WO1995009408A2

WO1995009408A2 - Tracking system

Info

Publication number: WO1995009408A2
Application number: PCT/GB1994/002125
Authority: WO
Inventors: Jonathan Ventress
Original assignee: Sensored Security Systems Limited
Priority date: 1993-09-29
Filing date: 1994-09-28
Publication date: 1995-04-06
Also published as: GB9320045D0; WO1995009408A3; AU7816894A

Abstract

A monitoring network, particularly for monitoring the movement of vehicles, comprises a plurality of transponders (1), a plurality of road side sensors (2), a local computer (3) for receiving information transmitted from the transponders to the road side sensors, the road side sensors being in communication with the local computer by a conventional telephone network (10) which also provides power supply to the road side sensors. Information transmitted by the transponder to the road side sensors uniquely characterises each vehicle.

Description

TRACKING SYSTEM

Field of the invention

The present invention relates to the field of monitoring apparatus, and particularly although not exclusively to vehicle identification and vehicle monitoring.

Background of the invention

It is known to provide a tracking system for a vehicle, in which the vehicle carries a transponder, for communication with a satellite, and in which the position of the vehicle at any particular time may be accurately determined, at a remote ground station via the satellite. However, the conventional satellite based systems have the problem of high cost of satellite equipment and high cost of vehicle mounted transponder equipment for communications with a satellite.

Object of the invention

An object of the present invention is to provide an improved method and apparatus for tracking and monitoring a vehicle or goods article from a remote location.

A further object of the present invention may be to provide an identification method and apparatus for uniquely identifying a particular article, for example a goods article.

A further object of the invention is to provide an improved vehicle security system. Description of the invention

According to a first aspect of the present invention there is provided a monitoring network characterised by comprising:

a plurality of sensor devices (2) in a geographical area the area divided into a plurality of zones, the plurality of sensor devices divided into a number of sets of sensor devices, each said set of sensor devices being deployed in a separate zone of the area;

one or a plurality of data collection devices (3) , each data collection device arranged to collect data from one or more said sensor devices; and

a communications interface for interfacing with a communications line for communicating between the sensors and the data collection device(s) .

Preferably, the monitoring network comprises a plurality of transmitter means adapted for attachment to one or more articles.

Preferably, each said transmitter means is adapted to transmit information relating to characteristics of the article to which the transmitter is attached.

Preferably, a said transmitter is capable of being programmed with said information which is unique to a particular said article.

Said transmitter device preferably comprises a transponder. The invention includes a sensor device comprising :

means for receiving a transmitted signal;

means for storing portions of said transmitted signal.

Preferably, a said sensor device is arranged to commun: ' :».te a said stored signal via said communications interface after storage of said signal in said storage means.

Preferably, said sensor device is arranged to communicate said signal via said communications interface in response to a request from a said data collection device.

Preferably, said sensor device is adapted to store a said signal for a predetermined time period prior to communicating said signal. Said sensor device comprises a microwave transmitter.

Preferably, a said communications interface comprises an interface for interfacing with a conventional telephone network.

Preferably, a said interface includes a means for automatically dialling, to establish a telephone line between a said sensor and a said data collection device.

The invention includes a monitoring network characterised by comprising:

a plurality of transmitter means adapted for attachment to a plurality of vehicles, each transmitter means arranged to transmit a signal relating to data uniquely identifying characteristics of a particular vehicle;

a plurality of road side mounted sensor devices, each road side sensor device arranged to sense a said signal transmitted by one or more said transmitters and to store one or a plurality of said transmitted signals;

one or more data collection devices, each data collection device arranged to communicate with one or more said sensor devices for transfer of data between one or more of said sensor devices and one or more said data collection devices; and

a communications interface for interfacing with a communications link between a said collection devices and said sensor device,

wherein the plurality of sensor devices may communicate with the plurality of data collection devices via a conventional telephone network, for down loading of said transmitted signals from one or more said sensor devices to one or more said data collection devices.

According to a second aspect of the present invention there is provided a method of monitoring one or a plurality of articles, the method characterised by comprising the steps of:

(i) attaching a respective transmitter device to each said article, each said transmitter device being adapted for transmitting data which uniquely identifies the article to which the particular each said transmitter is attached; (ii) sensing one or more transmitted signals transmitted by one or more said transmitter devices;

(iii) storing said transmitted signals;

(iv) after a predetermined amount of data has been stored, communicating said data into one or more data collection devices.

Preferably, said step of communicating the data is carried out at a predetermined time.

Preferably, said step of storing data includes the step of storing time data corresponding to a time of reception of a particular said stored signal.

