GB2051442A

GB2051442A - A security system

Info

Publication number: GB2051442A
Application number: GB8010651A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-03-30
Filing date: 1980-03-28
Publication date: 1981-01-14
Also published as: GB2051442B

Abstract

A security system for a car comprises a control unit for installation in the car and a portable unit to be carried by the driver. The portable unit, on recognising a uniquely coded first signal transmitted by the control unit, transmits a uniquely coded second signal to the control unit which, on recognising it, cancels disablement of the car ignition, petrol pump etc. Transmission of the first signal is produced on the driver inserting the car key in the driver's door lock. An alternative form of security system comprise a portable unit which transmits a uniquely coded signal to a control unit in the car, the control unit on recognising the transmitted coded signal enabling use of the car. <IMAGE>

Description

SPECIFICATION A security system This invention relates to a security system which will operate an alarm and/or disable a device or parts thereof to which the system is fitted when unauthorised use is attempted. The system is particularly useful when fitted to cars, lorries or boats to prevent theft.

There are numerous devices on the market to prevent a vehicle or the contents thereof from being stolen but all of these require the owner to take specific action to achieve the required security. For example on steering locks it is necessary to turn a key to lock the steering; with ignition disabling circuits it is necessary to operate a switch, and with hatch covers on boats it is necessary either to secure a padlock to a hasp fitted to the hatch or slide the bolt of a lock into a recess in the hatch frame.

The security system disclosed herein is entirely automatic and will secure a car or boat against unauthorised entry, or being towed away, without the owner taking any specific action.

Basically the system according to this invention comprises two units, one fitted to the car and one carried by the driver, communication between the two units being effected by a short range digital signal.

The system can be of two different types, one (type 1) in which both units include a short range transmitter and receiver, the other (type 2) in which the object to be secured acts in a purely passive mode and contains a receiver, the 'hand-held' unit then containing a short range transmitter.

The unit to be fitted in e.g. a car or boat has a number of locking circuits for immobilisation and for the prevention of tampering. It may include an audible alarm and a sub-unit for sending out a signal capable of being picked up by patrolling police cars.

In the type 1 system the car unit transmitter sends a characterising digital signal A to the receiver in the personal unit which, on recognising this signal, causes a unique digital signal B to be transmitted to the receiver in the car unit, which in turn responds to this signal B and renders inoperative the circuits which immobilise the car and allow the driver to drive the car away. An internal override, automatically disabled when the driver's door is opened, can be provided for safety on long journeys.

The use of the car is thus dependent on the existence of the unique signal B which can be either a modified form of the signal A or an independently coded signal.

In the type 2 system, depending on the application and life-time constraints, the 'hand-held' unit will transmit, either periodically or continuously or in an 'on demand' fashion, a unique code (equivalent to the code B in the type 1 system). This code is detected and analysed by the car unit and, if it matches the internally stored reference code, the unit will disable the alarm circuitry and proceed as for the first type of system allowing the driver the use of the car.

The basic circuits used in the transmitters and receivers are preferably integrated circuits, either single chip or hybrid, of standard form. The car unit for the type 1 system is preferably identical to the personal unit except that the memory in the receiver needs to store the same code A as the memory in the transmitter of the car unit and the memory in the car receiver needs to store the same code B as the memory in the transmitter of the personal unit.

The car receiver is connected to a number of immobilising and alarm circuits which disconnect the ignition circuit, immobilise the fuel pump, lock doors, bonnet and boot, and operate other security devices in the absence of the signal B from the personal unit. The personal unit may be in two interconnected parts, one being securely attached to say the inside pocket of the driver's jacket so that any attempt to steal the personal unit from the driver results in the connection between the units being broken as one is stolen thereby breaking the circuitry and preventing transmission of the code B signal.

In order that the invention may be fully understood, preferred embodiments thereof will now be described with reference to the accompanying drawings in which: Figure 1 shows the format of a message used in the personal and car units of a security system in accordance with this invention; Figure 2A, shows the basic components of the car and personal units of a security system type 1; Figure 2B, is a schematic diagram of the system shown in Fig. 2A; Figure 2C, is a schematic diagram of a security system type 2; Figure 3 is a schematic of the car unit in a security system type 1; Figure 4 is a schematic of the personal or hand-held unit of the security system type 1;; Figure 5 and 6 are schematics of personal and car units used in a security system type 2 such as that shown in Fig. 2C, whilst Figure 7 and 8 are simplified block diagrams of car and personal units of a security system type 2, Figure 9 is a block diagram of another form of car and personal unit type 1 system; Figure 10 is a block diagram of a preferred form of a car unit, and Figure 11 is a block diagram of a preferred form of portable unit for use in conjunction with the car unit illustrated in Fig. 10.

