WO2001032479A1

WO2001032479A1 - A vehicle anti-theft device

Info

Publication number: WO2001032479A1
Application number: PCT/IB2000/001604
Authority: WO
Inventors: Alvaro Bernardo Tafur-Castillo; Michael Zunde; Michael Collet
Original assignee: Cellstop International Limited
Priority date: 1999-11-05
Filing date: 2000-11-06
Publication date: 2001-05-10
Also published as: EP1230110A1; AU1167201A; CA2390202A1

Abstract

A vehicle anti-theft device (10) comprises an on-board cellular phone transceiver unit (14) that provides a two-way communications link, via a GSM-based telephone network, with an authorised user of the vehicle fitted with the device. The device (10) includes sensing means (72) for sensing a condition, the condition typically either being an alarm condition such as the unauthorized entry into the vehicle or an alert condition informing the user of a status of the vehicle or unit. The device (10) further includes a plurality of vehicle immobilizing devices (22) for immobilizing the vehicle. The transceiver unit (14) is arranged to transmit an alarm signal or an alert signal to the authorised user so as to inform the user of the condition, with the unit (14) in turn being responsive to a remote command signal emanating from the user. Typically, the device (10) includes a voice module (54) for providing voice prompts to the user via the telephone network, with the user then providing the command signals in response to the voice prompts.

Description

A VEHICLE ANTI-THEFT DEVICE

BACKGROUND TO THE INVENTION

THIS invention relates to a vehicle anti-theft and -hijack device.

The theft of vehicles is reaching epidemic proportions in South Africa. A large number of different anti-theft devices have been developed in response to this problem. Several companies have also set up, at considerable expense, dedicated vehicle tracking networks for tracking stolen and hijacked vehicles.

The owners of vehicles fitted with such tracking devices normally pay a monthly subscription fee to the tracking companies. A significant component of this fee is used to finance or to recover costs associated with the establishment of the dedicated tracking network. SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a vehicle anti-theft device comprising:

an on-board cellular or mobile telephone transceiver unit which provides a two-way communications link, via a telephone network, with an authorised user of a vehicle fitted with the device;

sensing means for sensing a condition;

immobilizing means for immobilizing the vehicle; and

control means for controlling the operation of the anti-theft device,

wherein the transceiver unit is arranged to transmit a signal to the authorised user via the telephone network in response to activation of the sensing means, informing the user of the condition, and the control means being responsive to a remote command signal delivered from the authorised user via the telephone network.

Typically, the anti-theft device includes a voice module for providing voice prompts to the user via the telephone network, the user providing the command signal in response to the voice prompts.

Advantageously, the transceiver unit includes recognition means for recognizing that the command signal originates from an authorized user. Preferably, the anti-theft device includes memory means for storing a list of authorised telephone numbers, the recognition means being arranged to recognise the telephone number of a person wishing to communicate with the transceiver module to determine whether the person is an authorised user or not.

In one example, the condition is an alarm condition arising from an unauthorized act being carried out on the vehicle or device, with the transceiver unit transmitting an alarm signal to the authorised user via the telephone network. In this case, the command signal is an immobilizing signal delivered from the authorised user, via the telephone network, in response to the alarm signal, for immobilizing the vehicle.

The immobilizing means typically includes fuel cut-off means for cutting off the supply of fuel to the vehicle, the fuel cut-off means being arranged to gradually reduce the fuel supply to enable the vehicle to be safely brought to a halt. Preferably, the fuel supply is pulsed in which the fuel supply is temporarily cut and then restored, with the period over which the fuel supply is cut gradually increasing whilst the period over which the fuel supply is restored simultaneously decreasing.

Alternatively, the condition is an alert condition for alerting an authorised user about a status of the vehicle or anti-theft device, with the transceiver unit transmitting an alert signal to the authorised user via the telephone network.

Advantageously, the command signal is arranged to operate a central locking system of the vehicle.

Conveniently, the command signal is arranged to flash the vehicle's lights and/or activate the vehicle's hooter. Typically, the sensing means includes tamper-detecting means for detecting any tampering with the device, with the control means being arranged to render the device useless in the event of tampering being detected.

