GB2292629A - Security system for computer - Google Patents

Abstract

An equipment enclosure eg a computer includes a plurality of environmental sensors which activate an alarm signal when any sensed change in the environment exceeds a preset standard value or the enclosure is opened or is moved. A keypad or an infra red transmitter enables or disables the activation of the alarm signal in accordance with a code. Associated equipment may also be protected by the use of suitable leads. Sensors include a motion detector 4, a light detector and a heat sensor. The power supply 3 may be independent of the equipment within which it is installed. <IMAGE>

Description

SECURITY SYSTEM This invention relates to security systems, particularly to a method of protecting electronic equipment having a modular construction, such as computers, from the unauthorised removal of modules.

Electronic equipment frequently consists of a series of modules each of which performs a particular function. The modules are customarily removeable in order to facilitate repair, to configure the equipment for a particular purpose or to permit an extended range of operation. Such modular construction is particularly common in computing equipment, particularly personal computers or microprocessor operated industrial control units, where the modules usually take the form of so-called 'cards'. Each card is a populated printed circuit board, often including software in the form of ROM or EPROM, adapted to plug into a slotted socket.

Such slots carry two parallel rows of contacts which allow a large number of conections to be made simultaneously to each side of the printed circuit board.

In most electronic equipment the modules are contained within an enclosed case however the case must be easily openable in order that modules can be repaired, exchanged or new modules added. Although a number of security devices and retaining systems are available for preventing the unauthorised removal of electronic equipment such devices do not generally provide security for the internal components such as plug in boards. For this reason unauthorised removal of modules, particularly cards from computers, is prevalent. In many cases the cards have a high value due to the ROM software or other copyright information associated with the operating system or special applications.

The present invention provides a security system for electronic equipment specifically designed to prevent the removal of modules, such as cards, and peripheral equipment by causing an alarm system to be activated.

According to the present invention there is provided a method of indicating the unauthorised interference with electronic equipment contained in or associated with an enclosure, characterised in that the enclosure includes a plurality of environmental sensors which activate an alarm signal when any sensed change in the environment exceeds a preset standard value or the enclosure is opened or the associated equipment is moved and in that control means for enables or disables the activation of the alarm signal in accordance with a code. There are also provided alarm units for use in the method.

The environmental sensors may include light sensors, heat sensors and motion sensors. The outputs from the sensors is supplied to a latch unit which has two states, a dormant state in which there is no output and an activated state in which there is a continous output. The latch circuit, once activated will not return to its dormant state until a reset control is operated manually or after a preset time period. In the latch unit the outputs from the sensors, after appropriate amplification and/or processing to form a first derivative value, are compared with preset standard values. In the event that any of the outputs exceeds the relevant preset standard value the latch is activated and an alarm signal is generated. Thus a transitory increase in level of any of the sensed properties, or rapid rate of change in a sensed property, initiates the alarm signal.

The alarm signal may be directly used to operate an audible alarm or to activate a remote alarm or both. Changes in the associated equipment may be sensed by direct electrical connection to the equipment of by severance of a lead attached to the equipment.

The sensors and alarm unit may be combined in a module which can be included within the case of which encloses an electronic unit. In one embodiment the unit takes the form of a standard computer card having a connector strip compatible with industry standard slot connection formats.

Alternatively the module may be included in an unused drive bay or similar cavity.

In order to avoid activating the security system when legitimate modification or repair is being carried out the unit including the alarm system preferably has an inactivation system which can be operated externally. The inactivation system may comprise a key switch or an alphanumeric pad with external access, or a code receiver adapted to respond to infra-red or radio signals, preferably in an encoded form. In the embodiment of the invention in which the unit comprises a plug-in card contained in a computer the unit may be inactivated by entry through the computer keyboard of a predetermined code. The predetermined code may only be changed by security guarded access to the control means.

The alarm unit preferably includes an independent power supply so that it can be activated when the associated equipment is not in operation. In a most preferred form the alarm unit contains a re-chargeable battery which is maintained in its fully charged state from power supplied by the associated equipment when it is in operation. When the alarm unit takes the form of a card connection to the power supply is obtained by contacts on its connection strip which access the main computer supply. When an independent power supply is available the alarm unit may be self-arming. In this embodiment when the power supply to the equipment is switched off the alarm units becomes and remains active until such time as the equipment is switched on and operated again.