According to a third aspect of the present invention, there is provided a sensor device for positioning within signalling distance of a traffic flow, the sensor device characterised by being adapted to receive coded information signals from a passing transmitter; store a predetermined number of said coded information signals; and to communicate said stored signals via a conventional telephone network.

Preferably, the sensor has a detection means for detecting a passing transmitter. A said said detection means may comprise an optical beam generator and detector.

The sensor device is preferably powered from a conventional terrestrial telephone line.

According to a fourth aspect of the present invention, there is provided a portable transponder for fitting to a vehicle, goods article, or person, the transponder comprising a transmitter, a receiver, a storage means for storing a unique code relating uniquely to the vehicle, article or person to which the transponder is attached, wherein the transponder is arranged to transmit said unique code in response to an interrogation signal.

According to a fifth aspect of the present invention, ther is provided a vehicle security apparatus characterised by comprising:

a first identification means adapted for fitment at a first position within a vehicle;

a second identification means adapted for fitment at a second location in the vehicle;

a communication link for communicating between the first and second identification means; and

an immobiliser for immobilising the vehicle,

wherein said first and second identification means are each programmed with a code unique to a particular vehicle to which the identification means are fitted, and the immobiliser is arranged to activate in the event of non communication between the first and second identification means.

The first identification means may be operable in response to a vehicle ignition key carrying a unique code.

Said communications link preferably comprises a fibre optic cable. Preferably a said unique code is transmitted between the first and second identification means via the communications link.

Preferably said first identification means is capable of recognising a received transmission containing a predetermined code relating to the unique code, and activating said immobiliser in response to said signal.

Preferably, the first identification means is capable of comparing a said unique code stored in the first identification means, with a said unique code stored in the second identification means, and in the event that the unique codes stored in the first identification means and stored in the second identification means do not match, the first identification means is arranged to activate the immobiliser.

Description of the drawings

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

Figure 1 shows a monitoring apparatus according to a first specific embodiment of the present invention;

Figure 2 shows a first circuit for detection of transmissions from a transmitter attached to an article;

Figure 3 shows a second circuit for sampling the transmissions; Figure 4 shows an example of a transponder signal corresponding to a transmission of a unique code.

Figure 5 shows another signal corresponding to a transmission;

Figure 6 shows a third circuit for storing and transferring article codes, corresponding to article codes contained in the transmissions;

Figure 7 shows a monitoring network lay out of a monitoring network of sensor, local computers, and an exchange, comprising the first embodiment;

Figure 8 shows an example circuit lay out of a transponder of figure 1 for sending a signal to a road side sensor, and for receiving a signal from the road side sensor;

Figure 9 shows a flow diagram, describing a specific method of operation of a sensor of the first embodiment;

Figure 10 shows another method of operating vehicle mounted transmitter comprised in the apparatus of figure 1 according to a second specific method of the present invention;

Figure 11 shows a vehicle immobiliser and identification system according to a second specific embodiment of the present invention.

Best mode for carrying out the invention Referring to figure 1 of the accompanying drawings, there is shown a monitoring apparatus according to a first specific embodiment of the present invention.

The tracking and monitoring apparatus is primarily directed for the tracking and monitoring of vehicles and this application is primarily described herein, although the apparatus may be directed to the tracking and monitoring of, for example, prisoners, or goods articles, eg. containerised goods.

The monitoring apparatus according to the first specific embodiment comprises a plurality of transponder units 1, each of which may be coded with details specific to a particular vehicle, for example the chassis number, registration number, post code of the owner of the vehicle, make, and model of the vehicle; a plurality of sensors 2, distributed at a plurality of road side locations in a geographical area; one or a plurality of data collection devices in the form of local computers 3-6 for receiving information from the road side sensors 2; a central exchange unit 7 for communicating with the one or the plurality of local computers, and for communicating with a plurality of data networks 8-11, comprising for example a police data network, or a company data network.

Each sensor comprises at least a receiver circuit for receiving a coded signal, a storage circuit for storing one or more said coded signals and a communications interface for communicating one or more said coded signals with a telephone network.

The plurality of road side sensors 2, are provided at various locations around the geographical area, which is divided into a number of zones, a predetermined number of the sensors being deployed in each of the zones. The sensors may suitably be located at convenient sites through which traffic in the area is likely to pass, for example at major traffic lights, at bridges crossing rivers, at motorway junctions, or at major road junctions.

