Patent Publication Number: US-10766745-B2

Title: Universal and software-configurable elevator door monitor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/736,175, filed Sep. 25, 2018, the disclosure of which is hereby incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to elevator control systems. More specifically, this disclosure relates to a device working in tandem with an elevator controller to facilitate the control of elevator operations. 
     BACKGROUND 
     Elevator door monitors are devices that enhance the functionality and safety of elevator control systems. Conventional door monitoring systems rely on customization of the input stage, so that they can be compatible with different types of control systems. The most common device for interfacing with an elevator controller is a relay. A relay is an electromechanical switch that activates only if: (i) an input voltage applied to the relay equals or exceeds a built-in threshold voltage value, and (ii) the current entering the relay is of the type (AC or DC) at which the relay is configured to operate. Input relays are used for translating voltage at different levels into a normalized voltage that can be used by an elevator controller. Each monitoring device within conventional systems monitors the door(s) of a single elevator car. Each such device monitors several different types of signals to accomplish that task, including but not limited to Door Fully Closed (DFC), Door Fully Open (DFO), Door Gate Switch (DGS), Hoistway Door Lock (HDL), and Fireman Service 2 (FS2). Furthermore, many conventional input devices or modules (including but not limited to relay-based devices) use at least one relay per each signal that needs to be monitored in order to address variability in voltage level and types. When one of the signals that needs to be monitored changes state, the elevator controller transmits a voltage via a current (again, of type either AC or DC) to the input device. If that preset voltage equals or exceeds the built-in threshold voltage of that input device (and the current types match), the input device activates and thereby communicates the sensed state of that particular signal to the logic block of the door monitor. If the voltage entering the relay is below the built-in threshold voltage value, the input device remains inactive. Thus, successful operation of a conventional monitoring system requires that the built-in threshold voltage value of the input device match the preset change-of-state voltage of the elevator car, and that the current types are the same for both the elevator and the relay. 
     There is a lack of uniformity in the design of elevator controllers, such that one elevator of a building frequently generates a change-of-state voltage at a different magnitude than that of another elevator, and also possibly via differing current types. This can especially be the case if some elevator controllers are part of “legacy” systems that were included in the original construction of the building, and some were added later in the life of the building. Thus, each building may have different types of elevator controllers, each different elevator controller generating a different magnitude of a change-of-state voltage for a given event. For this reason, an elevator door monitoring system must frequently be custom-built so that its input modules or devices correspond with the elevators at matching built-in voltages and current types. 
     The use of relay switches and other input devices in conventional elevator door monitoring system presents several drawbacks. Having to custom-build each door monitoring system, as described above, is expensive and time-consuming. Additionally, the mechanical parts in the relays are vulnerable to failure that limit the life expectancy of the relay. Still further, relays are noisy when in operation. Furthermore, a system with a multitude of relays presents room for improvement, both in terms of power consumption and in physical size of the elevator door monitoring system. 
     SUMMARY 
     It is to be understood that this summary is not an extensive overview of the disclosure. This summary is exemplary and not restrictive, and it is intended to neither identify key or critical elements of the disclosure nor delineate the scope thereof. The sole purpose of this summary is to explain and exemplify certain concepts of the disclosure as an introduction to the following complete and extensive detailed description. 
     In an aspect of the present disclosure, an elevator door monitor can comprise a differential amplifier having an input and an output, the input configured to electrically communicate with a source configured to output one of a change-of-state voltage with respect to an elevator control parameter and a change-of-state voltage value with respect to the elevator control parameter, the differential amplifier configured to produce an output voltage correlating to a magnitude of one of the change-of-state voltage and the change-of-state voltage value; and a microcontroller in communication with the output of the differential amplifier, the microcontroller configured to convert the output voltage from the differential amplifier to a numeric value, compare the numeric value to a setting value, and responsive to a determination that the numeric value reaches a threshold associated with the setting value, send a signal to a to an output relay control module, the signal comprising one selected from the group of a “true” signal and a “false” signal. The elevator door monitor can thereby be adaptable to a range of change-of-state voltages output by the source. 
     In another aspect of the present disclosure, a method of monitoring an elevator door, can comprise the steps of receiving a change-of-state voltage from a source, the change-of-state voltage generated by the source upon the occurrence of an event associated with an elevator control parameter; generating a numeric value corresponding to a magnitude of the change-of-state voltage; comparing the numeric value to a setting value; and responsive to a determination that the numeric value reaches a threshold associated with the setting value, send a signal to an output relay control module, the signal comprising one selected from the group of a “true” signal and a “false” signal. 
     Various implementations described in the present disclosure can comprise additional systems, methods, features, and advantages, which may not necessarily be expressly disclosed herein but will be apparent to one of ordinary skill in the art upon examination of the following detailed description and accompanying drawings. It is intended that all such systems, methods, features, and advantages be included within the present disclosure and protected by the accompanying claims. The features and advantages of such implementations can be realized and obtained by means of the systems, methods, features particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or can be learned by the practice of such exemplary implementations as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and components of the following figures are illustrated to emphasize the general principles of the present disclosure. Corresponding features and components throughout the figures can be designated by matching reference characters for the sake of consistency and clarity. 
         FIG. 1  is a schematic view of an elevator door monitor constructed in accordance with an aspect of the present disclosure, shown in relation to an elevator controller, with electrical connections extending between respective differential amplifiers of the elevator door monitor and corresponding contacts (pairs of electrical terminals) in the elevator controller. 
         FIG. 2  is a schematic view isolating a subset of the connections between an elevator controller and the elevator door monitor illustrated in  FIG. 1 . 
         FIG. 3  is a schematic view of the elevator door monitor of  FIG. 1 , showing direct wired connections between the elevator door monitor and sensors attached to an elevator car. 
         FIG. 4  is a schematic view of an elevator door monitor constructed of  FIG. 1 , showing direct wireless connection between the elevator door monitor and a sensor attached to an elevator car. 
         FIG. 5  is an exploded perspective view of the elevator door monitor illustrated in  FIG. 1 . 
         FIG. 6  is a right perspective view of the elevator door monitor illustrated in  FIG. 1 . 
         FIG. 7  is a left perspective view of the elevator door monitor illustrated in  FIG. 1 . 
         FIG. 8  is a top of the elevator door monitor illustrated in  FIG. 1 . 
         FIG. 9  is an end view of the elevator door monitor illustrated in  FIG. 1 . 
         FIG. 10  is a top perspective view of the power printed circuit board and associated components illustrated in  FIG. 5 . 
         FIG. 11  is an isometric view of the power printed circuit board and associated components illustrated in  FIG. 10 . 
         FIG. 12  is a block diagram illustrating the interconnections of components on the power printed circuit board illustrated in  FIGS. 10 and 11 . 
         FIG. 13  is a schematic diagram illustrating components in the power supply portion of the power printed circuit board illustrated in  FIGS. 10-12 . 
         FIG. 14A  is a block diagram of an exemplary microcontroller unit according to aspects of the present disclosure, in which a first memory resource is contained within the microcontroller unit, the memory resource storing an output relay control module as well as settings associated with various elevator control parameters. 
         FIG. 14B  is a block diagram showing the relationship of the microcontroller unit of  FIG. 14A  to a second memory resource, which is shown to store event history information along with other data. 
         FIG. 15  is a perspective view of the bottom side of the microcontroller unit printed circuit board illustrated in  FIG. 5 . 
         FIG. 16  is a top perspective view illustrating the microcontroller unit printed circuit board of  FIG. 15  assembled onto the power printed circuit board of  FIGS. 10-12 . 
         FIG. 17  is a block diagram illustrating exemplary interfaces between the microcontroller unit of the microcontroller unit printed circuit board of a memory unit, a real time clock, and an LCD and touch screen. 
