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FIELD OF THE INVENTION 
     The present invention relates to code responsive barrier movement operators and more particularly to code learning methods and apparatus for such systems. 
     BACKGROUND 
     Barrier movement operators are known in the art which respond to access or security codes wirelessly transmitted from hand held or mounted transmitters by controlling the position of a barrier. One common example of such a barrier movement operator is the ubiquitous automatic garage door operator, however other barrier movement operators for controlling doors, shutters, windows and gates are also known. 
     Some barrier movement operators store representations of one or more authorized access codes which are compared to received access codes to determine whether permission is to be given to control the barrier. During the early days of security code responsive operators, switches were set in both the transmitter and a receiver of the operator to identify the code to be transmitted and the operator code to which the received codes were compared. Product evolution has provided an advantage whereby security codes are learned at the operator by placing the operator in a learn mode and wirelessly transmitting a security code to be learned. The operator, entered the learning mode at the press of a pushbutton and while in the learning mode, received the transmitted security codes and stored them in memory. Such a learning mode was initiated by manually pressing a learn button on a part of the operator and/or by transmitting a predetermined signal from a transmitter already learned by the operator. The learning mode then terminated for example, a predetermined period of time after its initiation. The learning mode would be entered each time the appropriate pushbutton was pressed. When not in the learning mode the operator is in an operate mode in which received wireless access codes activate the operator if they bear a known relationship to codes already learned by the operator. 
     The use of an automatic learn mode to learn wirelessly transmitted access codes has simplified the use of barrier operators. Since the simplification of learning access codes there has remained a possibility that an unauthorized individual could press the learn button, cause the operator to enter the learn mode and transmit an unauthorized code to the operator where it was learned. Later, the unauthorized individual could return and transmit the unauthorized code to the operator which would respond by controlling the barrier. A need exists for a method and arrangement of controlling a barrier operator which retains the ease of security code learning and which provides resistance to the learning of unauthorized codes. 
     SUMMARY 
     This need is met and a technical advance is achieved in accordance with the barrier movement operator methods and apparatus described and claimed herein. The barrier movement operator includes the capability of responding to a learn mode signal by learning access codes which later can be used to control the movement of the barrier. In addition, the operator detects the occurrence of a predetermined event and responds thereto by prohibiting further learn mode operations. In this way, prior to the predetermined event easy code learning is achieved, but is prohibited after the event. Such a predetermined event may be the storage of a number of security codes initially set by a user or by the manufacturer of the operator. Alternatively, the predetermined event might be the receipt of a signal from the throwing (pressing) of a switch or the receipt of a particular wireless signal. While in the prohibiting learning mode, no further access codes will be learned by the apparatus. Such protects from unauthorized users teaching their codes to the operator. The operator may include an overriding of the learning prohibition which can be closely controlled by the individuals in control of the barrier movement operator. In one embodiment, the operator includes a key switch which can only be thrown by a person in control who is in possession of a physical key. New codes are entered into an operator in the learning prohibition mode by throwing the keyed switch-which again permits use of the learn mode until the prohibition is again activated. The learning prohibition signal may be originated from a particular master transmitter which the owner keeps secure or which only the manufacturer or distributor of the barrier movement operator can use. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of a garage interior having an installed garage door opener; 
         FIG. 2  is a block diagram of a head end portion of the garage door opener; 
         FIG. 3  is a flow diagram of a function performed to prohibit further access code learning; and 
         FIG. 4  is a flow diagram of a function to re-activate access code learning after it has been prohibited. 
     
    
    
     DESCRIPTION 
       FIG. 1  illustrates a barrier movement operator  10  implemented as a garage door operator. It is to be understood that barrier movement operators for other types of barriers and other types of access code responsive systems are within the scope of the present invention. Barrier movement operator  10  includes a head end  12  mounted from the ceiling  16  of a garage  14 . The head end  12  includes an electric motor  106  and a controller  83  for controlling the operation of the motor. A trolley rail  18  extends between the head end  12  and the garage front wall and conveys a trolley  20 . A chain connects the trolley  20  to the motor  106  to move the trolley back and forth along rail  18 . Trolley  20  is connected to a multi panel door  24  by a member  22  and as the trolley  20  moves back and forth the door  24  is raised and lowered on a pair of tracks  28 . A wall control unit  39  is connected to the controller  83  of head end  12  so that when a button  39 B is pressed a command to move or stop the door is given to the controller. Controller  83  also receives commands transmitted from two hand held transmitters  30  ad  31  and from an externally wall mounted transmitted  34 . 