Conveniently, the telephone network is a GSM-based cellular network.

Preferably, the sensing means includes at least one door switch and a movement sensor for sensing unauthorized movement of the vehicle or movement within the vehicle.

Advantageously, the transceiver unit is arranged automatically to dial up the authorised user first, and if the user does not answer, the unit will then telephone an emergency control centre as part of the initial alarm signal.

According to a second aspect of the invention there is provided a method of operating a vehicle anti-theft device comprising the steps of:

providing an on-board cellular or mobile telephone transceiver unit for allowing real time two-way communications, via a telephone network, between an authorised user of a vehicle fitted with the device and the transceiver unit;

sensing a condition;

informing of the user, via the telephone network, that a condition has been sensed; and

receiving a remote command signal from the authorised user via the telephone network in response to being informed of the condition. Typically, the steps of informing the user and receiving the remote command signal includes the step of providing voice prompts to the user via the telephone network, the user providing the command signal in response to the voice prompts.

Preferably, the method includes the step of determining whether the command signal originates from an authorized user.

Conveniently, the method includes the step of storing a list of authorised telephone numbers, with the determining step including the step of recognising the telephone number of a person wishing to communicate with the transceiver module so as to determine whether the person is an authorised user or not.

Typically, the method includes the step of determining whether the condition is an alarm condition arising from an unauthorized act being carried out on the vehicle or device, with the method then including the step of transmitting an alarm signal to the authorised user via the telephone network.

Preferably, the method includes the step of transmitting an immobilizing signal, via the telephone network, in response to the alarm signal, for immobilizing the vehicle.

Advantageously, the method includes the step of gradually decreasing the fuel supply to the vehicle which includes the step of pulsing the fuel supply is temporarily cut and then restored, with the period over which the fuel supply is cut gradually increasing whilst the period over which the fuel supply is restored simultaneously decreasing.

Conveniently, the method includes the step of determining whether the condition is an alert condition for alerting the authorised user about a status of the vehicle or anti-theft device, with the method including the step of transmitting an alert signal to the authorised user via the telephone network.

Preferably, the method includes the step of operating a central locking system of the vehicle.

Typically, the method includes the step of flashing the vehicle's lights and/or activating the vehicle's hooter.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic block diagram of a vehicle anti-theft and - hijack device according to a first embodiment of the invention;

Figure 2 shows a circuit diagram of an immobilizer control unit of the invention;

Figure 3 shows a circuit diagram of a battery backup switch of the invention;

Figure 4 shows a circuit diagram of a battery low voltage detector of the invention;

Figure 5 shows a circuit diagram of a battery fail detector of the invention;

Figure 6 shows a circuit diagram of a reset button of the invention;

Figure 7 shows a circuit diagram of a vehicle locator module of the invention; and Figure 8 shows a schematic block diagram of a vehicle anti-theft and - hijack device according to a second embodiment of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the figures, a vehicle anti-theft and -hijack device 10 includes a pre-programmed microprocessor 12, a cellular phone transceiver module 14, having an associated sim card module 16 for enabling the operation of the transceiver module 14, and a remote cellular phone 18 which is linked to the transceiver module 14 via a conventional and established GSM-based cellular telephone network. The microprocessor 12 is controlled by proprietary, customized software.

The microprocessor 12 is connected to an immobiliser control unit 20, which is shown in further detail in Figure 2. The immobiliser control unit 20 controls the immobilising devices 22 of the vehicle such as the ignition circuit relay, via the ignition circuit input 24, the starter motor circuit relay and the fuel cut-off relay 26, as well as the vehicle's indicator lights, via input 28. A buzzer 30 connected to plug 32 and driven by buzzer amplifier circuit 34 may also be activated to indicate the sensing of an alarm condition.