The preferred alarm units for use in the method comprise a a single or double sided printed circuit board with contact areas at one edge spaced to fit into a standard chassis mounted edge connector, often referred to as a 'slot', which provides access to the power supply, data buses, etc.

for the equipment. The alarm unit board carries a re-chargeable battery and appropriate charge control circuitry to enable the battery to be maintained at its charged potential and also to prevent discharge into the equipment in which it is installed. The alarm unit board carries a light sensor, a movement sensor and an associated latch circuit which can activate an audible alarm also carried by the board. The size of the components on such boards is chosen to allow them to be plugged into any spare slot in an array of slots (edge connectors).

Associated equipment, so-called peripherals, is preferably physically connected to a multiconductor alarm cable which enters the equipment and is connected to the control means.

Severance of one or more of the conductors in the cable activates the alarm signal. The physical connection of the cable may be made by threading the cable through slots or appertures in the equipment or by attachment using adhesive clips. One or both ends of the cable will terminate in the control means in known manner.

In order that the invention may be clearly understood it will now be described with reference to the accompanying drawings in which: Figure 1 is a block diagram of one form of alarm module for use in the method of protecting electronic equipment according to the invention, Figure 2 is a side view of the module shown in Figure 1 in the form of a plug-in card, and Figure 3 is a circuit diagram of the module shown in Figure 3.

An alarm module, see Figure 1, has a charge control circuit 1 supplied with power at its input 2. Input 2 is connected to the operating DC power supply of a host unit, such as a personal computer, in which it has been installed. The circuit 1 supplies a constant voltage output to a rechargeable battery 3 comprising one or more re-chargable cells. The circuit 1 also isolates the battery 3 from the host supply so that discharge into the host cannot occur when the latter is switched off. The sensor 4 is a motion detecting device in the form of a mercury switch. Such a device makes or breaks an electrical contact when subjected to sudden movement or when tipped to an extent that the mercury moves to or from the associated contacts. The output from the sensor 4 is connected to a latch circuit 5.

The circuit 5 is supplied with electrical power from the rechargeable battery 3. The latch circuit 5 is normally in its dormant state consuming little or no power. When the mercury switch 4 closes or opens, according to its type and physical disposition, the circuit 5 changes to its latched state and remains in this state until such time as it is reset. A brief signal from the sensor 4 will thus latch the circuit 5. When latched the circuit 5 supplies power to a sounder 6, such as a piezo sounder, and to an indicator 7, such as a light emitting diode (LED). To return the circuit 5 to its dormant state reset means 8, such as a key operated switch, supplies a reset signal. A number of other environmental sensors, such as light sensors or heat sensors, may be coonected to the latch circuit in addition to the motion sensor described so that any one of them can trigger the latch.

In a practical embodiment of the module described above, see Figure 2, a standard format plug-in board 10 has a contact strip 11 which permits it to be inserted into a standard slot socket and access the power supply of a host unit (not shown). The board 10 carries a from panel 12 which fits into an outer surface of the host unit. The board 10 includes a mercury switch 13 which makes an electrical contact when the host is tipped. A piezo sounder 14 is activated when a latching circuit, not shown, is activated by movement of the mercury switch 13. The power for the module is supplied from a re-chargeable battery 15 which is maintained in its charged state by the host unit when the latter is operating. A key switch 16 can deactivate the latch circuit prior to maintenance or modification of the host unit. An LED indicator 17 is illuminated when the module is in its activated state.A second environmental sensor 18 senses the ambient illumination falling on the upper edge of the board.

A practical embodiment in circuit form of the alarm module, see Figure 3, consists of a re-chargeable battery 20 maintained in its charged state by means of a charge control circuit. The circuit is connected to the positive and negative power supply rails of the power supply of a host unit in which the module is installed through board edge contacts 21 and 22 respectively. The connection through contact 21 includes a diode 23 to prevent discharge of the battery into the host when it is not operating. The connection through the contact 22 includes a current limiting resistor 24. The voltage across the battery 20 is limited to its fully charged value by means of a zener diode 25. The module includes two environmental sensors, a mercury switch 26 to detect movement and a photoconductive cell 27 to detect light changes.The switch 26 connects the positive rail of the power supplyi, through a limiting resistor 28, to the gate of a thyristor 29 in the event of movement. Once triggered the thyristor 29 will remain conducting and current passes through it and also a piezo sounder 30 until the supply is interupted.

