Title:
Security system for lock and key protected secured areas
United States Patent 3906447


Abstract:
An electronic lock security system including a control console and several remote secured areas, the entrance to each of the secured areas being controlled by an electronic lock mechanism responsive to a digital coded key. A key code is stored in each lock mechanism and compared with the key code on a digital coded key. If correspondence exists, entrance to the secured area is granted. The lock mechanism stored key code can be changed in response to an order code imprinted directly on the key. This obviates the requirement of wired or wireless wave communications links between the control console and each of the remote secured areas. A further feature of the invention resides in the provision of apparatus for automatically changing the stored key code at each secured area after a variable predetermined time interval.



Inventors:
CRAFTON PAUL A
Application Number:
05/328179
Publication Date:
09/16/1975
Filing Date:
01/31/1973
Assignee:
CRAFTON; PAUL A.
Primary Class:
Other Classes:
340/5.3, 340/5.67
International Classes:
G07C9/00; (IPC1-7): H04Q3/00
Field of Search:
340/149A,149R,147MD 179
View Patent Images:
US Patent References:



Primary Examiner:
Pitts, Harold I.
Attorney, Agent or Firm:
Sughrue, Rothwell Mion Zinn And Macpeak
Claims:
What is claimed is

1. A lock mechanism for generating an unlock trigger signal, said mechanism including storage means storing a key code and comparison means for comparing the stored key code with an applied key code to cause the generation of the unlock trigger signal when the two key codes coincide, the improvement comprising:

2. The lock mechanism of claim 1, wherein said order code represents time, said lock mechanism including means for generating a time representative signal, said first comparison means comprising means for subtracting the time represented by said order code from the time representative signal, said lock mechanism further including threshold means responsive to the output of said subtracting means for producing a key code accept signal when the value of the output of the subtracting means is below the threshold level of said threshold means.

3. The lock mechanism of claim 2, wherein said key has further formed thereon an identification code, said lock mechanism further including means for storing a lock mechanism identification code, means for reading the identification code from the key, second comparison means for comparing the stored lock mechanism identification code with the read identification code and means for blocking said key code accept signal when the stored lock mechanism identification code does not correspond to the read identification code.

4. The lock mechanism of claim 3, wherein said lock mechanism further includes a lock bolt control circuit responsive to said unlock trigger signal and a lock bolt responsive to the lock bolt control circuit, said lock mechanism being coupled to an entrance door of a room, said key having further formed thereon a time of departure code, said lock mechanism including third comparison means responsive to said time of departure code and lock mechanism generated time representative signal for producing a key code non-accept signal when said time representative signal is greater than the time of departure code, means for storing a randomly generated key code and means responsive to said non-accept signal for resetting said key code storage means and entering said randomly generated key code therein.

5. A security system for a lock mechanism comprised of a lock belt, a lock bolt control circuit and unlock trigger command circuitry, said unlock trigger command circuitry including means for storing a key code and means for comparing the stored key code with a key code read from a key, said security system including apparatus for encoding said key comprising:

6. The apparatus of claim 5, wherein said order code represents time, said apparatus further comprising a second binary, counter clock means for incrementing the count in the binary counter at predetermined time intervals, and means responsive to a request for coding said key for transferring the contents of said counter to said order code storage means.

7. The apparatus of claim 6, wherein said lock mechanism is coupled to an entrance door of a hotel room further including means for storing a room number, said adding means including means for adding said room number to said order code, departure time and key code, said key card writer means including means for forming the room number on said key in decimal form.

8. The apparatus of claim 7, further comprising a central memory means storing the key code and its associated room number, card reader means for reading the codes on said key, comparison means for comparing the key code and room number stored in said central memory with the read codes from said key and means for producing a billing accept signal when correspondence is determined.

