Electronic Combination Lock And Lock System

Abstract

An electronic lock system utilizes a function generator at each access point to generate a pair of digitally encoded lock combinations, which, when matched by a digitally encoded lock combination borne by a key, permits access. One of the combinations, when matched, additionally controls the function generator to change the other combination to a next combination based on a pseudo-random number sequence. A central station utilizes a corresponding function generator to appropriately encode the various keys which constitute the sole communication link between the central station and plural access points.

Description

BACKGROUND OF THE INVENTION

Prior art electronic lock systems of type contemplated herein, as exemplified by U.S. Pat. Nos. 3,694,810, 3,673,569, 3,662,342, 3,622,991 and 3,599,454, require special wiring to link a central station to each of the various access points in the system. This has the distinct disadvantage of rendering installation very expensive. On the other hand, standalone electronic locks, such as exemplified in U.S. Pat. Nos. 3,700,859, 3,688,269, 3,587,051 and others, are not conducive to convenient changing of the access enabling code, since to do this requires adjustment of each lock at the various access points.

It is accordingly an object of the present invention to provide an electronic security, access control or lock system which efficiently overcomes the drawbacks of the prior art.

A more specific object of the invention is to provide a system of the above character wherein each access point or location functions in standalone fashion, without special wiring linking it to a central station.

Still another more specific object of the invention is to provide a system of the above character wherein the access enabling code or lock combination is automatically changed in pseudo-random fashion on appropriate, preselected occasions so as to provide a virtually secure system.

Other objects of the invention will in part be obvious and in part be made apparent from the specification and claims.

SUMMARY OF THE INVENTION

The electronic lock system of the present invention, while disclosed herein in its application in a hotel or motel lock system, is equally applicable to a wide variety of security systems where controlled access at a plurality of remote locations is desired. In accordance with the invention, a standalone electric combination lock is provided at each controlled access point. A function generator included in each combination lock generates a "current" digitally encoded access enabling code or combination in conjunction with a digitally encoded access enabling "change" code or combination. Electronic logic, upon detection of a match between either one of the internally generated combinations and a combination entered by a person seeking access, generates an access enabling signal to, for example, release a lock mechanism. However, when the "change" combination is matched, the logic additionally triggers the function generator to generate a "new" combination in lieu of the previous "current" combination anf further provides that the previous "change" combination becomes the "current" combination, while the "new" combination becomes the "change" combination. Thus, a person equiped with the previous "current" combination is denied access, while persons having the now "current" combination and/or the now "change" combination are afforded access.

The successions of different combination pairs generated by the function generators in the various combination locks follow a predetermined pseudo-random number sequence which is capable of duplication by a corresponding function generator located at a central station. A memory at the central station separately stores one or both of the combinations then prevailing at each access point. When the appropriate occassion arises, the change combination for the combination lock at a selected access point is retrieved from the memory or the change combination is derived by the function generator based on the current combination for the combination lock at the selected access point as retrieved from the memory and is given to the person or persons authorized for access.

In the illustrated embodiment of the invention, the change combination or, in some instances, the current combination is digitally encoded on a record element, which takes the form of a key, by an encoding mechanism, such as a keymaker. The key is then taken by the authorized person to the access point where the combination is entered into the combination lock by a key reader or the like. It is understood that the key may take a variety of physical forms and be fashioned from numerous materials. Also, the encoding thereof may utilize a variety of well known techniques. It will also be appreciated that the access enabling combination could be communicated to the authorized person in a readily intelligble form, such as orally or imprinted in numeric form, and the authorized person may then enter the combination via a keyboard or the like to gain access.

In the hotel lock system application of the present invention herein specifically disclosed, a current combination is given to each guest, thereby giving access to the room for which he is registered. When this guest checks out, the next guest to occupy that room is given the change combination applicable thereto. The first time this next guest uses his change combination to access his room, the electronic combination lock automatically, in effect, cancels the previous current combination to deny room access to the previous guest. The combination possessed by this next guest becomes the current combination, while the internally generated new combination becomes the change combination preparatory for the arrival of the next subsequent guest.