         FIG. 18  is a schematic diagram detailing an exemplary differential amplifier used in an elevator door monitor constructed in accordance with an aspect of the present disclosure. 
         FIG. 19  is a schematic diagram detailing a circuit for supplying the reference voltage represented in  FIG. 18 . 
         FIG. 20  is a flow chart illustrating processing steps executed by an elevator door monitor according to aspects of the present disclosure. 
         FIG. 21  is a series of graphs, I and II of which respectively represent theoretical analog and theoretical digital voltage outputs associated with a change of state of a signal without consideration of hysteresis thresholds, and III and IV of which respectively represent such analog and digital voltage outputs with hysteresis thresholds implemented according to aspects of the present disclosure. 
         FIG. 22  is a graph similar to graph IV in  FIG. 21 , except showing bouncing controlled through implementation of de-bouncing delays. 
         FIG. 23  is a schematic view of a connection arrangement between an elevator controller and an elevator monitor according to aspects of the present disclosure, the arrangement being an alternate to that shown in  FIGS. 1 and 2 , and in which the disclosed alternate arrangement assigns a differential amplifier for each switch in the elevator controller that is desired to be individually monitored. 
         FIGS. 24A-24L  illustrate example screen shots demonstrating various aspects of graphical user interfaces presented by an LCD and touch screen in an elevator door monitor according to aspects of the present disclosure. 
         FIG. 25  is a block diagram depicting an elevator door monitor operating in an exemplary interactive environment according to aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure can be understood more readily by reference to the following detailed description, examples, drawings, and claims, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this disclosure is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. 
     The following description is provided as an enabling teaching of the present devices, systems, and/or methods in their best, currently known aspect. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects described herein, while still obtaining the beneficial results of the present disclosure. It will also be apparent that some of the desired benefits of the present disclosure can be obtained by selecting some of the features of the present disclosure without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present disclosure are possible and can even be desirable in certain circumstances and are a part of the present disclosure. Thus, the following description is provided as illustrative of the principles of the present disclosure and not in limitation thereof. 
     Reference numerals common to more than one accompanying figure identify the same component throughout the figures. 
     As used throughout, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a quantity of one of a particular element can comprise two or more such elements unless the context indicates otherwise. 
     Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect comprises from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about” or substantially,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. 
     For purposes of the present disclosure, a material property or dimension measuring about X or substantially X on a particular measurement scale measures within a range between X plus an industry-standard upper tolerance for the specified measurement and X minus an industry-standard lower tolerance for the specified measurement. Because tolerances can vary between different materials, processes and between different models, the tolerance for a particular measurement of a particular component can fall within a range of tolerances. 
     As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may or may not occur, and that the description comprises instances where said event or circumstance occurs and instances where it does not. 
     The word “or” as used herein means any one member of a particular list and also comprises any combination of members of that list. 
     To simplify the description of various elements disclosed herein, the conventions of “top,” “bottom,” “side,” “upper,” “lower,” “horizontal,” and/or “vertical” may be referenced. Unless stated otherwise, “top” describes that side of the system or component that is facing upward and “bottom” is that side of the system or component that is opposite or distal the top of the system or component and is facing downward. Unless stated otherwise, “side” describes that an end or direction of the system or component facing in horizontal direction. “Horizontal” or “horizontal orientation” describes that which is in a plane aligned with the horizon. “Vertical” or “vertical orientation” describes that which is in a plane that is angled at 90 degrees to the horizontal. 
     Disclosed is an elevator door monitor that eliminates the need to use customized input devices or modules (including but not limited to relays) in an elevator door monitoring system. Instead of customized input devices or modules, the disclosed elevator door monitor employs the use of “differential amplifier” circuits, one circuit for each signal to be monitored regarding an elevator car. In some implementations, anywhere from six (6) to ten (10) different signals may need to be monitored regarding the elevator car, each signal corresponding to a separate input into a microcontroller unit (“MCU”). Whereas each relay in a conventional system must frequently be configured differently to match different elevator change-of-state voltages and current types, all of the differential amplifier circuits of the elevator door monitor herein disclosed can be constructed identically. Each such circuit can accommodate a wide range of change-of-state voltages, one example range being 5V-300V, either AC or DC. Each differential amplifier circuit electrically communicates with a respective input terminal of the MCU, which can include a memory resource storing settings associated with respective elevator control parameters. Each setting can be a numeric value representing a magnitude of voltage (which can be expressed in units of V rms ) reached between selected contacts in the elevator controller when the elevator control parameter associated with the contacts undergoes a change of state. 
     A user can enter the setting for each MCU input terminal (i.e., each elevator control parameter) in various ways, one example of which can be via a small touchscreen display. Thus, the system of this invention can be constructed identically from one building to another. Customization is achieved through the settings input into the elevator door monitor via software, instead of using differing hardware components. This provides a universal system that can monitor doors of a variety of elevators without the drawbacks associated with an assembly of customized input devices or modules. These and other benefits are attendant to the elevator door monitor and method disclosed herein. 
       FIG. 1  is a schematic view of an elevator door monitor  100  constructed in accordance with an aspect of the present disclosure, shown in relation to a conventional elevator controller  102 , with electrical connections  104  extending between respective differential amplifiers  101   a - 101   g  of the elevator door monitor  100  and corresponding contacts (pairs of electrical terminals)  106   a - 106   g  in the elevator controller  102 . The differential amplifiers  101   a - g  can be constructed identically to one another and embody the circuitry discussed herein with regard to  FIG. 18 . As will be explained herein with reference to  FIGS. 10-12 , the elevator door monitor  100  can be powered with a battery. As shown in  FIG. 1 , the elevator door monitor  100 , in some implementations, can be provided with a terminal pair  108  from which it receives power via lines  110  from power terminals  112  in the elevator controller  102 .  FIG. 1  also illustrates elements that, in some implementations, can be in communication with a microcontroller unit (MCU) (not shown, to be described herein with reference to  FIG. 15 ), namely, a touch screen  114 , a buzzer  116 , and a wireless module  118  connected to a port (such as serial port)  120  in the elevator door monitor  100 , said elements functioning in a manner to be described herein. 
     Elevator door monitor  100  is also provided with output contacts, exemplified at  122 ,  124 ,  126 , and  128 . Switch  123  selectively electrically connects pairs of terminals (such as at  125 ), so as to close one of the contacts (such as  124 ) while leaving the other contact (such as  122 ) open. Thus, when switch  123  closes contact  124  (as shown), the elevator door monitor  100  sends an output signal via lines  132   a,b  to respective terminals  130   a,b  of the elevator controller  102 . On the other hand, when switch  123  closes contact  122  (shown in  FIG. 1  as open), the elevator door monitor  100  instead sends an output signal via lines  132   a,c  to respective terminals  130   a,c  of the elevator controller  102 . Terminals  130   a,b,c  can be associated with an aspect of elevator control, such as motion of the elevator car door. Thus, the switch  123 , when in the position illustrated in  FIG. 1  (closing the contact  124 ), can result in an output signal being sent to the elevator controller  102  to allow the elevator car to move. In such an arrangement, if the switch  123  were to instead close contact  122 , then such closure could instead result in the sending of an output signal to the elevator controller  102  allowing the elevator controller  102  to halt motion of the elevator car. Similarly, switch  134  selectively electrically connects pairs of terminals (such as at  135 ), so as to close one of the contacts (such as  128 ) while leaving the other contact (such as  126 ) open. Thus, when switch  134  closes contact  128  (as shown), the elevator door monitor  100  can send an output signal via lines  136   a,b  to respective terminals  138   a,b  of the elevator controller  102 . On the other hand, when switch  134  closes contact  126  (shown in  FIG. 1  as open), the elevator door monitor  100  instead sends an output signal via lines  136   a,c  to respective terminals  138   a,c  of the elevator controller  102 . Such an arrangement can be directed to, for example, the opening and closing of the elevator car doors, such that when the switch  134  assumes one of the aforementioned positions, it allows the elevator controller  102  to open the doors, and when in the other of the aforementioned positions, switch  134  allows the elevator controller  102  to close the doors. Other implementations of elevator door monitor  100  contemplate additional sets of output contacts; for example, an additional set of contacts could control a light (such as an LED) display on the elevator controller  102 , or activation of an audio alarm. The above discussion of the output contacts exemplified in  FIG. 1  illustrates operation of output relays, to be discussed herein with regard to  FIG. 10 . The output relays are controlled as a result of a determination performed by an output relay control module  1417  ( FIG. 14A ), which comprises an algorithm (programming instructions) stored into a memory resource  1402  of a microcontroller unit (MCU)  1400  ( FIG. 14A ). 
