GB2146892A - Key control system - Google Patents

Abstract

A key control system has a first coding element 12 which is located in a key hanger 10 and has a plurality of possible rotational positions which are selected to differentiate between different key hangers 10. The first coding element has a peg 13 extending therefrom, which co- operates with an opening 23 in a second coding element 22 located in a key holder 20. The second coding element 22 also has a plurality of rotational positions within the key holder 20 such that the first and second coding elements can be rotated to co- operating positions wherein the holder 20 may be hung from the hanger 10. If an attempt is made to hang a holder 20, which has its coding element 22 rotated to the wrong position, from the hanger 10, the holder 20 will not hang correctly from the hanger 10. <IMAGE>

Description

SPECIFICATION Key Control System The present invention relates to key control systems and provides an improved system of key control for use in situations where security is important.

Prior art key control systems usually comprises a board or cupboard having numbered hooks and a plurality of correspondingly numbered key rings. In these prior art systems, keys can be placed on the incorrect hook, providing an incorrect indication that a particular key is present when it is not. To a degree this problem can be overcome by colour coding the key rings of important keys, however, this does not prevent keys from being removed from key rings or swapped about.

In key control systems where keys are controlled closely by a signing-out and signing-in procedure, the security of the system is dependent upon the diligence of the supervising officer. When short-cuts are taken with these procedures it is possible for the wrong keys to be handed in and whether this is done by accident or otherwise, a serious security risk can arise.

In a key control system according to the present invention, key rings or holders are encoded in such a way that they cannot be placed incorrectly on the key control board without the error being obvious, thereby at least reducing the possibility of errors which may lead to a security risk.

According to a first aspect, the present invention consists in a key control system comprising a plurality of hanging means, and a plurality of key holder means each of which is adapted to hold a key, each of said hanging means including a first coding element, and each of said holder means including a second coding element, said first and second coding element each having a plurality of possible states and each of the possible states of the first coding elements corresponding to a cooperating state of the second coding elements, and the hanging of one of said holder means in correct orientation on one of said hanger means being possible only when the first coding element of said one hanger means is in the co-operating state corresponding to the state of the second coding element of said one holder means.

According to a second aspect, the present invention consists in a key storage unit for a key control system, said key storage unit comprising a plurality of hanging means, each of which includes a coding element having a plurality of possible states, said each hanging means being adapted to hang a key holder in correct orientation when a cooperating coding element of said holder is in a state corresponding to the state of the coding element of the hanger means, the coding element of the holder having a plurality of possible states each of which corresponds to a respective one of the possible states of the coding element of the hanging means.

According to a third aspect, the present invention consists in a key holder for a key control system, said holder being adapted to hold a key or keys and including coding means having a plurality of possible states, said holder being adapted to hang in correct orientation from a hanger when a cooperating coding element of said hanger is in a state corresponding to the state of the coding element of the holder, the coding element of the hanger having a plurality of possible states each of which corresponds to a respective one of the states of the coding element of the key holder.

Preferably the key holder is attached to the key in such a manner that the two cannot be separated without destruction of the key holder. This may be achieved for example by providing a loop extending from the body of the holder which may be threaded through the head of a key, the end of the loop being provided with a locking projection which can be irreversibly inserted into an opening in the body of the holder such that the key cannot then be removed from the holder without breaking the loop or the body of the holder. Alternatively the end of the loop may be terminated with a pin adapted to be secured in a screw terminal mounted within the body of the holder, the holder body being in two halves which are irreversibly locked together once the pin has been secured.

In one form of the invention the coding element of the hanger comprises a peg having a cross section which can be of any shape other than circular, the peg having a coding portion by which the peg is mounted to a base which has an opening into which the coding portion is inserted. The codirig portion is of a different cross section to the peg, the cross section of the coding portion having a regular shape which is capable of occupying a plurality of discrete rotational positions when inserted into an opening of a co-operating cross-sectional shape.The peg, on the other hand, will preferably have a crosssectional shape which when inserted into a cooperating opening in the coding element of the key holder is capable of occupying a number of discrete rotational positions therein, having no common factor with the number of possible discrete positions which the coding portion of peg may occupy. This condition is best achieved by providing the peg with a cross-section which has only one possible rotational position in the co-operating opening.