9. The apparatus of claim 3, wherein said lock mechanism is attached to a baggage locker.

10. The apparatus of claim 3, wherein said lock mechanism is attached to an automobile starter circuit.

11. The security system including the apparatus of claim 5 wherein said lock bolt control circuitry comprises:

12. The security system of claim 11 wherein the apparatus for encoding further includes means for storing a departure time code, and said lock bolt control circuit further includes means for generating a time representative signal, second comparison means for comparing the time representative signal with the departure time code to produce a non-accept signal when a one-to-one comparison exists, and means responsive to the non-accept signal for changing the lock mechanism stored key code; said adder means in said apparatus for encoding further including means for adding said departure time code to said key code, said pseudorandom sequence generator receiving as the output of the adder the sum of the key code, order code and departure time code.

13. The apparatus of claim 6 further including means for storing a departure time code, said adder means further including means for adding said departure time code to said key code, said pseudorandom sequence generator receiving as the output of the adder the sum of the key code, order code and departure time code.

14. The apparatus of claim 13, further including first transformation matrix means for scrambling said order code and departure code prior to their application to the adder means, second transformation matrix means for scrambling the output of the adder means and key code prior to their application to the pseudorandom sequence generator, and third transformation matrix means responsive to the output of said adder means and pseudorandom sequence generator for scrambling and means for applying the output of said third transformation matrix means to said key writer means.

15. The security system including the apparatus of claim 14 wherein said lock bolt control circuitry comprises:

16. The security system of claim 15 further including means for generating a time representative signal, fifth comparison means for comparing the time representative signal with the departure time code to produce a non-accept signal when a one-to-one comparison exists, and means responsive to the non-accept signal for changing the lock mechanism stored key code.

17. The security system of claim 11 wherein said order code represents time, said apparatus for encoding further comprising a second binary counter, clock means for incrementing the count in the binary counter at predetermined time intervals, and means responsive to a request for coding said key for transferring the contents of said counter to said order code storage means.

18. The security system of claim 17, said lock bolt control circuit including means for generating a time representative signal, said first comparison means comprising means for subtracting the time represented by said order code from the time representative signal, threshold means responsive to the output of said subtracting means for producing a key code accept signal when the value of the output of the subtracting means is below the threshold level of said threshold means.

19. The security system of claim 11, said encoding apparatus further including means for storing a departure time code, said adder means further including means for adding said departure time code to said key code, said pseudorandom sequence generator receiving as the output of the adder the sum of the key code, order code and departure time code.

20. The security system of claim 19 wherein said reading means also reads said departure time code, said lock bolt control circuitry including means for generating a time representative signal, second comparison means for comparing the time representative signal with the departure time code to produce a non-accept signal when a comparison exists, and means responsive to the non-accept signal for changing the lock mechanism stored key code.

21. The security system of claim 20, said second comparison means comprising means for subtracting the time represented by the departure time code from the time representative signal, threshold means responsive to the output of said subtracting means for producing a non-accept signal when the value of the output of the subtracting means is above the threshold level of said threshold means.

Description:
BACKGROUND OF THE INVENTION

At the present time, most secured areas such as rooms in hotels, motels and office buildings, as well as baggage lockers and ignition systems on rental cars, are provided with locks operated by the mechanical interaction of a key and lock tumbler. In recent years this ancient mechanical system has, to some extent, given way to new electronic lock systems responsive to digitally coded keys. In brief, the entrance to a secured area is controlled with an electronic lock which includes an unlocked trigger command circuit, responsive to a digitally coded key, a lock bolt, and an associated lock-bolt control logic circuit responsive to an unlock trigger signal. Included in the unlock trigger command circuit is a memory storing a unique digital key code. When a coded key is inserted into the electronic lock mechanism, the code on the key is read and compared with the stored key code to determine correspondence. If correspondence exists, an unlock trigger command signal is generated to activate the lock bolt control logic to cause the lock bolt to move to its unlocked position.

An example of an unlocked trigger control circuit, responsive to digitally coded keys is described in U.S. Pat. No. 3,668,269 to Edwin Miller. An example of a lock bolt control circuit, responsive to an unlock trigger command and its associated lock bolt is described in copending application, Ser. No. 84,085 by Stephen Paull and Paul A. Crafton, filed Oct. 26; 1970 and assigned to an affiliate of the assignee of the present invention.