     Each of the differential amplifiers  101   a - g  can be dedicated to receiving a signal corresponding to just one specific elevator control parameter. The principal elevator control parameters discussed herein are described below with regard to each specific differential amplifier  101  and a corresponding specific elevator controller contact  106 ; however it is to be understood that such association is discussed only for purposes of illustration and that a physical position of a differential amplifier  101  in the elevator door monitor  100 , or physical position of a contact  106  in the elevator controller  102 , need not always be associated with a particular elevator control parameter. For instance, though the left-most differential amplifier  101   a  is associated with a “Door Fully Open” signal in the example below, that signal in other implementations could instead be associated with any of the other differential amplifiers  101   b - g . It is also to be understood that each such signal can originate from a different contact  106  within the elevator controller  102 . The physical location, within the elevator controller  102 , of a contact  106  corresponding to a particular elevator control parameter is determined by knowing, based on schematics of the particular elevator controller  102  being used, where a voltage change between two electrical points can be measured at a time when a sensor signals a change of a state to the elevator controller  102 . (This determination is discussed in greater detail with regard to the example provided in  FIG. 2 .) Also regarding the discussions of the parameters below, the sensors mentioned can be encoders (absolute and incremental), hall effect sensors, metal sensors, photoelectronic sensors, inductive sensors, RFID sensors, a camera, ultrasonic proximity sensors, a mechanical switch and laser-based sensors, though this exemplary list of types of sensors and switches is not intended to be limiting. 
     Door Fully Open (“DFO”): Differential Amplifier  101   a , Contacts  106   a.    
     This elevator control parameter can be detected by a sensor communicating with contacts  106   a , such as an electromechanical switch with electrical contacts mounted on the elevator door in such a way that when the elevator car door is fully open the contacts are open, and closed otherwise. The sensor could also be, for example, a photosensor or a magnetic sensor. A DFO signal indicates whether the elevator car door is fully open. For example, the signal will be “true” if the elevator car door is fully open and “false” otherwise. A DFO signal is used, for example, to halt operation of a door-opening mechanism when the elevator door is fully open. 
     Door Fully Closed (“DFC”): Differential Amplifier  101   b , Contacts  106   b.    
     This elevator control parameter can be detected by a sensor communicating with contacts  106   b , such as an electromechanical switch with electrical contacts mounted on the elevator door in such a way that when the elevator car door is fully closed the contacts are open, and closed otherwise. The sensor could also be, for example, a photosensor or a magnetic sensor. A DFC signal indicates whether the elevator car door is fully closed. For example, the signal will be “true” if the elevator car door is fully closed and “false” otherwise. A DFC signal is used, for example, to halt operation of a door-closing mechanism when the elevator door is fully closed. 
     Door Gate Switch (“DGS”): Differential Amplifier  101   c , Contacts  106   c.    
     Though listed in conjunction with the other elevator control parameters identified herein, DGS is a signal that is used for safety purposes, rather than elevator control purposes per se. Nevertheless, for purposes of the present disclosure, DGS shall be understood to be a type of “elevator control parameter,” as that term is used herein. Instead of being concerned with door-opening and door-closing mechanisms (DFO and DFC, respectively), a DGS signal focuses upon the state of elevator car movement. Like DFC, this signal indicates whether the elevator car door is fully closed, and like DFC, will be “true” if the elevator car door is fully closed and “false” otherwise. Unlike DFC, however, a “false” DGS signal cuts power to the drive mechanism that moves the elevator car. 
     Hoistway Door Lock (“HDL”): Differential Amplifier  101   d , Contacts  106   d.    
     This elevator control parameter concerns landing doors instead of elevator doors. An HDL condition can be detected by a sensor communicating with contacts  106   d , such as an electromechanical switch with electrical contacts mounted on a landing door in such a way that when the landing door is fully closed and locked, the contacts are closed (resulting in a “true” HDL signal), and open otherwise (resulting in a “false” HDL signal). Like a “false” DGS signal, a “false” HDL signal cuts power to the drive mechanism that moves the elevator car. 
     Fire Service Phase II (“FS2”): Differential Amplifier  101   e , Contacts  106   e.    
     In a Phase I condition, an elevator car travels to the lowest floor of a building for repair and/or maintenance. In that condition, the elevator does not react to a call from users. While elevator is in the Phase I condition, a fireman or repairman can activate a key switch inside the elevator. That activation brings it into Phase II. Such activation sends an indication that there is someone inside the elevator. The fireman or repairman has manual control over the elevator in the Phase II condition. That transition from a Phase I condition to a Phase II condition generates a measurable voltage across two points in the elevator controller  102  which, in some implementations, for example, can be a pair of electrical terminals driving an indicator lamp, if the particular type of the elevator controller  102  includes such a lamp. In other implementations, two such points could be two electrical terminals driving a relay coil that gets activated when the elevator controller transitions to Phase II. Other locations of measurable terminals can be possible with still other types of elevator controllers, and are contemplated as being within the scope of the present disclosure. An FS2 signal indicates whether the elevator car is in the Phase II condition (“true” signal), or not in that condition (“false” signal). 
     Inspection Mode: Differential Amplifier  101   f , Contacts  106   f.    
     Inspection mode is used by a member of a maintenance crew to perform repairs and/or maintenance of the elevator. An elevator car can be set to this mode in a variety of ways, such as a switch at the top of the elevator car, a key switch inside the elevator car, or a button in the elevator controller  102 . An inspection mode signal indicates whether the elevator car is in inspection mode (“true” signal), or not in inspection mode (“false” signal). 
     Other Signals: Differential Amplifier  101   g , Contacts  106   g.    
     Differential amplifier  101   g  can be available to receive signals other than the elevator control parameters discussed above. For instance, contacts  106   g  may be those that generate a change-of-state voltage when the elevator controller  102  changes from an operational condition to a fault condition. In such implementations, an output signal from differential amplifier  101   g  can prompt the microcontroller (to be described herein) activate an alarm and/or, in some implementations, wirelessly send a communication to a user in a manner to be described with reference to  FIG. 25 . 
       FIG. 2  is a schematic view isolating a subset of the connections between the elevator controller  102  and the elevator door monitor  100  illustrated in  FIG. 1 . The elevator door monitor  100  is shown in a top view, showing that the elevator door monitor  100  can comprise a housing  140 , terminal blocks  142 , 144  extending outwardly with respect to the housing  140 , and an overlay  146  positioned atop the housing  140  and touch screen  114 . Terminal blocks  142 , 144  have a length L 1  ( FIG. 8 ) that promotes the compactness of elevator door monitor  100 . For example, L 1  can have a length ranging from 3 to 6 inches, and in one implementation can measure 4.1 inches. The elevator controller  102  is illustrated as a partial schematic, showing a line (“L”) rail  148 , which carries active voltage, and a neutral (“N”) rail  150 . Rails  148 , 150  are in communication with respective power connection inputs  152 , 154  in terminal block  142 , via respective power lines  156 , 158 . A hoistway door lock (“HDL”) line  160  extends between rails  148 , 150  and is interrupted by a plurality of HDL contacts  162 , 164 , 166 , one contact per each floor serviced by the associated elevator car. Three HDL contacts are shown for purposes of illustration only, it being understood that the elevator controller  102  can have differing numbers of HDL contacts, depending on the number of floors in the building so serviced. To find a magnitude of a voltage generated upon a change of state of one of the HDL contacts  162 , 164 , 166  from an open position to a closed position (and thus, the change of an HDL signal from “false” to true”), or vice versa, for such an HDL contact, a user must find two points where a change in voltage can be measured as a corresponding such a change of state. One example would be measuring the voltage at an HDL relay coil  168 , residing between terminals  170  and  172  (with terminal  170  residing on the neutral rail  150 ), when any one of the HDL contacts  162 , 164 , 166  undergoes a change of state of the type described above. Upon measurement of such a voltage when the HDL relay coil  168  gets active, it would be established that the occurrence of a voltage change equaling the measured magnitude corresponds to a change of state in HDL line  160 , and thus the terminals  170 , 172  could be electrically connected to respective inputs of differential amplifier  101   d  ( FIG. 1 ). Such electrical connection can be achieved by connecting terminal  170 , via input signal connection line  174 , to input terminal  176  in terminal block  144 , and by connecting terminal  172 , via input signal connection line  178 , to input terminal  180  in the same terminal block  144 . 
