GB2269253A - A security system - Google Patents

Abstract

A security system in which a lock or sensor is provided with code storage means 12 electrically connected to remote function-enabling means 10 which act to enable the operation of a function only upon receipt of a correct code from the code storage means 12. The system includes means for generating a random or pseudo-random code upon the occurrence of a given event and for transmitting it to the code storage means 12. The remote function-enabling means 10 include means for storing the code transmitted to the code storage means 12, and means for interrogating the code storage means 12 to verify the code stored therein before enabling the function.

Description

A SECURITY SYSTEM The invention relates to a security system which may be applied generally to any security installation in which a lock or a sensor is operated electrically or connected electrically to other equipment, and in particular, but without prejudice to the generality of the invention, may be applied to a security system installed in a motor vehicle.

Although the invention may be applied to any lock system it will be described hereinafter with reference specifically to its application to motor vehicles. It will be understood, however, that the terms "motor vehicle" encompasses any form of vehicle driven by a motor, and includes watercraft and aircraft. Likewise, where used herein, the term "motor" will be understood to include any form of power unit for propulsion of a vehicle and in particular includes internal combustion engines and electric motors.

Known security systems which are suitable for motor vehicles generally comprise audible and/or visible alarms which, when armed, are triggered by unauthorised attempts to enter or start the vehicle. Similar security systems are known for buildings where access to interior parts is restricted by electrically operated locks, often provided with a magnetic card as the key, or where access through doors or windows is protected by sensors for detecting attempts at unauthorised entry. Variously sophisticated systems have been devised in order to try and ensure that the security system is not circumvented by disconnecting or bypassing the sensors. Such systems include continuity detectors and inductive loops. All of these have weaknesses and disadvantages, however, so that some attempts at unauthorised entry are still able to succeed.

For example, as far ac motor vehicle security systems are concerned known such security systems can all too easily be bypassed or silenced so that despite them vehicle thieves can nevertheless enter and drive away a parked vehicle. This is especially the case with the relatively recent phenomenon of joy-riding, where the culprits have no long term intention to keep or sell a stolen vehicle and thus have little regard for its value and pay no heed to any damage which they may cause in forcing an entry.

Once having entered a vehicle it is a relatively simple exercise to start it and drive away, requiring only a knowledge of the vehicle wiring system to identify easily made connections which bypass and thus circumvent the vehicle ignition lock which for many years has been the only security measure provided by motor vehicle manufacturers against unauthorised use of motor vehicles.

More recently vehicles have been fitted with mechanical steering locks, but these, like almost any mechanical locking arrangement, can be overcome by the use of force to break the mechanical locking interconnection.

The present invention seeks to provide a simple and economical means by which it is possible to prevent a remote sensor, such as a key-operated switch or å window or door sensor from being disconnected or bypassed, with the intention that even professional thieves may be deterred from trying to circumvent the security system.

Accordingly, in one aspect of the invention there is provided a security system in which a lock or sensor is provided with code storage means electrically connected to remote function-enabling means which act to enable the operation of a function only upon receipt of a correct code from the said code storage means, the system including means for generating a random or pseudo-random code upon the occurrence of a given event and for transmitting it to the said code storage means for storage therein, and the said remote function enabling means including means for storing the current code transmitted to the said code storage means, and means for interrogating the code storage means to verify the code stored therein before enabling the said function.

In embodiments of the invention in which the code storage means is a window or door sensor of an alarm system the said given event may be arming of the alarm system. In embodiments in which the code storage means is associated with a lock the said given event may be closure or locking of the lock. The term "vehicle lock" which will be used hereinafter will be understood herein to refer to any locking mechanism with which a vehicle may be provided and specifically to include door and boot locks, steering lock, ignition lock or a special purpose lock provided for the function enabling unit, where the function may be motor-operation interdiction. In this case "enabling" the function will mean lifting the interdiction.

In embodiments of the invention as defined above the interdiction of motor operation may be introduced automatically, for example, whenever the motor is stopped, or may require specific action on the part of the user. Automatic setting is preferred, however, because of the greater degree of security offered In this way the wiring harness between the lock and the remote function enabling means is protected, and it is no longer possible simply to interconnect any of the wires leading to the function enabling means, or to earth such wiring in order to be able to bypass the lock or sensor.