Although the electronic key lock is indeed an important improvement over the prior mechanical key and tumbler arrangement, many of the security problems associated with the mechanical key and tumbler arrangement remain with the electronic key lock. For example, with respect to secured areas such as motels and hotels, where numerous people have access to room keys, an unauthorized person might easily gain access to a guest's room. For example, a hotel guest may retain his key after checking out of the hotel and at a later date illegally enter the room now occupied by another guest.

Attempts at solving this problem have involved changing the key code which permits entrance into a secured area each time the identity of the person authorized to enter the area is changed. Examples of such systems can be found in U.S. Pat. No. 3,622,991 to Lehrer et al., issued Nov. 23, 1971 and U.S. Pat. No. 3,662,342 to Hedin et al., issued Feb. 16, 1971. In such prior art systems, alteration of the stored key code at each of the remote areas requires the use of wired or wireless wave communications links. More specifically, a control console is connected to each of the remote secured areas by way of wires. When a key code is to be changed, the control console transmits over a wired or wireless wave communication link an address signal identifying the secured area at which the key code is to be changed along with a new key code.

This type of system is extremely expensive and oftentimes not feasible especially in older buildings where the installation of additional electrical lines between some central control console and each of the rooms of the building is not practical.

SUMMARY OF THE INVENTION

The present invention is directed to an improved electronic lock security system.

In accordance with the teachings of the present invention, each secured area has associated therewith an electronic lock mechanism storing a unique key code. When an individual seeks to enter a secured area, he presents a digitally coded key to the lock mechanism wherein the key code on the key is compared with the stored key code and if correspondence exists an unlock trigger command is generated and applied to lock bolt control circuitry to unlock the secured area. The key code stored in each lock mechanism is easily and rapidly changed in response to an order code contained directly on the digitally coded key. As a result, no wired or wireless wave communication links are required between a control console and the remote secured areas to accomplish the selected changing of the stored key codes.

Imprinted on the key is an order code which, according to one embodiment of the invention may be made to correspond to the time the key is issued. The lock mechanism operates to compare the order code on the key presented to it with the time of presentation, and if the time difference is within a predetermined time interval, the key code on the key is set into the lock mechanism. According to an alternative embodiment of the invention, the order code corresponds to the key code formerly set into the lock mechanism. The former key code would have been stored, for example, in the central control console for imprinting as an order code on the next issued key for the secured area. Other order codes will be readily apparent to those of ordinary skill in the art and, in any choice of an order code, subsequent presentation of the key to this lock mechanism causes the generation of an unlock trigger command.

A further feature of the invention, particularly applicable to hotels and motels and the like, involves the generation of a time of departure code. This time of departure code is imprinted on the key when issued and entered into the lock mechanism when the order code is presented thereto. When the departure time is reached, the lock mechanism automatically changes at random the stored key code, thus preventing the guest from entering the room.

A still further feature of the invention resides in apparatus, responsive to the key code on a digitally coded key which permits the hotel to verify the guest's authority to use the hotel's restaurant, bar, shops, parking lot and other servide facilities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b are a detailed functional block diagram of the control console of the instant invention;

FIG. 2 is a drawing of one example of a digitally coded key, which may be used with the security system of the invention;

FIGS. 3a and 3b are a functional block diagram of the lock mechanism of the instant invention; and

FIG. 4 is a block diagram illustrating the application of the invention to a hotel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For ease in understanding the present invention, the security system will be described with reference to its use in a hotel, although it is to be understood that the security system is not limited to this use alone, having a more general application. The security system can be used to secure any area to which access is given to many people, each for only short periods of time. Once a person's permissible access time is over, he is barred from entering the area. In addition to hotels, the present invention will find application in securing baggage lockers, the ignition lock system of rental vehicles, protected cargo areas and office buildings.

