GB2501679A

GB2501679A - Fuel theft surveillance system

Info

Publication number: GB2501679A
Application number: GB1207130.4A
Authority: GB
Inventors: Peter Lloyd
Original assignee: STEALTH AND SECURE Ltd
Current assignee: STEALTH AND SECURE LIMITED
Priority date: 2012-04-23
Filing date: 2012-04-23
Publication date: 2013-11-06
Also published as: GB201207130D0

Abstract

A surveillance system 10 combats theft of fuel from motor vehicles. The system 10 comprises a fuel cap sensor 12 operative to detect movement of the fuel cap, and a fuel tank sensor 14 operative to detect any attempt to penetrate the tank. The sensors are arranged to activate a local alarm 22 and a remote alarm 24 by way of a communications subsystem 20. A control subsystem 26 is operable, by means of a key fob operated by a driver of a vehicle, to switch the system 10 between a first (armed) state and a second (disarmed) state. In the first (armed) state, either of the alarms 22,24 is activated if either of the sensors 12,14 detects unauthorised movement. In the second state, only remote alarm 22 is activated if either of the sensors 12,14 detects unauthorised movement. By this means, a driver of a vehicle cannot gain unauthorised access to fuel by disarming the system 10. The fuel cap sensor 12 may be a magnetic sensor. The fuel tank sensor 14 may be a vibration sensor arranged to detect cutting, piercing or spiking of the tank.

Description

Surveillance System This invention concerns surveillance systems particularly but not surveillance systems for signalling theft or attempted theft of fuel from fuel tanks of motor vehicles such as trucks and motor caravans and from static installations such as central heating fuel tanks and fuel supply tanks in vehicle depots or on farms.

It is well known that, with fuel prices rising, more and more fuel is being stolen, and many theft alarm systems have been proposed to combat this, generally including a key fob controller or the like whereby the system is armed when vulnerable -eg when a vehicle is parked -and disarmed when in use or when, say, a tank is to be refilled. Less well known is that, particularly in relation to thefts from motor vehicles, much of the theft is attributable to drivers of the vehicles. Consider the case of a truck driver it is easy for him to syphon off a few litres of fuel when the alarm system is not armed, and the loss is barely measurable when the fuel tank capacity may be hundreds of litres or more.

It is an object of the present invention to provide a surveillance system that guards against theft at all times, and not just when it is in an armed state.

Thus according to a first aspect of the invention there is provided a surveillance system comprising: a plurality of sensors associated with items of value (eg stocks of vehicle fuel) under surveillance by the system, which sensors are responsive * to unauthorised movement of said items; a plurality of alarms; a communications subsystem operatively connecting the alarms to the sensors, whereby a said alarm is activated if a said sensor detects unauthorised movement in relation to a said item; and a control subsystem operable to switch the surveillance system between a first state and a second state; characterised in that when the surveillance system is in said first state a first said alarm is activated if a first said sensor detects unauthorised movement in relation to a said item associated therewith and when the surveillance system is in said second state a second said alarm is activated if the first said sensor detects unauthorised movement in relation to the item associated therewith.

Those skilled in the art will readily perceive the benefits of the invention in guarding against fuel theft from motor vehicles (although it is to be noted that the invention is not limited to this purpose). Let the first state of the present invention equate to the armed state of a conventional vehicle alarm system. The driver parks the vehicle and, before he leaves it, presses a locking button on the ignition key which locks the doors and simultaneously arms the alarm system. With a conventional system, when the driver returns to the vehicle and presses the unlocking button on the ignition key, the doors are freed and the alarm system is disarmed -and when the alarm system is disarmed the driver can access the contents of the vehicle fuel tank, with a very low risk of detection. With the present invention, however, pressing the unlocking button does not disarm the alarm system, but rather switches it to a second state in which it is still active.

Either of the first and second alarms may be activated locally (ie in the vicinity of a motor vehicle) or remotely (eg at a control or security centre) but it is particularly advantageous if the second alarm is activated remotely, with no local indication. This enables the behaviour of a suspect driver to be monitored without alerting him.

The control subsystem may be operable both locally and remotely.

* Thus in relation to motor vehicles, for instance, the control subsystem may operable locally by means of a keypad used by the vehicle driver or it may be operated remotely by transmitting a text message or the like to the system : from a control or security centre.