As an additional feature of the invention, the function generator in each combination lock also generates a current combination and a change combination specifically for use by hotel personnel, such as maids, who require daily access to the rooms. The electronic combination lock and central station of the invention utilize these maid combinations to afford room access in the same manner as in the case of the guest combinations. The electronic combination lock logic is also equipped to respond to a special and individually unique lockout code given to the guest, which is effective to temporarily inhibit room access to the maid. Also, the logic is equipped to respond to a reset code applicable to either the guest or maid combinations to permit the entry of a predetermined access enabling combination into the function generator to, in effect, reset it to a known point in its pseudo-random number generation sequence. This reset function would be typically implemented in the event the function generator in a particular electronic combination lock gets out of step with the central station, i.e., desk.

The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a logic block diagram of an electronic combination lock constructed in accordance with the invention for specific application in a hotel lock system;

FIG. 2 is a functional block diagram of the construction of a central station adapted for system operation with a plurality of the electronic combination locks exemplified in FIG. 1; and

FIG. 3 is a logic block diagram of one form of a function generator utilized in each electronic combination lock of FIG. 1 and in the central station of FIG. 2.

DETAILED DESCRIPTION

The electronic combination lock, shown in FIG. 1 in a form applicable to a hotel lock system application, includes a key reader 10 for reading a digitally encoded access enabling combination recorded on a key 12 inserted therein. The particular recording and encoding techniques employed are not material to the present invention, but, by way of example, the access enabling combination may be recorded in the shank of key 12 in the form of digitally encoded perforations or holes, such as disclosed in U.S. Pat. No. 3,688,269. The combination read from key 12 by key reader 10 is temporaily stored in a register 14 and from which it is put out on a data bus 16. The combination in register 14 is thus supplied over connection 17 to a guest comparator 18, over connection 19 to a maid comparator 20, over connection 21 to a next maid comparator 22, and over connection 23 to a next guest comparator 24.

A function generator 26, included in each electronic combination lock of the invention, simultaneously generates a current or guest combination G COMB in digitally encoded signal form for application over connection 27 to the guest comparator 18, a current or maid combination M COMB in digitally encoded signal form for application over connection 28 to maid comparator 20, a change or next maid combination NM COMB for application over connection 29 to next maid comparator 22, and a change or next guest combination NG COMB for application over connection 30 to next guest comparator 24. If the combination stored in register 14 and impressed on data bus 16 compares with any one of the four combinations generated by function generator 26, one of the four comparators 18, 20, 22 and 24 will generate a true output, either G COMP on output lead 34 from guest comparator 18, M COMP on output lead 35 from maid comparator 20, NM COMP on output lead 36 from next maid comparator 22 or NG COMP on output lead 37 from next guest comparator 24. A true output from any one of these comparators is gated through an OR gate 40 as an access enabling signal on output lead 42 to a lock mechanism 44. This access enabling signal may serve to initiate actuation of a solenoid, or the like, releasing the lock mechanism to thereby afford room access to the possesser of key 12.

As long as the access enabling combination entered into register 14 is either a current guest combination G COMB or a current maid combination M COMB, the resulting comparator output, either G COMP or M COMP, is gated through OR gate 40 as an access enabling signal to the lock mechanism. If the person seeking room access possesses a change combination, i.e., either the next maid combination NM COMB or the next guest combination NG COMB generated by function generator 26, the resulting comparator output, either NM COMP or NG COMP, in addition to releasing lock mechanism 44, is fed back over leads 36a or 37a to the function generator. As will be seen more clearly from FIG. 3, the function generator 26 operates in response to the receipt of either of these signals to generate a new current combination and a new change combination for either the guest or the maid, as the case may be. In practice, the logic of the function generator 26 is designed such that the change combination, NM COMB or NG COMB, becomes the current combination, G COMB or M COMB, and the function generator is, in effect, indexed or incremented so as to generate a new combination which is the next combination derived from a pseudo-random number sequence for which the function generator 26 is programmed to generate. The logic of the function generator, in effect, adopts this next combination as the new change combination NM COMB or NG COMB, as the case may be.