A secured area is generally protected from unauthorized entrance by a lock mechanism. Those with authority to enter are given a key which gains them access to the secured area. Since keys are easily reproduced, security against unauthorized entrance by a person formally having authority to enter an area is very weak. The quality of security increases greatly if the lock mechanism is changed each time the identity of the authorized user changes, so that even if he reproduces or keeps the key which formally admitted him to the area, it becomes ineffective once his authorization has expired.

The present invention, which involves an improved security system of the type which uses electronic key locks, provides a reliable and inexpensive technique for changing the key code stored in the lock mechanism. As previously indicated, in electronic lock systems, the stored key code is compared with the key code on a key presented to the lock mechanism by the individual who desires access to the secured area and if the two codes correspond, entrance is granted. The present invention provides for alteration of the stored key code in the lock mechanism by incorporating on the key issued to the authorized user what is termed herein an order code which, upon presentation to the lock mechanism, causes the mechanism to be set to the key code on the key of the authorized user. Thereafter, each time the user presents his key to the lock mechanism, he is permitted to enter the secured area.

FIG. 1 illustrates the central control console of the invention adapted for use in a hotel or motel. When a guest is assigned a room, his room number is entered into the control console through the decimal keyboard 100 which is coupled to the room number register 11. For a three digit room number, the register may take the form of three ten stage registers, each stage of a register representing a different digit. Register 11 is coupled to a decimal to binary converter 9, wherein the room number is converted into a binary code. Subsequently the binary coded room number is stored in binary register 6.

The guest key code, which will be imprinted on a room key and subsequently presented to the lock mechanism at the guest's assigned room, is a randomly generated number produced by a random number generator 105 and stored in shift register 2. The key code and the room number in binary form may be directly imprinted on the room key. However, this would be detrimental to the security of the area since the codes could easily be counterfeited and reproduced. As an added measure of security, the room number and the key code are enciphered in a manner to be described in detail below, prior to its formation on the key.

The order code and its generation will now be described. The order code, according to one embodiment is a time representative code and corresponds to the time a guest checks in, that is, his arrival time. At each lock mechanism there is provided, as described in greater detail below, mechanism which compares the order code, that is, the arrival time, with the time that the guest presents his key to the lock mechanism located at the entrance to his room and if the difference in time is within a predetermined time interval, the new guest code is entered into the room lock mechanism. The measure of time used in this system is advantageously not real time, but rather non-real time corresponding simply to a count in a binary counter. The counter may be preset to any arbitrary number with the lock mechanisms at each of the hotel rooms synchronized to this preset number. Each count in the counter corresponds to a known unit of time, such as 1/60 of a second. The counter would have a recycle time longer than the longest expected guest stay. For example, the counter may be made to recycle once every two or three years. A long recycle time is desirable when the security system is provided with the optional time departure feature, wherein the guest's check-out time is also set into the lock mechanism and at this time, the key code assigned to the guest's room is automatically changed so that this key will no longer gain him entrance to the room.

The order code generator is comprised of binary counter 16 and clock 17. Clock 17 may be a conventional oscillator, powered from the 60 Hertz building power source. Thus, each pulse produced by clock 17 and each increment of the counter 16 corresponds to 1/60 of a second. The system may be initialized by resetting counter 16, to zero. A signal at terminal A, which may be generated manually, through the use of a simple pushbutton switch, resets the counter 16. The counter then begins to increment in 1/60 of a second intervals. Recalling that a day is comprised of 86,400 seconds, in a system wherein each count in the counter represents a time interval of 1/60 of a second, a 32 stage counter has a recycle period greater than the two weeks, and a 48 stage counter has a recycle period greater than 100,000 years.

The arrival time is set into counter 5 and applied to transformation matrix 4 which simply interleaves the bits from registers 5 and 6 in a manner determined by the wiring of the matrix 4.

