Multiplexer for controlling and monitoring coded key operated accesses

[57] ABSTRACT

A multiplexer for scannings a plurality of controlled accesses, or doors, for determining if access or entry has been attempted. The scanner is coupled to a multiplicity of such accesses for determining if a key has been placed in its receptacle for operating a controlled latch. The key is preferably an electrical key having unlocking and identification information recorded thereon. If a key-in condition is determined, the scanner is momentarily stopped to allow the 'information derived from the key to be processed for determining the validity of the unlocking information and the key user identification information. This I.D. control information is also recorded for providing a record of the key usage relative to the time of day, the door and the recorded control information. If the control information is completely valid as to the unlocking information and the identification information only, then is the controlled latch operated.

Claims, 4 Drawing Figures

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PATENTED JUM 2 7 1972

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PATENTED JUN 2 7 1972

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PATENTED JUN 271972

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PATENTED JUN 271972

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MULTIPLEXER FOR CONTROLLING AND MONITORING CODED KEY OPERATED ACCESSES

This invention relates to multiplexing apparatus and more specifically to multiplexing apparatus for scanning a multiplicity of controlled accesses or doors for monitoring the operation of the accesses or doors and recording same.

The present invention in some of its aspects is related to the copending application bearing Ser. No. 35,061 and entitled ELECTRONIC IDENTIFICATION KEY ACTUATED CONTROL SYSTEM.

At the present time there is in commercial use electrical keys for electrically controlling a door latch or similar apparatus wherein an electrical key is operative for locking and unlocking the latch. One such electrical key that has been extensively used is the subject of U.S. Pat. No. Re. 27,013 granted on Dec. 22, 1970, and based on U.S. Pat. No. 3,392,558 granted on July 16, 1968. In this type of electrical key, the key itself is constructed of an electrical insulating material having a preselected number of open and closed conductive circuits or segments recorded thereon for defining a particular combination for unlocking a latch by means of a control circuit operative with the key. The control circuit is generally defined in terms of a “logical” network for decoding the pattern of conductive and non-conductive signals for determining whether or not the key is valid or if it has the correct combination for unlocking the controlled latch. It will be recognized that in this type of apparatus each key for a particular door will have a unique combination of circuits so that it will only be operative for a particular controlled access or door. This type of key has been further developed wherein the key also includes user identification information recorded thereon whereby each individual user is issued a key for a particular controlled access having a unique identification information or an identification number recorded thereon. The identification information is also recorded on the key in terms of preselected combination of conductive and nonconductive circuits or segments thereon. The control circuitry for such a key having unlocking and identification information recorded thereon has been developed so that despite the fact that the key may have the correct unlocking information thereon, if the identification number is not valid, the key having an invalid identification number will not be operative for operating a latch. Key identification numbers may be rendered valid or invalid readily by means of associated electrical apparatus. This type of key is described in detail in the copending application bearing Ser. No. 35,061.

When an installation requires a large number of such electrical keys, it has become advantageous to be able to monitor the operation of the controlled accesses or doors and to record the fact that a key has been employed in an attempt to operate a latch or the like. It is further desirable to not only record the fact of the key insertion and the operation of the latch but also to record the identification or identification number of the individual using the key and whether or not the key is a valid key relative to the door it is employed with. In a large structure such as an office building, for example, there is a need for monitoring the operation of the doors at all of the various offices and to record the time of use and point of use of the various keys that may be attempted to be employed at the various doors. It has been found to be relatively expensive to monitor these operations and record the events at a controlled access by employing a recording device or printing device associated with each door. Accordingly, at the present time there is a need for a relatively inexpensive, simple multiplexing apparatus for monitoring a multiplicity of controlled accesses for allowing the recording of the operations of the lock at the controlled access or door preferably by means of a printer. It is also desired to not only identify the fact that a particular latch has been operated but also the individual opening the latch or attempting to open the latch and the particular time of day the entry was made or attempted.

The present invention provides a relatively inexpensive and simple multiplexing apparatus that allows a multiplicity of controlled accesses or doors to be continuously scanned at a relatively high speed and allow the recording of the insertion of a key into a door in an attempt to operate the latch. The apparatus of the present invention may scan at a relatively high speed up to 40 doors or controlled accesses and record the desired operational information for the particular access. The apparatus of the present invention further allows the operator to void out or render invalid any particular key for a controlled access for a preselected period of time or for an indefinite period and then record any attempt to use an invalid key or a key having the wrong unlocking combination.