The circuitry of the immobiliser control unit 20 is designed to ensure that if the vehicle is in motion, any interruption of the device 10 or any hardware failure within the device 10 will not result in the vehicle being immobilised. This is achieved by the latching of the SCR transistors 36, 38 of the circuit 20 which ensure that the immobiliser circuit relays are not unintentionally activated. However, the circuit 20 is arranged to allow the intentional activation of the immobilising devices 22 when the vehicle has, for example, been hijacked. The device 10 is powered by a 12/24V main power supply 40, typically the vehicle's own battery. The device 10 also includes a backup battery 42 for powering the device 10 when, for example, the main power supply 40 is cut off or, for some other reason, is unable to power the device 10. The device 10 includes a circuit 44 for controlling the operation of the backup battery, the circuit 44 now being described with reference to Figure 3. The circuit 44 includes a switch 46 that ensures that the backup battery 42 is only allowed to power the device 10 once the device 10 has been installed. This switch 46 will thus prevent the backup battery 42 from draining to 0V before installation. This is achieved by connecting the ground loop connection 48 to ground only upon installation, thereby closing the backup battery circuit 44.

A data interface unit 48 facilitates the transfer of data between the microprocessor 12 and the transceiver module 14. A dual-tone multi-frequency (DTMF) interface unit 50, driven by an associated amplifier circuit 52, facilitates the transfer of dual-tones between the microprocessor 12 and the transceiver module 14. In addition, a voice module 54 converts data and commands from the microprocessor 12 into an analog voice signal which is sent to the transceiver module 14, and from there to the user's cellular telephone 18.

A 64K RAM memory module 56 stores all the information required by the microprocessor 12, including the authorized user's cellular, home and office telephone numbers. This module 56 also stores information regarding past triggerings of the device 10, including details as to the cause of the trigger, the date and time etc.

The user can override the device 10 for a maximum period of 48 hours, with the time being measured by means of a real time clock 58. The user can override the device 10 via his or her cellular telephone 18, with the device 10 then confirming that the device has been overridden. The device will then automatically return to the status that it had prior to the override being initiated. Conventional regulators 60, 62, 64 and 66 are used to regulate the voltage to the device's various components.

A battery low voltage detector 68, shown in detail in Figure 4, measures the voltage of the main power supply 40, with the typical voltage of the main power supply 40 being approximately 13.8 V. If the power supply's 40 voltage drops to below 11V, in that, for example, the user left the vehicle's lights on, the device 10 will alert the user, via a user alert detector module 69. In this case, the microprocessor 12 will telephone the user, via the transceiver unit 14, and inform the user by means of the voice module 54 that the voltage of the main power supply 40 is dropping to a dangerously low level. In this mode, the device 10 is not acting in response to an alarm condition, but merely alerting the user of a particular condition of the vehicle of which the user should be aware. If, however, the connection to the power supply 40 is cut by a would-be thief, the battery fail detector circuit 70 shown in Figure 5 causes the microprocessor 12 to activate an alarm condition in which, in addition to the user being informed of the condition, an emergency service is contacted for assistance.

An alarm detector interface 72 controls the inputs of plug 32 which are primarily used to sense whether a plurality of the vehicle's switches are on or off. The ignition input 74 comprises a wire connected to the ignition circuit of the vehicle for sensing the condition of this circuit and, in appropriate circumstances, to arm the device 10. The passenger door switch input 76 senses if the passenger door is open or closed. Similarly, the driver's door switch input 78 senses whether the driver's door has been opened, but can also be used to sense whether all of the other doors are opened or closed. Thus, depending on the circumstances, as will be detailed further below, the door switch inputs 76, 78 may either provide an arming signal or an alarm signal to the device 10. The remaining connections 80 are used to either provide power to the device's various relays or to receive power from the main power supply 40. A further sensor for activating the immobiliser control unit 18 responds to the SIM card being removed, in which, upon such removal and subsequent reinsertion of the card, the device 10 will alert the user and then automatically enter a disabled mode in which the device is inactive.

