deterrent to a potential thief. A further advantage of the first embodiment is that the vibration detector is automatically switched to its more sensitive setting when the protected apparatus is switched off. The user need not remember specifically to set the security device. Also, while the apparatus and security device are switched on, the vibration detector, although operating at a reduced sensitivity, provides a degree of protection against relatively large disturbances to the apparatus, such as those resulting from an attempt to open its casing. It will be apparent to those skilled in the art that a plurality of security devices in accordance with the first embodiment may be used to protect a plurality of different pieces of apparatus simultaneously, for example computers, printers, photocopiers and fax machines. Each security device may have a unique code or address stored in its memory, such that when the vibration detector of a particular security device is triggered, the alarm signal transmitted may contain information indicative of the piece of equipment being tampered with. Although not shown in any figure, one or more receiver units for receiving transmitted signals may be positioned in the vicinity of the apparatus. These receivers may be hidden or disguised, for example to look like standard PIR ~s, and may of course be set to activate a variety of different alarms, including lights, bells and/or sirens, a call to the Police or Security Company/Guards, or any other signal/warning device. Also, it will be apparent that the levels of sensitivity of the vibration detector, rather than being fixed, may be adjustable. For example, variable capacitors and/or resistors may be incorporated in the vibration detection circuit, whilst retaining the same vibration detection element, providing the advantage that the security device may be adjusted to provide optimum sensitivity levels for a variety of applications. In the case of embodiments comprising microprocessors, at least one of the levels of sensitivity may be programmable. In the first embodiment described above, the security device 50 is connected in line with the mains electricity supply to the protected apparatus 40, and is attached to the outside of the apparatus 40. Fig. 4 shows a second embodiment in which the security device 50 is attached to the inside of the apparatus 40, and mains power supply to the security device 50 is from the protected apparatus 40 by means of an internal connection 150. In this embodiment, the switching means switches the vibration detector to its higher sensitivity when the mains supply to the device is disconnected, and to its lower sensitivity when the mains supply is connected. Figure 5 shows a third embodiment in which the security device 50 is supplied directly with mains power, but does not have a mains power output, such that separate power supplies are required for the device and apparatus. In addition, the device is provided with a radio receiver, connected to the switching means, and the switching means is operable to switch the sensitivity of the vibration detector in response to signals received by the receiver. Advantages of this embodiment are that the vibration detector may be set to high sensitivity remotely, without the need for a user to remember to switch the apparatus or security device off after use, and can be used to provide high sensitivity anti- tampering protection to equipment which is left switched on by accident or for a purpose. In a further embodiment, the security device again comprises a receiver, and is solely battery powered, no means for connecting a power supply being provided. The switching means is responsive to the state of the attached apparatus, and to signals received by the receiver. In yet another embodiment, the security device is again connected in line with the mains supply to the apparatus, but the lower level of sensitivity of the vibration detector is in fact zero, i.e. in this setting the vibration detector cannot be triggered - it is disabled. The device switches to high sensitivity when the apparatus is switched off, or when the mains supply to the device is disconnected. Thus, no alarm can be triggered during operation of the protected apparatus, providing advantages in applications where inadvertent triggering would be unacceptable, or in which large movements are encountered during normal use of the protected apparatus. In a further embodiment, a signal is transmitted from the security device 50 each time the mains electricity supply to it is switched on, thereby alerting an alarm system to any attempt to reduce the sensitivity of the vibration