It is thus seen that the possesser of the key 12 bearing the change combination is afforded room access while at the same time triggering the electronic combination lock of the invention to change the internally generated access enabling combinations which must be matched to be afforded subsequent room access. However, since the change combination which precipitated the changing of the lock combinations now becomes the current combination, the possesser of this key is assured subsequent room access since the combination encoded therein is thereafter treated as a current combination and not as a change combination. It will be appreciated that possessers of the keys bearing the previous current combination are denied room access.

In the application of the electronic combination lock of FIG. 1 in a hotel lock system, a registered guest is provided with a key 12 having the guest combination G COMB encoded therein for the electronic combination lock to the room for which he is assigned. Using this key, this guest is afforded continuing room access. When this guest checks out and a next guest is assigned the same room, the next guest receives a key encoded with the next guest combination NM COMB (change combination). The first time this new key is used in the electronic combination lock whose function generator 26 is generating the same change combination, the access enabling signal is generated to lock mechanism 44 and the function generator is incremented to generate the next combination in the pseudo-random number sequence. The logic circuitry of the function generator then converts the next guest combination NG COMB to the guest combination G COMB, and the new combination becomes the next guest combination NG COMB.

Maid keys encoded with the maid combination M COMB and the next maid combination NM COMB are used in the same manner as the combination encoded guest keys to control room access. Typically, in the case of the maids, a plurality of electronic combination locks of the invention, e.g., those on the same floor, will contain the same maid combination M COMB and next maid combination NM COMB.

Still referring to FIG. 1, guests may be provided with a key having a special lockout combination encoded therein. This lockout combination imposed on data bus 16 is compared in a comparator 50 with a lockout combination held in a register 52 unique to each electronic combination lock. When the lockout combinations match, the output of comparator 50 sets a flip-flop 54, causing its reset output on lead 56 to go false. This false reset output is supplied as an inhibiting input to the maid comparator 20 and the next maid comparator 22, with the result that the comparator outputs M COMP and NM COMP otherwise issuing upon the entry into the electronic lock of the maid and next maid combinations are supressed. It is thus seen that the guests can effectively lock out the maid. To remove this lockout function, the guest enters the appropriate access enabling combination, either the guest combination G COMB or the next guest combination NG COMB. The resulting comparator output signal, either G COMP or NG COMP, is gated through OR gate 40 as the access enabling signal to lock mechanism 44. This access enabling signal is also gated through an OR gate 58 to force flip-flop 54 to its reset condition, thereby imposing a true condition on its reset output and thereby removing the inhibiting input from the maid and next maid comparators 20 and 22.

On occassion, it may become necessary to reset the function generator 26 in a particular electronic combination lock to a starting position, suct that it is generating a predetermined guest or maid combination pair. To this end, a key 12 is provided having encoded therein a reset flag digit or digits and the particular combination to which the function generator 26 is to be reset. Desirably, the guest and maid combinations are reset separately, but may be reset concurrently with a single key. As seen in FIG. 1, a reset register 60 stores a guest reset flag digit GR FLAG which is imposed on output connection 62 and a maid reset flag digit MR FLAG which is imposed on an output connection 64. The guest reset flag digit is supplied as one input to a comparator 66 while the maid reset flag digit is supplied as one input to a separate comparator 68. The other input to each of these comparators is derived from data bus 16. If a guest reset flag digit GR FLAG is entered, comparator 66 supplies an output GR COMP on lead 70 to the function generator, conditioning it to accept the guest reset combination also present on data bus 16 and supplied thereto over connection 72. As will be seen from FIG. 3, function generator 26 derives the next guest combination NG COMB from the guest combination G COMB, and thus to reset function generator 26, it is only necessary to enter the guest reset combination as encoded on key 12 which then becomes the guest combination G COMB.