The coding element of the holder will have an outer shape which has the same rotational states as the coding portion of the peg and occupies a co-operating opening in the holder such that a holder assigned to a particular peg may have its closing element set to the same rotational position as the coding element of the peg thereby allowing the holder to occupy the correct orientation when placed on the peg. Holders having the coding element set to the wrong position will sit askew when placed on the peg and will therefore be immediately recognisable as being incorrectly placed in the key storage unit.

In addition to the visual indication of an incorrectly placed key holder, an extended embodiment will also include additional indicating means such as electrical contacts positioned to make contact only when the holder is in the correct orientation. These contacts can be incorporated into an alarm system or a computerised logging system and in a preferred embodiment the key holder will include a circuit which must be broken in order to remove the key from the holder, thereby preventing a holder with its key removed from closing the contacts in the key storage unit.

It is also envisaged that colour coding or different shaped pegs be used to increase the number of unique codes available and electrical encoding may also be employed within the key holder to distinguish key holders of different key control systems, for example.

In a preferred embodiment, each hanger includes two pegs, each having a coding portion in the shape of a wheel from which a plurality of equally spaced projections extend about its periphery. The coding pegs preferably have a cross-sectional shape which is a non-equilateral triangle and in the preferred embodiment each coding portion has 20 peripheral projections. By providing 2 coded pegs for each key hanger, the number of possible codes is increased significantly, the number of possible combinations being 400 in the preferred embodiment.

In an extended form of the invention this number of combinations is further increased by providing a plurality of cross-sectional shapes for the pegs.

In the preferred embodiment, an electrical connection between the hanger and the holder is provided by way of an earphone jack and socket, the circuit within the holder including a wire passing through the loop upon which the key hangs, the loop forming part of a circuit which is closed while the key is correctly hung on the hanger such that removal of the key from the holder, by breaking the loop, also breaks the closed circuit Preferably the holder also includes a coding circuit which allows the holder to be interrogated and identified electrically when the holder is hanging on the hanger.In the preferred embodiment the electrical coding means comprises a fixed resistance selected from a predetermined set of resistances and the interrogating circuit includes an analog to digital converter connected to a computer or microprocessor, the microprocessor being programmed to monitor key usage and to provide alarms for incorrect usage.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawing, in which: Figure 1 illustrates a holder and hanger according to a first embodiment of the present invention; Figure 2 illustrates a holder and hanger according to a preferred embodiment of the present invention; Figure 3 illustrates the holder and hanger of Figure 2 in a partially assembled state; Figure 4 illustrates a partial side view of a board to which the hangers of Figures 2 and 3 are attached; Figure 5 illustrates a partial sectional view through section line V-V of the hanger of Figure 3 when mounted on a board such as that of figure 4; Figure 6 schematically illustrates an electric system adapted to monitor a key control system made in accordance with the embodiment of Figures, 2,3,4 and 5; and Figures 7 and 8 are flow charts of routines which control the operation of the key control monitoring system of Figure 6.

Referring to Figure 1, a base 10 is provided with a hexagonal opening 11 designed to accept the base portion 12 of a coding peg 13. The base portion 12 is provided with ridges 14 along some or all of its edges which co-operate with groove 15 within the hexagonal opening 11 to lock the base portion 12 into the opening 11 once it is inserted therein. Other retaining methods such as gluing or welding may also be used to retain the base portion 12 in the opening 11. The base portion 12 may occupy any one of six discrete rotational positions such that the peg 13 may have six different orientations. It will be recognized, however, that the base portion may have any number of sides, a hexagonal base being chosen for the purpose of description to simplify the illustrations.

A key holder or key ring 20 has a loop or ring 26 passing through a key 27 and the end of the loop 26 being provided with a serrated end portion 28 which co-operates with an opening in the body of the holder 20, such that when the end portion 28 is inserted into the opening, it cannot then be retracted without destroying the body of the holder 20.

Therefore, a key placed on the loop 26 cannot be removed without either breaking the loop or destroying the holder.

The body of the holder 20 is provided with an opening 21 of a similar shape (i.e. hexagonal) to the opening 11 in the base 10, and a coding element 22 is shaped to fit into the opening 21, the coding element having a hole 23, with a sectional shape corresponding to the shape of the peg 13, passing through it. The coding element 22 may therefore be inserted into the opening 21 with the hole 23 oriented in any one of six directions corresponding to the six possible orientations of the peg 13. It should be noted that the sectional shapes of the peg 13 and the hole 23 should not be chosen to be equilateral triangles or any other symmetrical shape where the number of discrete rotational positions of the peg 13 in the hole 23 has a common factor with the number of rotational positions of the base 12 in the opening 11.The preferred sectional shapes for the peg 13 and hole 23 include isocelestriangles and semi-circles.