detector prior to an attempt to separate the security device from the apparatus, or to tamper with the casing of the apparatus . Figure 6 shows a security device in accordance with an embodiment of the present invention for inhibiting the unauthorised tampering with the casing of a piece of computer hardware such as a personal computer or a computer peripheral. The device 50 comprises a housing 2 for containing the circuitry required to operate the device. A mounting plate 4 allows the device 50 to be mounted in an expansion port of the computer hardware which is being monitored. A resilient electrical conductor 6 is attached to the housing 2 of the device such that one end 6a of the conductor will come into contact with the inside metal casing of the computer hardware when the device 50 is mounted in position as defined by the mounting plate 4 in the expansion port. An aerial 90 is used to transmit an alarm signal from the device to a remote device. Also visible on the exterior of the device 1 are LEDs 10, 12. A block diagram and flow chart of a circuit for use with the security device is shown in Figure 7 and the detailed circuitry is shown in Figure 8. A power supply 16 is used to power the device and includes connections to the power supply to the computer hardware together with a rechargeable battery. When the computer hardware is switched on, 12 V is taken from the computer power supply and applied to the anode of D15. This is then taken through Dl and current limiting resistor R2 and fed to the other components in the circuit. The 12 V input is also fed through D2 and Rl to charge back-up battery Bl. If power to the computer hardware should fail or be turned off, Bl will supply the other circuitry through D3. D17 is a reverse polarity protection diode. The resilient electrical conductor 6 of Figure 6 forms part of a case tamper circuit 18. When the conductor 6 is in good electrical contact with the computer case, pin 4 of integrated circuit IC4 is held low. If the case of the computer hardware is moved or tampered with, the resistance of the electrical connection between conductor 6 and the computer case, and hence the potential of conductor 6 rises. The non-zero voltage at pin 4 of IC4 triggers pin 3 of IC4 to generate a pulse. IC4 comprises a comparator for comparing the voltage at pin 4 with a reference potential, ideally common ground, and a timer circuit. If the voltage at pin 4 of IC4 remains high, then a pulse will be generated periodically. The timing of the re-triggering is set by R10, Rll, C4 and D7. In the example shown, a pulse will be generated every eight seconds if the voltage at pin 4 of IC4 remains high. The output of case tamper circuit 18 from pin 3 of IC4 is input to a flip-flop 20. (In the embodiment of Figure 8, an integrated circuit ICl includes two flip-flops and so references to the pins for flip-flop 20 will refer to IC1/2 while references to the pins of the other flip-flop (flip-flop 28 of Figure 2) will refer to ICl/1) . When the flip-flop of IC1/2 is triggered, pin 13 switches high, turning on transistors TR1 and TR2 through R14 and R15 in the encoder circuit 22. Pin 13 remains high until C6 has charged to two thirds supply voltage and flip-flop 20 is re-set. The period for which pin 13 remains high allows sufficient time for a signal to be generated by encoder circuit 22. Obviously, if the case is not replaced, then pulses will be generated repetitively by the case tamper circuit 18 and hence pulses will be generated repetitively by the flip-flop 20. When TR2 in encoder circuit 22 is turned on, power is applied to IC3, which includes an oscillator circuit and to a three-position dip switch SW2. The dip switch SW2 is used to set a code identifying the security device so that an alarm signal encoded with the code can be transmitted from transmitter 24 to a remote receiver. If the remote receiver is monitoring many pieces of computer hardware, and hence security devices, the range of codes that can be set by dip switch SW2 may be insufficient to identify each security device, and hence piece of computer hardware, individually. Further switches e.g. SW3 may therefore be used to modulate the alarm signal to define address zones. The signal from the oscillator circuit in IC3 is fed through R21 to the transmitter module TXM1. Transmitter module TXM1 operates at 400-450 Mhz with either AM or FM modulation. Other frequencies can be catered for by substituting TXM1 with the appropriate module . In addition to the resilient conductor used to sense tampering of the case, the security device of figures 6, 7 and 8 also includes a movement or vibration detector. The