In use, each transponder is arranged to transmit either continuously, intermittently or in response to a unidirectional interrogation signal from a road side sensor, an address signal for addressing a sensor. When the sensor detects a transmitted address signal, the sensor responds by sending a response signal. This prompts the transponder to transmit omnidirectionally a code signal containing the predetermined data, for example the chassis number of the vehicle, the registration number of the vehicle, the registration number of the vehicle, the owner of the vehicle. The sensor 2, which is equipped with a receiver for receiving the transmitted information, receives the unique code information and may store the code information in a memory, along with other information, for example information relating to the location of the road side sensor, and the time and date of reception of the code signal.

Periodically the sensor down loads the stored code information, which was transmitted from the transponder and stored in the sensor, to the local computer 3. Each local computer may receive down loaded code information from one or a plurality of such sensors. Down loading of the code information may take place over a conventional telephone network by predetermined automatic dialling to the local computer by the road side sensor. The road side sensor may be pre-programmed to automatically dial a specific local computer at a predetermined time every day, or at other predetermined periods. For example, collected code information relating to a plurality of passing vehicles, and collected from transmissions made from the transponders of those vehicles, may be stored in an internal memory of the road side sensor, until the internal memory is, for example, 80% full. The data stored in the internal memory may then be down loaded once a predetermined amount of memory space has been filled, for example 80%. The sensor may also transmit the code information to the local computer, in response to a request from the local computer.

Each road side sensor unit may operate from a power supply of the telecommunications network. Use of the power supply of the telephone line may give a cost effective means of powering the road side sensors, compared to batteries, which need regular recharging. Nevertheless, a road side sensor may include a backup battery supply, so that the road side sensor may continue to collect code information in the event of a malfunction of the telecommunications line. Once the telecommunications line is repaired, the sensor may then down load any stored code information collected whilst the telecommunications line was out of operation. For the period when the telecommunications line was out of operation, the sensor may derive power from the stored battery supply.

In other specific embodiments, the sensors may communicate with the local computer by a radio transmission link, which may include communications code information to the local computer via a conventional cellular telephone network or mobile telephone network incorporating a radio link. A said sensor may be arranged to sense the presen e of vehicles fitted with a said transponder unit by use of an induction link between the transponder and the road side sensor.

There may be an optical beam emitted from the sensor, and the sensor may detect reflections of the optical beam, reflected from the passing vehicle. Where a detector is provided on an opposite side of a road, the detector, which comprises part of the sensor, may produce a signal whenever an optical beam across the road is disturbed. The detector may be capable of detecting vehicles in which no transponder is fitted.

For example where an optical beam, produced by laser of a road side sensor, is shone across a road to be detected by a detector on an opposite side of the road, the optical beam may be disturbed by a passing vehicle, whether the passing vehicle is fitted with a transponder or not. Using a detection means which is capable of detecting vehicles which are not fitted with a transponder, information relating to vehicle density etc. may be collected by the sensor.

The first specific embodiment of the present invention may have an advantage over satellite based tracking systems, of removing the need for a dedicated satellite link to the transponders, and thereby reducing the cost of a tracking apparatus by eliminating the expense of a satellite communications link. Where a satellite communications link is used in the first embodiment, it is used in the form of a known mobile telephone network, which is already commercially available. The sensors and local computer of the first embodiment may be adapted for transmission of signals over a conventional telephone link, which may include a satellite telephone link. There may be a cost saving in using the present invention over a tracking system which uses a satellite link, since the present system may be adaptable to use any convenient telephone network. Thus, a commercially available telephone network having the lowest current charge tariffs may be automatically selected by the sensor device, or selected by an operator of the system at the local computer 3, or exchange. 7

The exchange 7 is linked to each of the local computers by, for example, telephone line, and also linked to the networks 8-11, for example a police data network, or one or more company data networks 9-11, enabling the local computers to communicate with one or more networks via the exchange. The exchange 7 may comprise a conventional telephone network exchange apparatus.

The local computers may receive regular up dates from the sensors, up dating stored information. The information is passed at 2240 Hz down a normal telephone line. As the power requirement for the sensors is low, they can be powered from a standard telephone power supply. Reliable transmissions can occur at any frequency over about 3.5 kHz.

Time share access of the local computers may be available to subscribers, for example police or company data networks. The company vehicle code could include a telephone number which the sensor could automatically dial via the communications interface for communicating the information relating to that particular vehicle directly to a predetermined telephone number address. Each vehicle passing a road side sensor may be addressed by a narrow microwave beam, thus reducing interference from the transponders of other vehicles causing competing code transmissions. By using a narrow beam microwave signal, the sensor can be placed sufficiently far away from a road side, to enable a moving vehicle to remain within the footprint of the sensor interrogation signal, and to allow the sensor to remain within range of the transponder code signal. For example for a vehicle travelling at 61 mph, the vehicle may travel approximately 3 metres during the course of a transponder signal transmission. Increasing the distance between the vehicle and the sensor increases the distance which the vehicle may travel whilst making a signal, and hence increases the speed of vehicle which can be interrogated.