When the departure time feature is used, the scheduled departure time of the guest is entered into register 7. The departure time is a function of the check-in time. That is, the departure time is merely the arithmetic sum of the check in time plus the duration of the guest's stay. To enter the departure time into the system, the duration of stay is entered into decimal keyborad 200, the output of which is supplied to decimal to binary converter 202. The duration of stay is preferably determined in hours, since guests often do not check into a hotel at the beginning of the hotel's day, usually beginning around noon and ending the following noon. Binary register 208 stores a count corresponding to an hour in system time. In the system under discussion, register 208 stores the binary equivalent to 60 ×to 360 = 21,600 which corresponds to the number of counts in a one hour period. The contents of register 208 are multiplied by the output from decimal to binary converter 202 to generate a binary number equivalent to the duration of stay in system time. This number is added to the arrival time from counter 16 in adder 206 and stored in departure time register 7.

The contents of register 7 together with the contents of registers 5 and 6, are applied to transformation matrix 4 through the register 8 whereby they are interleaved. Further encipherment is accomplished by adding the output of transformation matrix 4 with the randomly generated key code in register 2 in a modulo 2 adder 3. The output of the adder 3, together with the contents of the key code register 2 are applied to a further transformation matrix 20 to further scramble the codes. The output of the matrix 20 is supplied to the input of a conventional psuedorandom sequence generator 21. The output of the adder 3 is also supplied directly to counter 13 to preset this counter.

When counter 13 is loaded, a signal B, which may be manually generated using a push button switch, or automatically generated in response to the loading of counter 13, enables coincidence gate 23. Gate 14, coupled to the output of counter 13, provides a logic 1 when the counter has reached its full count. Thus, when counter 13 is preset from the output of adder 3, with a count other than a full count, the output of gate 14 is a logic 0, which is inverted to a logic 1, by operation of inverter 26, to enable gate 24. When gates 23 and 24 are enabled, clock pulses from clock 22 simultaneously increment counter 13 and register 18 of the psuedorandom sequence generator 21. Incrementing continues until counter 13 reaches its full count, at which time the output of gate 14 assumes a logic 1 thereby disabling gate 24 through the operation of inverter 26. In this manner, the key code, and the output of adder 3 are further enciphered increasing still further the security of the system. This encipherment prevents an individual from isolating the arrival time from the codes imprinted on the room key and subsequently counterfeiting a room key including thereon an order code corresponding to the time at which he seeks to enter the room illegally.

The output of the psuedorandom sequence generator 21, together with the output of adder 3 is further enciphered in transformation matrix 25 and applied to a key writer 27, which imprints, as illustrated in FIG. 2, an encipherment 300 of the key code, room number, order code and departure time on the key. In addition, the room number 302, in decimal form, may also be imprinted on the key. As illustrated in FIG. 2, the key may take the form of a key card having a configuration equivalent to that of an ordinary credit card.

Alternatively to entering the encipherment 300 as an array of holes as shown in FIG. 2, the encipherment may be a printed or magnetized array of marks, or any kind of signal in any form representing the information in the encipherment.

In addition to the above information, the key card may also have imprinted thereon hotel advertising 304.

The lock mechanism at each room will now be described. Referring to FIG. 3, each lock mechanism is provided with an electronic key reader 37, such as that described in U.S. Pat. No. 3,688,269. The reader 37 reads the encipherment of the key code, room number, order code and time of departure, from the inserted key card 28. This encipherment is partially unscrambled by transformation matrix 38, which is the reverse of transformation matrix 25. The output of transformation matrix 38 therefore corresponds to the output of the adder 3 and the output of the psuedorandom sequence generator 21 after gate 24 has been disabled. The information on bus 32 corresponds to the output of adder 3 which was previously supplied as the preset input to counter 13. At the remote lock mechanism, this preset count is applied to register 43. The remaining bits from transformation matrix 38 are applied to the shift register 31 forming part of psuedorandom sequence generator 39. When register 31 is loaded, clock 40 increments shift register 31 backwards, while decrementing binary counter 45 previously preset to its full count. Decrementing of register 31 and counter 45 continues until comparator 44 detects correspondence between the preset count in register 43 and the count in counter 45. At this point, the output of comparator 44 goes to a logic 1, which, through the operation of inverter 60, disables coincidence gate 41 to thereby block further clock pulses from entering register 31 and counter 45. Register 31 now stores a binary number identical to that which was supplied from transformation matrix 20 to shift register 18 of the psuedorandom sequence generator 21 at the control console.