:: At least one of the sensors may responsive to movement of a container containing said item, eg to opening a cap of a motor vehicle fuel tank. At least one of the sensors may include a magnetic detector,eg arranged to respond to opening a cap of a motor vehicle fuel tank. And at least one of the sensors may be responsive to vibration, eg that caused by any attempt to cut into or pierce some part of the vehicle; and such sensor is preferably configured and arranged to activate a said alarm selectively, eg so as not to trigger a false alarm of theft from a moving vehicle.

Preferably the surveillance system is configured and arranged to protect the sensors themselves against interference by providing that an alarm is activated if a said sensor is subject to unauthorised movement.

The system may include activation means, eq a panic button operated by a vehicle driver, whereby one or more of the alarms may be activated manually.

As noted earlier the invention is particularly (but not exclusively) for use in relation to motor vehicles, and to this end the sensors of the surveillance system may include any one or more of the following: a sensor responsive to unauthorised movement in relation to a fuel tank of the vehicle, wherein such unauthorised movement excludes movement occasioned by a driver boarding the vehicle and movement occasioned by rain falling on the tanks; a sensor responsive to unauthorised movement in relation to a closure of a fuel tank, wherein such unauthorised movement generates a covert signal (that is, a signal with no local indication) recording vehicle identity, location, speed and time; a sensor responsive to unauthorised movement in relation to a catalytic ". : converter of the vehicle; * a sensor responsive to unauthorised movement in relation to a diesel C.....

* particulate filter of the vehicle; a sensor responsive to unauthorised movement in relation to an electrical battery of the vehicle; and a geofence configured and arranged to activate a said alarm if the vehicle crosses the perimeter thereof.

Also for use in relation to motor vehicles, the alarms of the system may include any one or more of the following: a horn of the vehicle activated automatically if a said sensor detects unauthorised movement; lights of the vehicle activated automatically if a said sensor detects unauthorised movement; an annunciator activated automatically if a said sensor detects unauthorised movement and providing a local announcement that unauthorised movement has been detected; an immobiliser for the vehicle; and a GPS tracking system for the vehicle.

Preferably, also, for use in relation to motor vehicles, the surveillance system is powered by an electrical power source independent of the vehicle battery.

Particularly for use in relation to fixed premises, the sensors of the system may include a sensor responsive to unauthorised movement in relation to a fuel tank on the premises, wherein such unauthorised movement excludes effects of wind and rain, and a senor responsive to unauthorised movement in relation to a closure of the fuel tank, the system also including a sensor responsive to power failure at said premises.

The alarms of such a system for use on fixed premises may include an alarm activated on said premises and/or a said alarm activated away from the premises. And the system may be configured and arranged to signal to a supplier that an item under surveillance is to be replenished on said premises, eg to order fresh fuel supplies automatically.

According to a second aspect of the invention there is provided a sensor assembly for the surveillance system, which sensor assembly * S comprises a sensor responsive to vibration in relation to a said item of value and a connector in use connecting the sensor to said item, characterised in that said connector conduct vibration from the item to the sensor and * separates the sensor from the item.

:.: Preferably the connector is configured and arranged to amplify the conducted vibration, to which end it may comprise a helical coil whereby the vibration is amplified. For surveillance of a catalytic converter in the exhaust system of a motor vehicle, the connector may an end remote from the sensor configured and arranged to be secured to an exhaust clamp of the motor vehicle.

According to a third aspect of the invention there is provided a sensor assembly for the surveillance system as arranged for surveillance of fuel oil, particularly in a static tank, characterised in that the sensor assembly comprises a first float and a second float interconnected by a bridge, each said float being buoyant in the oil and carrying a magnetic sensor element, wherein the sensor elements are configured and arranged to detect relative vertical movement between the first float and the second float.

One said sensor element may comprise a magnet and the other said sensor element may comprise a coil operatively connected to deliver a signal representative of the relative movement.

The first float may mounted for vertical sliding movement on a guide, and the guide may carry an additional sensor operative when engaged by the float to deliver a signal indicating low oil level.

The bridge may be connected to the first float and/or the second float by means of a plastic hinge permitting said relative vertical movement, and preferably the first float and the second float are respectively less buoyant and more buoyant in the oil.

Other features of the present invention will be apparent from the following description, which is made by way of example only with reference to the accompanying drawings in which -Figure 1 is a schematic illustration of a basic motor vehicle surveillance system according to the invention; **..#.

