GB2073808A - Electronic locks - Google Patents

Abstract

A key-operated switch for an electrical circuit, e.g. to control the ignition system of a vehicle, has a key removable from a co-operating socket, the key including a programmable read-only memory 14 connected to electrical contacts 12 on the key which contacts co-operate with contacts in the socket 15. A digital signal comparator compares the information in memory 14 with data stored in another read-only memory and gives an output to effect operation of a relay only if the compared data in the two memories agrees. <IMAGE>

Description

SPECIFICATION Improvements in or relating to key controlled electrical circuits This invention relates to key controlled electrical circuits. It is well-known to make use of removable keys for controlling electrical circuits.

Such arrangements are commonly employed for security purposes; for example the electrical ignition system for vehicles is commonly controlled by a removable key so that the vehicle cannot be operated without an appropriate key.

Heretofore it has been a common practice to provide a key shaped to co-operate mechanically with a lock system so that the user has to have an appropriate key. It is possible to make a large number of different key shapes but, within the practical limitations of cost, it is not possible, for example, to provide every individual vehicle owner with a key which is unique to the lock in his car. It is one of the objects of the present invention to provide an improved form of key-operated switch which can readily be made to provide a very large number of unique combinations of key and lock, that is to say combinations in which the lock and key are co-operatively arranged so that the lock can be operated only by the appropriate key and in which a key can only operate the appropriate lock.

According to this invention, a key-operated switch for an electrical circuit comprises a removable key and a socket arranged to receive the key, wherein the key includes a read-only memory for digital signals together with electrical contact elements on the key co-operating with contacts in the socket to provide an addressing circuit from the socket to the memory in the key and also to provide power supply connections to the memory from supply terminals in the socket, and wherein there is provided, in the socket or in a housing therefor, or electrically connected thereto, a second read-only memory, a digital signal comparator, means for addressing the two memories to feed data simultaneously from corresponding addresses to the comparator in sequence from different addresses in the two memories and circuit means operative on completion of a cycle of data comparison operative only if all the compared data in the two memories agrees to effect operation of a relay.

It is readily possible at present to obtain programmable read-only memories on a single chip containing storage for 32 words each of 8 bits. There are therefore 25632 possible combinations of binary digital data which can be stored in such a memory. A smaller memory containing storage for 1 6 words each of 4 bits would give 1 616 possible combinations, that is about 1.8 x 1 014. It is thus readily possible with such a system to provide far more possible combinations of data than would be required to give a unique key and lock for any practical requirement.Every road vehicle could have for example its own unique key and an associated electrical circuit which might be used for controlling the ignition system or which might be an electrical locking system or other security arrangement for the vehicle or some part thereof.

The key and socket may be made physically similar to conventional keys and lock-sockets; for example the key may be shaped so that only if the correct key is inserted, it can be turned in the socket. Such an arrangement is convenient so that the key can be inserted and rotated to a position where it is mechanically located in a correct position in the socket where co-operating electrical contacts on the key and in the socket engage one another.

By using electrically coded keys as described above, large number of keys, e.g. alleys for vehicles or a class of vehicles may be made visually identical in external appearance, although possibly having a registration or other identification number.

Preferably the key includes further contacts arranged to ensure that power supply from a power supply source is connected only to the electronic circuitry if the key is inserted in the lock socket to complete a power supply contact to the circuity.

The aforementioned relay is preferably located in a position such that it is not readily possible to obtain physical access to the relay. In a vehicle, such a relay might be mounted integrally in a starter motor housing and arranged so that, if the -relay contacts were open, the starter motor circuit cannot be completed. A similar relay could also be physically associated with the induction coil of an ignition system to prevent the ignition system operating without closing of the relay contacts. In a vehicle having an electrical fuel pump, a further relay might be associated with the fuel pump. By such arrangements, it can readily be made almost impossible for anyone to drive away a vehicle without the appropriate key even if deliberate attempts are made to obtain access to electrically energised components in order to short cut relay contacts.

Physically the key may be made similar to a conventional key, e.g. having a relatively large head with a shank for insertion into the lock socket. The memory in such an arrangement conveniently is embedded in the head with connections to a plurality of contacts spaced along the length of the shank. For securing the key in the socket, conveniently the key shank has a transverse projection or spigot which engages in a longitudinal slot in the socket and which, when the key is turned after insertion, holds the key in the socket.

The memory units conveniently are programmable read-only memories which can be pre-set to the required unique combination for each lock and key. Such programmable read-only memories can therefore readily be arranged so that, if required, two keys are avaiiable for a given lock or so that any one key may operate more than one lock if that is required.

The following is a description of one embodiment of the invention, reference being made to the accompanying drawings in which: Figure 1 is a view in side elevation of a key; Figure 2 is a plan view of the key of Figure 1; Figure 3 is an end elevation of a lock showing a socket adapted to receive the key of Figures 1 and 2; and Figure 4 is a block schematic diagram of the electrical components of the key-operated system.