As with the base 12, the coding element 22 may be retained in the opening 21 by ridges 24 which co-operate with grooves 25 or alternatively may be glued or welded in place.

The hood 18 may optionally be provided as a guide to ensure correct orientation of the key holder 20 with respect to the base 10, the bottom surface of the hood co-operating with the top surface of the holder to prevent the holder from being placed on peg 13 unless the top surface of the holder is essentially horizontal. Retaining means may also be incorporated in the hood if desired. The guiding function of the hood 18 may also be provided by posts of various sections, co-operating with peripheral surfaces of, or openings provided in, the holder 20.

In an extended form of the invention electrical contacts may be provided in the base 10 by way of springs 17, co-operating contacts (not shown) being provided on the back of the holder 20 such that when the holder 20 is hanging in a vertical orientation on the base 10 (base 12 and coding element 22 in the same relative rotational positions), the contacts on the holder 20 make contact with the springs on the base 10. By providing a connection within the holder 20 between the contacts (not shown) an interrogation circuit associated with the key control system may be used to determine when a key is in position in the key control board.

Preferably the connection between the contacts on the holder 20 are connected by a conductor which passes through the centre of the loop 26 such that if the loop is broken and the key removed, the placement of the holder 20 on the base 10 will not be registered by the interrogation circuit. The connection may be further encoded by providing a component such as a resistor or capacitor which co-operates with the interrogation circuit to identify the key holder as being one of the set of holders belonging to the system in question. The internal component of the holder 20 could, for example, provide one of the elements of a timing circuit within the interrogation circuit.

When contact springs are used to provide electrical contact between the base 10 and the holder 20, friction between the peg 13 and the hole 23 may not be great enough to prevent the holder from being pushed away from the base by the spring pressure in which case a small projection 16 may be provided on the peg 13 which co-operates with a small depression within the hole 23 to retain the holder 20 on the peg 13, however, this method of retention may be replaced by retaining means provided under the optional hood 18, and similarly, the electrical contacts 17 may be replaced by contacts positioned under the hood 18 and making contact with co-operating contacts (not shown) provided in the top surface of the holder 20. Clearly many other mechanical equivalents to these arrangements are also possible.

If more than two electrical connections are provided between the holder 20 and the base 10 digital encoding techniques may also be employed wherein any particular key holder or set of holders provide connections between a unique combination of the connecting points.

Referring now to Figures 2 and 3, a hanger 30 and holder 40 made in accordance with a preferred embodiment of the invention are illustrated, the hanger 30 having two pegs 33 upon which the holder 40 is hung, each of the pegs 33 being adapted to pass through an opening 43 in a coding element 42 to thereby suspend the holder 40. Each of the pegs 33 are inserted from the back of the hanger 30 through an opening 31 such that the pegs 33 project out of the openings 31 to provide a means of suspending the key holder 40. The coding portion 32 of the peg 33 engages with a co-operating portion of the opening 31, when the peg is fully inserted, such that, once inserted the peg retains a fixed rotational position, which is one of 20 possible positions defined as a result of the shape of the coding portion 32 and its co-operating opening.Similarly, each of the coding elements 42 has a shape which can occupy 20 different rotational positions within its corresponding opening 41. The sectional shape of each peg 33 and the shape of its co-operating opening 43 are selected such that the peg 33 can only be inserted into the opening 43 in one orientation in order to maximize the number of coding combinations available. Suitable shapes for the coding peg 33 are, non-equilateral triangles, semicircles and any other shape which lacks rotational symmetry. Symmetrical shapes can also be used for the pegs 33 if the coding portion 32 of the pegs were to be located off centre with regard to the remainder of the peg in which case the opening 43 of the coding element 42 would be similarly located in an off centre position.

Electrical connection between the hanger 30 and the holder 40 is provided by way of an earphone jack 37 projecting from the hanger 30 and a co-operating socket (not shown, except for rear connections 57) mounted in the back of the holder 40 under the printed circuit board (PCB) 56 with its rear connections 57 soldered thereto. The PCB 56 is maintained in position by mounting screws 55 and in turn provides for the mounting of components associated with the electrical detection and identification of the holder. In the present embodiment, the holder is identified electrically by the provision of a series resistor in the detection circuit, the detection circuit comprising a closed loop connected between the contacts 57 of the earphone socket and including a wire loop 46 passing through the head of the key 47.A first end of the wire 46a is soldered to the PCB 56 while the second end 46b is fitted with a terminal pin 48 adapted to be inserted into a terminal block 54 and secured with a grub screw 53, the terminal block providing electrical connection with the PCB 56.