     Still referring to  FIG. 2 , another example of locating change-of-state voltage contacts in the elevator controller  102  is illustrated with regard to the Door Fully Open (DFO) parameter. A DFO line  182  extends between rails  148 , 150  and is interrupted by a DFO contact  184  (only one is shown for purpose of illustration, but additional such contacts should be understood to be present in actual implementations). Voltage at a DFO relay coil  186 , residing between active terminals  188  and  190 , can be measured when DFO contact  184  undergoes a change of state of the type described above. Upon measurement of such a voltage when the DFO relay coil  186  gets active, it would be established that the occurrence of a voltage change equaling the measured magnitude corresponds to a change of state in DFO line  182 , and thus the terminals  188 , 190  could be electrically connected to respective inputs of differential amplifier  101   a  ( FIG. 1 ). Such electrical connection can be achieved by connecting terminal  188 , via input signal connection line  192 , to input terminal  194  in terminal block  144 , and by connecting terminal  190 , via input signal connection line  196 , to input terminal  198  in the same terminal block  144 . 
       FIGS. 3 and 4  are schematic views of elevator door monitor  100 , showing direct connections between the elevator door monitor  100  and sensors attached to an elevator car  301 . Such arrangements can be used for an elevator controller  302  constructed differently than elevator controller  102 , when for some reason it is not possible to ascertain two points within the elevator controller  302  for which a measured voltage difference can correspond to a change of state.  FIG. 3  illustrates an environment  300  in which differential amplifiers such as  101   a ,  101   b  are connected to sensors  304   a ,  304   b  via wired electrical connections  306   a ,  306   b , respectively.  FIG. 4  illustrates an environment  400  in which a direct wireless connection  402  is established between the wireless module  118  of the elevator door monitor  100  and a sensor  404  attached to an elevator car  401 . The sensors  304 ,  404  provide change-of-state voltage values. In the wireless arrangement of  FIG. 4 , the sensor  404  transmits the change-of-state voltage value directly to a microcontroller unit (MCU), such as MCU  1400  ( FIGS. 14A and 15 ) via a wireless transceiver, using serial communication. Alternatively, the MCU could be of a type that also includes wireless transceiver. 
       FIGS. 5-11, 15, and 16  best illustrate the physical structure of elevator door monitor  100  and its components. 
     Referring first to  FIGS. 5-9 , starting with the exploded view of  FIG. 5 , elevator door monitor  100  includes a base  500  upon which is mounted a power printed circuit board (PCB) assembly  902 , a microcontroller unit (MCU) PCB assembly  903  assembled atop the power PCB assembly  902 , the MCU PCB assembly  903  including an MCU circuit board  904 , and the housing  140 , which is also mounted to the base  500 . Housing  140 , which protects the assemblies  902 , 903  when the elevator door monitor  100  is in an assembled state, comprises a lower section  141 , a stepped middle section  143  extending upwardly from the lower section  141 , and a stepped upper section  145  extending upwardly from the stepped middle section  143 .  FIG. 5  shows all sections  141 , 143 , 145  joined together integrally as a single piece, though it is to be understood that housing  140  need not be limited to that type of construction. Upper section  145  terminates in a ridge  147  defining a periphery of the upper section  145 . A recessed region  149  is sunken into the upper section  145  at an elevation lower than that of an upper surface of ridge  147 . The recessed region  149  defines an opening  151  therein to permit touching and viewing of the touch screen  114  assembled onto the MCU circuit board  904  beneath the housing  140 . The overlay  146  can optionally be received within the recessed region  149  such that the upper surface  153  of the overlay  146  can be substantially flush with the upper surface of ridge  147  when the overlay  146  is so assembled onto the housing  140 . Upper surface  153  defines an opening  155  therein, which can be substantially coextensive with opening  151  in the recessed region  149  of the housing  140 . Opening  155  likewise allows access to the touch screen  114 . Stepped middle section  143  defines a plurality of ventilation openings  161  ( FIGS. 6 and 7 ) to permit escape of any heat generated by the power PCB assembly  902  or the MCU PCB assembly  903 . As seen in  FIGS. 6 and 7 , housing  140  defines a right end  502  and a left end  602 . Right end  502  defines an opening  504  therein for the purpose of keeping the housing  140  attached to the base  500  through use of a self-locking mechanism. For the same purpose, left end  602  defines an opening  604  therein. Left end  602  also defines a port opening  606  therein to permit electrical connection between the elevator door monitor  100  and a compatible peripheral, such as a wireless sensor, a cellular modem, a personal computer, or a configuration device (module) that stores various settings and/or firmware for the elevator door monitor  100 . Referring to  FIG. 9 , housing  140  can have height dimensions h 1  and h 2  that promote the compactness of elevator door monitor  100 . For example, height h 1 , measured from the bottom of base  500  to the top surface  800  of middle stepped section  143 , can range from 1 to 4 inches, and in some implementations can measure 1.9 inches. For further example, height h 2 , measured from the bottom of base  500  to the top surface  802  of ridge  147  ( FIGS. 6 and 7 ), can range from 1.25 to 5 inches, and in one implementation can measure 2.25 inches. 
       FIGS. 10 and 11  illustrate the power circuit board assembly  902  in greater detail.  FIG. 10  is a top perspective view of the power PCB assembly  902 , and  FIG. 11  is an isometric view of that assembly  902 , differing slightly from  FIG. 10  in that  FIG. 11  shows only the outer casings  142   a,   144   a  of respective terminal blocks  142 , 144 , for purposes of illustration. Power PCB assembly  902  includes a power PCB  1000  on which is are mounted several components, including operational amplifiers  1007   a - 1007   f  used in the differential amplifiers  101   a - 101   f  illustrated schematically in  FIG. 1 . (Not shown in  FIGS. 10 and 11  is an operational amplifier corresponding to differential amplifier  101   g  of  FIG. 1 .) Various resistors  1003 , mounted on the power PCB  1000 , communicate with operational amplifiers  1007   a - 1007   f  to attenuate change-of-state voltages in a manner to be described below with regard to  FIG. 18 . Also mounted on the power PCB  1000  is a power supply  1002 , which in some implementations can supply the power PCB assembly  902  with voltage ranging from 5V DC to 24V DC, such as 15V DC, and can include an analog-to-digital (ADC) converter to convert AC power to DC power. A plurality of output relays  1004   a - 1004   f,  which function in the manner described above with regard to the switches exemplified at  123  and  134  of  FIG. 1 , are mounted on the power PCB  1000 . Output relays  1004   a - 1004   f  are standard relays that are commercially available. One of these relays can be used to generate a signal that tells the elevator controller  102  whether the elevator door monitor  100  is functioning properly. The rest of the relays can be used by the elevator door monitor  100  to inform the elevator controller  102  of other situations, like an internal error or malfunction, as well as to program any custom logic that the customer might require or want to be implemented. The output relays  1004   a - 1004   f  are driven by a relay driver  1005  ( FIG. 10 ) mounted to the power PCB  1000 . The output relays  1004   a - 1004   f  are only an example of an interface between the elevator door monitor  100  and the elevator controller  102  ( FIGS. 1 and 2 ). In other implementations, such an interface may take other forms, such as solid state digital outputs. Power PCB assembly  902  also includes power pole assemblies  1006   a,   1006   b,  which are mounted to power PCB  1000  and which electrically and mechanically interconnect power PCB assembly  902  and PCB MCU assembly  903  in the manner illustrated at  FIG. 16 . A voltage regulator  1008 , mounted to power PCB  1000 , communicates with power supply  1002  to reduce voltage entering PCB MCU assembly  903 , as shown in  FIG. 12 . In some implementations, voltage regulator  1008  can be a commercially-available low drop voltage regulator. 