Referring to figure 2 of the accompanying drawings, there is shown a first circuit for detection of transmissions from a transmitter or transponder mounted on a vehicle.

The first circuit comprises an active filter .amplifier

20 for amplifying a signal received from an antennae receiver 21, and optionally, a darlington pair arrangement 22 for improving the characteristics of a received signal from the receiver 21, as amplified by the amplifier 20.

The signal received by the receiver 21 may be either an analogue signal or a digital signal. In either case, the active filter amplifier 20 amplifies the signal, before a modified signal appears on the sample line 23 at the output of the darlington pair. The first circuit may be arranged to sample once each pulse level of a digital signal received by the receiver. A received signal from a vehicle mounted transponder is detected on the receiver 21. The signal may indicate the presence of a vehicle. The sensor responds to the presence of the vehicle by transmitting a directional microwave signal directed by means of a wave tube pointed generally towards the detected vehicle, triggering the vehicle*' transponder to transmit its code information. The coded information is preceded by a negati i edge pulse, which is followed by a logic "O" complete blank time period, eg. of seven internal clock pulses of an internal clock of the transponder clock, prior to transmission of the code information by the transponder. The blank time period enables the sampling circuit of figure 3 enough time to lock in phase with the signal transmitted from the transponder. The sampling circuit then reads the code information, relating to the chassis number etc. of the vehicle, as shown in figures 4 and 5 of the accompanying drawings.

Referring to figures 4 and 5 of the accompanying drawings, there is shown a signal received by the sensor, and which is output on the sample line 23 of figure 2 and received on the sample line 23 of the sampling circuit of figure 3. The received signal comprises a series of high and low voltage levels 25, 26 respectively which are digitised in conventional manner by determining whether a voltage level of the signal is above or below a predetermined voltage reference 27.

The signal of figure 4 shows a typical start period of a signal received by the sensor 2. The signal commences with a negative edge 30 which crosses from a positive logic level (eg. a "one" to a "zero" logic level 31) . The negative edge indicates the start of the received signal. This is followed by a blank period 31, corresponding to seven clock cycles. The data content of the signal ie. the coded information then begins. In the example of figure 4 this comprises seven "one" digits 32, followed by a series of "zero" digits and a further series of "one" digits, the series of digits correspond to coded information relating to the chassis number, vehicle owner, vehicle registration number etc. as described herein above.

Referring to figures 3 and 6 of the accompanying drawings, there is shown a sampling circuit of the sensor. The sampling circuit receives a transponder signal from the detection circuit of figure 2, on an input sample line 23. The sample line 23 is fed into a NAND gate 49, which is connected to a NOT gate 50. An output from the NOT gate 50 is fed into a counter 40. The counter 40 counts the number of high signals over the seven samples, and results in an output to a shift register and data storage memory, as described in figure 6 of the accompanying drawings for indicating seven samples containing four or more "high" (logic 1) pulses. A second counter circuit 43 comprising a counter, a NAND gate and a NOT gate, receives a signal from a reset output of the counter 40 and emits a pulse to initiate down loading to a random access memory from a shift register of the memory.

Referring to figure 6 of the accompanying drawings, there is shown a storage memory of the sensor, comprising a series of shift registers 70 for receiving data signals from the sampling circuit of figure 3. The storage circuit comprises a plurality of random access memories 1- 8. The random access memories receive data signals from an array of 32 D-type flip flops arranged in a shift right shift register arrangement. At the output of the shift right shift register arrangement, is a toggle type flip flop 58 for toggling between alternate RAM memory blocks. A control device, in the form of NOT gate, directs the code information received in the shift right shift register memories into an appropriate random access memory, for storage of the down loaded code information corresponding to the vehicle characteristics. The shift right shift register is interfaced with the plurality of random access memories by a plurality of NAND gates 70, which allow data to flow between the shift register and the random access memories only when a control bit is present from the second counter circuit 43 of figure 3.

In the lower half of figure 6 is shown a shift register, as is connected to the random access memories, in the upper half of figure 6, for down loading code information stored in the random access memories onto a telephone line, in response to a control bit. The control bit may be present in response to a predetermined time signal produced by an on board timer in the sensor unit, or the control bit may be produced in response to a request from a local computer or from the exchange.