The multiplexing system of the present invention comprises a plurality of controlled accesses each having a latch and a key operable with control circuit means for unlocking the latch. The keys operable with the control means preferably have preselected combinations of control actuation information recorded thereon unique for operating the control means of a particular controlled access for unlocking the latch and preselected identification or identification information wherein the I.D. information is unique to a particular user to whom the key is issued. In order to unlock the latch, then, each access must be operated by a key having the correct unlocking information and the correct identification information and which identification information may be selectively rendered valid or invalid. Associated with each such controlled access is a high-speed scanning apparatus which is coupled to each controlled access for scanning and signalling the presence of a key in the controlled access. The scanning apparatus is controlled to continuously scan each controlled access and upon sensing the presence of a key at any one access or door the scanner is caused to momentarily stop the scanning operation. During the interval that the scanner is momentarily stopped the key information is sensed to determine the validity of the key from both the standpoint of the combination of unlocking information and the user identification information. If all of the information is correct and the key is determined to be a valid key the controlled latch is unlocked. As a result of the sensing of a particular key-in condition, the identification information along with the determination of the validity of the key is presented to the recording apparatus or printer for printing out the fact that the key has been attempted to be employed at the particular door or controlled access along with 1he identification information of the point of use of the key or door identification. The scanner is controlled so that during the interval that the printer is printing out the information relative to the key-in condition it can continue to scan the remaining controlled accesses. During successive scanning intervals the scanner may once again sense the previous key-in condition and for this purpose control apparatus is provided for inhibiting the recording of the same usage of a key to prevent the excessive redundant recording of information. Specifically, in the event that a key is maintained in its receptacle for an extensive period of time or an electrical malfunction results in the same type of signal being coupled back to the scanner, a key-in timer is provided for sensing such a long time interval and rendering the printer inoperative for printing out the information at a particular door and allow the printing to continue at the other doors. The control apparatus also includes means for sensing the operation of the printer and in the event it malfunctions, eliminates the printer operations to allow the scanner to continue to scan the various doors.

These and other features of the present invention may be more fully appreciated when considered in the light of the following specification and drawings, in which:

FIG. 1 is a block-schematic diagram of the multiplexing system embodying the present invention for a single controlled access or door;

FIG. 2 is a block diagram of a printer that may be employed in the system of FIG. 1;

FIG. 3 is a logical-block diagram of the multiplexing system of the present invention, and

FIG. 4 is a block-schematic diagram of a typical door circuit employed in the system of FIG. 3.

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The multiplexing system of the present invention can be most readily appreciated when the multiplexing system is implemented in terms of the electrically controlled latches which is the subject of the aforementioned U.S. Pat. No. Re. 27,013 and the type of keys disclosed in the copending patent application bearing Ser. No. 35,061. It will be recognized that the aforementioned copending patent application includes the basic features of the particular electronic lock and key that is the subject of U.S. Pat. No. Re. 27,013. This patent discloses an electrical key wherein the key is basically defined on an insulative substrate carrying a plurality of conductive and nonconductive segments recorded thereon and arranged in a preselected pattern or combination for unlocking a particular latch. The key is insertable into an energizable receptacle for providing a plurality of output signals from the receptacle in accordance with the pattern of segments recorded thereon. The signals derived from the receptacle are representative of the pattern of conductive segments on the key and are coupled to a sensing circuit which may be a “logical” circuit for determining the validity of the combination on the key for operating the latch. This type of key and control apparatus is employed in the present invention. If a more detailed disclosure of this type of key and control apparatus is required, reference may be had to U.S. Pat. No. Re. 27,013 which is incorporated herein by reference. The type of electrical key employed for the purposes of the present invention also incorporates the teachings of the copending application bearing Ser. No. 35,061 in that the key is also constructed as including user identification information or I.D. information. The key, then, is operable only for unlatching a door or controlled access when the key includes not only the correct unlocking information but also a valid identification number. The determination of the validity of the identification number may also be effected by means of sensing circuits employing logical networks as more specifically described in the aforementioned copending Patent application Ser. No. 35,061. It will be recognized that the keys per se disclosed in the latter mentioned copending application are not the subject of the present application.

To further facilitate the understanding of the present invention the recording apparatus employed for the purposes of the present invention may be the type of printing apparatus described in said copending application bearing Ser. No. 35,061. In particular, the printing unit is a commercially available printer which is described in the copending application as being available from the Datatotal Company and now known as the Hecon Corporation, 31 Park Road, New Shrewsbury, NJ. The particular feature of this printer is that it can be advantageously employed to not only record the information as to usage of the key but also may be readily adapted for rendering certain identification numbers valid or invalid. The present invention will be described on the basis of the structure for recording and voiding out identification numbers as specifically disclosed in the copending application and more specifically FIG. 5 thereof. For the purposes of the present invention the information derived from the printing unit includes the electrical signal indicative that a key inserted has a void identification number and also the print command that is applied to the print hammer (identified as the hammer 71 in the copending patent application) for printing out all of the information once the printing wheels have been rotated to the correct character for printing out the sensed information. This print command signal and the signal indicative of a void identification number is utilized in the control apparatus for the present invention and the detailed disclosure with respect to the printer and its associated operations are incorporated herein by reference from the copending patent application bearing Ser. No. 35,061.