The wire 46 extends from the PCB 56, about a plurality of anchor posts 52 and through an opening 51 in the housing of holder 40. When a key 47 is attached to the holder 40, the wire 46 is threaded through the head of the key 47 and then fed through a second opening 58 in the housing of the holder 40, passed around anchor posts 59 and then to terminal block 54.

The housing of the key hanger 40 comprises two housing halves 60a and 60b, the first of which 60a is illustrated in Figure 3 and holds the coding elements 42, and the PCB 56, while the second housing half 60b simply closes the housing and retains the coding elements 42 in position. The two housing parts are held together by a series of pins and sockets the pins 52, 59 and 61 of the first housing half 60a being barbed and the co-operating sockets (not shown) of the second housing half 60b being internally ribbed, such that when the two housing halves are pressed together, the barbed pins 52, 59 and 61 irreversibly engage with their co-operating sockets to permanently connect the housing halves.

Accordingly, once the key 47 is threaded onto the wire 46, the terminal pin secured in terminal block 54 and the housing halves connected together, the key cannot be removed from the holder without cutting the wire 46 or physically damaging the holder.

The hanger 30 is provided with mounting holes 70, including a hexagonal recess 71 adapted to accept the head of a bolt used to mountthe hanger to a mounting panel 72 (referto Figure 4). The mounting panel 72 is formed of ribbed steel, with the ribs running horizontally, such that with the hangers 30 located on the raised portions of the panel, the keys hanging from the suspended holders (not shown in Figure 4) would hang well clear of the panel, thereby reducing noise and avoiding damage being caused to the panel by scratching of the keys on the surface of the panel. The use of ribbed steel also provides spaces 73, behind the ribs, through which electrical wiring to the rear contacts 74 of the earphone jacks 37 can be conveniently run.

Referring to the detailed cross-section of Figure 5, each of the hangers 30 is bolted to the ribbed steel panel 72 by a nut 76 and bolt 75, the head of the bolt being located in the hexagonal recess 71 to prevent tampering and the nut 76 being located behind the panel 72 where it is inaccessible without removing the panel.

The panel 72 is pivotably mounted by hinges (not shown) to a backing panel 77 and is lockable in a closed position wherein access to the back of the mounting panel 72 is prevented by the proximity of the backing panel 77.

Turning to Figure 6 an electronic monitoring system includes a microprocessor unit (MPU) 80 connected to Data Address and Control Busses 81, 82 and 83 which enable communication of the MPU 80 with Random Access Memory (RAM) 84, Read Only Memory (ROM) 85, an Analog to Digital Converter (ADC) 86 and various other InputlOutput (I/O) Interfaces 87. The ADC 86 is in turn connected to a plurality of hangers 30 by way of an analog multiplexer (MUX) 88, which selects one of a plurality of analog input channels in accordance with a channel select word held in a Channel Select Register 89.The channel select register also communicates with the MPU 80 via the Data, Address and Control Busses 81, 82 & 83 to enable the MPU to load a channel address, for the next analog channel to be read, under program control .15 The analog inputs to the MPX 88 are each generated by a resistor divider comprising a coding resistor Rc located in a key holder 40 which is suspended from a hanger 30, and a fixed reference resistor RF associated with the hanger 30. The divider circuit is supplied from a fixed reference voltage (VREF) and the valves of Fc and RF are selected to give an output greater than V,,EF,2 when the key holder 40 is in position on the hanger 30, divider outputs of less than REF/2 being interpreted as indicating that the holder 40 is not correctly positioned.The valve of the resistor Rc is selected from a predetermined set of permissable values to enable electronic identification of keys which supplements the physical coding system.

The MPU 80 runs under the control of a stored program, contained in ROM 85 and any restrictions relating to the issuing of keys are defined within the stored program. The stored program logs key movements and generates reports at periodical intervals by way of the printer 91 to which information is passed via one of the l/O interfaces 87. Under certain circumstances an alarm 92 will also be operated, via one of the I/O interfaces 87 under control of the stored program, in response to the occurrence of predefined conditions.