A simple auto dialling system may be included to dial the local computer and down load the contents of inactive memory portions, whilst active portions of the memory continue to record signals. When empty, the down loading may toggle at the end of the next vehicle transmission and the active memory may become inactive, the inactive memory becoming active. This toggling may be activated by the use of a T-type flip flop.

The shift right shift register construction is of 32 series D-connected D-type flip flops, which allows the necessary parallel on serial data control between the memories. The complete sensor requires only a simple control mechanism to run it comprising the JK flip flop mechanism.

The sensor has an allotted time when it may dial up the local computer for down loading of coded information. Down loading may take place at regular periods regardless of the fullness of memory. The regularity of down load depends upon expected traffic flow and available memory. 2240 Hz is used for the internal sampling clock rate, which is seven times the frequency transmitted from the vehicle and provides an adequate sampling rate for the required reliability.

Referring to figure 8 of the accompanying drawings, there is in more detail a transponder circuit. The transponder circuit comprises an aerial receiver 91; for detecting a signal from a road side sensor; a plurality of

JK flip flops 80-82, a plurality of logic gates, a first counter 83, and a second counter 84; a clock circuit 85 for producing a clock signal; a memory 86 having an output

87 which is fed into a transmitter 88 for transmitting to the road side sensor; a logic circuit to determine whether a counter value indicates whether a predetermined time period has passed 89; and a tuned circuit 90 for receiving a signal emitted by a sensor and detected by the aerial

91.

The transponder circuit of figure 8 operates in three phases, a Wait phase, in which the transponder monitors the air waves for signals to be received by the receiver 91 until a signal above a predetermined amplitude is received; a Transmission phase, in which the transponder transmits a signal, including a coded information signal relating to unique vehicle characteristics such as chassis number, engine number, registration number, owner, etc. and a Pause phase, in which the transponder pauses before recommencing the Wait phase.

The circuit of figure 8 operates as follows: when a signal of a predetermined frequency is received by the receiver 91, provided the received signal is above a certain minimum magnitude, then the transponder circuit transmits to the road side sensor via the transmitter 88. The first counter, which is an address counter, counts up through the addresses of a random access memory (RAM) causing the contents of a least significant bit of each location in the RAM to be transmitted through the transmitter 88, which is enabled by the control circuit comprising the flip flops 80-82. The first few locations in the random access memory address are used to produce a negative edge signal in the transmitted signal, which is required by the road side sensor to trigger phase locking of the road side sensor circuitry to the signal transmitted by the transponder circuit.

For example a digital output signal may be issued by the transponder transmitter as follows : "111010110110....". Such a signal is shown in figure 4 of the accompanying drawings. The first four digits, 1110 designate the negative edge, and the successive digits 10110110... relate to portions of coded information relating to the chassis number, vehicle registration number etc. of the vehicle to which the transponder is fitted.

The final location of the negative edge is marked by a digital "1" stored in the most significant bit in that location. This "1" causes a shift in the control signal produced by the transponder to a Pause phase. In the Pause phase, the second counter 86 begins to count. If, before the second counter reaches a predetermined value depending upon the clock pulse rate, a signal is received from the road side sensor, then the clock 85 resets and counting restarts. Only when a complete count of the second counter to the final predetermined value has passed, will the circuit of figure 8 reset to the Wait phase as described above.

A vehicle may transmit a coded signal to a road side sensor only once whilst it is in a particular area, resulting in less confusion from multiple transmissions in many vehicles transmitting simultaneously, and avoiding multiple recordings of transmission from the same vehicle. A road side sensor may regularly transmit a pulsing output signal until a response is detected from a transponder, and then the sensor may suppress such output pulses whilst the transponder sends its unique codes signal to the road side sensor.

Referring to figure 10 of the accompanying drawings, the Pause mode of the transponder may ensure that a vehicle communicates with a road side sensor only once in a predetermined zone, to avoid repeated transmission between the transponder and a particular road side sensor when the vehicle is passing the road side sensor only once.