The heart of the security system to be described lies in the codes used by the car and personal units. These codes are incorporated in a message which comprises several segments of (n + 1) 8-bit words the format being shown in Fig. 1. The value of n is determined by the transmission link to be used and the stability of the frequency determining components in both the transmitter and receiver. The number of segments is then uniquely determined by the length of the individual identifying codes and the chosen value of n. Within each segment, the first word is identified by its first two bits, which are 1, 0 respectively. The first word is completed by the first 6-bits of the user identifying code. It will of course be appreciated that the words comprising the unique code may be of any predetermined number of bits.The unique codes are stored in programmable read-only-memories and are read out therefrom on receipt of a signal from the control logic located in the car or personal unit as shown in Figs. 3 and 4. As shown in Fig. 2A the car unit 1 and the personal unit 2 each comprise a transmitter 3 and a receiver 4.

Programmable read-only memories (PROM) 5 each storing the same uniquely coded words A, are associated with the transmitter of the car unit and receiver of the personal unit whilst PROM's 6, each storing the same uniquely coded words B, are associated with the receiver of the car unit and the transmitter of the personal unit. A number of security circuits 6 are coupled to the receiver of the car unit and, in the absence of the personal unit, disable the car's ignition circuit and petrol pump, lock the doors, bonnet and boot and enable alarm circuits which give a visual and/or audible alarm signal if any attempt is made to remove the vehicle or any contents therefrom or tow the vehicle away. The range of the transmitters in the car and personal units need only to be metre or so.

In operation the receiver in the personal unit carried by an authorised driver on approaching the car picks up a message containing the code words A transmitted from the car unit transmitter and compares them with the code words A stored in the personal unit. If the comparison indicates that the received and stored words A are the same, the personal unit transmitter is enabled to send a message containing the uniquely coded words B to the car unit receiver where they are compared with the code words B stored therein. If the comparison indicates that the received and stored words B are the same, a signal is sent to the security circuits 6 which allow the doors to be unlocked and the car driven away without any of the alarm circuits being energised. The normal running of the car is therefore dependent of the presence of the personal unit which is uniquely associated with the car unit.Any attempt to drive or tow the car away or gain unauthorised access will result in the alarm circuits being operated.

In the type 2 system shown in Figs. 2C, 5 and 6, only one code is required, the authorised drivers personal unit transmitting this code in one of the time modes disclosed previously and on approaching the car, the car unit compares the incoming data stream with that stored in the memory of the car unit. On a comparison indicating that the incoming data stream contains the correct code, the alarm circuits are disabled. Practical implementation of the car and personal units for a security system 2 are shown in Figs. 7 and 8.

Referring now to Fig. 9 showing a system 1 type security system in more detail the personal unit 1 comprises an aerial 7 for receiving a message containing the unique code words A transmitted from the car unit, the message is passed on to the receiver 4 which includes a demodulator 8 for demodulating the received signals and passes the resultant data stream to a serial to parallel converter, for example, an 8 bit shift register 9 and a clock extractor 10 which is synchronised with the bit rate of the incoming data stream by the 1 6 clock run-in bits.At the end of the 1 6 clock run-in bits the 8 bit start code is fed to the register 9 whilst a counter 11 emits pulses to the progammable read-only-memory (PROM) 5 to read out the stored start code to a comparator 1 2 to which is applied the incoming start code from register 9 via a latch 1 3.

On recognition by the comparator 1 2 of the correct start code, the first 8 bit word of the unique code A is fed to the comparator 1 2 as it receives the first 8 bit word in the received message from the shift register 9 via the latch 1 3. On recognition of the correct word in the received message a latch signal is emitted by the comparator 1 2 to a latch 1 4 and the counter 11 then applies pulses to the PROM 5 which reads out the next 8 bit word of the unique code A to the comparator 1 2 as the latter receives the next word from the shift register 9 via latch 1 3. Again if the received 8 bit word is recognised by the comparator 1 2 as the same as that fed from the PROM 5, another latch signal is emitted to latch 14. The third word in the received signal is processed in an identical fashion to the first two words resulting in the comparator emitting a third latch signal to the latch 14 which then emits an enabling signal to the transmitter 3. The transmitter 3 of the personal unit then sends a stream of data containing the unique code B to the receiver 4 in the car unit which processes it in exactly the same way as the receiver 4 in the personal unit to provide an enabling signal to all the circuits 6 disabling various functions such as ignition, boot and bonnet locks, lights etc.