The aforementioned copending application bearing Ser. No. 35,061 also discloses and claims an elementary multiplexing system incorporating print-out or recording of key and user information of the type under consideration by the present application.

Now referring to FIG. 1, the general organization of the multiplexing apparatus of the present invention will be examined. The general organization illustrated in FIG. 1 is directed to the multiplexing operations as it applies to a typical controlled access or door. It will be recognized that file multiplexing operations will be the same for additional doors. For this reason, then, each controlled access or door will have a door latch control A and a door circuit B that is associated with the scanner C for time sharing a printer D. It will be recognized that the scanner C is effective for providing unique signals for sequentially scanning each door latch control A to determine whether or not a key is in the receptacle. If it is determined that a key is “in”, the scanner is adapted for deriving the information recorded on the keys and for printing out same at the printer D. In this fashion the scanning element C may be utilized for all of the controlled doors and a single printer D is time shared in accordance with the present invention. As indicated hereinabove the door latch control A comprises an electrically controlled latch 10 controlled by means of the electrical key 11 having unlocking information and I.D. information recorded thereon as disclosed hereinabove and in particular in U.S. Pat. No. Re. 27,013 and the aforementioned copending application bearing Ser. No. 35,061. The key 11 is associated with the key receptacle 12 for receiving the key 11 therein and the placement of the key in the receptacle allows the information coded on the key for unlocking the latch and providing the I.D. or identification information to the printer D for recording the fact of the placement of the key 11 in the key receptacle 12 or the “key-in” condition. The combination data or the unlocking data derived from the receptacle 12 is applied to a combination decoding element 13 associated with the control latch 10 for operating the latch only when a valid key signal is provided therefrom. The valid key signal in this instance comprises not only the correct combination or unlocking data from the key 11 but also the correct I.D. data. The determination of the validity or invalidity of the identification information is derived from the printer D and is utilized in combination with the conventional logical circuits described in the aforementioned reissue patent and the copending application for providing the valid key output coupled to operate the control latch 10. The structure described with respect to the door latch control A is defined in accordance with the structures disclosed in the aforementioned reissue patent and the copending patent application and as such the door latch control A is not a novel element of the combination disclosed herein.

Each controlled access or door also has a door circuit B for receiving the information from the door latch control A in response to the signal from the scanner C for application and processing by the printer D. The door circuit B is defined for responding to a decoded door signal from the scanner C that is unique to the particular door or controlled access. The door circuit B includes the inhibit gates 14 which receive the I.D. data derived from the key receptacle 12 of the door latch control A. In addition, the inhibit gates 14 receive the output indication from the combination decode element 13 indicative that the key in the receptacle 12 has a wrong unlocking combination thereon. The inhibit gates 14 are defined for receiving the indication from the receptacle 12 that key 11 has been inserted into a receptacle or a “key-in signal. It will be recognized that for this purpose the inhibit gates 14 comprise an individual inhibit circuit for each data bit or piece of information applied to the gates 14. The gates 14 are defined so that they inhibit any information applied thereto from appearing at their outputs in the absence of a decoded door signal from the scanner C.

The control of the inhibit gates 14 is under the control of a decoded door signal from the scanner C and a logical network identified as the inhibit gates control 15 provided with each door circuit. The input signals to the inhibit gates control 15 are the signals derived from the gates 14 indicative of the signal that the key 11 in the receptacle 12 has the wrong combination as well as the signal from the printer D that the key 11

3,673,569 in the receptacle 12 has a void I.D. number. In the event that the combination recorded on the key is correct and the identification number is correct the inhibit gate control 15 will couple a signal back to the door latch control A and specifically the combination decode circuit 13 for “logical” combination with the combination data to provide the input indication to the element 13 for deriving the correct code signal from the element 13 to operate the latch 10.

The scanner C comprises a scanning element 16 under the control of a scanner control element 17. The scanner 16 may comprise a binary coded decimal counter having a binary to decimal decoder coupled thereto for providing a decimal output indication or a unique signal representative of each count of the counter. The counter is under the control of the scanner control element 17 and continually pulses or counts up the counter to cause the plurality of the unique output signals to be generated from the scanner 16 for the purposes of scanning or determining the key-in condition of each door controlled by the scanner C. For this purpose, the key-in signal is applied to the scanner control element 17 from the inhibit gates 14 when a key is sensed as being in the receptacle 12. The key-in signal applied to the scanner control 17 is effective for stopping the scanner 16 or stopping the counter momentarily to allow the information to be derived from the key receptacle 25 12 and processed and printed out by the printer D. At the completion of the printing operation, the printer D will provide a signal identified as a “print command” to the scanner control element 17 that will reactivate the scanner to allow it to continue to scan the remaining doors. It will be recognized that each decimal output signal from the scanner 16 is uniquely coupled to a particular door circuit for sensing the presence or absence of a key in the corresponding receptacle. If there is no key in the receptacle for a particular door the scanner is pulsed to the next count so as to scan the successive door and to successively and continuously scan for each count of the counter and recommence its scanning operation at door “0” after the maximum count of the counter is reached.