       FIG. 2  is a block diagram of head end  12  and the connections between controller  83  and external signal sources. Controller  83  includes a micro-controller  84  which includes memory to store the program and data to implement control of door movement. Micro-controller  84  is connected to additional non-volatile memory  88  which is used to store operational data such as the access codes learned by the barrier movement operator in a manner discussed below. Head end  12  includes an up limit and a down limit detector  93  which are used by the controller  83  to stop the door when open and closed. An optical transmitter and receiver pair  90  are connected to the controller  83  to indicate when an obstruction is present in the doorway. In the present embodiment transmitters  30 ,  31  and  34  transmit using rf which is received by a receiver  80  via an antenna  32 . The receiver  80  sends the results of signal detection to the micro-controller  84  via a path  82 . It should be mentioned that the transmitter of the present embodiment send signals by rf, other types of wireless signaling such as optical or acoustic may be employed. 
     Controller  83  responds to the various input signals by controlling the movement or stoppage of motor  106 . Accordingly, micro-controller  84  sends motor control signals via a path  102  to relay control logic  104  which sends power to the motor, to drive the motor in one direction or the other or to stop the motor from movement. Head end  12  may also comprise a light  81  which may be controlled by the relay logic  104  in response to controller  83 . 
     For security reasons the head end  12  should respond to signals from wireless transmitters e.g.,  30 ,  31  and  34  only when those transmitters are authorized. For security purposes the signals from each transmitter include an access code which may be different for each transmitter. In one known arrangement the access code is twenty trinary digits in length, providing good security. The barrier movement operator of the present embodiment includes the ability to learn the access codes from various wireless transmitters by entering a learn mode and receiving a transmitted code. Head end  12  includes a learn switch  16  which is a push button switch connected to micro-controller  84 . When learn switch is pressed micro-controller executes a pre-programmed sequence of instructions to learn the access code of a wireless transmitter e.g.,  31  which is activated to transmit after the learn mode is entered. While in the learn mode receiver  80  receives the transmission from the sending transmitter and sends a representation to micro-controller  84  representing the received signal. Micro-controller  84  identifies the access code portion of the received signal and validates it. The code is then stored in non-volatile memory  88  and the learn mode is terminated. When not in the learn mode the barrier movement operator is in an operate mode during which received access codes are compared with the stored representations of learned access codes and when a proper relationship is present micro-controller  84  responds to the signal by controlling the door  24 . In order to prevent the learning of unauthorized transmitter access codes controller  83  includes the ability to inhibit or prohibit learning new access codes. 
       FIG. 3  is a flow diagram of a learn process including learn prohibit activities. Initially, a learn request is received by the apparatus and analyzed in a step  51 . When step  51  determines that prohibit learn is active the process returns without implementing any learning. Alternatively, when step  51  determines that prohibit learn is not active flow proceeds to block  53  where the learn mode is entered. After the beginning of the learn mode flow proceeds to block  55  where the transmitted code is received and on to block  57  where the access code portion of the received code is stored. A check is then performed in block  59  to determine whether the event which begins the learn prohibit mode has occurred. As discussed below, such an event may be the receipt of a specified signal or the storage of a predetermined number of access codes. When block  59  determines that the event has not occurred flow returns to await another learn mode activity. Alternatively, when block  59  determines that the event has occurred flow proceeds to block  61  where the prohibit learn is marked active and flow returns. When prohibit learn is marked active such will be detected on the next occurrence of block  51  and flow will return without learning a new access code. 
       FIG. 4  is a flow diagram of the process used to disable the prohibit learn function so that further performances of block  51  ( FIG. 3 ) will allow the learning of new access codes. Periodically, the flow checks in block  63  whether the system has-received a signal to re-activate the learn mode. Flow proceeds to a block  65  to determine whether the received signal is proper. If proper flow proceeds to a block  67  where learn process is again marked active and flow returns. Alternatively, when block  65  determines that the request to re-activate the learn process is not proper flow returns without marking learn active. The following embodiments illustrate the principles of the above flow diagrams. 