movement detector circuit 26 receives power from the power supply 16 through a relay RLA1. When power is available from the 12 V supply of the piece of computer hardware, the contacts of RLA1 are open and so the movement detector circuit 26, and associated circuitry flip-flop 28 and triggered latch 30, are disabled. Thus, the sensitivity of the vibration detection means in this case is zero. When the power supply to the piece of computer hardware is switched off, the contacts of the relay close bringing R3 into the circuit. When movement is detected, VI momentarily closes and charges Cl through R3, putting a voltage on pin 3 of ICl/l of the flip- flop 28. When the voltage on pin 3 of ICl/1 exceeds two thirds of the supply to ICl/1, pin 1 of ICl/1 goes high, turning on TR1 of encoder circuit 22 through R14 and R15. A sufficiently high voltage may be generated at pin 3 of ICl/1 by a single movement detected by VI if this movement is sufficiently great. Alternatively, several smaller movements detected by VI will each generate a charge on Cl and accumulate to generate a sufficient voltage at pin 3 of ICl/l to turn on pin 1 of ICl/1. However, isolated small movements will be insufficient to cause the flip-flop 28 to be triggered. Two seconds after the voltage on pin 1 of ICl/1 goes high, the voltage of C2 which has been charging through R5 exceeds two thirds supply voltage and causes the flip-flop to reset, discharging C2 through 05 in the process. The effect of TR2 in encoder circuit 22 being switched on has already been described with reference to operation of the case tamper circuit. When pin 1 of ICl/1 goes high, this also puts a high on pin 1 of IC2 of triggered latch 30 through D13 causing pin 4 of IC2 to latch and turn on LED . This can be reset by closing switch SW1 or removing power to the circuit. R6 and CIO ensure that when power is first applied to the circuit, pins 8 and 9 of IC2 are held low disabling the latch circuit for five seconds. As described with respect to Figure 6, the security device includes two LEDs 10, 12. One LED 10, is LED2 of triggered latch 30 which indicates which security device has been moved sufficiently to cause an alarm signal to be generated. A second LED 12 is provided in the encoder circuit 22 and is switched on either if the movement of the entire piece of hardware is sufficiently great (movement detector 26) or if the case of the computer hardware has been tampered with (case tamper circuit 18) . The second LED 12 will also be switched on if the conductor 6 is not making a sufficiently good contact with the inside of the case during setting up of the security device. Figure 9 shows a security device in accordance with a further embodiment of the present invention. This security device comprises a microprocessor and is intended for the protection of computer equipment. The device has two sensors: a vibration switch VB1; and a contact assembly SW1 to test for computer case removal. There are two main modes of operation of the device. In a first mode power is supplied to the device at 12 volts via the computer's internal power unit. In the second mode the device operates on its own rechargeable battery. In the first mode, 12 volts is supplied by the computer power supply through the fuse FI and diode Dl. LI, L2, Cl, C2 and C3 filter noise from the computer power supply and ZD1 protects against surges and power spikes above 16 volts. Transistor TR1 with associated components D2 , D3 , R2 , C4 and D5 provide a constant current to trickle charge the 9 volt rechargeable nicad battery BT1. ICl is a micro power voltage regulator. With 12 volts present, the microprocessor IC6 is rebooted via TR3 and C21. The collector of TR3 keeps port A4 of the microprocessor IC6 low whilst external power is supplied to the security device. This ensures that when IC6 reboots port A4 is sampled and if port A4 is low then the unit must be in external power mode (usually corresponding to daytime use ie. while the computer is switched on) . If the security device is moved, the vibration switch VBl makes contact and changes the state on port RB5 to a low condition. However, the microprocessor IC6 is programmed to ignore the signal on pin RB5 while A4 is low, ie. while the security device is being supplied with electrical power from the computer device it is protecting. Thus in this first mode the vibration detector sensitivity is zero, ie. the vibration detector is disabled. Switch SWl is arranged to be activated when an attempt is made to remove or open the casing of the protected computer equipment. In this example the switch SWl is arranged to be normally closed when the computer