The printer D is shown in broad block form in FIG. 1 and in more detailed block diagram form in FIG. 2. It will be recog- 40 nized that the printer D is the printer identified hereinabove that is commercially available from the Datatotal Company, now known as the Hecon Corporation of New Shrewsbury, N.J. In addition it will be recognized that the detailed implementation and operation of such a printer is described in the 45 copending application bearing Ser. No. 35,061. The description of the operation and the structure for this printer from said copending application is incorporated herein by reference. For the purposes of the present invention, the printer D can be considered as comprising the major elements as particularly identified in FIG. 2. The printer D comprises the I.D. decode element 18 associated with the I.D. void element 19. The I.D. decode element is responsive to the key identification data received from the inhibit gates 14 of the door circuit B. The I.D. decode element 18 receives the generated binary coded decimal bits from the inhibit gate 14 and decodes it into decimal form. This information is applied to the print control element 20 for the print wheel associated with the print hammer for printing out the decoded decimal gQ information derived from the key 11 in the receptacle 12. The print wheel and print hammer are illustrated in block form and identified in FIG. 2 by the reference numeral 21. The operation of the print wheels is such that when the print wheels are rotated in the correct relationship with respect to the print hammer a print command is generated to cause the print hammer to strike the print wheels for printing out the characters opposite the hammer on the record medium. Specifically, the characters on the periphery of the print wheels will be rotated until the particular decimal information decoded from 70 the element 18 is in a position to be printed out by the hammer of the printing element D.

The print control 20 is also responsive to a key-in signal derived from the individual inhibit gates of the inhibit gates 14. The door I.D. signal and the wrong combination signal are 75 also coupled to the print control to allow the printer D to print out the door identification as well as the wrong combination in response to the placement of a key 11 in a receptacle 12 for a controlled access.

Another important aspect of this type of operation is the ability to determine from the I.D. data whether or not the key has a valid I.D. number. For this purpose the decoded I.D. data from the element 18 is utilized by the I.D. void element 19 to determine the validity or invalidity of the I.D. information. If the I.D. void element 19 determines that the I.D. recorded on a key 11 is void it produces an output signal that is coupled back to the inhibit gates control 15 of the door circuit to prevent the latch 10 from being operated.

With the above general organization in mind, the operation of the multiplexer can be examined. The operation is such that the scanner element 16 is continuously under control of the control element 17 to cause the scanner 16 to continuously produce decoded door signals therefrom. With no keys placed in the receptacles for any of the door circuits, then, the scanner continuously produces output signals in accordance with the maximum count capacity of the scanner and upon completion of its count will recycle or recommence its count. Accordingly, the unique signals from the scanner C are coupled to each of the controlled door circuits, and 40 such decoded signals are indicated in FIG. 1. For the purposes of understanding the present invention, it will be assumed that a key 11 having the correct unlocking combination data recorded thereon and the correct I.D. data thereon is placed in the key receptacle 12. The door circuit B will be considered relative to the decoded door signals from the scanner C to be door “0”. With the placement of the key 11 in a receptacle 12, then, the combination data derived from the receptacle 12 is applied to the decoding network 13. In addition, the I.D. data is applied to the inhibit gates 14 for the door circuit B. It will be recognized that although a key 11 has the correct unlocking combination data recorded thereon that the combination decode element 13 will not operate a latch 10 until it receives the indication from the inhibit gate control 15 that the key is a valid one, i.e., the I.D. number is correct. The I.D. data, along with the key-in signal, then, is applied in parallel circuit relationship to the gates 14. This information will not be available at the outputs of the inhibit gates 14 except when a decoding door signal unique to the particular door is applied to the gates 14 for rendering them conductive. In this instance, then, when the scanner 16 provides the “0” door signal the I.D. data from the door latch control A and the key-in signal from the receptacle 12 and the wrong combination signal from the combination decode element 13 will all be available at the output circuits from the inhibit gates 14. The key-in signal will be applied to the print control element 20 as well as to the scanner control element 17. The detection of the key 11 in the receptacle 12 by the “0” door signal appearing at the inhibit gates 14 will cause the scanner control 17 to stop the scanning operation or stop the counting up of the counter to maintain the decoded door signal at the “0” door. At this time, the I.D. data along with the door number or I.D. is coupled to the printer D along with the key-in signal and the wrong combination indication. This will cause the printer to print out the door number, the key I.D. number and the time of day, or any other information required to be identified for controlling the door circuit B. If the I.D. void element 19 determines that the I.D. number is void, a void I.D. signal will be applied from the inhibit gates control 15. If this condition exists, then, the correct code signal from the combination decode element 13 will not be generated and the latch 10 will not be operated. Since it is assumed that the I.D. number is valid, a void I.D. signal will not be generated and since neither the void I.D. signal nor the wrong combination signal is applied to the inhibit gates 15, a valid key signal will be generated and applied to the decode element 13. This will complete the logical combination of the correct input indications to the combination decode element 13 to allow it to produce a correct code signal for the controlled latch 10 to operate same. Along with the initiation of