     Referring to  FIGS. 12 and 13 ,  FIG. 12  is a block diagram illustrating the interconnections of components of the power PCB assembly  902 , and  FIG. 13  is a schematic diagram illustrating components in the power supply portion of power PCB assembly  902 . Power supply  1002  is shown as receiving power from a power source  1300 , which may be either AC or DC as shown in  FIG. 12  but which in  FIG. 13  is represented schematically as an AC power source  1300 ′. Power supply  1002  outputs a predefined DC voltage, which in some implementations can be the 15V DC shown, and which powers the output relays  1004 . Next, for certain other components in the power PCB assembly  902 , the power must be stepped down to a reduced predefined voltage, which in some implementations may be the 5V DC shown. A step-down voltage converter  1010 , which communicates with power supply  1002 , accomplishes that reduction and can be, in some implementations, a DC/DC buck converter. One component receiving the 5V DC output from the step-down voltage converter  101  is buzzer  116 , which can sound an alarm if an invalid condition is present, or if there is a warning or internal malfunction. It is intended to give an audible notification of the status of the elevator control monitor  100  and to, if so configured by a user in the manner discussed herein with regard to  FIG. 24H , provide a beep when touch screen  114  ( FIGS. 5-7 ) is pressed. Buzzer  116  can be a component commercially available from known sources. As seen in  FIG. 12 , a voltage differential amplifier  1200 , which can be constructed identically to differential amplifier  101   a  according to  FIG. 18 , attenuates voltage from source  1300  such that the voltage supplied to the PCB MCU assembly  903  is normalized to a predefined voltage range, such as the 0-5 V range recited in  FIG. 12 . That range is also output by the various differential amplifiers  101 , represented schematically in  FIG. 1 , and supplied to the PCB MCU assembly  903 . For certain other components in, or communicating with, the power PCB assembly  902 , voltage must be reduced even further from the 5V provided by the step-down voltage converter  1010 , and the voltage regular  1008  described above provides such further reduction and can, in some implementations receive the 5V output from the step-down voltage converter  1010  and reduce it to a predefined voltage such as 3.3V. The 3.3V is suitable to send to the MCU  1400  ( FIG. 15 ) of the PCB MCU assembly  903  and further to certain components of the power PCB assembly  902  such as temperature sensor  1012 , which can send an alarm if temperature within the elevator door monitor  100  exceeds a predefined threshold. Temperature sensor  1012  can be a sensor commercially available from known sources. Also shown in  FIG. 12  is a Universal Asynchronous Receiver/Transmitter (UART) interface  1202 , which allows two-way communication between any compatible device inserted into serial port  120  and the MCU of the PCB MCU assembly  903 . 
       FIGS. 14A through 17  illustrate various aspects concerning the MCU PCB assembly  903 . 
     Referring first to  FIGS. 15 and 16 ,  FIG. 15  is a perspective view of the bottom side of the MCU PCB assembly  903 , and  FIG. 16  is a top perspective view illustrating the MCU PCB assembly  903  assembled onto the power PCB assembly  902 . The MCU PCB assembly  903  includes the MCU circuit board  904  and a microcontroller unit (MCU)  1400  mounted to the underside of the MCU circuit board  904 . MCU  1400  can be, in some implementations, a 16-bit microcontroller and digital signal controller. As seen in the block diagram of  FIG. 14A , such a MCU  1400  includes a first memory resource  1402 , on which one can store the output relay control module  1417 , which can be an algorithm (programming instructions) for controlling operation of the output relays  1004   a - f  (previously discussed with regard to  FIGS. 10 and 11 ) or of other interface modules, the instructions causing the MCU  1400  to perform the techniques discussed above with regard to those output relays  1004   a - f . One can also store, within first memory resource  1402  of MCU  1400 , various settings with regard to the elevator control parameters discussed in greater detail below with regard to  FIGS. 24A-24L , namely DGS settings  1404 , HDL settings  1406 , DFO settings  1408 , DFC settings, FS2 settings  1412 , and inspection mode settings  1414 .  FIG. 14A  also shows that other settings  1416  can be stored in the first memory resource  1402 . Examples of such other settings  1416  will be described herein with reference to  FIG. 24H . 
     Referring again to  FIG. 15 , through various electrical connections on the MCU PCB  904 , MCU  1400  communicates with several other components also mounted on the MCU PCB  904 , including but not limited to a real-time clock (RTC)  1502 , a crystal  1504 , and a Uniform Serial Bus (USB) connector  1506 . Crystal  1504  uses the MCU  1400  to generate its operating clock signal. USB connector  1506  can be used to electrically connect a variety of compatible peripherals to the MCU PCB assembly  903  once housing  140  is temporarily removed, including but not limited to a wireless sensor, a cellular modem, a personal computer, or a configuration device (module) that stores various settings and firmware for the elevator door monitor  100 .  FIG. 15  also illustrates a pair of power pole receptacle units  1508   a,   1508   b,  each receptacle in those units being complementary to each of the power poles in the power pole assemblies  1006   a,   1006   b  ( FIGS. 10 and 11 ). MCU PCB assembly  903  can be further provided with a connector  1510  having pins  1512  extending from the opposite side of MCU PCB  904 . Connector  1510  is used for connecting to devices such as a personal computer or configuration device, for purposes of updating firmware, debugging, or programming software for the MCU  1400 . 
     Also shown in  FIG. 15  is a second memory resource  1418 , mounted on the MCU PCB  904  and in communication with the MCU  1400 . In some implementations, second memory resource  1418  can be a non-volatile memory (NVM) such as EERAM, which is an  12 C static RAM (SRAM) with a shadow electrically erasable programmable read-only memory (EEPROM) backup. Second memory resource  1418  can also comprise other NVM types, such as read only memory (ROM), EEPROM, flash memory, and the like. Referring to the block diagram of  FIG. 14B , second memory resource  1418  can store events history  1420 , comprising information of the type to be discussed herein with regard to  FIG. 24J . However, such events history  1420  need not be stored only in the second memory resource  1418 . Events history  1420  can also, in other implementations, be stored in the first memory resource  1402  ( FIG. 14A ), either instead of, or in addition to, the second memory resource  1418 . The second memory resource  1418  can also store other data  1422 , which can comprise, for example, date and time information and device information (illustrated to  FIGS. 24G and 24K , respectively, to be discussed herein). 
     Regarding the above discussions of the first memory resource  1402  and the second memory resource  1418 , these storage units may be configured to store any combination of information, data, instructions, software code, etc. Computer-executable programming instructions such as the output relay control module  1417  ( FIG. 14A ) can be stored in one or more of the memory resources  1402 , 1418  and run on the same or different microprocessors and/or computer systems. Programming instructions can be stored in any computer-readable storage media for the non-transitory storage of information. For example, computer-readable storage media includes, but is not limited to NVM of the types discussed above with regard to second memory resource  1418 , compact disc ROM (“CD-ROM”), digital versatile disk (“DVD”), high definition DVD (“HD-DVD”), BLU-RAY or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage, or other magnetic storage devices and the like. 
       FIG. 17  is a block diagram illustrating exemplary interfaces between the MCU  1400  of the MCU PCB assembly  903 , the second memory resource (EERAM)  1418 , the RTC  1502 , and the LCD and touch screen  114 . In some implementations, touch screen  114  can be resistive touch screen with a color display. MCU  1400  is connected to the aforementioned components via the interfaces shown in  FIG. 17 . Interface  1702 , which enables communication between the MCU  1400  and controls for the relays  1004  and buzzer  116  ( FIG. 12 ) can, in some implementations, be a commercially-available analog interface. MCU  1400  can also be provided with an in-circuit debugger (ICD)  1704 , which facilitates any needed debugging of firmware. 
       FIG. 18  is a schematic diagram detailing an exemplary differential amplifier  101   a  used in the elevator door monitor  100 . As mentioned previously, the remaining differential amplifiers  101   b - 101   f  disclosed schematically in  FIG. 1 , as well as the power differential amplifier  1200  ( FIG. 12 ), can be constructed identically to differential amplifier  101   a  according to  FIG. 18 . Differential amplifier  101   a  attenuates a change-of-state voltage received at input terminals  1802 , 1804 , and outputs the resulting attenuated voltage at output  1806 , and thence to an input pin (not shown) of the MCU  1400 . Differential amplifier  101   a  includes operational amplifier  1007   a  having the connections shown to resistors R 1 -R 11 , each of which corresponds to the resistors  1003  illustrated in  FIGS. 10 and 11 . Operational amplifier  1007   a  is provided with respective positive and negative terminals  1801 , 1803 . The differential amplifier  101   a  attenuates the voltage at input terminals  1802 , 1804  through the illustrated resistor arrangement and the operational amplifier  1007   a . Additionally, a reference voltage  1808 , which in some implementations can be the 6V shown, can be implemented in order to center the voltage waveform about the midpoint of the positive and negative waveform amplitudes. In the exemplary arrangement of  FIG. 18 , regarding resistance values, R 1 =R 6 , R 4 =R 5 , R 7 =R 8 , and R 9 =R 10 . The various values for these resistances can be ascertained by those of skill in the art. Designating the input voltage at input terminals  1802 , 1804  as VI, and the reference voltage  1808  as V REF , the output voltage V O  can be calculated by the formula: 
     
