KEY OPERATED SWITCH

Abstract: Key operated switches comprising a programmable key and a socket having interrogating electronics have hitherto used a system of electrical contacts to transmit power and further signals between the key and the socket. Such arrangements are susceptible to mechanical failure and vulnerability to static charges. In an embodiment of the invention disclosed, power is inductively transmitted (6), and further signals are opto-electronically transmitted (5) between the key and socket. The need for electrical contacts is, consequently, eliminated.

Description: KEY OPERATED SWITCH ^ 5 The present invention relates to a key operated switch and in particular to a key operated switch having a removable key with an electrical data memory and a receptacle with interrogating electronics arranged to receive the key. 10 It is well known for power and signals to be transmitted and received between the key and the interrogating electronics by means of a duplicity of phosphor-bronze self-cleaning contacts. Although potentially having a relatively long life, the 15 possibility of a mechanical failure resulting in the breakdown of the system does exist: such a breakdown would require the attention of a skilled engineer involving considerable time and expense. In addition, the known design involves the 20 inclusion of electro-sensitive components in the key: high static charges could gain access to these via the contacts resulting in catastrophic failure. Interrogation of the internal coding is also possible, necessitating a self-destruct circuit. 25 The object of the present invention is to provide a key operated switch which obviates the need for electircal contacts between the key and receptacle. In accordance with the present invention a key 30 operated switch for an electrical circuit comprises a removable key and a receptacle arranged to receive the key wherein the key includes electronic memory means containing key identifying data, a transmitter co-operable without contact with a corresponding 35 receiver in the receptacle for transferring key identifying data from the electronic memory means to the receiver, and a first inductor for connection to provide a power supply for the electronic memory means, and wherein the receptacle includes a second inductor for inductively coupling with said first inductor to supply power to the first inductor, a further electronic memory means containing lock identifying data, and circuit means for comparing key and lock identifying data and providing an output control signal in dependence upon the comparison. In one embodiment, the transmitter on the key comprises a light emitting opto-electronic device and the receiver in the receptacle comprises a light sensitive opto-electronic device. In another embodiment, the receptacle includes an alternating current power source for energising the second inductor and the key is responsive to the output of the first inductor to synchronise transmission, via the transmitter, of the key identifying data from the electronic memory means with the alternating current frequency. This allows the key identifying data to be clocked at a rate suitable for the subsequent comparison with the lock identifying data. In a further embodiment, the key is insertable into the receptacle and is adjustable to a position therein to allow the contactless engagement between the transmitter and the corresponding receiver. It will ' be apparent that the data transmitted from the key to the receptacle, at a rate determined by the clock, can be duplicated so that when the key is turned in one direction, the light emitting opto-electronic device couples with a receiver initiating an unlocking facility whereas when the key is turned in the opposite direction the light emitting opto-electronic device couples with a second receiver, initiating a locking facility. In one embodiment of the invention, the memory means may comprise an Electrically Programmable Read-only Memory. This type of key could be us ' ed in situations where it is desirable that data could be updated or modified for any reason. Alternatively, the lock could have a modifiable memory so that the standard type key could itself program a lock through the medium of a communicating system. This woulα be particularly useful in hotels where a random supply of keys would be available at reception, and, through the mains supply, it would be possible for the receptionist to program a specific room's lock for the period of a visitor's stay. If the key is lost then its particular coding would never again be used owing to the unique nature of this code. With 36 bits the total number of unique codes would be in the region of 64,000,000,000. In addition, keys could have a code allowing the rooms of one particular floor built in for the use of the staff for selective access and a master version for the management. If the requirement is that the Key Operated Switch be completely unpowered before the insertion of the Key then power could be connected via a suitable switch contact assembly operated accordingly. This could be achieved by means of a pair of contacts brought together by the pressure of the key's insertion. This does, however, introduce the possibility of mechanical failure. If a small quiescent amount of current is allowable, then full power could be switched by means of the inclusion of a proximity switch, or one involving a photo-electric switch. An example of the invention is illustrated in the accompanying drawings, in which Figs. 1 and 2 depict, partially in section, the key. Fig 3 depicts, in block diagram form, the electrical components in a pre-programmed key. Fig 4 depicts, in block diagram form the electrical components in the receptacle. Fig 5 depicts, in the block diagram form, the electrical components in a user-programmable key. The key is constructed so as to look and feel as much as possible like a normally accepted key. The' tab (1) includes a hole (2) suitable for its mating with a standard key-ring. The stem (4) which is comparable with the tang of a normal key, houses the secondary winding (6) as well as the infra-red emitting diode (5). The end (7), is fitted to the stem (4), and carries a locating pip (8) to ensure that the orientation of the key is maintained correctly to its related receptacle. It engages with an associated slot in the receptacle thus guiding and stopping it at the appropriate position so that the infra-red diode (5) is in the correct position to transmit information to an opto-transistor (19) located in the receptacle. The tab (1) also houses the custom designed integrated circuit (3) containing the circuit (9). The key can be made from any plastic material, except, to reduce wear, its tip (7) which could be in brass or similar metal. For convenience the tab (1) could carry a colour insert so that the user could recognise a particular key from many others on a ring, and also a code, known only to the manufacturer, to identy the code that is programmed into the embedded electronics. This makes it possible for replacement keys to be made available if it is so desired. Although this facility could be made available it should be recognised that its desirability is questionable. The electronics built into the key are depicted in figure 3 with the primary of the transformer (15) feeding a diode (16) to rectify the signal, charge the capacitor (17) and thus produce a smoothed direct current to energise the custom-designed integrated circuit (9). In addition the infra-red emmitting diode (18), is fed by the driver circuit (4) and transmits the data to the outside world. The custom-designed integrated circuit (9) contains a shaping circuit (12) to square up the incoming signal from the primary (15) and so present a more acceptable signal to the shift-register (11). This shift register can be any length as is reasonable but it is suggested that the number of bits be between 32 and 40 for the general economic factors involved in the manufacture of such a device. The programmable logic circuit (10), containing the resident code of the key is constructed so that the program is non-volatile. Programming would be by means of fusable link techniques or by the connection of logic gates to positive or common to produce logic ones and zeroes by means of lasers during the programming phase of manufacture. The program would therefore be permanently resident in the device (9) and unavailable for modification by any means. A 1 power-on-load' circuit (13) would ensure that the program was loaded into the shift register (11) on energisation and the output from the shift register (11) drives the infra-red diode (18) by means of a driver circuit (14). The key may be made re-programmable if the programmable logic is replaced with an Electrically Programmable Read-only Memory (20) as shown in Figure 5, and a photo-transistor (21) is fitted in the stem. This would be supplied with a signal containing a code plus new data from the outside electronics which would initiate the writing of the new data into the memory via a shaper and decoder (22) and a read/write control (23). The interrogating electronics could be integral with the receptacle or maybe at a distance from the secure area. In the standard condition and referring to Figure 4, the data from the key is detected by the photo-transistor (19), shaped by the circuit (20), and compared, digitally, with a similar custom-designed integrated circuit to that in the key. The comparison is made sequentially, each bit is strobed (22) and those providing equality are counted (28) and, if the total number of strobe pulses equals the total number of bits, a 'flag' is generated to energise the controlled device through a suitable interface (29). The clock generator (23) runs at any convenient rate and is gated by circuit (25) so that after the correct number of bits designed ^ into the system has been generated a slot where no clock pulses are available is produced. This initiates a loading of the program into the shift register (13) and (38) and to the reset gate (27), thus resetting the strobe counter (28) before the next interrogation. The gated counter (25) controls the power switcher (30) to supply the key via the primary winding (31). A power conditioner (32) generates the correct operating supply for the system from whatever input is available. In the version where the system is totally quiescent, a switch (33) is operated by the insertion of the key. Uses for the design are particulalrly in the area of vehicle security, where the interrogating electronics may be integrated in the solenoid of a p ' re-engaged starter. This obviates the casual user of the vehicle without the key from starting the engine by normal means and if an additional switched clock is produced from this circuitry other components such as the ignition coil, fuel pump, etc., may be controlled through signal switches again integrated into their interiors. Further possible protection could be afforded by way of an alarm facility which is only disabled by the correct key. Other access control could be available in housing, boats, offices, factories, filing cabiets, brief cases, computers and in particular, control of software by a specific authorised person. Software could be actually protected by means of the key's code being embedded in the relavant media, denying access to casual operators and ensuring security with a more easily acceptable approach.