casing is in place. If a computer case tamper is sensed, SWl will be opened, and a high will be present on port RB4 of IC6. This forces IC6 to enable the code memory stored in memory chip IC7, read the individual address code stored in IC7, and send the code data to transmitter chip IC8. In the second mode, when the computer device is switched off the external 12 volt supply to the security device will not be present. The security device will revert to running off the stand-by battery BTl via diode D6. TR3 is turned off and port A4 of the microprocessor IC6 goes high. The high on port A4 of IC6 is sensed under software control and places IC6 in a sleep mode to reduce current consumption. However ports RB4 and RB5 have the capability to interrupt (i.e. wake IC6 from sleep mode) on change of state. If the computer device or the security device is moved, the vibration switch VBl makes contact and changes this state on port RB5 to a low condition. IC6 senses the change of state and is woken from the sleep condition, and the identity code is read from memory means IC7. Data including the security device's identity is sent to IC8 for transmission to a remote receiver. If the computer case tamper switch goes open circuit, port RB4 goes to a high condition. IC6 senses the change of state and is woken from the sleep condition, and the unit's identity is read from IC7. Data including the address code and a case tamper signal are transmitted via IC8. Thus, in this embodiment the security device may be supplied with electrical power from the apparatus it is protecting. Whilst power is being supplied from this external source the vibration detector is disabled, ie. the vibrator detector sensitivity is zero. The security device comprises a microprocessor and this effect is achieved by the microprocessor ignoring the signal from the vibration detector while it is also receiving an indication that power is being supplied to the security device from an external source. When the external power supply is disconnected the microprocessor ceases to ignore the vibration detector, and so the vibration detection means switches to a higher level of sensitivity. The device also includes a case tamper switch which may be a microswitch. In this embodiment the tamper switch was normally closed, but it will be apparent that in alternative embodiments the switch may normally be open. In an alternative embodiment, rather than the security device being supplied with external power from the apparatus it is protecting, the security device comprises a transformer and is supplied with electrical power directly from the mains via its own mains supply lead. Such a security device may be used for the protection of computer peripherals and, for example, office equipment. Again, the device may have two sensors, a vibration switch, and a tamper switch, which can be arranged to be triggered if the security device is removed from the apparatus or equipment it is protecting. In alternative embodiments, in addition to switching sensitivities in response to changes in the state of the protected apparatus, or changes in the power supply to the device, means may also be provided for manual switching of the vibration detector sensitivity to the higher level, for example by a user turning a key or inputting a code. In a final described embodiment, the security device is in fact an integral part of a piece of electrical and electronic apparatus, the apparatus being connected to a power source. The switching means switches the vibration detector to high sensitivity when the power source to the apparatus is disconnected, or the apparatus switched off. It will be apparent to those skilled in the art that any reference in the description or claims to a vibration detector or vibration detection means also contemplates a movement detector or movement detection means. Equally, any reference to the detection of vibration contemplates the detection of movement, and vice versa. Also, although in the embodiments described, the switching means switched the vibration sensitivity according to whether the apparatus was in the on state or the off state, it will be apparent that the switching means could be responsive to other states, for example whether the apparatus was hot or cold, or in fully active mode or idle mode (drawing reduced, but non-zero, power) . It will also be apparent that the present invention contemplates the inhibition of unauthorised interference with electrical and/or electronic apparatus supplied with electrical power from sources other than the mains, or from a mains supply having an output voltage other than 240V, for example 110V.