A central locking interface 82 allows the device 10, in conjunction with the user's cellular telephone 18, to remotely open the doors of the vehicle, assuming of course that the vehicle has a central locking system. The various outputs 84 on plug 86 of the device 10 enable the device to work with most central locking systems currently being used. In use, the user would dial the transceiver unit 14, which would then recognise that the person dialing the device 10 is an authorized person, and would then operate the vehicle's central locking device to unlock the vehicle's doors. This recognition is controlled by the telephone network's call line identification (CLI) protocol which allows a cellular telephone or transceiver unit 14 to recognise the telephone number of an incoming call and to compare this number to a list of authorized numbers. As soon as the transceiver unit 14 recognises the incoming call as being transmitted by an authorized user, the unit 14 terminates the call, thus saving the user from having to pay for the cost of that particular telephone call. In an alternative embodiment, the invention may allow the user to only have the central locking feature in which the user uses a conventional remote control unit having suitable code encrypted therein, to which the transceiver unit 14 is receptive, for allowing the user to operate the vehicle's central locking system.

The alarm detector interface 72 has as an input a reset button 88, which is more clearly illustrated in Figure 6, and which is in turn connected to a reset button interface 90. The reset button 88 can only be used when the vehicle's ignition is on, and is used to reset the device 10 when the user's cellular telephone 18 cannot be operated because its battery is flat, or because there is no network coverage or simply because the user does not have the telephone 18 with him The user may then enter the required PIN code by pressing the button a number of times corresponding to the number of the code Thus, for example, if the PIN code is 2345, the user will press the button twice, wait for the device to indicate that the next number may be entered, then press the button three times, etc , until the entire number has been entered The device 10 will then be able to determine whether the "number" that has been entered is a valid one, and if so, will reset the device 10

The monitor switch 92 of plug 86, which is connected to the user alert detector interface 69, can be used to notify the user when any particular switch of the vehicle has been activated, for example when any door of the vehicle has been opened The auxiliary input 94 of plug 86 can be used to monitor any other type of sensor which may be required to be fitted onto the vehicle, for example, ultrasonic or radar sensors

A motion detector input 96 is used to detect a condition in which the vehicle is being moved, for example being towed away, without any of the vehicle's doors being opened or the ignition being tampered with In this case, activation of the motion detector switch results in an alarm condition arising with the device 10 then telephoning the subscriber to inform him or her of this alarm condition

The device 10 includes a vehicle locator module 98, which can be best described with reference to Figure 7 and to its application If, for example, the user is trying to find his or her vehicle in a parking lot, the user can dial the transceiver module 14 The device 10 will recognise the incoming call as coming from an authorized user, by means of the CLI protocol, as described above The device 10 will accordingly activate the vehicle's indicators, unlock the doors, via the central locking interface 82, and activate the relay 54 so as to switch power to the interior light of the vehicle for a period of 45 seconds If the device 10 does not sense a door being opened within this 45-second period, the device 10 will automatically rearm itself. Upon the user opening the door within this 45-second period, the interior light will remain on, and the vehicle's indicators will switch off. In addition, the relay 54 will be switched off so that the door's switch, which will now be on, will ensure that the interior light remains on. When the vehicle's door is then closed, the interior light will then turn off, as per usual. Once the door is opened, a new 45-second period commences in which the ignition must be turned on, failing which the device 10 will automatically rearm.

After installation of the device 10 into a vehicle, the buzzer 30 will be activated continuously as a reminder that the user needs to change the device's PIN code. The device 10 remains inactive until the code has been changed, and once done, the buzzer 30 will be switched off. To change the code, the voice decoder 54 will prompt the user to enter the default code, and then to enter the new code twice. The device will then also request additional information to be inserted, for storage in the RAM memory, including the user's cellular, home and office numbers. The inputted data is entered via the user's telephone keypad, with the data then being interpreted by the DTMF decoder 50. After the PIN code has been changed, the ground loop wire 48 ensures that if the device 10 is unplugged from the vehicle or its electrical harness is cut, the device 10 will disable itself so that it becomes inactive until it is reprogrammed by the manufacturer or by an authorized dealer of the device.

In use, once the ignition switch 74 has been turned off, and the door, and hence the door switch 78, has been opened and closed, the device 10 will automatically arm itself after 5 seconds. In this armed mode, the immobilising relays 22 ensure that the fuel circuit relay 26 and the ignition circuit relay 24 are disconnected. The device 10 will notify the user that it is armed by activating the indicators and/or the buzzer 30 three times. To access the vehicle, the user needs to phone the transceiver unit 14. The device 10 will recognise the number as being a valid one, via the CLI protocol, and will go through the vehicle locator module 98 process described above. The user then has 45 seconds in which to switch the vehicle on, else the device will reactivate the vehicles immobiliser circuits 22. In this case, the user will then need to phone the transceiver unit again in order to deactivate the immobiliser circuits 22.