Referring to figure 9 of the accompanying drawings, there is shown a specific method according to the present invention, for operating the monitoring apparatus of figures 1 to 8. Items 100-111 in figure 9 relate to various phases of operation of the transponder and road side sensor as follows: At 100, the road side sensor determines whether a vehicle has been detected entering a predetermined zone. If the sensors do not determine a vehicle has entered the zone, the sensor continues to wait until a vehicle does enter the zone. If the sensor determines that a vehicle has entered the zone, the sensor stores data relating to the direction of the vehicle, the t -αe, and the date, in a temporary memory location within the sensor at step 101. The sensor then transmits a signal to the vehicle at step 102 and at step 103 waits until a negative edge of a signal transmitted by the transponder is received by the sensor, or until an end of the vehicle is detected from a detector at step 103. If the end of the vehicle is detected, and in the absence of any negative edge of a transponder signal being received, this may indicate that the vehicle is not fitted with a transponder, and the sensor returns to step 100 in which it awaits a new vehicle entering the zone. If an end of the vehicle is not detected, or if a negative edge of a transponder signal is detected, the sensor circuitry waits for seven sampling time periods and then proceeds, in step 106, to determine the value of the next portion of transponder signal to be received, and increments a counter accordingly. The sampled value is temporarily stored in a temporary memory location in step 107. When the sensor circuitry continues to store successive samples in the temporary memory location until 32 samples, or some other predetermined number of samples, have been recorded in the temporary memory location. When the predetermined number of samples have been recorded in the temporary memory location, at step 109, the sensor circuit determines whether a random access memory is full. If the random access memory is full, the sensor circuitry, at step 110 switches to another random access memory in order to perform multiple tasks of storing multiple data messages transmitted in one or more transmissions from one or more transponder transmissions from one or more transponders connected to a plurality of vehicles (hereinafter referred to as multi tasking) . If the current random access memory in which the sensor is storing a transponder signal is not yet full, the sensor circuit is free to store further transponder signals emitting from the same transponder from which signals are currently being received, or from other transponders of other vehicles, in the same random access memory as currently being addressed, as shown in step 111.

Referring to figure 10 of the accompanying drawings, there is shown a modification to the first embodiment, in which a vehicle transponder unit forms part of an infra red fibre optic or a security or immobiliser system of the vehicle. A microwave frequency transmission may be made from a road side sensor, the transmission from the road side sensor containing a unique code to uniquely identify a particular vehicle. The transponder may receive the unique code and, in response to the received code immobilise the vehicle.

Specific embodiments of the present invention may enable non vehicular applications, such as monitoring of prisoners who each may carry a transponder according to a specific embodiment of the present invention. The transponders may be detected by sensors placed in a geographical area, and the sensors may periodically be addressed by a central exchange, and coded information relating to details of the prisoners, their whereabouts and the time of their movements may be fed into a police computer network over a conventional telephone network. Because the road side sensors are connected to a conventional telephone network, there may be provide an advantage in allowing reduced maintenance of the road side sensors, compared to battery driven sensors.

Various commercial organisations may subscribe to receive information collected by the monitoring network. For example, the network may be used to monitor the movement of fleet vehicles, and information received from transponders mounted on the fleet vehicles and via the road side sensors, down loaded via a telephone line communications link to a central exchange may be compiled to produce lists of vehicle movements of a fleet of individual vehicles in a fleet. This information may be used for central planning of vehicle movements and for monitoring of sales personnel using fleet vehicles.

As the monitoring network avoids the use of a dedicated satellite link for communicating directly with a vehicle mounted transponder, but rather allows a low cost electronic transponder which can be either fitted to a vehicle or carried on a goods item, eg. a goods container, or an individual person, there may be achieved a significant cost transponder advantage compared to conventional satellite tracking systems. Further, as the road side sensors down load information via conventional telephone networks, there may be a considerable cost saving in the provision of basic elements of the monitoring network comprising the transponders and road side sensors.

A second specific embodiment and method according to the present invention will now be described with reference to figure 10 of the accompanying drawings. Referring to figure 11 of the accompanying drawings, a combined vehicle immobiliser and vehicle identification apparatus comprises a first identification device 200 which is physically fitted into a front portion of the car, for example to a portion of the car forward of the normal driving position of the car; and a second identification device 201, adapted for fitment to a rear portion of a vehicle, for example to a portion aft of the normal driving position of the vehicle; and a communications link 202 between the first and second identification devices 200, 201, the communications link preferably comprising a fibre optics cable.

The first identification device 2 may include a transmitter for transmitting to a road side sensor. The first identification device 200 is programmable with information which is unique to the particular vehicle to which the first identification device 200 is fitted. The first identification device is connected with an vehicle immobiliser 202, and an ignition key 204 which is responsive to a coded key. The key 205 contains part of a code which the first identification device 200 is arranged to recognise. If any other key, other than the correct specifically coded key is inserted into the ignition, the first identification device will not identify the key and will activate or maintain as active the immobiliser 202 to immobilise the vehicle. The immobiliser may immobilise the vehicle by transmitting infra red signals from the immobiliser to an ignition distributer, diesel pump, etc. for immobilising the vehicle.

The first identification device 200 communicates with the second identification device 201 fitted in the rearward portion of the vehicle, and periodically transmits the characterising data, which uniquely characterises the vehicle, along the fibre optic communications link 203.