If it is desired to reset the maid combination, a key 12 encoded with the appropriate maid reset flag digit and the maid reset combination is inserted in key reader 10. Recognition of the maid reset flag MR FLAG on data bus 16 causes comparator 68 to generate a maid reset signal MR COMP on output lead 74 which is returned to the function generator 26, conditioning it to accept the maid reset combination appearing on data bus 16 and supplied over connection 72. The generator 26 supplies this maid reset combination as the maid combination M COMB on output connection 28 and derives from this the next maid combination NM COMB which is imposed on output connection 29. The comparator outputs GR COMP are gated together in an OR gate 76 and supplied over lead 77 to OR gate 58, thereby insuring that flip-flop 54 is reset to remove any pre-existing lockout function.

The administration of a hotel lock system comprising a plurality of the electronic combination locks of FIG. 1 is carried out at a central station, such as the hotel desk, whose principle system components are shown in FIG. 2. As seen therein, these components include a keyboard 80, a random access memory 82, a key maker 84 and function generator 86 corresponding to the function generator 26 in each of the electronic combination locks. Keyboard 80 accesses the memory 82 by room number under which is stored the guest and maid combination G COMB and M COMB then being generated by the function generator 26 in the electronic combination lock located thereat. Also stored in the memory in each room number address access location is the appropriate lock-out combination, guest and maid reset flag digits, and guest and maid reset combinations.

To issue a new key to a guest just checking in, memory 82 is accessed by keyboard 80 under the room number of the room being assigned and the guest combination G COMB is retrieved. This guest combination is routed by a switch 88 to function generator 86 which proceeds to derive therefrom the change or next guest combination NG COMB. This next combination at the output of function generator 86 is returned to the memory for storage in the address location where the guest combination had just been retrieved to become the current guest combination G COMB. At the same time, this next guest combination is supplied to key maker 86 which encodes a key 12 accordingly. If it is desired to issue a duplicate key to a particular guest, the appropriate guest combination G COMB is retrieved from the memory 82 and routed by switch 88 directly to the key maker. Since the function generator 86 is not operative in this instance, the guest combination, as stored in its assigned memory location, is unaltered. Similarly, should a guest desire a maid lockout key, memory 82 is accessed by keyboard 80 to retrieve the lockout combination for the electronic combination lock to the guest's room, and this combination is routed by switch 88 directly to the key maker 84. To issue a guest or maid reset combination for a particular room, memory 82 is accessed and the reset flag digit and reset combination are routed by switch 88 directly to the key maker. In this instance, a second switch 90 is closed such that the reset combination retrieved from the memory is stored as the guest combination G COMB or maid combination M COMB, as the case may be, in place of the combination previously stored there. This reset combination then becomes the current guest combination affording room access. With the arrival of the next guest, the reset combination is retrieved from memory and supplied to the function generator through routing switch 88 with switch 90 open. The function generator then generates the next guest combination which is returned to memory 82 and also used by the key maker 84 to encode this next guest's key.

The function generator 26 seen in FIG. 3 includes a guest combination register 100 and a maid combination register 102. Register 100 stores the guest combination G COMB which is impressed on output connection 27 to the guest comparator 18 (FIG. 1), while register 102 stores the maid combination M COMB which is supplied on output connection 28 to maid comparator 20. The next guest combination NG COMB supplied on output connection 30 is derived from the guest combination G COMB by adding to the latter a number which corresponds to the increment by the pseudorandom number sequence generated by function generator 26. Thus, se seen in FIG. 3, the guest combination stored in register 100 is added to the increment number stored in a register 104 by an adder 106 to derive the next guest combination NG COMB on output connection 30.

Similarly, in the case of the maid combination, the content of register 102 is augmented by a fixed increment member stored in a register 108 by an adder 110 to derive the next maid combination NM COMB on output connection 29.