If, however, an unauthorised act is performed on the vehicle whilst it is armed and stationary, the device 10 will enter an alarm condition. A plurality of acts fall into this category, and include the ignition 74, 24 being turned on, a door 76, 78 being opened, the motion sensor being triggered, the main power supply 40 being cut, the sensor connected to the auxiliary input 94 being triggered and the device's connections or wiring harness being cut. In these cases, the device 10 will telephone the user three times and will inform the user of the type of violation that has taken place. If the owner then enters a predetermined code, the device will terminate the telephone call and then phone an emergency control centre and inform it of the type of violation that has occurred. The centre will then be able to identify the vehicle's user, using the transceiver's own telephone number and the associated telephone network's CLI protocols. The service will then notify the user that they have received notice of the violation, and can then, using the cellular telephone's network, obtain the approximate co-ordinates of the vehicle's location by means of triangulation protocols. If, however, the user does not answer after three times, the unit will telephone the emergency control centre, and will then telephone the user's pre-programmed alternate number. Additional alarm means may also be activated, including the activation of the vehicle's indicators.

An alarm condition could, of course, also occur when the vehicle is in motion, such as in the event of the vehicle being hijacked. The device 10 is able to detect when the vehicle is on by the alarm detector interface 72, via the ignition input 74. Once the user has been forcibly removed from the vehicle, the user must dial the transceiver device 14 via either his or her cellular telephone 18 or, in the case of the telephone 18 being stolen by the hijackers, a conventional land line telephone and thereafter enter a pre-determined code. This code will direct the device 10 to activate the relay controlling the vehicle's indicators and to commence a fuel starvation procedure. This procedure allows a gradual cut in the fuel supply to the vehicle to enable the hijacker to safely come to a halt. The procedure typically comprises the fuel relay 26 being turned off and then on, with the off periods then being gradually increased, and the on periods then simultaneously being decreased. Once the vehicle has come to a stop, the device 10 will telephone the emergency service, which will then confirm receipt of the hijacking and then determine the vehicle's location and notify the user, as described above. To reset the device after retrieval of the vehicle, the user must telephone the device 10, which will then prompt the user to enter a reset command. The user may either send the reset code via a telephone, or may use the reset 88 button as described above.

Figure 8 shows a second microprocessor-based embodiment of an anti-theft and -hijack device 100. A microprocessor 102 includes an immobilizing output interface unit 104 which is connected to various immobilizing outputs such as the starter motor disabling circuit 106 and the fuel cut-off solenoid 108, as well as the indicator lights 110 of the vehicle. The microprocessor 102 is also connected to a sensor interface unit 112 which includes at least one door switch 114 for sensing whether a door of the vehicle has been opened and a motion detector switch 116 for detecting when the vehicle is being moved. In addition, the sensor interface 1 12 is also connected to a buzzer 118 and a reset switch 120.

The microprocessor 102 is powered by the vehicle battery 122 via a voltage regulator 124. The regulator 124 is also connected to the ignition switch 126 as well as to a back up battery interface 128 which allows the microprocessor 102 to be powered by a back up battery 130 when the power supply from the vehicle's main battery 122 is interrupted.

A keypad interface unit 132 controls the vehicle's cellular transceiver module 134 and is connected to the microprocessor 102. A data interface unit 136 facilitates the transfer of data between the microprocessor 102 and the transceiver module 134. A dual-tone multi-frequency (DTMF) interface unit 138 facilitates the transfer of dual-tones along an audio channel 140 between the microprocessor 102 and the transceiver module 134. In addition, a voice/data interface 142 converts data from the microprocessor 102 into an analog voice signal which is sent via the audio channel 140 to the transceiver module 134, and from there to the subscriber's cellular telephone 144.