The photoconductive cell 27 is directly connected from the positive rail of the power supply and through a load resistor 31 to the negative rail. The cell 27 will normally pass little current as it will be screened from ambient illumination by the case of the host unit. In consequence the junction between the cell 27 and its load 31, connected to the gate of the thyristor 29, will be at a low value. If the module is illuminated, for instance by opening the case of the host unit, the conductivity of the cell 27 will increase raising the potential at the junction to a level which triggers the thyristor 29. The piezo sounder 30 will thus be activated either by movement or illumination of the module.

To deactivate the module a switch 2 is opened which interupts the power supply to the thyristor 29. The operational status of the module, i.e. that it is switched on and sufficient operating power is available from the battery 20, is shown by LED 33.

It will be seen that the system and apparatus is capable of protecting computer and similar equipment and at the same time peripheral equipment. The presence of an external keypad for entering the de-activation code for the alarm system acts as a warning. False attempts to enter a code, cutting the keypad lead will instantly result in the generation of an alarm signal.

In a further embodiment the alarm system includes connection means enabling the signal to be transmitted audibly, by direct connection, by radio or other link to a central security office when the room in which the alarmed equipment is empty such as at night and weekends. Such an arrangement alerts security guards to potential interference and take appropriate action.

The connections to the alarm module are preferably made internally to prevent interference. However connections to a keypad encoder or to external alarms sytems may be made using conventioanl ports, such as printer ports, on the equipment. The configuration of the connector wiring can be arranged so that unauthorised detachment of the connector results in operation of the alarm.

Claims (22)

1. A method of indicating the unauthorised interference with electronic equipment contained in or associated with an enclosure, characterised in that the enclosure includes a plurality of environmental sensors which activate an alarm signal when any sensed change in the environment exceeds a preset standard value or the enclosure is opened or the associated equipment is moved and in that control means for enables or disables the activation of the alarm signal in accordance with a code.

2. The method as claimed in claim 1, characterised in that the enclosure includes a motion detector which activates an alarm when the equipment is moved or tilted.

3. The method as claimed in claim 1, characterised in that the enclosure includes a light detector which activates an alarm when the ambient light within the equipment increases.

4. The method as claimed in claim 1, characterised in that the enclosure includes a heat sensor which activates an alarm when the amient temperature changes rapidly.

5. The method as claimed in any of the preceding claims, characterised in that the enclosure includes a power detector which activates a latched alarm system when any sensed change in the environment exceeds the preset standard value or the enclosure is opened.

6. An alarm unit for use in the method of any of the preceding claims comprising a battery, a light sensor, at least one environment sensor, a latch circuit and an alarm signal generator.

7. The alarm unit as claimed in claim 6, characterised in that one environment sensor is a heat sensor.

8. The alarm unit as claimed in claim 6 or claim 7, characterised in that one environment sensor is a motion detector.

9. The alarm unit as claimed in any of the claims 6 to 8, characterised in that the unit is carried by a single board or chassis and is adapted to interface with the electronic equipment in which it is installed.

10. The alarm unit as claimed in any of the claims 6 to 9, characterised in that the unit includes a device which generates an audible alarm signal.

11. The alarm unit as claimed in any of the claims 6 to 10, characterised in that the unit includes means to activate a remote alarm.

12. The alarm unit as claimed in any of the claims 6 to 11, characterised in that the unit is comprises a standard printed circuit board having a connector strip compatible with industry standard edge connection formats.

13. The alarm unit as claimed in any of the claims 6 to 12, characterised in that the unit can receive electrical power from the equipment in which it is installed when operating.

14. The alarm unit as claimed in any of the claims 6 to 13, characterised in that the inactivation system comprises a key switch with external access.

15. The alarm unit as claimed in any of the claims 6 to 13, characterised in that the inactivation system comprises a key pad connected to the equipment through a tamperproof cable.

16. The alarm unit as claimed in any of the claims 6 to 13, characterised in that the inactivation system comprises a code receiver adapted to respond to infra-red or radio signals.

17. The alarm unit as claimed in claim 10, characterised in that the inactivation system comprises a predetermined code signal entered into the equipment.

18. The alarm unit as claimed in any of the claims 6 to 17, characterised in that the battery is a re-chargeable type.

19. The alarm unit as claimed in claim 18, characterised in that the battery is a re-charged from the equipment when the latter is in operation.

20. Methods indicating the unauthorised interference with electronic equipment as claimed in claim 1 and as herein described.

21. Alarm units as claimed in claim 6 and as herein described.

22. Alarm units as herein described with reference to and as shown in the accompanying drawings.