* Figure 2 shows a fuel tank sensor of a system as shown in Figure 1; Figure 3 shows a catalytic converter sensor of a system as shown in Figure 1; * * Figure 4 is a schematic illustration of an extended motor vehicle :.: surveillance system according to the invention; Figure 5 is a schematic illustration of a surveillance system according to the invention for use in fixed premises; and Figure 6 illustrates a sensor assembly for use in a surveillance system for a static oil tank.

Referring first to Figure 1, this illustrates a motor vehicle surveillance system indicated generally at 10. The system 10 is used to guard against theft from a large truck (not shown) and to this end it comprises a fuel cap sensor 12 and a fuel tank sensor 14.

As shown in Figure 2, the fuel cap sensor 14 is located adjacent the filler cap 16 of the vehicle fuel tank 18. The sensor 14 is sensitive to changes in magnetic field and the cap 16 is equipped with small magnets (not visible in Figure 2) so that any movement of the cap 16 is detected by the sensor 14. In other respects the cap 16 is conventional, although it will be understood that for greater security it may be a locking cap.

In an alternative embodiment the sensor 14 may be wrapped at least partially around a neck whereon the cap 16 is screwed, so as to be very close to the magnets in the cap.

It is to be noted that a sensor like the sensor 14 may be arranged to detect any attempt to unscrew the fuel gauge sender unit conventionally filled to the vehicle fuel tank.

Returning now to Figure 1, the fuel tank sensor 14 is sensitive to vibration. Thus the sensor 14 detects any attempt to cut into or pierce (eg by what is known as "spiking") the tank 18.

The sensors are operatively connected to a communications subsystem 20, and in turn to a local alarm 22 and a remote alarm 24 are operatively connected to the communications subsystem 20. (For the avoidance of doubt, the term "operatively connected" is used herein to include wireless, ultrasonic e..

* or other like links as well as physical connections). The alarms 22 and 24 may 25. be of any appropriate form, but typically the local alarm 22 may include a siren and/or be arranged to sound the vehicle horn repeatedly and/or flash the * ** vehicle lights and the remote alarm may include transmission of a message by a mobile network to a designated number eg at the vehicle owners office and/or a fleet management office and/or a security centre.

The surveillance system 10 includes a control subsystem 26 operable by a driver of the vehicle and conveniently embodied in a hand-held controller, eg in the form of a key fob, with ALARM ON and ALARM OFF buttons of known form.

In regular operation, the system 10 works as follows. When the vehicle is to be parked, eg overnight, the driver removes the key from the ignition and presses the ALARM ON button on the key fob. This action (which, it may be noted, is independent of locking the vehicle or setting a vehicle intruder alarm) sets the surveillance system 10 in a first state. Then (as well as the vehicle alarm being activated by any attempt to break into or steal the vehicle) the local alarm 22 and/or the remote alarm 24 is activated if there is any attempt to open or otherwise enter the fuel tank 18 (Figure 2), triggered by the fuel cap sensor 12 or the fuel tank sensor 14. When the driver returns to the vehicle, he presses the ALARM OFF button (as well as unlocking the vehicle).

However, and critically, pressing the ALARM OFF button does not disarm the surveillance system 10 but rather sets it in a second state in which it remains active, as will not be described. Suppose the driver is dishonest, and in the habit of helping himself to a few litres of fuel from time to time. He controls the alarms system and he can, he believes, open the tank whenever he wants and syphon off a little fuel. With a large truck the individual loss wilt barely register. But the cumulative cost to the vehicle owner can be considerable, and the present invention combats this. Thus, in the second state of the surveillance system 10, any attempt to open the cap 16 of the fuel tank 18 is signalled to the remote alarm 24 -even if the vehicle alarm system is disarmed at the time, and even though the ALARM OFF button has been pressed. Thus the vehicle owner is warned of any and every attempt to steal fuel from the vehicle, in both the first and second states of the surveillance system..

Information (time, place, vehicle ID etc) for every opening and closing of * ** the cap is logged at the remote location. And in the second state of the :.: surveillance system, the local alarm 22 is not activated by an attempt to steal fuel, so the thief is not warned. In this way a case for the drivers dismissal and/or prosecution can be readily assembled.