Further as seen in FIG. 3, the next guest combination on output connection 30 is normally supplied through a multiplexer 112 to the input of guest combination register 100. When the next guest combination NG COMB is entered into the electronic combination lock, the comparator output signal NG COMB on comparator output lead 37a returned to the function generator 26 is gated through an OR gate 114 to control the guest combination register 100 to accept the next guest combination NG COMB supplied thereto by multiplexer 112. It is thus seen that register 110 now contains the next guest combination which becomes the guest combination G COMB generated on output connection 27, while the new next guest combination NG COMB is generated on output connection 30 from adder 106.

Similarly, when the next maid combination NM COMB is entered into the electronic combination lock, the comparator output NM COMP on lead 36a returned to function generator 26 is routed to OR gate 116 causing the maid combination register 102 to accept the next maid combination supplied thereto from the output of adder 110 via a multiplexer 118.

When the situation arises to reset the guest and/or maid combination, the appropriate reset flag digit and reset combination are entered into the electronic combination lock of FIG. 1 via key reader 10, as previously described. If the guest combination is to be reset, the entry of the guest reset flag digit causes comparator 66 to generate the output GR COMP on lead 70, returning to function generator 26. This signal conditions multiplexer 112 to connect data bus 16 via connection 72 to the input of guest combination register 100. This signal GR COMP is also supplied through OR gate 114 to condition the guest reset register 100 to accept the reset combination from data bus 16 via multiplexer 112. Upon entry of the guest reset combination therein, it becomes the guest combination G COMB on output connection 27 and, since this same combination is also impressed on data bus 16, guest comparator 18 generates its output G COMP to afford room access.

To reset the maid combination, entry of the maid reset flag digit and maid reset combination into the electronic lock combination lock causes the issuance of the signal MR COMP at the output of comparator 68. This signal is returned over lead 74 to the function generator to condition multiplexer 118 so as to connect the data bus via connection 72 to the input of the maid combination register 102. This signal also conditions the maid combination register 102 via OR gate 116 to accept the entry of the maid reset combination which is then generated as the maid combination M COMB on output connection 28 to afford room access. It will be appreciated that upon the removal of the reset compare signals GR COMP and MR COMP from their respective multiplexers, the multiplexers revert to their normal condition of connecting the associated adder outputs to the inputs of registers 100 and 102.

The function generator 86 (FIG. 2) at the desk would simply comprise an adder corresponding to adder 106 and a fixed increment register corresponding to register 104 in order to derive the next combinations for the various electronic combination locks based on their current combinations as retrieved from memory 82.

It will be appreciated that the function generator shown in FIG. 3 may in practice be considerably more complex and sophisticated to enhance the security of the lock system. For example, the function generator 26 may be a trigonometric function generator or a logarithmic function generator. Alternatively, a random number generator may be employed which uses the guest and miad combinations as seed numbers for generating the next combinations in accordance with a pseudo-random number algorithm. In this connection, for example, the fixed increment registers 104 and 108 in the function generator 26 (FIG. 3) could take the form of pseudo-random number generators which are respectively indexed by the NG COMP and NM COMP signals, such that variable numbers are supplied to adders 106 and 110. Additional security can be afforded by compounding, manipulating, and/or computating the random numbers generated pursuant to establishing the next combinations. Using these more sophisticated function generators would permit the internal derivation of reset combinations rather than requiring the external entry of the reset combinations via the key reader.

From the foregoing description, it is seen that the present invention provides an electronic combination lock system including a plurality of electronic combination locks which are conducive to being administered from a central location without requiring electrical connections therebetween. The only link between the central station and the various electronic combination locks of the invention are the combination encoded keys possessed by those persons authorized for access. Consequently, no special wiring is required to implement the lock system of the invention. Since the combinations of the various electronic combination locks of the invention can be changed simply by using a new key encoded with the appropriate change combination there is no necessity for security personnel to visit each access point to adjust the lock thereat. Moreover, upon use of the change combination, possessers of the previous access enabling combinations who are no longer authorized access are automatically denied future access.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings should be interpretated as illustrative and not in a limiting sense.