Claims: CLAIMS : 1. A security device for inhibiting unauthorised interference with electrical and/or electronic apparatus, the security device comprising: vibration detection means having a first sensitivity and a second sensitivity, said second sensitivity being higher than said first sensitivity; switching means operable to switch said vibration detection means between said first sensitivity and said second sensitivity in response to the state of said apparatus; and means for initiating an alarm signal, said means for initiating being connected to said vibration detection means and operable to initiate an alarm signal in response to an indication from said vibration detection means that a vibration has been detected. 2. A device in accordance with claim 1 wherein at least one of said first sensitivity and said second sensitivity is adjustable. 3. A device in accordance with claim 1 or claim 2 wherein said first sensitivity is zero, such that at this sensitivity, no vibration or movement may be detected by said vibration detection means. 4. A device in accordance with any one of claims 1-3 wherein said switching means is operable to switch said vibration detection means to said second sensitivity in response to said apparatus being disconnected from a power source. 5. A device in accordance with any one of claims 1-4 wherein said switching means is operable to switch said vibration detection means to said second sensitivity in response to said apparatus being switched off. 6. A device in accordance with any preceding claim, comprising electrical and/or electronic circuitry. 7. A device in accordance with claim 6, further comprising a battery for supplying electrical power to operate said circuitry. 8. A device in accordance with claim 6 or claim 7 wherein said means for initiating an alarm signal comprises a transmitter including an aerial, said transmitter operable to transmit a signal for reception at a remote sensor. 9. A device in accordance with any one of claims 6 to 8, further comprising means for connecting an external supply of electrical power to receive electrical power to operate said circuitry. 10. A device in accordance with claim 9, wherein said switching means is operable to switch said vibration detection means to said second sensitivity when said device is disconnected from said external supply. 11. A device in accordance with any one of claims 8 to 10, further comprising an encoder and memory means, said encoder operable to encode information stored in said memory means together with an output from said vibration detection means and to pass the encoded material to said transmitter for transmission. 12. A device in accordance with claim 11, wherein said memory means contains an address. 13. A device in accordance with any one of claims 6 to 12, further comprising a receiver connected to said switching means, said switching means operable to switch said vibration detection means between said first and second sensitivities in response to signals received by said receiver. 14. A device in accordance with any one of claims 9 to 13 as dependent from claim 8, wherein said transmitter is operable to transmit a signal each time said external supply is connected to said device. 15. A device in accordance with any of claims 9 to 14 , wherein said device comprises means for connecting said device to said apparatus to receive electrical power from said apparatus. 16. A device in accordance with any one of claims 9 to 14, further comprising power output means for supplying power to said apparatus, whereby said apparatus may be connected to said power source via said device. 17. A device in accordance with any preceding claim, further comprising a highly distinctive and visible casing. 18. A device in accordance with any preceding claim, further comprising relative movement detection means connected to said means for initiating an alarm signal and arranged to detect relative movement of at least a portion of said apparatus with respect to at least a part of said device, said means for initiating an alarm signal being operable to initiate an alarm signal in response to an indication from said relative movement detection means that a relative movement has been detected. 19. A device in accordance with claim 18, wherein said relative movement detection means comprises a switch arranged to be activated when the casing of said apparatus is opened or removed. 20. A device in accordance with claim 18 or claim 19, comprising a switch arranged to be activated when said security device is separated from said apparatus. 21. A security device in accordance with any preceding claim further comprising mounting means for mounting the security device to said apparatus. 22. A security device in accordance with any preceding claim further comprising mounting means for mounting the security device in an expansion port of a computer or an associated peripheral device. 23. A security device in accordance with any preceding claim, comprising a microprocessor. 24. A security device in accordance with claim 23, wherein at least one of said first and second sensitivities is programmable. 2 5. A security device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. 26. Electrical and/or electronic apparatus comprising: means for connecting a power source; vibration detection means having a low sensitivity and a high sensitivity; switching means operable to switch said vibration detection means between said low sensitivity and said high sensitivity in response to the state of said apparatus; and means for initiating an alarm signal, said means for initiating being connected to said vibration detection means and operable to initiate an alarm signal in response to an indication from said vibration detection means that a vibration has been detected. 27. The apparatus of claim 26 wherein at least one of said high sensitivity and said low sensitivity is adjustable. 28. The apparatus of claims 26 or 27 wherein said low sensitivity is zero, such that at this sensitivity, no vibration or movement may be detected by said vibration detection means. 