Transformation matrix 46, which receives the contents of shift register 31 is the reverse of the transformation matrix 20. Thus, the bits on bus 35 correspond to the guest key code, while those on bus 33 correspond to the output of adder 3. The bits on bus 33 are applied to modulo-2 subtractor 48, while the key code on bus 35 is applied to the subtrahend input of the subtractor 48. The output of the subtractor thus corresponds to the input to adder 3 from the transformation matrix at the control console. Transformation matrix 49 is the reverse of transformation matrix 4 and thus, the output of transformation matrix 49 corresponds to the order code, room number and time of departure. The order code is supplied to subtractor 50, the room number to comparator 51 and the time of departure to the comparator 52 and subtractor 90.

Each lock mechanism is provided with a binary counter 65 operating in synchronism with the binary counter 16 of the control console. Clock 66 corresponds to clock 17, and thus when clock 17 provides clock pulses spaced at 1/60 of a second, clock 66 also provides pulses at 1/60 of a second intervals. Any lack of synchronism is acceptable to the system as long as the time interval is within the allowable time interval between check-in time and the time of presentation of the key card 28 to the lock mechanism.

The count in binary counter 65 is applied to the subtrahend input of the subtractor 50, while the minuend input receives the order code from the transformation matrix 49. The output of the subtractor 50 is supplied to a conventional threshold detector 68, the threshold of which is set to correspond to the allowable time interval between check-in time and the time of presentation of the key card 28 to the lock mechanism. If the key card 28 is presented to the key reader 37 within the predetermined time interval, the output of the threshold gate 68 is at a logic 0, enabling the coincidence gate 53, through inverter 67. The second input to gate 53 is coupled to the output of comparator 51 which compares the room number derived from the transformation matrix 49 with the room number stored in register 72. If a match exists, the output of comparator 51 goes to a logic 1 causing the output of coincidence gate 53 to also obtain a logic 1 enabling coincidence gate 69, while simultaneously resetting shift register 54. Shift register 54 is now ready to receive a new key code. This new key code is provided by the key code on bus 35, which is applied to the shift register 54 through enabled coincidence gate 69 and OR gate 71. In addition, the logic 1 at the output of gate 53 is applied to the lock bolt control circuit 62 through the OR gate 55 to cause the lock bolt associated with the room to move to its unlocked position. The lock bolt control circuit may correspond to that described in co-pending patent application Ser. No. 84,08, by Stephen Paull and Paul A. Crafton, filed Oct. 26, 1970 and assigned to an affiliate of the assignee of the present invention.

The guest continues to gain access to his room even after the preset time interval determined by the threshold of threshold gate 68 has passed. Once the lock mechanism has been set with the new key code, each time the guest presents his key card 28 to the key reader 37, the encipherment is read therefrom and passed through transformation matrix 38, psuedorandom sequence generator 39 and the transformation matrix 46 to recover the key code and place it on bus 35 in the manner just described.

More specifically, the bits on bus 32 correspond to the preset count applied to the binary counter 13 of FIG. 1, while the code applied to the shift register 31 from the matrix 38 corresponds to the output from the shift register 18 of the psuedorandom sequence generator 21 when coincidence gate 24 has been disabled. Clock 40, operating through coincidence gate 41, shifts register 31 backwards while decrementing counter 45, which has been preset to its full count. When the preset count in register 43 corresponds to the count in counter 45, the output of comparator 44 goes to a logic high disabling gate 41. At this time, the output from shift register 31, which is applied to the transformation matrix 46 corresponds to the guest key code and the output of the adder 3 after it has been interleaved by matrix 20. Transformation matrix 46 is the inverse of transformation matrix 20 and thus, the key code is recovered on bus 35 and applied to comparator 47. Since the key code on the guest's key card 28 now corresponds to the key code stored in shift register 54, the output of comparator 47 goes to a logic 1 generating an unlock trigger signal which is applied to the lock bolt mechanism 62 causing the lock bolt of the room to move to its unlocked position.