       
         
           
             
               V 
               O 
             
             = 
             
               
                 [ 
                 
                   
                     V 
                     I 
                   
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                     ( 
                     
                       
                         R 
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                         1 
                       
                       
                         
                           R 
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                           1 
                         
                         + 
                         
                           R 
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                           ⁢ 
                           4 
                         
                       
                     
                     ) 
                   
                   × 
                   
                     ( 
                     
                       
                         R 
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                         10 
                       
                       
                         R 
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                         7 
                       
                     
                     ) 
                   
                 
                 ] 
               
               + 
               
                 V 
                 REF 
               
             
           
         
       
     
     For situations in which the MCU  1400  cannot operate above Vo, then the attenuated voltage is further reduced by voltage dividers  1810 , 1812 , each comprising the diode arrangements shown, each of which, in some implementations, can convert a signal range from 0-6V to 0.5-2.8V. The resulting voltage (denoted in the above example by “IN 1  An”) is output from the differential amplifier output  1806  and sent to the MCU  1400  for calculation as a numeric value. 
     Still referring to  FIG. 18 , elements of the differential amplifier  101   a  also perform low pass filtering. For input voltages that are AC-based, higher frequencies should be filtered out since they could affect subsequent calculations. Capacitors C 1  and C 2  can have equal capacitance values. Those capacitors, in combination with certain resistors connected in parallel to them, implement the low-pass filter. Specifically, the filter is formed by the combination of R 1  and R 4  in parallel to C 1 , and the combination of R 5  and R 6  in parallel to C 2 . 
       FIG. 19  is a schematic diagram detailing a circuit  1900  for supplying the reference voltage represented in  FIG. 18  at  1808 . Circuit  1900  comprises an operational amplifier  1902 , having a positive terminal  1902   a  and a negative terminal  1902   b , connected as shown to resistors R 12  and R 13 , and to capacitor C 3 . Voltage from source  1904  enters the positive terminal  1902   a  of operational amplifier  1902 . In some implementations, circuit  1900  effects the amplification of a source voltage of 3.3VA to an output voltage of 6V. 
       FIG. 20  is a flow chart illustrating a method  2000  executed by an elevator door monitor  100  according to aspects of the present disclosure. At block  2002 , method  2000  begins with the attenuation of an input voltage  2001 , i.e., a change-of-state voltage such as that which would be received from an elevator controller  102  in the arrangement of  FIG. 1 . The input voltage can have a signal voltage waveform as shown in the waveform diagram  2004  (which exhibits the maximum amplitude of 300V AC). The attenuation at block  2002  is performed using the techniques described above with regard to  FIG. 18 . Next, at block  2006 , the attenuated voltage can undergo low pass filtering, also due to the circuit elements described above with regard to  FIG. 18 . An example of a resulting filtered waveform is illustrated in the waveform diagram  2008 . 
     Still referring to  FIG. 20 , at block  2010 , the filtered waveform enters MCU  1400  ( FIGS. 15 and 17 ) and is there converted from a voltage signal to a numeric value. In some implementations, the MCU  1400  may calculate a root-mean-square (“RMS”) value using the known formula:
         The rms value of a set of n values for (x1, x2, . . . xn) is given by       

               x   rms     =         1   n     ⁢     (       x   1   2     +     x   2   2     +   …   +     x   n   2       )               
The “x” values underneath the radical represent voltage readings of any waveform at the MCU input. In instances where an input voltage already represents an RMS value, the MCU will merely perform an ADC conversion of the signal. Note that while determination of a numeric value has been described with regard to the RMS value calculation above, other methods of converting a voltage waveform to a numeric value are contemplated as being within the scope of the present disclosure. Programming stored in the first memory resource  1402  ( FIG. 14A ) of the MCU  1400  enables the MCU  1400  to correlate the numeric value (such as a V rms  value) determined at block  2012  to the actual change-of-state (input) voltage  2001 .
 