Claims

Having described the invention, what is claimed as new and desired to secure by Letters Patent is:

1. A combination lock comprising, in combination:

A. entry means for accepting a lock combination entry;

B. means for establishing first and second lock combinations:

C. comparing means responsive to a match between a lock combination entry and either one of said first and second lock combinations for developing an access enabling signal; and

D. logic means responsive to a match between a lock combination entry and said second combination for controlling said establishing means to cancel said first combination and establish a third combination in conjunction with said second combination, wherein said first, second and third combinations are successive lock combinations derived from consecutive numbers in a pseudo-random sequence.

2. The combination lock of claim 1, wherein said logic means further controls said establishing means to establish said second combination in place of said first combination and said third combination in place of said second combination for any subsequent lock combination entry.

3. The combination lock of claim 2, wherein said establishing means is a function generator capable of being indexed by said logic means through the consecutive numbers in said pseudo-random sequence.

4. A combination lock system comprising, in combination:

A. a combination lock located at each of a plurality of access points, each said lock including

1. entry means for accepting a lock combination entry,

2. means for establishing first and second lock combinations,

3. comparing means responsive to a match between a lock combination entry and either one of said first and second lock combinations for developing an access enabling signal, and

4. logic means responsive to a match between a lock combination entry and said second combination for controlling said establishing means to cancel said first combination and establish a third combination in conjunction with said second combination, wherein said first, second and third combinations are successive lock combinations derived from consecutive numbers in a pseudo-random sequence; and

B. a central station including

1. a memory storing at least one of said first and second lock combinations established in each said combination lock,

2. means for accessing said memory to retrieve the stored lock combination for a selected one of said combination locks,

3. means for deriving the next successive lock combination to said retrieved lock combination for said selected one combination lock and entering said next successive lock combination in said memory, and

4. readout means for communicating said retrieved and next successive lock combinations to persons seeking access.

5. The combination lock system of claim 4, wherein said retrieved lock combination corresponds to said first lock combination established at said selected one combination lock and said next successive lock combination corresponds to said second combination at said selected one combination lock.

6. The combination lock system of claim 4, wherein said establishing means in each said combination lock and said deriving means in said central station are corresponding function generators capable of being indexed through the consecutive numbers in said pseudo-random sequence.

7. The combination lock system of claim 6, wherein the lock combinations are encoded on a record member, said readout means at said central station is a recorder for recording a lock combination on a record member and said entry means in each said combination lock is a reader for reading the lock combination from a record member.

8. An electronic combination lock comprising, in combination:

A. a lock mechanism;

B. means for generating a digital readout of an encoded lock combination borne by a key;

C. a function generator for generating first and second digitally encoded lock combinations;

D. a first comparator for comparing said first lock combination with said key readout and, upon comparison, generating a first compare signal effective to initiate actuation of said lock mechanism;

E. a second comparator for comparing said second lock combination with said key readout and, upon comparison, generating a second compare signal also effective to initiate actuation of said lock mechanism; and

F. logic means responsive to said second compare signal for controlling said function generator to cease generating said first lock combination and to generate a third digitally encoded lock combination, wherein said first, second and third lock combinations are successive lock combinations derived from consecutive numbers in a pseudo-random number sequence.

9. The electronic combination lock of claim 8, wherein said logic means further controls said function generator to generate said second lock combination in place of said first lock combination and to generate said third lock combination in place of said second lock combination signal for any subsequent key readout.

10. The electronic combination lock of claim 9, wherein said logic means indexes said function generator through the consecutive numbers in said pseudo-random sequence.

11. The electronic combination lock of claim 10, which further includes reset means responsive to a key readout signifying a combination reset function for conditioning said function generator to generate first and second lock combinations based on a predetermined lock reset combination.

12. The electronic combination lock of claim 11, wherein said predetermined reset combination is derived from a key readout entered into said function generator.