Preferably the output from latch 14 is applied to a 5 bit shift register whose stages are connected to a 5 input AND gate so that five cycles of checking the three 8 bit word unique code is required before the security circuits are operated by the output from the AND gate.

The personal unit is powered by the self contained, preferably, rechargable batteries and may include economiser circuitry which only energises the transmitter when the receiver receives a message and responds to the start code. Also the car unit is preferably powered by rechargable batteries so that it is independent of, but can be floated across, the vehicle's battery.

Figs. 10 and 11 illustrate a practical form of a type 1 security system in which the car and portable units each comprise identical integrated circuits with the car unit having additional security circuits incorporating alarm circuits 1 and 2 each formed from one half of IC7. Alarm circuit 2 produces an audible warning and alarm circuit 1, via latches (not shown) controls the car's ignition circuit, pump electrical supply, boot and bonnet locks.

In a preferred form of this embodiment the car and portable units include the following circuits.

IC1 type 4060 14 stage ripple carry binary counter with oscillator IC2;

1C3; type 4040 IC8 1 2 stage ripple carry binary counter IC4 type 4053 triple 2-channel analog multi plexer/demultiplexer IC5 type 4001 quadruple 2 input NOR gate IC6 type MC14500B microprocessor IC7; IC10 type 4013 dual D flip flop IC9 type lM6654 EPROM In Figs. 10 and 11, which illustrate the car and portable unit respectively, each EPROM, IC9 stores the programme for the microprocessor IC6 and the uniquely coded signals A and B, which are fed to the respective microprocessor under control of the programme in the EPROM and counter IC8.Timing signals are provided in the car unit by the serially connected chain of ripple carry binary counters IC1, IC2 and IC3, a crystal Cx of 32.768 KHz being coupled to the input of IC1 to provide the basic frequency. Only one counter IC1 with its crystal Cx controlled oscillator of 32.768 KHz is provided in the portable unit.

Latches connected to alarm circuit 1 hold the various ignition, pump and alarm circuits etc. in an open circuited or inactivated state until the car unit indicates that it has received the correct code from the portable unit.

In operation an 'Interogate' signal is provided by the driver's door lock, either when the correct key is inserted or as the lock is turned. This sets one half of IC10 through the S input and stops resetting of the counter IC3 which provides timing signals causing the code A signal to be fed from the EPROM to the microprocessor under control of the programme stored in the EPROM and the clocking signals provided by IC8, the other half of IC10 forcing the microprocessor IC6 into the transmit mode. The transmitter Tx, is switched on by a positive signal from the W output of the microprocessor which then feeds the A signal in serial bit form from the D input/output to the transmitter for transmission to the portable unit shown in Fig.

11. The receiver Rp receives the transmitted A signal and the microprocessor IC6 locks onto the incoming bit stream of the A signal by the timing signals provided by the counter IC1 and selected by a section of the multiplexer/demultiplexer IC4. The programme stored in the EPROM IC9 controls the microprocessor IC6 to compute the difference between code signal A and the A code stored in the EPROM. If the two correspond then the code B signal is fed from the EPROM to the microprocessor which is controlled by the programme stored in the EPROM and then fed to the transmitter Tx2 for tranmission to the car unit shown in Fig. 1 0.

The code B signal is received by the receiver Rc, fed to the microprocessor which then computes the difference between the received B signal and the B coded signal stored in the EPROM IC9 and if the two correspond it activates the flip flops IC7 to energise via the latches the ignition, boot, bonnet, pump circuits and hold off the audible alarm circuits 2.

So long as an interogate signal has been produced for at least 1 ms, the units repeat the above operation every 32 seconds, the timing provided by the Q3 output of IC3 in the car unit.

After the car unit transmits the A signal, it de-energises the transmitter and energises the receiver. If after one second no code B signal has been received from the portable unit then the car unit switches off the receiver Rc and switches on the transmitter Tx, which then transmits the code A signal again. If after four cycles of transmit/receive operation still no code B signal is received from the portable unit then four seconds later, i.e. after a total of eight seconds, the alarm circuit is energised to sound an audible alarm, the eight second timing signal being provided by the Q.2 output of IC2.After 1 7 minutes, a signal from the Q8 output of IC3 shuts off the audible alarm, the ignition circuits still being held in the de-energised state by the latches connected to alarm circuit 1.