     The next steps in  FIG. 20  are described in conjunction with  FIG. 21 , which is a series of graphs  2100 , I and II of which respectively represent theoretical analog and theoretical digital voltage outputs associated with a change of state of a signal without consideration of hysteresis thresholds, and III and IV of which respectively represent such analog and digital voltage outputs with hysteresis thresholds implemented according to aspects of the present disclosure. Blocks  2012 - 2018  of  FIG. 20  represent steps performed when the elevator door monitor  100  is configured to operate in an “active high” setting. At blocks  2012  and  2016 , the correlated numeric value calculated at block  2010  is compared to a setting value, one example of which is a threshold voltage corresponding to a particular elevator control parameter, as described below with reference to  FIGS. 24D and 24E . Other examples of setting values will become apparent upon a review of those and other figures to be described herein. Generally described with reference to both blocks  2014  and  2018 , responsive to a determination that the numeric value reaches a threshold associated with the setting value, a signal is sent to the output relay control module  1417  ( FIG. 14A ), the signal comprising one selected from the group of a “true” signal and a “false” signal. The concept of a “threshold” in the context of the present disclosure is best understood with reference to  FIG. 21 , which comprises a series  2100  of plots or graphs, I-IV, each graph plotting voltage amplitude (axis  2102 ) versus time (axes  2104   a - 2104   d ). Without taking hysteresis into account, then whenever an analog voltage waveform  2106  (Graph I) exceeds a threshold  2108 , the MCU  1400  would output a digital signal  2110  (Graph II) that would switch from a “true” signal level  2110   a  down to a “false” level  2110   b  the moment that the analog voltage waveform  2106  drops below the threshold  2108 . This would result in unwanted frequent back-and-forth toggling between “true” and “false” signals when the waveform  2106  fluctuates proximate the threshold  2108 . To prevent such unwanted frequency of toggling, the door elevator monitor  100  implements use of a high threshold setting  2112  (“HTS” in Graph III) and a low threshold setting  2114  (“LTS” in Graph III). Using the HTS and LTS values exemplified in  FIGS. 24D and 24E , HTS could be 66% of the value of the threshold  2108 , while LTS could be 33% of the value of the threshold  2108 . Thus, when the analog waveform  2116  in Graph III has an amplitude less than the LTS  2114 , the reactive digital signal  2118  (Graph IV) remains at a “false” level  2118   a  but becomes a “true” signal  2118   b  once the analog waveform  2116  crosses the HTS  2112 . Digital signal  2118  remains at the “true” level  2118   b  even after the amplitude of the analog waveform  2116  drops below HTS  2112 . Only when the amplitude of the analog waveform  2116  drops below the LTS  2114  will the digital signal  2118  return to the “false” level  2118   a . In this manner, rapid toggling between “true” and “false” states is avoided. 
     Referring again to  FIG. 20 , block  2012  represents a determination that the numeric value equals or exceeds the HTS  2112  ( FIG. 21 ) for the particular type of control parameter signal being monitored. In response, the MCU  1400 , at block  2014 , sends a “true” signal to the output relay control module  1417  ( FIG. 14A ). If, however, the MCU determines at  2016  that the numeric value is less than the LTS  2114  ( FIG. 21 ), it sends, at block  2018 , a “false” signal to the output relay control module  1417  ( FIG. 14A ). But, as described above, and as indicated by the “No” line extending between blocks  2016  and  2014 , a “true” signal status is maintained even if the numeric value of analog waveform  2116  is less than the HTS  2112 , so long as that value is still greater than the LTS  2114 . If the elevator control monitor  100  operates in an “active low” setting, then blocks  2014  and  2018  would be switched in method  2000 . In other words, at the “active low” setting, the MCU  1400  sends a “true” signal to the output relay control module  1417  when the numeric value is less than the LTS  2114 , and sends a “false” signal to the output relay control module  1417  when the numeric value equals or exceeds the HTS  2112 . 
       FIG. 22  is a graph  2200  similar to Graph IV in  FIG. 21 , except showing bouncing controlled through implementation of de-bouncing delays. Graph  2200 , which is a plot of amplitude  2202  versus time  2204  undergone by a digital signal  2206 , presents a more realistic plot of a digital signal than the plot  2118  in Graph IV of  FIG. 21 , because in actuality, transitions from a “false” level to a “true” level, and vice versa, do not necessarily assume the sharp-cornered profile of Graph IV. Instead, signals frequently exhibit “bouncing,” illustrated graphically at sawtoothed regions  2206   a , 2206   b . According to some implementations, the elevator door monitor  100  should be understood to include methods and components to de-bounce the digital signal from the MCU  1400 , to bring it closer to the ideal profile of Graph IV at  2118 . 
       FIG. 23  is a schematic view of a connection arrangement between an elevator controller and an elevator monitor according to further aspects of the present disclosure, the arrangement being an alternate to that shown in  FIGS. 1 and 2 , and in which the disclosed alternate arrangement assigns a differential amplifier for each switch in the elevator controller that is desired to be individually monitored.  FIG. 23  depicts this alternate arrangement as a circuit  2500  including a voltage source  2502  and a load L 1  connected by a line  2504 , in which are situated a plurality of switches S 1 , S 2 , and S n , where “n” can represent any number of switches. Three switches are shown in  FIG. 23  for ease of illustration. Line  2504  represents any type of elevator control parameter line in an elevator controller  102  ( FIG. 2 ), such as, for illustrative examples, the HDL line  160  or the DFO line  182  in  FIG. 2 . Similarly, load L 1  represents any type of load connected to such elevator control parameter lines, such as, for illustrative examples, the HDL relay coil  168  or the DFO relay coil  186  in  FIG. 2 . Instead of connecting just a single differential amplifier to just two terminals per an entire elevator control parameter line, such as terminals  170 , 172  in the HDL line  160  of  FIG. 2 , the arrangement of  FIG. 23  assigns a differential amplifier for each of the switches in the elevator control parameter line that are desired to be individually monitored. This is symbolically depicted in  FIG. 23  by the voltages V s1 , V s2 , and V sn , where the “n” is the total number of switches S n  that are desired to be individually monitored. The voltages V s1 , V s2 , and V sn  represent each calculated V rms  value resulting from each input voltage  2001  ( FIG. 20 ) that enters each corresponding differential amplifier, where each such differential amplifier can be constructed as shown in  FIG. 18  at  101   a . Each such V rm s value can be calculated in the manner described above with regard to  FIG. 20  at block  2010 . Pairs of input lines  2506   a,b ,  2508   a,b , and  2150   a,b  correspond to the inputs of respective differential amplifiers, such as the input terminals  1802 , 1804  of differential amplifier  101   a  ( FIG. 18 ). Respectively connected between the input lines  2506   a,b ,  2508   a,b , and  2150   a,b  are impedances Z 1 , Z 2 , and Z n , each impedance primarily including, but not being limited to, the equivalent resistance resulting from resistors placed in the differential amplifier  101   a  as shown at R 2  and R 3  in  FIG. 18 . 
     The arrangement of  FIG. 23  allows a combination of an elevator controller  102  and an elevator door monitor  100  to adapt to local building codes and/or regulations that require individual monitoring of one or more switches, without having to rearrange or re-configure the existing circuitry in an elevator controller  102  that may be built in the conventional manner exemplified in  FIG. 2 . Such rearranging has the inconvenience of being time-consuming, as well as requiring the assistance of technicians who possess a certain level of proficiency in how a particular elevator system works in order to implement any needed changes. Additionally, such rearranging could result in later difficulties when trying to troubleshoot the system, since technicians who were familiar with only the original configuration of the elevator controller  102  will require down-time in order to become familiar with the rearranged elevator controller  102 . 
     Still referring to  FIG. 23 , if the impedance values for impedances Z 1 , Z 2 , and Z n  are properly chosen, one can independently sense the status of each of the switches S 1 , S 2 , and S n  without interfering with the original system behavior, that is, without affecting the behavior of the load L 1 . Properly-chosen impedance values will not affect such behavior, yet will result in a significantly different voltage at a switch when the switch is open instead of closed. As an example, assume that the voltage source  2502  is 120V, L 1  is a relay coil having an impedance Z L  of 10 kΩ, and the impedance Z 1  is 150 kΩ. If all switches S 1 , S 2 , and S n  are closed, V s1 , V s2 , and V sn  will all be close to zero volts, and the load L 1  will get 120V, so there is no interference with the load behavior, and the door monitor  100  can know that all the switches S 1 , S 2 , and S n  are closed because the voltage at each of the corresponding inputs is zero. Now assume that only S 1  is open. This results in the load L 1  being in series with the 150 kΩimpedance, forming a voltage divider. The 120V of the voltage source is now divided in the same proportion of the impedance of the input module and the load L 1 : V L1 =120*[Z L /(Z L +Z 1 )]=120*[10K/(10K+150K)]=7.5V, VS1=120−7.5=112.5V. Thus, with one switch open the load L 1  is guaranteed only to see a maximum of 7.5V, which is very low to change from an inactive state to an active state. Any load that L 1  could represent in an elevator system will need to see at least 35% of its rated voltage to change from an inactive state to an active state. In the example above, 7.5V corresponds to 6%. Also, since the voltage across S, is now 112.5V, the door monitor  100  knows that S, is open because it is reading a voltage level significantly different than zero. Now assume that all switches are opened. In this case, L 1  is in series with 3*150 kΩ, and the voltage divider is such that L 1  will see a much lower voltage than when only one switch was open, guaranteeing that L 1  will not change from inactive to active. Calculating the voltages at L 1  and at each input module (differential amplifier) in this scenario, the result is as follows: V L1 =2.60V, V S1 =V S2 =V S3 =39.13V. In this example, if the corresponding inputs of the door monitor  100  are set for 24V and HTH=66%, LTH=33% and Logic Active Low, it will know the status of each switch S 1 , S 2 , and S n , independent of each other, without interfering the original behavior of L 1 , and without changing the original wiring of the switches S 1 , S 2 , and S n . 