The second identification device 201 responds to a request from the first identification device for information, and re-transmits the coded data back to the first identification device. If for any reason the communications link 203 is broken, and the first identification device does not have access to the information transmitted from the second identification device, or if the information transmitted from the second identification device does not match the coded data sent by the first identification device, for example because the second identification device is programmed with the unique characteristics of a different vehicle, then the first identification device activates the immobiliser.

This may have an advantage that if, for example a vehicle is stolen, cut in half and re-welded together, such that a front end of a first original vehicle is welded to a second, rear, end of a second original vehicle, making a complete new vehicle out of two separate original vehicles, the first and second identification devices will contain different information, the first identification device containing information unique to the first original vehicle, and the second identification device containing information unique to the second original vehicle, and when information is transmitted between the devices, the information will not match, at which point the first identification device will activate the immobiliser. Additionally, if the first and second identification devices are not connected to each other, then the first identification device can not receive a comparison signal from the second identification device, and again, will immobilise the vehicle.

Specific embodiments of the present invention may provide a relatively inexpensive security system for a vehicle which will not allow the vehicle to be driven, even if the normal steering lock is broken.

As information unique to each vehicle, for example chassis number and registration number, is already stored in police computers, by equipping a vehicle with a receiver for receiving an immobilising code based upon the unique characteristic information of the vehicle, the apparatus may be used to immobilise a vehicle in response to a signal transmitted by the police, thus enabling the police to disable any stolen vehicle which has been stolen with access to the correct coded key.

A transponder fitted to the first identification device may transmit details of the unique vehicle code to road side sensor, for example in road side sensors as described according to a first aspect of the present invention, to enable tracking and immobilisation of stolen vehicles fitted with an apparatus according to the second aspect of the present invention.

Further features of the specific embodiments include the following:

Transmissions to the car from the sensor should be of a different frequency to that used from car to sensor. If this were not the case adjacent vehicles would detect signals which were not directed to them and hence initiate transmission inducing super positional wave problems. The two frequencies stop this problem. All logic on board should be made from NAND gates which are easily available for purchase, a few pounds for a chip containing many gates.

A vehicle not responding to the output from the vehicle sensor is assumed untagged, 32 bits of "zero" level recorded would indicate this. It is possible that a vehicle could be caused to not respond to the sensors signal. If tagging were compulsory a blank response would immediately alert suspicions. Non compulsory tagging would merely allow a company to note if a vehicle performed the required task, it could be further used by disabling the system and driving as an untagged vehicle. It may be possible for a criminal to swap vehicle tags. Many of these problems could be avoided by linking the sensor system into the other vehicle security system which uses code relays around a vehicle via fibre optic cabling. This would means swapping the tag to another vehicle would be impossible. It would however still be possible to blank out the transmissions. Multiple transmission points on the vehicle could reduce the ease of doing this.

Each vehicle uses 32 bits of memory for its individual code. This enables 4.3 billion separate vehicles to be tagged in an individual way. Storage of the chassis number would require the inclusion of alphabetical characters in the code. The 32 bits could be used in some way to represent this through a very simple computer database could provide a link between the two codes for a vehicle.

One computer (LOCAL) could cope with a number of sensors. The number of sensors depends upon how much internal memory each has and the speed of information passage down phone lines. Many improvements could be made to increase capacity and sampling rate through the system here would be effective enough currently. At peak expected traffic flow, ie. 40mph with 3m vehicle spacing, ten minutes sampling would require 14.3kbytes, or four 3575 byte rams. Two such blocks would be required, active and inactive, one for reading from sample analysis and one for writing to phone lines.

Down load at 2240 Hz of an entire memory block would take 3.4 minutes not including connection time. This poses possible problems for a system with more than two sensors running at full capacity. Compulsory vehicle tagging would require system modifications for function. The transmission time would be further increased due to the necessity of data markers to clearly show reading computer where transmissions begin and end. The limitations are present due to BT line sample rate. It could be possible to increase running frequency to more than one third of the BT rate but this could lead to erroneous code storage. Absolute maximum frequency is then 8/3, 2667Hz. Data compression systems could be incorporated this would take time to calculate the compressed form. Another option which would solve all transmission problems would be to have multi line connections to the local computer systems. The computer could sample each line in sequence at a very high rate enabling all subsidiary sensors to transmit simultaneously at full speed.