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the print-out of the information from the printer D, the same print command signal is coupled back from the printer D to the scanner C. Specifically, the print command signal is applied to the control element 17 to reactivate the counter to cause the scanner to continue its scanning operation.

Now referring to FIGS. 3 and 4 the detailed organization of the multiplexer of the present invention represented by the block diagram of FIG. 1 will be described for providing the signals to the printer D as represented in FIG. 2. FIG. 3 illustrates in logical-block diagram form the multiplexer as it is applied to a plurality of controlled doors identified as the doors 0, 1, 2, 3,. . . up to 40 controlled doors. It should be recognized that the door circuits B described in connection with FIG. 1 are the same for each of the controlled doors 0, 1,2, etc., as detailed in FIG. 3. The typical door circuits illustrated in FIG. 3 include further features relative to the control of the data from the inhibit gates 14 that are not apparent from the comprehensive organization illustrated in FIG. 1. Each particular door circuit as illustrated in FIG. 3 includes within the inhibit gates control 15 a “key-in” timing element 40 for determining when a key 11 remains in its receptacle beyond a predetermined time interval to allow the multiplexer and the printer D to continue its scanning operation without the printing out of redundant data. Once a key has been sensed as being in a particular door and the information relative to the key has been printed out by the printer D without the removal of the key for a time interval that allows the scanner D to return to the same door, the invention is defined to prevent the print-out after a set time interval of the information relative to such a key retained in a receptacle. A key-in timer 40 provided for each door circuit B allows the scanner to continue to operate and prevent the printer D from printing out the same information continuously.

It facilitates the understanding of the logical-block diagram of FIG. 3 if the detailed implementation of the inhibit gates 14 is first considered. This consideration is relative to the circuit diagrams illustrated in FIG. 4 and the logical-control gates associated with the gates 14. As indicated hereinabove, the inhibit gates 14 comprise a plurality of gates for individually receiving in parallel circuit fashion the data bits from the key receptacle 12. Each inhibit gate includes a transistor switch having its emitter lead connected directly to ground and its collector lead connected as an output element for the gate. The base lead for each transistor gate is connected in common to be responsive to the door I.D. signal derived from the scanner C. The data bits are applied to the inhibit gates by means of input circuits defined by means of the base-emitter circuit so that in the normal conductive conditions of the gates 14 no output indication is derived from any of the gates in the absence of a door I.D. signal applied to the respective base leads. Stated differently, the data bits applied from the key receptacle 12 do not appear at the output circuits of the individual gates until a door I.D. signal is received therefrom. As indicated in FIG. 4, for the purposes of determining the I.D. number of a key in a receptacle 12, the I.D. data bits are recorded on a key in terms of the binary coded decimal 8-4-21 notation. Accordingly, an individual gate is connected to be responsive to each of the corresponding data bits arranged in the 8-4-2-1 notation derived from the receptacle 12 for providing the appropriate signals therefrom in response to the triggering thereof. In the same fashion, an inhibit gate is provided for the key-in signal from the receptacle 12 and the wrong combination signal derived from the combination decoding element 13 of the door latch control A. It will be recognized with respect to the I.D. data bits, the same pattern of binary bits that appear on the key will be electrically represented on the output circuits for the 8-4-2-1 gates of the gating element 14. The presence of the correct door I.D. signal, then, at the inhibit gates 14 will be effective for coupling out the data bits, key-in, and wrong combination applied to the gates 14 in a parallel circuit relationship for application to the control gates 15 and to the printer D. For this purpose each of the inhibit gates 14 for each door circuit B is coupled to an individual OR circuit arranged between the outputs of the inhibit gates for each of the door circuits and the input to the I.D. decoder 18 of the printer D. For example, the “ 1 ” data bit of the I.D. data bits is applied to the “OR” circuit 30 along with the “ 1 ” data bits from the remaining controlled door circuits as diagrammatically represented in FIG. 4. In the same fashion, individual OR circuits 31, 32 and 33 are provided for the ‘.‘2”, “4” and “8” data bits and their output circuits are coupled to the I.D. decoder 18 for providing the decimal output indication corresponding to the binary coded data bits applied thereto.