The stored program which controls the MPU 80 comprises a plurality of routines, under the control of an Executive Program which ensures that the various tasks performed by the system are carried out in the correct order of priority. Many operational schemes are possibleforthe hardware illustrated in Figure 6, however, in the preferred embodiment, a timer is implemented either in hardware or in software or both, and the Executive Program calls the Key Monitor Routine and the Log Printing Routine at predetermined intervals measured by the timer. In the embodiment of Figure 6, a timer/ interrupt generator 93 is connected to the MPU 80 via the control bus and a timer software routine keeps track of elapsed time by counting these interrupts.

Referring to Figure 7, the routine for monitoring key status is illustrated in flow chart form. Upon entering this routine a variable used to keep track of key positions on the key storage board 73 is initialized to represent the first key position and the analog multiplexer address is set to select the input channel corresponding to the first key position. The Analog to Digital conversion is then commenced and the program then loops until conversion is completed. Upon completion of the conversion, the Analog to Digital Converter is read, the next MPX channel selected and a new conversion commenced. The output of the Analog to Digital Converter, which has just been read, is then checked to see if the key is present and if so whether the value read corresponds to the correct key.If the incorrect key code is returned, an alarm condition exists resulting in the setting of an alarm condition code. The key number is then checked against a table of restrictions to determine if the present status of the key represents a breach of those restrictions. Under some conditions a breach of restrictions will result in the setting of the alarm condition code. The time and key status are then logged in memory and the alarm condition code tested and if the condition code is set the alarm is sounded. Finaily the key number is incremented and tested to determine if all key positions have been scanned. If all key positions have been scanned, the program returns to the calling program, otherwise the program loops back to test if the next analog to digital conversion is complete.

At regular time intervals, the executive program calls a second routine, illustrated in flow chart form in Figure 8. This simple routine, formats the data which has been logged over the preceding period of time and then prints this information as a report, before returning control to the calling program.

The executive program may also perform various system tasks such as handling user interrogations of the logged data and providing access to system maintenance programs if access conditions are met.

It will be recognised by persons skilled in the art that numerous variations and modifications may be made to the invention as described above without departing from the spirit or scope of the invention as broadly described.

Claims (36)

1. A key control system comprising a plurality of hanging means, and a plurality of key holder means each of which is adapted to hold a key, each of said hanging means including a first coding element, and each of said holder means including a second coding element, said first and second coding elements each having a plurality of possible states and each of the possible states of the first coding elements corresponding to a co-operating state of the second coding elements, and the hanging of one of said holder means in correct orientation on one of said hanger means being possible only when the first coding element of said one hanger means is in the co-operating state corresponding to the state of the second coding element of said one holder means.

2. The key control system as claimed in Claim 1 wherein the first and second coding elements each have a plurality of rotational states defined by the interrelationship of the shape of said each coding element and a co-operating opening into which it is fitted.

3. The key control system as claimed in claim 2 wherein each said hanging means comprises a peg extending from the respective first coding element, the peg being adapted to co-operate with an opening in the corresponding second coding element to enable the respective holder means to be suspended from the peg and said peg having a number of rotational positions in said corresponding opening, the number having no factor in common with the number of rotational states of the first coding element.

4. The key control system as claimed in claim 3 wherein each peg may occupy only one rotational position in its corresponding opening.

5. The key control system as claimed in any one of the preceding claims, wherein means are provided to prevent one of the holder means from being suspended from any one of the hanging means unless the holder means can be suspended in a substantially vertical position.

6. The key control system of claim 5 wherein each hanging means includes a pair of said first coding elements and each of said holding means includes a pair of said second coding elements, each of said pairs of coding elements being disposed in similar relationship.

7. The key control system of claim 5 wherein each hanging means is provided with a guide which prevents a holder means from being suspended therefrom at an incorrect angle.

8. The key control system as claimed in any one of the preceding claims, wherein each hanging means and each holder means are provided with electrical contact means to enable electrical detection of holder means suspended from the hanging means.

9. The key control system of claim 8 wherein said electrical contact means comprises an earphone jack extending from the hanging means and a co-operating socket in said holder means.

10. The key control system of claim 9 wherein an electrical circuit is provided in said holder means comprising a loop connected between two contacts of said socket.

11. The key control system as claimed in claim 10 wherein said loop includes a wire used to attach said key to its holder means.