13. An electronic combination lock system comprising, in combination:

A. an electronic combination lock located at each of a plurality of access points, each said lock including

1. a lock mechanism,

2. reading means for generating a digital readout of an encoded lock combination borne by a key,

3. a function generator for generating first and second digitally encoded lock combinations,

4. a first comparator responsive to a comparison between said first lock combination and said key readout for generating a first compare signal effective to initiate actuation of said lock mechanism,

5. a second comparator responsive to a comparison between said second lock combination and said key readout for generating a second compare signal also effective to initiate actuation of said lock mechanism, and

6. logic means responsive to said second compare signal for controlling said function generator to generate said second lock combination in place of said first lock combination and to generate a third digitally encoded lock combination in place of said second lock combination, wherein said first, second and third lock combinations are successive combinations derived from consecutive numbers in a pseudo-random number sequence; and

B. a central station including

1. a memory storing at least one of said digitally encoded lock combinations being generated in each said electronic combination lock,

2. means for accessing said memory to retrieve the stored lock combination for a selected one of said electronic combination locks,

3. a function generator for deriving the next successive lock combination to said retrieved lock combination from said pseudo-random sequence for said selected one electronic combination lock and entering said next successive lock combination in said memory, and

4. recording means for encoding keys with said retrieved and said next successive lock combinations.

14. A hotel electronic combination lock system, comprising in combination:

A. a separate electronic combination lock for controlling access to each guest room, each said electronic combination lock including

1. reading means for generating a digital readout of an encoded lock combination borne by a key,

2. a function generator for generating separate and distinct digitally encoded guest, guest change, maid and maid change lock combinations,

3. a first comparator responsive to a comparison between said guest lock combination and said key readout for generating a first compare signal,

4. a second comparator responsive to a comparison between said guest change lock combination and said key readout for generating a second compare signal,

5. a third comparator responsive to a comparison between said maid lock combination and said key readout for generating a third compare signal,

6. a fourth comparator responsive to a comparison between said maid change lock combination and said key readout for generating a fourth compare signal,

7. gating means responsive to any one of said first, second, third and fourth compare signals for generating a room access enabling signal, and

8. logic means responsive to said second compare signal for controlling said function generator to generate said guest change lock combination in place of said guest lock combination and to generate a third new guest change lock combination in place of said guest change lock combination, wherein said guest, guest change and new guest change lock combinations are successive combinations derived from consecutive numbers in a pseudo-random number sequence, said logic means being further responsive to said fourth compare signal for controlling said function generator to generate said maid change lock combination in place of said maid lock combination and to generate a new maid change lock combination in place of said maid change lock combination, wherein said maid, maid change and new lock combinations are successive combinations derived from consecutive numbers in a pseudo-random number sequence; and

B. a central station for administering said electronic combination locks, said central station including

1. a random access memory storing at least one of said guest and guest change lock combinations and at least one of said maid and maid change lock combinations being generated in each of said electronic combination locks,

2. means for accessing said memory to retrieve a selected stored lock combination for the electronic combination lock controlling access to a selected guest room,

3. a function generator for deriving the said successive lock combination to said retrieved lock combination for said selected one electronic lock and entering same in said memory in the place of said retrieved lock combination, and

4. a recorder for encoding keys with said retrieved and next successive lock combinations for use by guests and maids authorized for access to the selected guest room.

15. The hotel lock system of claim 14 which further includes means responsive to separate guest or maid combination reset indications included in said key readout for controlling said function generator to generate predetermined guest or maid lock reset combinations as said guest or maid lock combinations, respectively.

16. The hotel lock system of claim 15 wherein said guest or maid lock reset combinations are derived from said key readout by said function generator.

17. The hotel lock system of claim 16 wherein said predetermined guest and maid lock reset combinations for each said electronic combination lock are separately stored in and retrieveable from said random access memory.

18. The hotel lock system of claim 14, which further includes means responsive to a maid lockout indication included in said key readout for suppressing said third and fourth compare signals.