     In one embodiment the controller  83  is programmed to accept only a preset maximum number of access codes, for example 8. The installer of such an operator enters the learn mode for each transmitter he or she wants the operator to learn and completes the above-described learn mode sequence for each. Should the installer want to teach/learn fewer than the maximum number he or she will then teach/learn the access codes of already learned transmitters until the maximum number of access codes has been learned. Although some learned access codes will be redundant the maximum number of access codes will be learned. When the maximum has been learned the controller  83  will no longer respond to the learn button  26  by entering the learn mode which may be prevented by numerous methods. When in the learn prohibitions mode the micro-controller can determine at each press of the learn button  26  that learn prohibition is active and as a result the learn access code sequence of program is skipped. Alternatively, when the learn mode prohibition is active the entire sequence of program instructions could be changed to one in which the input from the learn switch is ignored and/or which does not include the program steps performed to implement learning. Further, while in the learn prohibition mode the learn switch could be ignored by hardware or software arrangements. 
     In the preceding embodiment the maximum number of access codes was preset without installer intervention. In another embodiment the installer may be given control of the maximum number. For such installer control it is necessary for the installer to accurately count the total number of transmitter access codes to be learned then enter the learn mode by pressing the learn button  26 . The first time the learn mode is entered, the program allows the installer to set the maximum number of codes to be learned by repeatedly pressing the learn button  26  to represent the number of codes to be learned. The micro-controller  84  then records the maximum number and when the number of access codes learned equals the maximum number, the micro-controller  84  prohibits further learning of access codes. Optionally, the head end  12  may include a light such as an LED which the micro-controller blinks to represent the number of codes to be learned. It should be apparent that a numerical screen may be used to convey the number of access codes also. 
     A further embodiment allows the installer to limit the maximum number by turning on the prohibition against further learning after the access codes of all authorized transmitters have been learned. In this embodiment the head end includes an end learn switch  15  connected to micro-controller  84 . An installer teaches access codes from transmitters as described above. When all transmitters to be authorized have been learned the installer presses the end learn mode button  15  in response to which the controller enters the prohibit learn mode. The controller can alternatively be pre-programmed to respond to a press of the end learn mode button  15  followed by the receipt of an access code from a previously learned transmitter to enter the prohibit learn mode. Similarly, the use of a predetermined button on a transmitter may optionally be used to enter the prohibit learn mode. 
     In the case of professionally installed barrier movement operators an alternative embodiment may be used. In the alternative embodiment the professional installer has a special master transmitter, the access code of which was previously stored in the controller at the time of manufacturer and which is not used by transmitters given to routine owners or users. When a controller  83  receives a transmission from the master transmitter the prohibit learn mode could be toggled on and off. 
     The barrier movement operation might optionally be provided with a key switch  17  which is shown in  FIG. 1  as being mounted to the cover of the head end unit  12  although other secure placements of the key switch may be used. The key switch is a normal electrical switch the position of which is only changed by the use of a physical key. The key switch is then activated to enter and leave the prohibit learn mode. In an alternative embodiment the head end is not provided with a learn button  26  and the learn button function is replaced by the key switch  17 . That is, the operator only learns an access code in a learn mode entered by activating the key switch  17 . 
     The preceding description relates to the learn mode and how a prohibit learn mode can be activated. Further access codes cannot be learned after the prohibit learn mode is entered. Such may be too much limitation on the owner/user of the barrier movement operation. Accordingly, certain methods and apparatus may be implemented to stop the prohibit learn mode and allow the learning of access codes. 
     In one embodiment, when it is desired to have the operator learn one or more access codes after the prohibit learn mode is active, all previously learned access codes are erased and the learn mode is entered as before. Such a re-activation of a learn capability may be in response to a signal from a secure switch such as, key switch  17  or in response to a master transmitter held only by installers and sellers of the barrier movement operator. For added security these acts could be responded to only when accompanied by an access code from a previously learned transmitter. In embodiments for use where the maximum security is not needed the controller  83  is programmed to respond to a sequential press of the learn button  26  and the reception of a previously learned access code. The above re-activation of learn mode includes the erasure of all previously learned access codes and the subsequent re-learning of the access codes for authorized transmitters. In alternative embodiments the re-activation of the learn mode could be done without erasure. Such would then be dependant on the security of the re-activation process.

Summary:
A barrier movement operator is disclosed which learns wirelessly transmitted access codes during a learn mode and subsequently in an operate mode receives wireless transmissions and determines whether action should be taken by consulting the learned access codes. Methods and apparatus are included which can be used to prohibit the learning of unauthorized access codes.