12. The key control system as claimed in claim 11, wherein the electrical detection of the holder means is performed by a microprocessor system.

13. The key control system as claimed in claim 12, wherein said loop includes a series resistor.

14. The key control system as claimed in claim 13 wherein the microprocessor system includes means for measuring the series resistor.

15. The key control system as claimed in claims 12, 13 or 14, wherein the microprocessor logs the presence of each holder means when it is suspended from its respective hanging means.

16. The key control system as claimed in any one of the preceding claims, wherein each coding element is in the shape of a wheel from which a plurality of projections extend in equal spaced relation.

17. The key control system as claimed in claim 16 wherein each coding element has 20 projections located about its peripheral edge and extending radially outwardly.

18. A key storage unit for a key control system, said key storage unit comprising a plurality of hanging means, each of which includes a first coding element having a plurality of possible states, said each hanging means being adapted to hang a key holder said key holder including second coding element and being adapted to be hung only when the second coding element is in a state corresponding to the state of the first coding element of the hanger means upon which it is hung, the second coding element having a plurality of possible states each of which corresponds to a respective one of the possible states of the first coding element.

19. The key storage unit as claimed in Claim 18 wherein the first and second coding elements each have a plurality of rotational states defined by the interrelationship of the shape of said each coding element and a co-operating opening into which it is fitted.

20. The key storage unit as claimed in claim 19 wherein each said hanging means comprises a peg extending from the respective first coding element, the peg being adapted to co-operate with an opening in the corresponding second coding element to enable the respective holder means to be suspended from the peg and said peg having a number of possible rotational positions in said corresponding opening, the number having no factor in common with the number of rotational states of the first coding element.

21. The key storage unit as claimed in claim 20 wherein each peg may occupy only one rotational position in its corresponding opening.

22. The key storage unit as claimed in any one of claims 18to 21,wherein means are provided to prevent one of the holder means from being suspended from any one of the hanging means unless the holder means can be suspended in a substantially vertical position.

23. The key storage unit of claim 22 wherein each hanging means includes a pair of said first coding elements and each of said holding means includes a pair of said second coding elements each of said pairs of coding elements being disposed in similar relationship.

24. The key storage unit of claim 22 wherein each hanging means is provided with a guide which prevents a holder means from being suspended therefrom at an incorrect angle.

25. The key storage unit as claimed in any one of claims 18 to 24, wherein each coding element is in the shape of a wheel from which a plurality of projections extend in equally spaced relation.

26. The key storage unit as claimed in claim 25 wherein each coding element has 20 projections located about is peripheral edge and extending radially outwardly.

27. A key holder for a key control system, said holder being adapted to hold a key or keys and including a first coding element having a plurality of possible states, said holder being adapted to hang from a hanger having a second coding element, the second coding element having a plurality of possible states each of which corresponds to a respective one of the states of the first coding element and said holder hanging in correct orientation when said second coding element of said hanger is in a state corresponding to the state of the first coding element of the holder.

28. The key holder as claimed in claim 27 wherein the first and second coding elements each have a plurality of rotational states defined by the interelationship of the shape of said each coding element and a co-operating opening into which it is fitted.

29. The key holder as claimed in claim 28 wherein each said hanger includes an opening formed in the respective first coding element, the opening being adapted to co-operate with a peg extending from the corresponding second coding element to enable the respective holder means to be suspended from the peg and said peg having a number of rotational positions in said corresponding opening, the number having no factor in common with the number of rotational states of the first coding element.

30. The key holder as claimed in claim 29 wherein each peg may occupy only one rotational position in its corresponding opening.

31. The key holder of claim 30 wherein each holder means includes a pair of said first coding elements and each of said hanger, including a pair of said second coding elements each of said pairs of coding elements being disposed in similar relationship.

32. The key holder as claimed in any one of claims 27 to 31, wherein each coding element is in the shape of a wheel from which a plurality of projections extend in equally spaced relation.

33. The key holder as claimed in claim 32 wherein each coding element has 20 projections located about its peripheral edge and extending radially outwardly.

34. The key holder as claimed in any one of claims 27 to 33, wherein an electrical circuit is provided in said holder means comprising a loop connected between two contacts of an electrical socket.

35. The key holder as claimed in claim 34 wherein said loop includes a wire used to attach said key to the holder.

36. The key holder as claimed in claim 35, wherein said loop includes a series resistor.