In addition, the remote logging helps the vehicle owner to monitor fuel usage accurately.

It will be understood that the surveillance system 10 may include other sensors, and Figure 3 shows a sensor 28 connected by way of a connector 30 to an exhaust system 32 of the vehicle containing a catalytic converter (CAT).

CATs are of high value and a common target for thieves. The sensor 28 is sensitive to vibration, carried through the leg 32, and thus detects any attempt to cut the CAT out of the vehicle exhaust pipe. When the sensor 28 detects vibration movement indicating an attempt to remove the CAT it activates the local alarm 22 and/or the remote alarm 24 (Figure 2).

The connector 30 is formed of spring steel and it serves two purposes as follows. First, it separates the sensor 28 from the heat of the exhaust system 32. Second, it amplifies vibration movement indicating an attempt to remove the CAT, and to this end the connector 32 includes a helical coil 34 that amplifies the vibration. It will also be noted from Figure 3 that the end of the connector 30 remote from the sensor 28 is configured and arranged to be bolted on to an exhaust clamp 36 of standard form.

With regard to the CAT sensor 28 of Figure 3, those skilled in the art will appreciate that vehicle exhausts necessarily vibrate in use. According the surveillance system is arranged to avoid false alarms, by discounting signals received while the vehicle is on the move.

Figure 4 illustrates an extended surveillance system, indicated generally at 40, for a motor vehicle (not shown).

The surveillance system 40 comprises a plurality of sensors 42 to 52 and a plurality of alarms 54 to 60 all operatively connected to a communications subsystem 62. A control subsystem indicated in broken lines at 64 is operable to switch the surveillance system 40 between a first state and a second state. In the first state, one of the alarms 54 to 60 is activated if one * ** of sensors 42 to 52 detects unauthorised movement on or around the vehicle.

In the second state, another of the alarms 54 to 60 is activated if said one of the sensors 42 to 52 detects unauthorised movement on or around the vehicle.

The alarms 54 to 60 are as follows: -The alarm 54 is a local alarm arranged to operate a siren.

-The alarm 56 is a local alarm arranged to sound the vehicle's horn repeatedly and/or flash the vehicle's lights repeatedly.

-The alarm 58 is a local alarm arranged to immobilise the vehicle (advisedly, with some pre-indication, to avoid accidents).

-The alarm 80 is a remote alarm arranged to receive a text message or the like from the communications subsystem 62, eq by way of a mobile telephone network.

The sensors are as follows: -The sensor 42 is a first fuel tank sensor arranged to detect any attempt to drill into or spike the vehicle fuel tank. It detects any substantial force on the fuel tank but is not set off by the driver climbing onto the tank to reach the trailer or by rain falling on the tank. When set off, the sensor 42 causes one of the alarms 54 to 60 to be activated, by way of the communications subsystem 62.

-The sensor 44 is a second fuel tank sensor arranged to detect any attempt force open the fuel gauge sender unit fitted to the fuel tank.

It detects any substantial force but is not set off by the driver climbing onto the tank to reach the trailer or by rain falling on the tank. When set off, the sensor 42 causes one of the alarms 54 to 60 to be activated, by way of the communications subsystem 82.

-The sensor 46 is a vibration-sensitive sensor connected to the CAT of the vehicle and operative to detect any attempt to cut out the CAT or otherwise forcibly remove it. The sensor 46 is not set off by natural movement of the vehicle when stationary, for instance *fl.fl * a movement caused by gusts of wind. When set off, the sensor 46 causes one of the alarms 54 to 60 to be activated, by way of the communications subsystem 62.

-The sensor 48 is a vibration-sensitive sensor connected to the S ** DPF of the vehicle and operative to detect any attempt to cut out the DPF or otherwise forcibly remove it. The sensor 48 is not set off by natural movement of the vehicle when stationary, for instance movement caused by gusts of wind. When set off, the sensor 48 causes one of the alarms 54 to 60 to be activated, by way of the communications subsystem 62.

-The sensor 50 is an electrically-sensitive sensor connected to the battery of the vehicle and operative to detect any attempt to disconnect the battery. When set off, the sensor 50 causes one of the alarms 54 to 60 to be activated, by way of the communications subsystem 62.