The key-in signal applied to the individual key-in inhibit gate of the gates 14 appear at the output of the gate in response to the reception of a door I.D. signal and is applied to the printer control element 20, as best appreciated from FIG. 2. In the same fashion, the wrong combination signal will appear at the output of the wrong combination inhibit gate in response to the door I.D. signal. The wrong combination signal is applied to an OR gate 34 of the inhibit gate control element 15 along with the wrong combination signals from the remaining controlled doors. The output of the OR gate 34 indicative of the wrong combination from any one of the doors is applied to an emitter follower circuit 35 and then to the printer control element 20 and the no-error NOR gate 36. The emitter of the emitter follower circuit 35 is also responsive to the void I.D. signal provided from the I.D. void element 19 of the printer D. It will be recognized that the output signal from the emitter follower circuit 35 will be TRUE if the wrong combination signal or the void I.D. signal is present at the input. If this output condition exists it will inhibit the output signals from the no-error NOR gate 36. If neither input signal appears at the emitter follower circuit 35, then, the output of the emitter follower circuit 35 will be in a FALSE condition so as to provide one of the input signals to the NOR gate 36 for satisfying the input conditions thereof. It will be recognized that with the absence of the wrong combination signal and the void I.D. signal, that these are the necessary conditions for signalling a valid key is present in the receptacle 12. No-error NOR gate 36 also receives the decoded door I.D. signal from the scanning element C as an input signal. The remaining input to the NOR gate 36 is the print command signal that is initiated from the printer D and inverted and applied to the NOR gate 36 by means of the scanner control element 17, as will be more apparent hereinafter. At this point it is important to note that if a void I.D. and wrong combination signal is absent (FALSE) at the NOR gate 36 along with the print command and the decoded door I.D. signal that only under these conditions will an output signal be produced to trigger the one-shot element 37. The one-shot element 37 is essentially a timing element which allows a door to be held open while allowing the scanning element C to continue scanning and prevent the printer from printing out during the same dooropen period. For this purpose, the one-shot output signal will persist on the order of 3 to 5 seconds and apply its output signal to the OR gate 38. The resulting output signal from the OR gate 38, as a result of receiving the output signal from the one-shot element 37, will be applied to an OR gate 39. The other input signal to the OR gate 39 is the decoded I.D. signal received from the scanner 16. The presence of a signal from the OR gate 38 at the inhibit input terminal of the OR gate 39 is effective for overriding the door decoded I.D. signal applied to the individual inhibit gates of the inhibit gates 14 to thereby prevent the presence of the output indications at the gate 14 and to the printer D for printing out upon successive scanning of the same door under the same door-open condition.

It should also be noted that the output signal from the oneshot 37 is indicative of a valid key present in the receptacle 12 and this signal is coupled back to the combination decoding element 13 for completing the logical conditions necessary for operating the controlled latch 10. Stated differently, the valid key signal derived from the one-shot 37 is active for causing the valid key signal to appear at the output of the combination decode element 13 and operate the controlled latch 10. The

3,673,569 other input signal to the OR circuit 38 is a signal provided by a key-in timing element 40. The key-in timing element 40 is responsive to a key-in signal directly derived from the receptacle 12. The operation of the key-in timer 40 is such that if the key is left in its receptacle 12 for longer than a preselected 5 time interval the key-in control element 14 will provide a signal to the OR circuit 38 for inhibiting or overriding the door I.D. circuit signals applied to the inhibit gates 14 and prevent the data bits from being coupled to the printer D. If the key 11 is removed from its receptacle during the scanning interval the key-in timer 40 is ineffective and the operation of the gates 14 for each data bit is as discussed hereinabove, in response to a decoded door I.D. signal received at the gate 39. The “key-in” timer circuit 40 may comprise an RC timing circuit that is coupled to be responsive to a key-in signal from the receptacle 12 ¹and to automatically time out for providing the output indication in accordance with the selected time interval.

The output signal from the key-in timer 40 is also coupled to an OR circuit 40-E in parallel circuit relationship with the out- -₀put signals from the key-in timers for the remaining controlled doors. The output signal from the OR circuit 40-E may be applied to a door error lamp for visually indicating the “erroneous” door condition. This does not identify the door where the “key-in” condition exists and therefore the print out would 25 have to be examined to determine at which door the same information has been printed out.