In use, once the vehicle's ignition switch 126 has been turned off, and the door, and hence the door switch 114, has been opened and closed, the device 100 will automatically arm itself after approximately 5 seconds. The arming of the device 100 will be made known to the driver of the vehicle by, for example, flashing the vehicle's lights 110 and/or activating the buzzer 118. In the event of a person subsequently entering the vehicle via either the driver's door or the passenger's door, the door switch 114 is opened and this sets up a 30 second period within which to press the reset button 120. If the ignition switch 126 is turned on, but the reset button 120 is not pressed within this 30 second period, the device will alert the driver of this condition by, for example, causing the buzzer 1 18 to be activated. This in turn sets up a 5 second period within which the reset button 120 must be pressed, failing which the reset button 120 becomes inactive and the microprocessor 102 activates the dual-tone multi- frequency interface 138 which results in the subscriber's cellular phone 144 being called. The only way in which the device can now be reset is by the subscriber then entering his or her own specific identification code followed by a reset code which resets the device 100. In the event of a person forcibly entering the vehicle when it is turned off, the device 100 will provide the person entering the vehicle a 30 second period within which to press the reset button 120 If, however, the reset button 120 is not pressed, the reset button 120 will automatically become inactive and alarm outputs, such as the vehicle's lights 110 and buzzer 118 are activated The device 100 will then inform the subscriber, via his or her cellular telephone 144, that there is an unauthorized person in his or her vehicle, by transmitting an alarm condition signal The alarm condition signal can either be in the form of an alarm message which, by means of the data interface 136, appears on the screen of the cellular telephone 144 or a voice message which, by means of the voice interface 138, is transmitted via the audio channel 140 The subscriber will then be able to enter a code on his or her cellular phone 144 which will instruct the microprocessor 102, via the DTMF interface 138, to activate the fuel cut-off circuit 108 In addition, the transceiver module 134 will automatically dial an emergency service, such as the subscriber's private security company, who will then, by determining the approximate position of the vehicle, as previously described, be able to secure the vehicle's return

In the event of the vehicle being hijacked, the same procedure described in the first embodiment is followed, in that all of the arming software is rendered inactive, and the vehicle is operated normally Once the driver has been ejected he or she will then be able to dial up the cellular transceiver module 134, and initiate the various alarm and immobilizing steps, as previously described

As was mentioned, once the ignition switch 126 has been turned off, and the door, and hence the door switch 114, has been opened and closed, or in the case of there being more than one door switch, the last door to be opened and closed, the device 100 will automatically arm itself In one version of the invention, the subscriber can then only be able to gam access to his or her vehicle and disarm it by phoning the cellular transceiver module 134 with his or her cellular telephone 144. The device 100 will recognize that it is being called by an authorized person, and will thus allow access to the vehicle by, for example, unlocking its doors and disarming it.

Claims

C LAI MS

1. A vehicle anti-theft device comprising:

sensing means for sensing a condition;

immobilizing means for immobilizing the vehicle; and

control means for controlling the operation of the anti-theft device,

2. An anti-theft device according to claim 1 which includes a voice module for providing voice prompts to the user via the telephone network, the user providing the command signal in response to the voice prompts.

3. An anti-theft device according to either one of the preceding claims wherein the transceiver unit includes recognition means for recognizing that the command signal originates from an authorized user.

4. An anti-theft device according to claim 3 which includes memory means for storing a list of authorised telephone numbers, the recognition means being arranged to recognise the telephone number of a person wishing to communicate with the transceiver module to determine whether the person is an authorised user or not.

5. An anti-theft device according to any one of the previous claims wherein the condition is an alarm condition arising from an unauthorized act being carried out on the vehicle or device, with the transceiver unit transmitting an alarm signal to the authorised user via the telephone network.

6. An anti-theft device according to claim 5 wherein the command signal is an immobilizing signal delivered from the authorised user, via the telephone network, in response to the alarm signal, for immobilizing the vehicle.

7. An anti-theft device according to any one of the previous claims wherein the immobilizing means includes fuel cut-off means for cutting off the supply of fuel to the vehicle, the fuel cut-off means being arranged to gradually reduce the fuel supply to enable the vehicle to be safely brought to a halt.