29. The apparatus of any one of claims 26-28 wherein said switching means is operable to switch said vibration detection means to said high sensitivity in response to said apparatus being disconnected from said power source. 30. The apparatus of any one of claims 26 to 29 wherein said switching means is operable to switch said vibration detection means to said high sensitivity in response to said apparatus being switched off . 31. The apparatus of any one of claims 26 to 30, further comprising a battery. 32. The apparatus of any one of claims 26 to 31 wherein said means for initiating an alarm signal comprises a transmitter including an aerial, said transmitter operable to transmit a signal for reception at a remote sensor. 33. The apparatus of claim 32, further comprising an encoder and memory means, said encoder operable to encode information stored in said memory means together with an output from said vibration detection means and to pass the encoded material to said transmitter for transmission. 33. The apparatus of claim 32, wherein said memory means contains an address. 34. The apparatus of any one of claims 26 to 33, further comprising a receiver connected to said switching means, said switching means operable to switch said vibration detection means between said low and high sensitivities in response to signals received by said receiver. 35. The apparatus of any one of claims 32 to 34, wherein said transmitter is operable to transmit a signal each time said power source is connected to said apparatus and/or when said apparatus is switched on. 36. Apparatus in accordance with any one of claims 26 to 35, further comprising relative movement detection means connected to said means for initiating an alarm signal and arranged to detect relative movement of at least a first part of said apparatus with respect to at least a second part of said apparatus, said means for initiating an alarm signal being operable to initiate an alarm signal in response to an indication from said relative movement detection means that a relative movement has been detected. 37. Electrical and/or electronic apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. 38. A security system for inhibiting unauthorised interference with a plurality of pieces of electrical and/or electronic apparatus, each piece of said apparatus being connected to a power source, the security system comprising: at least one remote sensor for receiving signals, the or each remote sensor connected to an alarm system operable to raise an alarm; and a plurality of security devices, each security device being associated with a respective piece of said apparatus, each security device comprising: vibration detection means having a low sensitivity and a high sensitivity; switching means operable to switch said vibration detection means between said low sensitivity and said high sensitivity in response to the state of the respective piece of said apparatus; and a transmitter including an aerial, said transmitter connected to said vibration detection means and operable to transmit a signal for reception by the or at least one of said remote sensors in response to an indication from said vibration detection means that a vibration has been detected. 39. The system of claim 38 wherein at least one security device further comprises a battery for providing electrical power to said vibration detection means and said transmitter. 40. The system of claims 38 or 39 wherein in at least one security device at least one of said high sensitivity and said low sensitivity is adjustable. 41. The system of any one of claims 38 to 40 wherein in at least one security device the low sensitivity is zero, such that at this sensitivity, no vibration or movement may be detected by said vibration detection means. 42. The system of any one of claims 38 to 42 wherein the switching means of at least one security device is operable to switch said vibration detection means to said high sensitivity in response to the respective piece of said apparatus being disconnected from said power source. 43. The system of any one of claims 38 to 42 wherein the switching means of at least one security device is operable to switch said vibration detection means to said high sensitivity in response to the respective piece of said apparatus being switched off. 44. The system of any one of claims 38 to 43, wherein at least one security device further comprises means for connecting a power supply. - 33 - 45. The system of claim 44, wherein the switching means of said at least one security device comprising means for connecting a power supply is operable to switch said vibration detection means to said high sensitivity when the respective security device is disconnected from said power supply. 46. The system of any one of claims 38 to 45, wherein at least one security device further comprises an encoder and memory means, said encoder operable to encode information stored in said memory means together with an output from said vibration detection means and to pass the encoded material to said transmitter for transmission. 47. The system of claim 46, wherein said memory means contains an address. 48. The system of any one of claims 38 to 47, wherein at least one security device further comprises a receiver connected to said switching means, said switching means operable to switch said vibration detection means between said low and high sensitivities in response to signals received by said receiver. 49. The system of any one of claims 44 to 48, wherein said at least one security device comprising means for connecting a power supply further comprises power output means for supplying power to the respective piece of said apparatus. 50. The system of any one of claims 44 to 49, wherein the transmitter of said at least one security device comprising means for connecting a power supply is operable to transmit a signal each time said power supply is connected to the respective security device. 51. A security system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Inventors: HENDERSON PHILIP JAMES, HENDERSON, PHILIP, JAMES
Applicants: DASHCROWN LIMITED, HENDERSON PHILIP JAMES, HENDERSON, PHILIP, JAMES
Application year: 1997
Main classification: G08B13
IPC codes: G08B13