-The sensor 52 is a magnetically-sensitive fuel cap movement sensor like that shown in Figure 2. If the cap of the fuel tank is opened when the surveillance system 40 is in its first state, the sensor 52 causes one of the alarms 54 to be activated, by way of the communications subsystem 62. If the cap of the fuel tank is opened when the surveillance system 40 is in its second state the sensor causes the remote alarm 60 to be activated, by way of the communications subsystem 62, but without activating any of the local alarms 54 to 58. Thus the owner of the vehicle is notified but the intruder is not alerted. To effect this, a mobile telephone text message is automatically sent to an office, depot or security centre, recording the identity of the vehicle, its location, its speed, an alarm code and the date/time. (A similar process occurs when the fuel cap is replaced). The location data can be input to digital mapping systems to show where the cap removed/replaced. And if the vehicle is in a remote area where there is no mobile phone signal the text messages is transmitted as soon as the signal is established.

To guard against interference with the sensors 42 to 52, a safeguard . . 25 sensor 66 is connected to the sensors 42 to 52. The safeguard sensor detects any failure of the sensors 42 to 52 and signals this to one or more of the * ** alarms 54 to 60, by way of the communications subsystem 62.

:: Also operatively connected to the communications subsystem 62 is a * . hands-free mobile telephone unit 68. This allows the driver of the vehicle to be contacted and also allows the driver to send an SOS message by way of a panic button, but it does not have a full keypad and it does not support general mobile calls.

Also operatively connected to the communications system 62 is a GPS unit 70 which has several functions as follows.

-Movement of the vehicle can be tracked, during regular use or if it is stolen. Tracking can be continual or in response to a request sent to the communications subsystem.

-A geofence of selected dimensions can be set around the vehicle or around its depOt or other specified location. This triggers an alarm if the vehicle is taken outside the geofence range allowed. If the vehicle is moved more than say 50Cm then the alarm will trigger indicating a possible vehicle theft. And if the vehicle has no scheduled calls outside of say a 30 mile radius from the depot, an alarm may indicate that the vehicle is being used for unauthorised purposes.

The control subsystem 64 has two modes of operation. First, a key fob 72 is operable by the driver of the vehicle. Pushing a locking button on the key fob 72 sets the surveillance system 40 in its first state, in which theft attempts are signalled locally and remotely; and pushing an unlocking button sets the surveillance system 40 in its second state, in which unauthorised access to the fuel tank is signalled remotely but not locally. Second, a messaging unit 74 allows an owner or manager of the vehicle to contact the vehicle and/or to manage or interrogate the surveillance system 40.

The surveillance system 40 is normally powered from the conventional battery of the motor vehicle but it also includes a backup battery.

* Other features of the surveillance system may now be noted. If any * .fl* * I attempt is made to override or defeat the sensors 42 to 52 they automatically * 25 reset to continue normal operation. Mobile communications to and from the 40 utilise a SIM card with tamperproof access. The system is allocated a factory * ,* preset password which can be reset by the owner or manager (but not a driver who is neither).

* From the foregoing description it will be readily understood that the invention may be used in relation to static installations, and a system for this purpose will now be described with reference to Figure 5, which illustrates a surveillance system indicated generally at 80. The system 80 is located in a vehicle depOt equipped with a fuel tank (not shown) but may equally well be associated with fuel tanks on farms, in factories, for central heating systems or in other fixed premises. The system 80 comprises a fuel cap sensor 82 and a fuel tank sensor 84 of the kinds previously described herein and respectively arranged to detect movement of the cap of the fuel tank and movement indicating an attempt to effect forcible entry into the fuel tank. The sensors 82 and 84 are each operatively connected to a communications subsystem 86 and a local alarm 88 (such as a siren) and a remote alarm 90 (incorporated in the owners mobile telephone and/or located at a police station or other security centre) are also operatively connected to the communications subsystem 86.

The surveillance system 80 can be switched between a first state and a second state by means of a control subsystem 92.

In the first state of the surveillance system 80, any movement detected by either of the sensors 82 and 84 triggers the local alarm 88. In the second state of the surveillance system 80, any movement detected by either of the sensors 82 and 84 triggers the remote alarm 88. In this way an owner or manager can secure local alarms when he is on the premises and remote alarms when he is away.