Claims: CLAIMS 1. A key operated switch for an electrical circuit comprising a removable key and a receptacle arranged to receive the key wherein the key includes electronic memory means containing key identifying data, a transmitter co-operable without contact with a corresponding receiver in the receptacle for transferring key identifying data from the electronic memory means to the receiver, and a first inductor for connection to provide a power supply for the electronic memory means, and wherein the receptacle includes a second inductor for inductively coupling with said first inductor to supply power to the first inductor, a further electronic memory means containing lock identifying data, and circuit means for «comparing key and lock identifying data and providing an output control signal in dependence upon the comparison. 2. A key operated switch as claimed in Claim 1 wherein the transmitter on the key cooperating without contact with the receiver in the receptacle comprises a light emitting opto-electronic device, and the receiver in the ' receptacle comprises a light sensitive opto-electronic device. 3. A key operated switch as claimed in any proceeding claim wherein the receptacle includes an alternating current power source for energising the second inductor and the key is responsive to the output of the first inductor to synchronise- transmission, via the transmitter, of the key identifying data from the electronic memory means with the alternating current frequency. 4. A key operated switch as claimed in any preceding claims wherein the memory means comprises an Electrically Programmable Read-only Memory. 5. A key operated switch as claimed in any proceeding claims wherein the key is insertable into the receptacle and is adjustable to a position therein to allow the contactless engagement between the transmitter and the corresponding receiver. . 6. A key operated switch as herein described with reference to the accompanying drawings.

Inventors: BLOCH MAURICE, HASKELL HARRY AINSWORTH, BLOCH, MAURICE, HASKELL, HARRY, AINSWORTH
Applicants: AINSWORTH HASKELL HARRY, BLOCH MAURICE, BLOCH, MAURICE, HASKELL, HARRY, AINSWORTH
Application year: 1987
Main classification: E05B49
IPC codes: G07C9