8. An anti-theft device according to claim 7 wherein the fuel supply is pulsed in which the fuel supply is temporarily cut and then restored, with the period over which the fuel supply is cut gradually increasing whilst the period over which the fuel supply is restored simultaneously decreasing.

9. An anti-theft device according to any one the previous claims wherein the condition is an alert condition for alerting an authorised user about a status of the vehicle or anti-theft device, with the transceiver unit transmitting an alert signal to the authorised user via the telephone network.

10. An anti-theft device according to any one the previous claims wherein the command signal is arranged to operate a central locking system of the vehicle.

1 1. An anti-theft device according to claim 10 wherein the command signal is arranged to flash the vehicle's lights and/or activate the vehicle's hooter.

12. An anti-theft device according to any one the previous claims wherein the sensing means includes tamper-detecting means for detecting any tampering with the device, with the control means being arranged to render the device useless in the event of tampering being detected.

13. An anti-theft device according to any one of the preceding claims in which the telephone network is a GSM-based cellular network.

14. An anti-theft device according to any one of the preceding claims wherein the sensing means includes at least one door switch.

15. An anti-theft device according to any one of the preceding claims wherein the sensing means includes a movement sensor for sensing unauthorized movement of the vehicle or movement within the vehicle.

16. An anti-theft device according to any one of the preceding claims in which the transceiver unit is arranged automatically to dial up the authorised user first, and if the user does not answer, the unit will then telephone an emergency control centre as part of the initial alarm signal

A method of operating a vehicle anti-theft device comprising the steps of

providing an on-board cellular or mobile telephone transceiver unit for allowing real time two-way communications, via a telephone network, between an authorised user of a vehicle fitted with the device and the transceiver unit,

sensing a condition,

informing of the user, via the telephone network, that a condition has been sensed, and

receiving a remote command signal from the authorised user via the telephone network in response to being informed of the condition

A method according to claim 17 wherein the steps of informing the user and receiving the remote command signal includes the step of providing voice prompts to the user via the telephone network, the user providing the command signal in response to the voice prompts

A method according to either one of the preceding claims 17 and 18 which includes the step of determining whether the command signal originates from an authorized user

A method according to claim 19 which includes the step of storing a list of authorised telephone numbers, with the determining step including the step of recognising the telephone number of a person wishing to communicate with the transceiver module so as to determine whether the person is an authorised user or not.

21. A method according to any one of claims 17 to 20, which includes the step of determining whether the condition is an alarm condition arising from an unauthorized act being carried out on the vehicle or device, with the method then including the step of transmitting an alarm signal to the authorised user via the telephone network.

22. A method according to claim 21 which includes the step of transmitting an immobilizing signal, via the telephone network, in response to the alarm signal, for immobilizing the vehicle.

23. A method according to any one of claims 17 to 22 which includes the step of gradually decreasing the fuel supply to the vehicle.

24. A method according to claim 23 which includes the step of pulsing the fuel supply in which the fuel supply is temporarily cut and then restored, with the period over which the fuel supply is cut gradually increasing whilst the period over which the fuel supply is restored simultaneously decreasing.

25. A method according to any one of claims 17 to 24, which includes the step of determining whether the condition is an alert condition for alerting the authorised user about a status of the vehicle or anti-theft device, with the method including the step of transmitting an alert signal to the authorised user via the telephone network.

26. A method according to any one of claims 17 to 25 which includes the step of operating a central locking system of the vehicle.

27. A method according to claim 26 which includes the step of flashing the vehicle's lights and/or activating the vehicle's hooter.

28. A method according to any one of claims 17 to 27 in which the sensing step includes the step of sensing at least one door switch.

29. A method according to any one of claims 17 to 28 wherein the sensing step includes the step of sensing any unauthorized movement of the vehicle or movement within the vehicle.

30. A method according to any one of claims 17 to 29 which includes the step of dialling up an emergency control centre through the telephone network.

31. A method according to any one of claims 17 to 30 which includes the step of resetting and/or disarming the device in the event of the transceiver unit not recognising the telephone number of the person wishing to reset the button or the person is unable to telephonically communicate with the transceiver unit.