Another so far unconsidered problem is that of a vehicle bypassing the signal and sensor. Single file traffic is fine but if the sensors were on two way roads nothing stops a vehicle crossing the central reservation and registering its presence as leaving an area rather than entering. Accurate logging of date and time of vehicle passage would allow determination from logical thought. It would still be possible for a vehicle to fool the system and some mechanism detecting vehicle direction should be installed. In conclusion the above system should be updated to record both vehicle code and time of vehicles passage. 1 bit in the code could be used to represent direction. Direction could be detected with the use of an intelligent vehicle presence sensor. A commonly used method of doing this is to utilise two separate detectors, the order in which each detects vehicle presence determines direction of passage of the vehicle. A simple add-on to the system could use this data to determine vehicle speed and log this with other data hence rendering the system a useful automatic speed trap as well as its other uses.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification

(including any accompanying claims, abstract and drawings) , may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A monitoring network characterised by comprising:

one or a plurality of data collection devices (3), each data collection device arranged to collect data from one or more said sensor devices; and

2. A monitoring network according to claim 1, characterised by comprising a plurality of transmitter means adapted for attachment to one or more articles.

3. A monitoring network according to claim 2, characterised in that each said transmitter means is adapted to transmit information relating to characteristics of the article to which the transmitter is attached.

4. A monitoring network according to claim 3, characterised in that a said transmitter is capable of being programmed with said information which is unique to a particular said article.

5. A monitoring network according to claim 1 , characterised in that a said sensor device comprises : means for receiving a transmitted signal;

means for storing portions of said transmitted signal.

6. A monitoring network according to claim 5, characterised by a said sensor device being arranged to communicate a said stored signal via said communications interface after storage of said signal in said storage means.

7. A monitoring network according to claim 6, characterised by a said sensor device being arranged to communicate said signal via said communications interface in response to a request from a said data collection device.

8. A monitoring network according to claim 6, characterised in that a said sensor device is adapted to store a said signal for a predetermined time period prior to communicating said signal.

9. A monitoring network according to claim 1, characterised in that a said sensor device comprises a microwave transmitter.

10. A monitoring network according to claim 1, characterised in that a said communications interface comprises an interface for interfacing with a conventional telephone network.

11. A monitoring network according to claim 10 characterised in that said interface' includes a means for automatically dialling, to establish a telephone line between a said sensor and a said data collection device.

12. A monitoring network characterised by comprising:

13. A method of monitoring one or a plurality of articles, the method characterised by comprising the steps of:

(i) attaching a respective transmitter device to each said article, each said transmitter device being adapted for transmitting data which uniquely identifies the article to which the particular each said transmitter is attached;

(ii) sensing one or more transmitted signals transmitted by one or more said transmitter devices;

(iii) storing said transmitted signals;

14. A method according to claim 13, wherein said step of communicating the data is carried out at a predetermined time.

15. A method according to claim 13, wherein said step of storing data includes the step of storing time data corresponding to a time of reception of a particular said stored signal.

16. A sensor device for positioning within signalling distance of a traffic flow, the sensor device characterised by being adapted to receive coded information signals from a passing transmitter; store a predetermined number of said coded information signals; and to communicate said stored signals via a conventional telephone network.

17. A sensor according to claim 16, characterised by having a detection means for detecting a passing transmitter.

18. A sensor device according to claim 17, characterised in that said detection means comprises an optical beam generator and detector.

19. A sensor device according to claim 16, characterised by being powered from a conventional terrestrial telephone line.

20. A portable transponder for fitting to a vehicle, article, or person, the transponder comprising a transmitter, a receiver, a storage means for storing a unique code relating uniquely to the vehicle, article or person to which the transponder is attached, wherein the transponder is arranged to transmit said unique code in response to an interrogation signal form a remote sensor.

21. A vehicle security apparatus characterised by comprising:

a second identification means adapted for fitment at a second location in the vehicle;.

an immobiliser for immobilising the vehicle,

22. A vehicle security apparatus according to claim 21 characterised in that the first identification means may be operable in response to a vehicle ignition key carrying a unique code.

23. A vehicle security apparatus according to claim 22 characterised in that said communications link comprises a fibre optic cable.

24. A vehicle security apparatus according to claim 22 characterised in that a said unique code is transmitted between the first and second identification means via the communications link.

25. A vehicle security apparatus according to claim 22 characterised in that said first identification means is capable of recognising a received transmission containing a predetermined code relating to the unique code, and activating said immobiliser in response to said signal.

26. A vehicle security apparatus according to claim 22, characterised in that the first identification means is capable of comparing a said unique code stored in the first identification means, with a said unique code stored in the second identification means, and in the event that the unique codes stored in the first identification means and stored in the second identification means do not match, the first identification means is arranged to activate the immobiliser.

27. A monitoring network according to cla im 2 , characterised in that a said transmitter device comprises a transponder.