In the case of a motor vehicle in which the function enabling unit controls the engine operation it will not be possible, with this system, to open a vehicle door forcibly and bypass the igniter switch by "hot wiring" the engine motor, since neither of these actions will result in generation of the security code without which the motor will not start or run.

In one embodiment of the invention, the stored code is changed periodically. More preferably, the code is changed each time the engine is turned off.

Alternatively, the code may be changed each time the lock is used.

The code signal may be generated for storage in any convenient way. For example, the code may be generated on board the vehicle, in which case it may be derived from a data source such as the electronic engine management system. In a preferred embodiment the last eight digits of the number of engine ignition pulses during the last use of the engine may be used as a random number for the code. Alternatively, other variable reference sources within the electronic management system may be used to generate the coded signals.

The function enabling means may be motor operation interdiction means, which may be located on or in the motor itself, preferably within a tamper-resistant housing. The interdiction means may be a special purpose immobilizer or, if the motor is an internal combustion engine, may form part of the vehicle's engine management system.

In a preferred embodiment of the invention, the lock storage means comprises a shift register into which the control means clocks the coded signal upon actuation of the security system. The shift register outputs the coded signal to the control means when the lock is operated, by the legitimate key.

In one embodiment the shift register is operatively connected to the control unit via three lines, a first line of which is a power line which also carries a clock signal to the shift register, a second line of which forms a bi-directional data transmission line, and the third line of which is a ground line.

The coded signal may be provided to the control unit upon operation of a microswitch indicating to the control unit that operation of the lock has taken place. This causes the control unit to send a clock signal to the shift register and hence enable transmission of the stored coded signal from the lock storage means to the control unit.

Two embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic block diagram of a security system according to the invention; Figure 2 is schematic view on an enlarged scale of the lock and code storage part of the system shown in Figure 1; Figure 3 is a block schematic diagram of the code storage unit of the engine-operation interdiction unit embodiment of Figures 1 and 2; and Figure 4 is a schematic diagram illustrating a further embodiment of the invention, for building door locks and alarm systems.

Referring now to the drawings, in the first embodiment illustrated in Figures 1 to 3, the security system, generally indicated 11, comprises an engine-operation function-enabling unit 10, which may be a central controller forming part of the engine management system, which is connected to an electronic code storage unit 12, hereinafter referred to as an encoder, positioned adjacent a lock barrel 16. The lock could, for example, be that on the driver's door which when operated by a key causes the lock barrel 16 to turn and move a lock actuator lever 18 to open or lock the vehicle door. The lock also carries a cam 20 which engages the actuating button of a micro-switch 14 which in turn is connected to the electronic encoder 12.The central controller 10 may be located at any secure position on the engine, in such a way that its connections to the engine are effectively incorruptible, and is connected to the encoder 12 by a power/clock line 24, a bi-directional data line 26 and a ground line 28. These lines form part of the vehicle wiring harness which extends between the electronic units 10 and 12 inter alia for the purposes of energising a central locking system.

When the vehicle engine is turned off the central controller 10 operates to immobilise the vehicle engine in any convenient way, for example by introducing an interruption into the ignition system control current path. This may be an existing part of the engine management system or may be provided specially for a purpose. Conveniently, however, this immobilising device will be part of the existing electronic engine management system since the micro-processor with which such a system is provided lends itself to secure disablement. In this way, the immobiliser forms an integral part of the engine such that the connections between it and the engine cannot be corrupted or bypassed by a would-be thief.

In this embodiment the security system 1 is enabled, thereby immobilising the engine, when the engine is turned off. In other embodiments (not shown) however, the system is enabled when the vehicle is locked. In either case, upon activation the central controller 10 clocks a coded signal into the lock encoder 12. In this embodiment the central controller 10 uses a random number for the coded signal which is taken from the last eight digits of the number of engine ignition pulses during the last operation of the engine, It is to be stressed, however, that the random number may be generated or otherwise determined in any other convenient way, such as from a pseudo-random number generator, it being merely a number drawn from any other source, such as one which is monitored by the vehicle management system.For vehicles without a central microprocessor management system a pseudo-random or random number generator micro chip may be operatively connected to the central controller 10.