Referring to Figures 1 and 2, there is shown a key having a head portion 10 and a cylindrical shank 11 of electrically insulating material The shank carries a number of electrical contacts 12, the function of which will be described later. Some of these contacts 12 are connected by conductors embedded in the key to a programmable read-only memory 14 which is embedded in the head of the key. In this particular embodiment, this memory has a capacity of 1 6 words each of 4 bits, although it would readily be possible to use a larger memory, e.g. 32 words of 8 bits if an increased number of distinct combinations is required. As shown in Figure 3, the lock has a socket 1 5 of generally circular section to accept the cylindrical shank of the key with the slightly protruding contact elements.The socket also has a guideway 1 6 for receiving a projection 1 7 on the end of the key shank so ensuring that the key has to be properly oriented about its axis for insertion into the socket. After insertion in the socket, the key can be rotated so that the projection 1 7 enters into a co-operating recess serving to hold the key in the socket. The socket has co-operating contacts (not shown) which engage the contact elements on the key.

Referring now to Figure 4, there is shown in block schematic form the electrical arrangement of the key together with the control system controlling a relay. As previously explained, this relay typically controls the application of electrical power to some equipment so that this equipment can be operated only by a key holder inserting a key in the lock. In Figure 4 the key is indicated diagrammatically by the unit 20. This key has a number of contacts indicated generally at 21,22 and 23 which co-operate with contacts 24, 25 and 26 respectively in the socket. The remainder of the electrical equipment is preferably.

associated physically with the equipment to be protected, the socket contacts being connected by ribbon or multicore cable or cables shown at 27, 28 and 29 to this equipment and to a power supply which is illustrated diagrammatically as having a positive terminal 30 and an earth terminal 31. The contacts 23, inter alia, provide connections when the key is inserted between the power supply terminal 30 and the remainder of the electronic circuitry so that no power is available for operation of the circuits unless the key has been inserted and rotated to a position where the appropriate contacts engage.

The key includes a programmable read-only memory as previously described which is shown in Figure 4 as a block 32 having output connections to connectors 21 for connection via contacts 24 and lead 27 to a comparator 33. The lead 28 forms an address highway which via contacts 25 and 22 serves for addressing the memory 32.

Power supply for the memory 32 is provided by leads 34 in the key which leads, by means of contacts 23, 26, are connected to a regulated power supply line 35 fed by a regulator 36 from the power supply source 30, 31.

A second programmable read-only memory 40, similar to the memory 32 is connected by a data link 41 to the aforementioned comparator 33. This memory 40 is supplied with power from the power supply 35 and is connected to the address highway 28 so that the two memories 32 and 40 are simultaneously addressed with the same address obtained from a binary counter 42. An oscillator 43 is provided which generates pulses for incrementing the counter. The oscillator frequency is not critical except in that it should be high enough to enable the required programme to be accomplished in a reasonably short time. The counter provides a 5 bit output to address each stored word in succession.The comparator unit 33 compares the addressed words in the two memories 32, 40. If the addressed words are found identical by the comparator, it produces a pulse on a lead 44 which increments a counter 45.

A "greater than and less than" detect circuit 60 with a latch 61 having external reset 62 controls an alarm 63 so that, if the compared numbers are, at any time, not equal, the comparator would produce an output indicative of this. The aiarm 63 may be local or may be remote and may, for example, be visual or audible. A strobe signal at the end of the first count-down from counter 42 is applied to gates in the inputs to the counter 45 and the detect circuit 64 so that these circuits operate only on completion of the count-down.

When the counter 45 reaches the full number of correctly compared addresses which are selected by counter 42, the counter 45 provides an output on a lead 46 which is converted to a stretched pulse in a pulse stretcher unit 47. This pulse stretcher unit 47 comprises a retriggerable monostable having a time constant determined.by a capacitor 48 and resistor 49, the time constant being selected so that the output pulse from the unit 47 is slightly longer than the time period taken to interrogate all the addresses. This output pulse is applied via a current limiting resistor 50 to the base of a relay driver transistor 51 controlling the current to the coil 52 of a relay having a contact shown at 53. A diode 54 across the relay coil safeguards the transistor 51 from reverse voltage spikes arising from the inductance of the coil 52.

It will be seen that unless a key is correctly inserted in its socket, there is no power supply to the electronic equipment, in particular to the relay operating coil 52. Thus removal of the key ensures that no power is consumed. When the key is inserted correctly so that the key contacts engage those in the socket, the electronic circuitry is energised. The counter 42 might initially be at any address and the first scan of the addresses would be abortive. If an alarm is provided, provision may be made to ensure that the alarm cannot be operated until after the end of the first scan. At the end of the first scan, the counter 42 resets itself and, via a lead 55, resets the counter 45. The equipment now addresses the two memories with the complete programme of addresses determined by the counter 42.The stored data is compared in the comparator 33 and, provided the stored data in the two memories'agree through the full sequence of addresses, then an output is provided to the pulse stretcher unit 47. Since this gives an output pulse longer than the period taken to interrogate all the addresses, a continuous signal will be provided on the base of transistor 51 so long as the two memories continue to be interrogated, that is to say so long as the key remains in its socket.