The surveillance system 80 also facilitates another feature as follows. A fuel gauge sensor 94 is operatively connected to the communications subsystem 86. When fuel falls to a low level in the fuel tank, this is automatically signalled to a receiver 96 located at a supplier's premises, to call * up replenishment. This is particularly useful in relation to central heating systems, in avoiding possible shutdown of a system (and hence frost damage etc) in an owner is away.

A sensor assembly being an enhanced form of the sensor 94 of Figure is illustrated in Figure 6. The sensor assembly of Figure 6 is indicated * ** generally at 100. It comprises a first float 102 and a second float 104 each buoyant in the oil, the surface of which is indicated at 106. The first float 102 is mounted for vertical sliding movement on a guide extending into the oil in the tank. The second float 104 is connected to the first float 102 by a bridge 110 including a plastic hinge that permits relative vertical movement between the first float 102 and the second float 104. The second float 104 carries a magnet 114 and the first float 102 carries a coil 116, on the end of an arm 118 extending from the first float 102 so as to be close to the magnet 114 cartied by the second float 104. Thus relative vertical movement between the first float 102 and the second float 104 causes relative vertical movement between the coil 116 and the magnet 114 and thereby the coil can (by way of an electrical connection not shown and a communications subsystem like the subsystem 86 of Figure 5) signal such relative movement.

In use, the sensor assembly of Figure 6 operates as follows. Any disturbance of the oil (including, for instance, penetration of the tank by a hot lance) causes some movement of the oil surface 106 in the form of a ripple.

This causes relative vertical movement between the first float 102 and the second float 104, because the two floats will not be simultaneousLy positioned at a crest or at a trough or at some common intermediate position on the surface ripple. Accordingly there is relative vertical movement between the coil 116 and the magnet 114, and oil disturbance indicating an attempt to steal the oil is signalled, to activate one or more alarms.

An additional sensor 120 such as a reed switch is positioned on the guide 108 to be engaged by the first float 102 when the surface of the oil falls to a low level, whereby a replenishment order can be automatically signalled to a supplier as described above with reference to Figure 5. For this purpose, and to amplify relative vertical movement between the first float 102 and the * second float 104, it is preferred that the first float 102 be only just buoyant in the oil (with sufficient weight to trigger the additional sensor 120) and the second float 104 be very buoyant in the oil (to sit very close to the surface * 106).

:.: The arm 118 has a hinged connection 122 with the first float 102. Thus, for convenience of installation, both the arm 118 and the second float 104 can be tilted up to fit through a hole bored in the tank -a 50mm hole can accommodate a sensor assembly 100 has a diameter of 48mm.

Various modifications and adaptations of the systems described may be made without departing from the scope of the invention.

Claims

Claims 1. A surveillance system comprising: a plurality of sensors associated with items of value under surveillance by the system, which sensors are responsive to unauthorised movement of said items; a plurality of alarms; a communications subsystem operatively connecting the alarms to the sensors, whereby a said alarm is activated if a said sensor detects unauthorised movement in relation to a said item; and a control subsystem operable to switch the surveillance system between a first state and a second state; characterised in that when the surveillance system is in said first state a first said alarm is activated if a first said sensor detects unauthorised movement in relation to a said item associated therewith and when the surveillance system is in said second state a second said alarm is activated if the first said sensor detects unauthorised movement in relation to the item associated therewith.
2. A surveillance system as claimed in claim I characterised in that the first said alarm and/or the second alarm is activated locally or remotely.S*SSe*eS
3. A surveillance system as claimed in claim 2 characterised in that when the second said alarm is activated remotely there is no local indication thereof. * S. * S S
4. A surveillance system as claimed in any of claims I to 3 characterised in that the control subsystem is operable both locally and remotely.
5. A surveillance system as claimed in claim 4 characterised in that the control subsystem is operable locally by means of a keypad and is operable remotely by transmitting a text message or the like to the system.
6. A surveillance system as claimed in any preceding claim characterised in that at least one said sensor is responsive to movement of a container containing said item.
7. A surveillance system as claimed in any preceding claim characterised in that at least one said sensor includes a magnetic detector.
8. A surveillance system as claimed in any preceding claim characterised in that at least one said sensor is responsive to vibration.
9. A surveillance system as claimed in claim 8 characterised in that said sensor is configured and arranged to activate a said alarm selectively. * 15