Now referring to FIG. 3, the detailed implementation of the scanner C will be examined. It should be appreciated from the above description with respect to FIG. 1 that the scanner C in- 30 eludes the scanner 16 and the scanner control element 17 operative therewith. The scanner 16 includes an oscillator 43 which may provide output pulses at the rate of 20 milliseconds coupled to a NAND gate 44. The second input to the NAND gate 44 is derived from the scanner control element 17 and is 35 normally arranged in a high voltage state to allow the output pulses of the oscillator 43 to appear at the output of the NAND gate 44. This output signal may be inverted by a conventional NAND gate 45 before it is applied to a two-stage binary coded decimal counter 46. The binary coded decimal 40 counter 46 comprises a first stage which has a ten-count capacity and a second stage coupled thereto having a fourcount capacity. The first stage or units counter is identified as the counter 46U and the second stage or tens counter is identified as a counter 46T. The counter 46 arranged in this 45 fashion is defined to count up to 40 counts in accordance with the usual binary coded decimal counting techniques. The binary coded output signals from the counter 46U and 46T provide a different pattern of output signals in accordance with each of the counts stored in the counter. It should also be ⁵⁰ recognized that when the counter reaches its last count or the count of 39, it is recycled and the counting sequence restarts at “0”. The operation of the counter 46 may be signalled by the operational lights 47 coupled thereto as illustrated. The output of the counter 46 is coupled to a binary to decimal decoder 48 which receives the output pattern of binary coded pulses from the counters 46U and 46T and decodes it in terms of the decimal system. The decoding of these signals by the element 48 will provide a unique output signal from one of 40 output lines (0 - 39) from the decoder 48. Stated differently, for each pattern of signals received by the decoder 48 from the binary coded decimal counter 46, only one of the 40 output leads from the decoder will be in a FALSE state. The 40 outputs from the decoder 48 are defined for identifying the 40 doors that may be controlled in accordance with the present invention and are identified as the doors 0 - 39. In this respect the “0 output from the decoder 48 is applied to door “0” circuit at the OR circuit 39 therefor. In the same fashion, the “ 1 ” output from the decoder 48 is applied to a corresponding OR circuit for the door 1 and the “2” output is similarly coupled to the door 2 circuit. The same arrangement prevails for the remaining 37 controlled doors.

The scanner control element 17 is adapted for controlling the voltage level of the signal applied to the NAND gate 44 75 and thereby controlling the pulsing of the counter 46 from the oscillator 43. For this purpose the scanner control element 17 includes the emitter follower circuits 50 and 50A that are connected to be responsive to the key-in signal from the individual gate of the gates 14 unless it is inhibited by inhibit key-in circuit SOB. The output of the emitter follower circuit 50A is applied to a “key-in” bistable element or flip-flop 51 which is responsive to the reception of the key-in signal from the emitter follower 50 to switch the flip-flop 51 into its low voltage state and therefore prevent the oscillator pulses of oscillator 43 from being applied to counter 46. Specifically, the changing of the state of the key-in flip-flop 51 prevents the input conditions at the NAND gate 44 from being satisfied and therefore no output signal appears at the NAND gate 44 and no output appears at the output of the NAND gate 45 to pulse the counter 46. Under these conditions the scanning operation is stopped to allow the information derived from the key in the receptacle to be printed out. The key-in flip-flop 51 is reset by means of the print command derived from the printer D. The print command signal will reset the flip-flop 51 so that its output will again be in its normal high voltage state and allow the pulses from the oscillator 43 to count up the counter 46 and continue the scanning operation from door to door.

For the purpose of facilitating resetting of the key-in flipflop 51 there is provided an inhibit key-in control flip-flop element 52. This K flip-flop gets its clock input from the output of the NAND gate 45 and its output connected to the inhibit key-in circuit SOB. This output is normally in the low voltage state, thereby conditioning the flip-flop 51 for the reception of the key-in signals. The set input of the flip-flop 52 receives the print command from the inverter 53. The provision of the flipflop 52 is provided merely to inhibit the key-in command during the period from the beginning of the print until the falling edge of the signal out of NAND element 45.

It should also be noted that the print command applied to the “key-in” flip-flop 51 is also coupled by means of the inverter 53 as the input signal to the norerror NOR gate 36 to the door circuits as illustrated for the 0 door circuit.

The scanner control element 17 also includes a malfunction reset timer 54 which functions as a “watchdog” timer for determining if a print command is received at the desired time intervals for resetting the “key-in” flip-flop 51. If the print command is not received within the predetermined time interval, the flip-flop 51 will be reset so that the scanning operation may continue. For this purpose the input to the malfunction reset timer 54 is coupled to the output circuit of the “key-in” flip-flop 51 in common with the coupling of the flip-flop output signal to the AND gate 44. The output of the malfunction reset timer 54 is coupled to an input of the key-in flip-flop 51 to reset it in the event the print command is not received from the printer D within the prescribed time interval, on the order of 2 seconds. The output of the malfunction reset may also be applied to an auxiliary flip-flop 55 having its output coupled to a malfunction indicating light 56. Accordingly, when the malfunction reset timer provides a signal for resetting the key-in flip-flop 51 it will also reset the flip-flop 55 and provide a 6θ visual indication of the malfunction of the printer D.