If a key without the correctly coded information in the memory store was inserted in the socket, no output would be provided to the monostable 45 and hence the relay would not be energised.

This form of key-operating equipment may be used for many different purposes. One example is for the security of vehicles. Typically the key socket may be on the dashboard of the vehicle and connected by a cable to an assembly containing the electronic components which assembly is preferably counted integrally in an item of equipment to be controlled. The assembly for example might be in the starter motor solenoid housing with the relay contacts 53 connected in series with the starter motor, thereby ensuring that the starter motor cannot be energised without the correct key having been inserted in the socket on the dashboard. The relay position inside the starter motor solenoid housing is not readily accessible and thus no one could readily bypass the relay contacts to render the key-operated security system ineffective.

Similar equipment might be incorporated in the ignition assembly or internal combustion engine, for example, inside the induction coil. In yet another example, an electrical fuel pump might be secured in the same way to prevent its operation without the correct key.

Another example of the application of the invention would be to the locking up of security areas, document storage rooms or cabinets, the relay serving to control the energisation of an electro-mechanical locking system. The required electrical power might be obtained in such an arrangement from a battery unit contained within the secured region or from a battery connected across contacts on the key for use when locking up or unlocking the secured region. Because of the very large number of possible ways of coding information in the memories, keys could not readily be copied. Much more generally, such keys could be used in a similar way for the securing of households, buildings or strongrooms. They may be employed additionally to or in substitution of other forms of locking systems.

For securing a door or the like, the relay 52 may be replaced by an electro-solenoid, powered by an integral battery which is normally float-charged from the standing supply, the battery being such that it can supply sufficient energy to operate the lock if power was temporarily disconnected or otherwise unavailable,

Claims (13)

1. A key-operated switch for an electrical circuit comprising a removable key and a socket arranged to receive the key, wherein the key includes a read-only memory for digital signals together with electrical contact elements on the key cooperating with contacts in the socket to provide an addressing circuit from the socket to the memory in the key and also to provide power supply connections to the memory from supply terminals in the socket, and wherein there is provided, in the socket or in a housing therefor, or electrically connected thereto, a second read-only memory, a digital signal comparator, means for addressing the two memories to feed data simultaneously from corresponding addresses to the comparator in sequence from different addresses in the two memories and circuit means operative on completion of a cycle of data comparison operative only if all the compared data in the two memories agrees to effect operation of a re-lay.

2. A key-operated switch as claimed in claim 1 wherein the key is shaped so that only if the correct key is inserted, it can be turned in the socket.

3. A key-operated switch as claimed in claim 2 wherein the key is rotatable in the lock only when it is mechanically located in a correct position in the socket where co-operating electrical contacts on the key and in the socket engage one another.

4. A key-operated switch as claimed in any of the preceding claims wherein the key includes further contacts arranged to ensure that power supply from a power supply source is connected only to the electronic circuitry if the key is inserted in the lock socket to complete a power supply contact to the circuitry.

5. A key-operated switch as claimed in any of the preceding claims wherein the key has a relatively large head with a shank for insertion into the lock socket

6. A key-operated switch as claimed in claim 5 wherein the memory is embedded in the head with connections to a plurality of contacts spaced along the length of the shank.

7. A key-operated switch as claimed in either claim 5 or claim 6 wherein, for securing the key in the socket, the key shank has a transverse projection or spigot which engages in a longitudinal slot in the socket and which, when the key is turned after insertion, holds the key in the socket.

8. A key-operated switch as claimed in any of the preceding claims wherein the memory units are programmable read-only memories presettable to the required unique combination for each lock and key.

9. A key-operated switch as claimed in any of claims 1 to 8 and installed in a road vehicle wherein said electrical circuit is arranged for controlling the ignition system and/or an electrical locking system or other security arrangement for the vehicle or some part thereof.

10. A key-operated switch as claimed in any of the preceding claims and installed in a road vehicle wherein said relay is located in a position such that it is not readily possible to obtain physical access to the relay.

11. A key-operated switch as claimed in either claim 9 or claim 10 wherein said relay is physically associated with the induction coil of an ignition system to prevent the ignition system operating without closing of the relay contacts.

12. A key-operated switch as claimed in either claim 9 or claim 10 and in a vehicle having an electrical fuel pump, wherein said relay is associated with the fuel pump.

13. A key-operated switch substantially as hereinbefore described with reference to the accompanying drawings.