Communication between the central controller 10 and the encoder module 12 is achieved using three wires where power/clock line 24 is set high in its normal state so that it powers the lock encoder. Upon generation the coded signal is fed to the encoder unit 12 along a bidirectional data line 26 which idles in a high state. As can be seen more clearly in Figure 3 electronic encoder unit 12 includes a shift register 33 which is normally in receive mode, the register being clocked by a signal transmitted along power/clock line 24. When the engine is turned off the encoder 12 is loaded with the random number signal and controller 10 goes into an idle state.

In order to disarm the security system, the legal key is inserted in the key hole of lock 16 and turned to unlock the vehicle door, at the same operating micro-switch 14, which causes a short signal to be transmitted from electronic encoder 12 to central controller 10 to activate the microprocessor from its quiescent or idle state. This then clocks the number back from the lock encoder 12 and expects to find the same number as it generated when the engine was turned off. If the correct signal is returned the engine is enabled to run.

The main elements of the electronic encoder 12 are shown in Figure 3. Micro-switch 14 is shown in an open position and is operatively connected to an inverter 30.

When micro-switch 14 is closed by cam 20 a signal is input to short monostable 31. This is connected to a monostable device 32 having a relatively longer time period. Additionally, short monostable 31 is connected to OR gate 35 which is connected to line driver 36 which feeds an output/input port 27 of encoder 12. Port 27 is connected to central controller 10 via the bi-directional data line 26. Hence, when microswitch 14 is closed the relatively short output pulse from monostable 31 is gated to micro controller 10 by driving the data line low for a short period.

The controller 10, thus raised to its active state causes a clock sequence to be carried on power line 24. This line is connected to input port 25 of encoder 12 and is in turn connected to the clock input port 33c of shift register 33. The shift register 33 having previously been loaded with the encoded signal is now caused to clock out the encoded signal at output port 33b. The outputs from long monostable 32 and shift register 33 are input to AND gate 34 the output from which passes sequentially to OR gate 35, line drive 36 and bidirectional data port 27. Thus, for the duration of the high output from monostable 32, shift register 33 clocks the stored signal to central controller 10 which then effectively compares the received code with its own stored code. If the two codes are the same the interdiction device or immobiliser is deactivated and the engine can be started.Because it has to carry a code signal before the engine can be operated, the vehicle wiring harness is protected from corruption by cutting, joining or grounding the wires.

If the battery goes flat during a. period when the security system is active then when power is restored the system requires disarming with the legal key before starting the engine. If it should be necessary to overcome the security system for any other reason this can be achieved by connecting a diagnostic tester to the control unit, to generate signals which can overcome the security. It is also envisaged, however, that a further arrangement for overcoming the security system could be for the driver to input an unusual sequence of signals to the central controller. In order to discourage thieves from inputting such a deactivation signal, it is envisaged that this could involve the driver's presence in the vehicle for a predetermined and extended period of time during which the driver would need to operate a dedicated switch and other switches such as the lights and/or horn.In this way, the operation of the disabling sequence makes the vehicle very conspicuous and should thereby discourage would-be thieves. An example is for the driver to pump the brake in sequence with the hazard warning lights. By providing an extended delay it is also possible to deter more sophisticated thieves who knowing that the central controller will load a coded signal into the lock on battery connection may be tempted to disconnect the battery, destroy the lock to force an entry, connect a new, undamaged lock to the wiring harness and reconnect the battery. Now the "lock" which they have substituted for the original is loaded by the central controller and they have the proper key in their possession.If a time delay of for example, fifteen or thirty minutes is incorporated into the programme, however, even this sophisticated approach will be relatively less attractive because of the risk of discovery during the delay period.

In order to reduce the possibility of activation of micro switch 14 by tampering a cover plate 22 of steel or other mechanically strong material is provided, which is located between micro switch 14 and the outer door panel of the vehicle. A secure housing of reinforced material or armoured steel may likewise be provided.