The time of departure feature will now be described. The guest's time of departure has been recovered as previously explained and applied to comparator 52 and subtractor 90. The comparator 52 also receives the count in binary counter 65. When the count in the binary counter 65 corresponds to the count representing the time of departure, the output of the comparator 52 raises to a logic 1, setting latch 96 to enable gate 94. The purpose of subtractor 90 is to provide the guest with a check-out grace period. While the subtrahend input of subtractor 90 receives the departure time, the minuend input receives the count in counter 65. The difference signal is applied to threshold circuit 92 having a threshold level corresponding to the grace period. As long as the input to threshold circuit 92 from subtractor 90 is below the threshold, and thus within the grace period, the output of circuit 92 is at a logic 0. When the grace period has lapsed, the output of threshold circuit 92 assumes a logic 1 causing the output of coincidence gate 94 to assume a logic 1, enabling coincidence gate 70, while resetting register 54. Each lock mechanism has associated therewith a random number generator 73 and a shift register 74 storing the random number generated by the generator 73. When coincidence gate 70 is enabled, the number stored in shift register 74 passes through the gate 70 and OR gate 71 to the shift register 54. Subsequent presentation of the guest key card 28 to the key reader 37 of the lock mechanism does not result in a logic high from comparator 47 since the key code on the guest key card differs from the key code now stored in shift register 54. Therefore, lock bolt mechanism 62 is not triggered.

Provision is also made for allowing hotel employees to enter rooms with a pass key. Pass keys are prepared in the same manner as the guest's key cards. At each room, the entire circuitry illustrated in FIG. 3, except for binary counter 65 and clock 66, are duplicated. The room register associated with the pass key circuitry at each lock mechanism, contains a common arbitrary room number. The grace period determined by the threshold circuit 68 in the pass key portion of the lock mechanism is set equal to the length of the work shift and the time of departure is set to correspond to the end of the work shift. In this manner, an employee's key card is valid only for the duration of his work shift.

FIG. 4 is a block diagram representation of the application of the present invention to a hotel. Central console 500 may be connected by means of wires to the hotel's restaurant 502, bar 503, shops 504 and the parking lot gate 505. Returning to FIG. 1, it can be seen that the encipherment imprinted on the guest key card 28 is also inserted into a central computer memory 400. This memory is accessed by a card reading terminal 406 at each service area in the hotel such as the bar or restaurant, using conventional computer techniques. If the guest key card is still valid, the comparator 404 displays an accept signal at a signaling means 402 at the service areas a reject signal otherwise.

By generating a random guest key code plus the room number, at the cashier's console 408, the cashier can change at random the guest key code in the central computer memory 400, thereby preventing the guest from continuing to charge services after he has paid his bill.

If a family or a group of persons is registered and assigned to two or more rooms as a group, the rooms may be master keyed by storing the key code used for the first key (as for example in a shift register) and using the stored key code instead of a new key code to generate the encipherment for the other room (s) of the group of assigned rooms. Each key of the group of keys would be used in the correct room lock mechanism the very first time the key is inserted, but after the first insertion all keys may be used interchangeably with each other. If it is desired to permit each key to be used for any room of the group even the first time used, the room numbers of all assigned rooms would be included in the encipherment on each key, and the lock mechanism would accept that one of the room numbers extracted from the encipherment that corresponds to its own room number. The output of transformation matrix 49 would involve all the assigned room numbers and would be compared in turn with the binary register 72. If one compares favorably, the output of comparator 51 becomes high.

As previously indicated, the system has application to baggage lockers. When so used, the time of departure feature would generally be omitted. Further, the inventive system has applicability to the field of rental vehicles. The automobile ignition lock, for example, may include a lock bolt mechanism and control circuit such as the circuit 62 used in hotels. The circuitry of FIG. 3 would be included in a box mounted in the vehicle, while circuitry of FIG. 1 would be included in the rental office.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.