*
10. A surveillance system as claimed in any preceding claim characterised in that said system is configured and arranged so that an alarm is activated if a said sensor is subject to unauthorised movement.
II. A surveillance system as claimed in any preceding claim characterised in that said system includes activation means whereby a said * alarm may be activated manually. *
12. A surveillance system as claimed in any preceding claim for use in relation to a vehicle, characterised in that said plurality of sensors includes * any one or more of the following: :: a sensor responsive to unauthorised movement in relation to a fuel tank *.: of the vehicle, wherein such unauthorised movement excludes movement occasioned by a driver boarding the vehicle and movement occasioned by rain falling on the tanks; a sensor responsive to unauthorised movement in relation to a closure of a fuel tank, wherein such unauthorised movement generates a covert signal recording vehicle identity, location, speed and time; a sensor responsive to unauthorised movement in relation to a catalytic converter of the vehicle; a sensor responsive to unauthorised movement in relation to a diesel particulate filter of the vehicle; a sensor responsive to unauthodsed movement in relation to an electrical battery of the vehicle; and a geofence configured and arranged to activate a said alarm if the vehicle crosses the perimeter thereof.
13. A surveillance system as claimed in claim 12 characterised in that said plurality of alarms includes any one or more of the following: a horn of the vehicle activated automatically if a said sensor detects unauthorised movement; lights of the vehicle activated automatically if a said sensor detects unauthorised movement; an annunciator activated automatically if a said sensor detects unauthorised movement and providing a local announcement that unauthorised movement has been detected; an immobiliser for the vehicle; and a GPS tracking system for the vehicle.

*
14. A surveillance system as claimed in claim 12 or claim 13 characterised in that said system is powered by an electrical power source independent of the vehicle battery. * .* * . * *** * ** * * * * * **
16. A surveillance system as claimed in any of claims Ito II for use in relation to fixed premises, characterised in that said plurality of sensors includes a sensor responsive to unauthorised movement in relation to a fuel tank on the premises, wherein such unauthorised movement excludes effects of wind and rain, and a sensor responsive to unauthorised movement in relation to a closure of a fuel tank; and wherein said system includes a sensor responsive to power failure at said premises.
16. A surveillance system as claimed in claim 15 characterised in that said plurality of alarms includes a said alarm activated on said premises and/or a said alarm activated away from the premises.
17. A surveillance system as claimed in claim 15 or claim 16 characterised in that the system is configured and arranged to signal to a supplier that an item under surveillance is to be replenished on said premises.
18. A sensor assembly for a surveillance system as claimed in any preceding claim, which sensor assembly comprises a sensor responsive to vibration in relation to a said item of value and a connector in use connecting the sensor to said item, characterised in that said connector conduct vibration *: * : from the item to the sensor and separates the sensor from the item.

*
19. A sensor assembly as claimed in claim 18 characterised in that the connector is configured and arranged to amplify the conducted vibration.
20. A sensor assembly as claimed in claim 19 characterised in that * : * the connector compnses a helical coil whereby the vibration is amplified.
21. A sensor assembly as claimed in any of claims 18 to 20 included in a said surveillance system for surveillance of a catalytic converter in the exhaust system of a motor vehicle, characterised in that said connector has an end remote from the sensor configured and arranged to be secured to an exhaust clamp of the motor vehicle.
22. A sensor assembly for a surveillance system as claimed in any of claims I to 17 arranged for surveillance of fuel oil, characterised in that the sensor assembly comprises a first float and a second float interconnected by a bridge, each said float being buoyant in the oil and carrying a magnetic sensor element, wherein the sensor elements are configured and arranged to detect relative vertical movement between the first float and the second float.
23. A sensor assembly as claimed in claim 22 characterised in that one said sensor element comprises a magnet and the other said sensor element comprises a coil operatively connected to deliver a signal representative of said movement.
24. A sensor assembly as claimed in claim 23 characterised in that the first float is mounted for vertical sliding movement on a guide.
25. A sensor assembly as claimed in claim 24 characterised in that the guide carries an additional sensor operative when engaged by the float to deliver a signal indicating low oil level.
S * * .
27. A sensor assembly as claimed in any of claims 22 to 2G characterised in that the bridge is connected to the first float and/or the second float by means of a plastic hinge permitting said relative vertical movement.
28. A sensor assembly as claimed in any of claims 22 to 27 characterised in that the first float and the second float are respectively less * . buoyant and more buoyant in the oil.
29. A surveillance system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.