A further feature of the scanner control element 17 is the provision of a “daytime” switch which allows the printer to be eliminated from the door circuits during the daytime, or during business hours, to prevent the unnecessary usage of paper 65 while the business or room is open for the normal course of business. The daytime switch may be a manually operated switch and is identified by the reference numeral 57 and is coupled between the print signal from the printer D or the one-shot multivibrator 59 to the input of the flip-flop 51 by 70 means of a delay circuit 58 having its input connected to the emitter follower circuit 50 and its output connected to a oneshot multivibrator 59. When the switch 57 is in a normal position the print command will come from the printer D and while in the no-print position the command will come from the one-shot multivibrator 59 to let the scanning continue.

3,673,569

With the above structure in mind, then, the detailed operation of the multiplexer will be described. If there are no keys present in any of the 40 doors under the control of the multiplexer then the inputs to the NAND gate 44 will be satisfied and the pulses from the oscillator 43 will be coupled directly to the counter 46 and the counter will be stepped through its 40 counts sequentially and re-cycled to “0” and continuously count the pulses applied thereto. During this interval the decoder 48 will provide the scanning signals to each of the 40 doors to determine whether or not a key is present in any of the 40 doors. If no key is present in any of the doors the counter will continue to scan since the input conditions of the NAND gate 44 are continuously being satisfied.

If it is assumed that a key 11 is inserted in one of the doors, then, during the scanning interval when the signal from the decoder 48 is applied to the individual door circuit B having the key placed in its receptacle, a key-in signal will be transferred from the inhibit gates 14 to the emitter follower circuit 50 for switching the state of the key-in flip-flop 51. With the switching of the flip-flop 51, the NAND circuit 44 input condition will no longer be satisfied and the counter 46 will be halted. This causes the FALSE output signal for the decoder 48 to be maintained in its FALSE condition and applied to the respective door circuit B to allow the information to be derived from the key 11 and to be processed to determine the validity or invalidity of the key. During this interval, then, the I.D. data bits are derived from the inhibit gates 14 and applied to the printer D. The I.D. data bits are decoded by the I.D. decoder 18 and examined by the I.D. void element 19 to determine the validity or invalidity of the I.D. bits. The decoded I.D. data is applied to the print control 20 in combination with the key-in, door I.D. and wrong combination signals for rotating the print wheels in correct relationship to print out the decoded I.D. data, door I.D. data, etc. At this same interval, the “combination” data derived from the key receptacle 12 is examined by the combination decode element 13 for determining whether or not the unlocking or combination data is correct. If the unlocking data is incorrect, a wrong combination signal will be applied to the inhibit gates 14 and derived from the output of the gates 14 and will appear at the print control element 20 as well. The wrong combination signal from the inhibit gates 14 will also appear at the emitter follower circuit 35. A further signal with respect to the evaluation of the validity or invalidity of the I.D. number may appear at the emitter follower circuit 35. In the event that the key has a valid I.D. number and a correct combination, a FALSE (zero) output signal will be coupled from the emitter follower circuit 35 to the no-error NOR gate 36. During this same interval, the decoded door signal and the print command will be present at the no-error NOR gate 36 so as to cause the oneshot door-open circuit 37 to be triggered and thereby apply a valid key signal to the combination decode element 13. This last indication of the information on the key 11 will cause the combination decode element 13 to provide a valid key output signal therefrom for operating the controlled latch 10. It will, of course, be appreciated that in the event that a void I.D. signal or a wrong combination signal is received at the emitter follower circuit 35 that a TRUE output from the no-error NOR gate 36 will not be provided and therefore no valid key signal will be coupled back from the door circuit to the element 13 thereby preventing the operation of the controlled latch 10. During the interval, then, that the I.D. information is being decoded by the printer D and once the print wheels are in the correct position for a print out a print command signal is applied to the print hammer and is coupled back to the key-in flip-flop 51 to reset it and cause the counter 46 to continue its counting and thereby the scanning of the successive doors. If during the successive scanning intervals a key is maintained in its receptacle and it is once again sensed during successive scanning intervals, the key-in timer 40 will have been activated to provide an output signal at the OR gate 38. This signal will be applied as an inhibit signal to the OR gate 39 causing it to override the decoded door signal and therefore prevent the coupling out of the information from the inhibit gates 14 to the printer D. This condition will exist until a key is removed from the receptacle. A similar signal will exist if an electrical condition that causes an equivalent signal to a key-in signal to persist will exist until the electrical condition is removed. This prevents the printer D from continuously printing out the same information in response to a single application of a key to its receptacle.

It should now be appreciated that the present invention has advanced the state of the art through the provision of a multiplexing arrangement wherein a multiplicity of controlled accesses or doors may be continuously scanned at a rapid rate for determining a “key-in” condition. In the event such a condition is sensed, the scanning is interrupted to allow the desired control information to be printed out by a time shared printer.