Other provisions may be made in order to combat the possibility of connecting a second lock in parallel with the original lock, including the use of shift registers having a shift load input which is connected as a powerup reset such that, upon power-up, the shift register loads parallel data, but subsequently changes to serial mode. The number it loads is defined by either grounding or connecting to the supply the appropriate pins of the shift register. This can be unique to each lock. This number is "learned" by the central controller upon initial installation, and since the number is first sent out from the shift register upon subsequent power-up after a battery disconnection the controller is programmed to check for the presence of this unique number before allowing the system to progress to the subsequent stages of the power-up procedure.

The process for changing a lock legitimately may then involve procedures such as those outlined above, requiring the use of a diagnostic tester and/or a timeconsuming conspicuous activity or procedure which would be sufficiently long as to deter a criminal from attempting it. Likewise a long time delay and/or a password system may be employed. In any of these systems a central controller with a non-volatile memory is required.

Figure 4 is a schematic view of a building security system with an electric door lock. A door 37 has a lock 38 with a solenoid-operated bolt (not shown). Operation of a key (or entering a security code) in the lock causes a signal to be sent along line 39 to a remote functionenabling unit 41. This signal is not merely a binary or open/closed signal representing the key position, but includes a code stored in a shift register associated securely with the lock. Upon recognition of the code the unit 41 sends a lock-release signal along line 40 to energise the solenoid to release the lock bolt.The key may act to initiate transmission of the code or may simply send a demand signal to the remote unit 41 with this being programmed to interrogate the code storage means (which may simply be a shift register), to establish that this has retained its integrity, before transmitting a lock-release signal. A fresh code may be generated and stored each time the last one has been interrogated, or on some other event such as the next occasion the lock is closed or locked.

The system also includes window and door sensors 42, connected by associated lines 43 to the function-enabling unit 41 and from this to an otherwise conventional burglar alarm unit 44 having an acoustic warning device 45. The alarm unit 44 periodically requests the function-enabling unit to verify the integrity of the wiring and the sensors by interrogating for the stored code. If this does not return from the interrogation the alarm is triggered. The verify period may be of any convenient length, typically between a fraction of a second and several seconds. The normal function of the sensors to trigger the alarm in the event of the occurrence of an event to which they are sensitive is, of course, not affected.

Claims (12)

1. A security system in which a lock or sensor is provided with code storage means electrically connected to remote function-enabling means which act to enable the operation of a function only upon receipt of a correct code from the said code storage means, the system including means for generating a random or pseudo-random code upon the occurrence of a given event and for transmitting it to the said code storage means for storage therein, and the said remote function enabling means including means for storing the current code transmitted to the said code storage means, and means for interrogating the code storage means to verify the code stored therein before enabling the said function.

2. A security system according to Claim 1, in which the said given event is arming of the security system.

3. A security system according to Claim 1, in which the code storage means is associated with a lock and the said given event is closure or locking of the lock.

4. A security system according to any preceding Claim, in which the said function is lock release and the function-enabling means is a lock release mechanism.

5. A security system according to any of Claims 1 to 4, in which the said function is motor energisation and the function-enabling means is a motor immobiliser.

6. A security system according to Claim 5, in which the said function-enabling means are located on or in the motor within a tamper-resistant housing.

7. A security system according to any of Claims 1 to 3, wherein the said function-enabling means comprise control means which form part of the vehicle's engine management system.

8. A security system according to any of Claims 5, 6 or 7 in which the stored code is derived from a count of the engine ignition pulses during the previous operation of the engine.

9. A security system according to any preceding claim, wherein the lock code storage means comprises a shift register.

10. A security system according to Claim 9, when dependent on any of Claims 5, 6 or 7, wherein the power, supply and clock input to the shift register are provided along the same line from the control unit.

11. A security system according to any preceding Claim, wherein the code is transmitted between the storage means and the remote function-enabling means along a bidirectional data line.

12. A motor system according to any of Claims 3 to 11 wherein the said code storage means includes a microswitch operable to provide a signal to the remote function-enabling means to indicate operation of the lock thereby to cause the control unit to send a clock signal to the shift register.