The portable unit is energised by a battery, preferably of the re-chargeable type and has push button switch to de-energise the unit in an emergency. The portable unit when energised by the battery remains in the receive mode until the code A signal is received from the car unit after which it will switch to the transmit mode to transmit the code B signal after which it again reverts to the receive mode.

Thus the alarm circuits will be held off and the ignition, pump etc. circuits energised all the time the driver with the portable unit is near or in the car and the car unit is receiving the correct code signal B. Operation continues as the driver starts the car and drives off. Should an emergency occur, such as the driver being attacked by an unwelcome passenger or the driver feels unwell, the switch on the portable unit can be operated and on the occurrence of the thirty-two second timing signal, the ignition circuits via the latches will be de-energised stopping the car and the alarm circuits energised to give an audible alarm.

The car unit may be provided with separate transmit and receive aerials in which case the microprocessor can be programmed to feed the code A signal to the transmitter and then receive the code B signal from the portable unit instead of switching the transmitter Tx, and receiver Rc on and off alternately.

Whilst both the type 1 and type 2 security systems have been described with reference to their use in cars, it will be appreciated that these security systems may be used in any situation where unauthorised entry, for example to a building, is to be prevented. The alarm circuits may, again via latches operate electromechanical bolts or doors or photo-sensitive devices controlling the opening of doors in buildings.

Claims

1. A security system comprising a portable unit and a control unit, the portable unit including a transmitter, a first store for storing a first uniquely coded signal and control logic to enable the transmitter to transmit the first coded signal stored in said first store; the control unit comprising a receiver to receive the first uniquely coded signal transmitted by said portable unit, a second store for storing a second uniquely coded signal, means for determining if a predetermined relationship exists between the received first coded signal and said second coded signal stored in said second store to produce an output signal if said predetermined relationship is established and at least one security circuit held normally in a disabled state to prevent operation of other equipment to which, in use, the security system is connected, the security circuit being responsive to said output signal to switch to an enabled state to allow operation of said other equipment.

2. A security system as claimed in Claim 1 in which said first and second stores each comprise a ROM and said first and second coded signals stored in said ROM's are identical.

3. A security system as claimed in Claim 1 or Claim 2 including a re-chargeable battery in said portable unit which comprises an interconnected two part housing, the battery being contained in one part and the transmitter, first store and control logic being contained in the other part, and a separable battery connection being mounted between the two parts so that on seperation of one part from the other the battery is disconnected from the transmitter, store and logic circuit.

4. A security system comprising a portable unit and a control unit; the control unit including a first store for storing a uniquely coded first signal, a first transmitter to transmit said first signal, a first receiver, and at least one security circuit, held normally in a disabled state to prevent operation of other equipment to which, in use, the security system is connected, said portable unit including a second store for storing a uniquely coded second signal, a second transmitter to transmit said second signal, a second receiver to receive the first signal transmitted by said first transmitter and a first recognition circuit for producing a first output signal upon recognising the first signal received by said second receiver and a logic circuit responsive to said first output signal to enable the second transmitter to transmit said second signal; wherein said first receiver includes a second recognition circuit to recognise the received second signal transmitted by said second transmitter to produce an output signal, said security circuit being responsive to said output signal to switch to the enabled state and thereby allow operation of said other equipment.

5. A security system as claimed in Claim 4 wherein said first and second stores comprise read-only-memories and the first uniquely coded signal is identical to the second uniquely coded signal.

6. A security system as claimed in Claim 4 wherein said control unit further includes an alarm circuit, a recyling counter producing output signals at predetermined intervals and a processor coupled to said counter to enable said first transmitter to transmit said first coded signal and then enable said first receiver to receive said second coded signal, said first transmitter and said first receiver being alternately enabled over a predetermined period of time; after which if no second coded signal is received, said alarm circuit is actuated.

7. A security system as claimed in Claim 4 in which each said control and portable unit includes a microprocessor, and a ROM, the ROM storing said uniquely coded signal and a programme controlling the operation of the microprocessor to read out the coded signal stored in the respective ROM and compare it with the received coded signal to produce said output signal.