       FIGS. 24A-24L  illustrate example screen shots demonstrating various aspects of graphical user interfaces (GUIs) presented by LCD and touch screen  114  of the elevator door monitor  100  according to aspects of the present disclosure. The touch screen  114  is configured to provide a plurality of GUIs through which a user may store a plurality of setting values into either or both of the memory resources  1402  and  1418  ( FIGS. 14A and 14B ). 
       FIG. 24A  illustrates a GUI comprising a main status screen  2300 , the main status screen  2300  comprising a door status icon  2301 , an inspection status icon  2302 , a fire service icon  2303 , a gate switch status icon  2304 , an interlocks status icon  2305 , and a menu icon  2306 . The door status icon  2301  is illustrated as depicting a state of door failure, but it can change its appearance to reflect other states of the elevator door being monitored, such as door open, door open halfway, and door closed. The inspection status icon  2302  can toggle between two different colors along with its caption changing according to whether the elevator car being monitored is detected to be in inspection mode. The inspection status icon  2302  can, for example, turn blue when inspection mode is on, and turn gray when the elevator car is not in that mode. The fire service icon  2303 , which indicates whether the monitored elevator car is in FS 2  mode, can toggle between two different colors along with its caption changing according to whether the elevator car being monitored is detected to be in FS 2  mode. The fire service icon  2303  can, for example, turn red when the elevator car is in FS 2  mode, and turn gray when the elevator car is not in that mode. Regarding both the gate switch status icon  2304  and the interlocks status icon  2305 , a “closed” lock position indicates the signals are active, and an “open” lock position indicates the signals are not active. 
     Referring both to  FIGS. 24A and 24B , the menu icon  2306  is configured to, responsive to a touch by a user, cause the touch screen  114  to display a main menu screen  2307 , the main menu screen  2307  comprising a “Main Screen” button  2308  adjacent a house icon  2309 , a “Configuration” button  2310  adjacent a settings icon  2311 , an “Events” button  2312  adjacent a notification icon  2313 , and an “Information” button  2314  adjacent an information icon  2315 . The “Main Screen” button  2308 , when touched, causes the touch screen  114  to once again display the main status screen  2300 . 
     Referring to both  FIGS. 24B and 24C , the “Configuration” button  2310  is configured to, responsive to a touch by the user, cause the touch screen  114  to display a signal configuration screen  2316  comprising an “Inputs” button  2317 , a “Controller” button  2318 , a “Time &amp; Date” button  2319 , an “Other” button  2320 , and a “Back” button  2321  that, when pressed, causes the touch screen  114  to once again display the main menu screen  2307 . 
     Referring to  FIGS. 24C, 24D, and 24E , the “Inputs” button  2317  is configured to, responsive to a touch by the user, display a signal configuration screen  2322  comprising a “Signal” button  2323 , a signal selection region  2324  adjacent the “Signal” button  2323 , a “Voltage” button  2325 , a voltage selection region  2326  adjacent the “Voltage” button  2325 , a “Thresholds” button  2327 , a threshold selection region  2328  adjacent the “Thresholds” button  2327 , a “Logic” button  2329 , a logic selection region  2330  adjacent the “Logic” button  2329 , and a “Back” button  2331  that, when pressed, causes the touch screen  114  to once again display the signal configuration screen  2316 . The signal selection region  2324  is configured to display a name of an elevator control parameter (CGS in the example of  FIG. 24D , HDL in the example of  FIG. 24E ). The “Signal” button  2323  is configured to, responsive to a touch by the user, cause a name of another elevator control parameter to be displayed in the signal selection region  2324  in place of the name of the first-displayed elevator control parameter. Thus, using the illustrated examples, pressing “Signal” button  2323  can cause the signal selection region  2324  to transition from the “CGS” display in  FIG. 24D  to the “HDL” display in  FIG. 24E . Successive presses of “Signal” button  2323  by the user will cause the signal selection region  2324  to successively display still more names of different elevator control parameters. The voltage selection region  2326  is configured to display a change-of-state voltage magnitude for the parameter displayed in the signal selection region  2324 . The user will know what value to select based on the determination of contact location in the elevator controller  102  and the determination of the voltage associated with a parameter change of state, in the manner discussed above with regard to  FIG. 2 . The voltage selection region  2324  also displays an actual voltage across the aforementioned selected elevator control contacts (348V in the example of  FIG. 24D , 120V in the example of  FIG. 24E ). The “Voltage” button  2325  is configured to, responsive to a touch by the user, cause a second change-of-state voltage magnitude to be displayed in the voltage selection region  2324  in place of the first change-of-state voltage magnitude. The threshold selection region  2328  is configured to display a percentage pair (33% and 66% in the examples of  FIGS. 24D and 24E ), a first numeral in the pair defining a percentage that, when multiplied by the voltage magnitude recited in the voltage selection region  2326 , equals the low threshold setting (LTS  2114 ,  FIG. 21 ), and the second numeral in the percentage pair defining a percentage that, when multiplied by the voltage magnitude recited in the voltage selection region  2326 , equals the high threshold setting (HTS  2112 ,  FIG. 21 ). The “Thresholds” button  2327  is configured to, responsive to a touch by the user, cause a second pair of percentages to be displayed in the threshold selection region  2328  in place of a first pair of percentages. The logic selection region  2330  is configured to display either the words “Active High” or the words “Active Low.” The “Logic” button is configured to, responsive to a touch by the user, cause the logic selection region  2330  to toggle between displays of the words “Active High” and the words “Active Low.” 
     The “Controller” button  2318  of the signal configuration screen  2316  ( FIG. 24C ) is configured to, responsive to a touch by the user, cause the touch screen  114  to display a controller characteristics configuration screen  2332  ( FIG. 24F ), the controller characteristics configuration screen  2332  comprising an upper region  2333  and a lower region  2334 , the upper region  2333  containing two upper radio buttons  2335 , 2336  through which the user may indicate whether a FS2 signal is available, and the lower region  2334  containing two lower radio buttons  2337 , 2338  through which the user can select an elevator door type as between a sliding door and a swinging door. The controller characteristics configuration screen  2332  can also be provided with a “Back” button  2339  that, when pressed, causes the touch screen  114  to once again display the signal configuration screen  2316  ( FIG. 24C ). 
     The “Time &amp; Date” button  2319  of the signal configuration screen  2316  ( FIG. 24C ) is configured to, responsive to a touch by the user, cause the touch screen  114  to display the time-and-date screen  2340  shown in  FIG. 24G . Time-and-date screen  2340  includes a display region  2341  reciting both time information  2342  and date information  2343 . Region  2341  allows the user to select which item of information  2342 , 2343  to adjust. Using down-increment button  2344  or up-increment button  2345 , the user can adjust the selected information item. Time-and-date screen  2340  is provided with a “Back” button  2346  that, when pressed, causes the touch screen  114  to once again display the signal configuration screen  2316  ( FIG. 24C ). 
     The “Other” button  2320  of the signal configuration screen  2316  ( FIG. 24C ) is configured to, responsive to a touch by the user, cause the touch screen  114  to display the settings screen  2347  illustrated in  FIG. 24H . The settings screen  2347  comprises an upper region  2348  and a lower region  2349 , the upper region  2348  configured to enable the user to select at least one beeping condition during which the MCU  1400  ( FIG. 15 ) will command an audio element to beep. Such an audio element can be in communication with the MCU  1400 , the audio element configured to beep responsive to a command received from the MCU  1400 . Settings screen  2347  recites beeping conditions, a first beeping condition  2350  comprising detection of a failure, a second beeping condition  2351  comprising detection of a warning, and a third beeping condition  2352  comprising tapping the touch screen  114 . The lower region  2349  of settings screen  2347  contains a “Set Security Pin” button  2353 , which is configured to, responsive to a touch by the user, cause the touch screen  114  to display a numeric touchpad screen  2355  ( FIG. 24I ) configured to enable the user to store, by pressing the “OK” button  2356 , a personal identification number into a memory such as the second memory resource  1418  ( FIG. 14B ). Lower region  2349  also contains a touch screen calibration button  2354 . The settings screen  2347  is provided with a “Back” button  2357  that, when pressed, causes the touch screen  114  to once again display the signal configuration screen  2316  ( FIG. 24C ). Similarly, the numeric touchpad screen  2355  is provided with a “Back” button  2358  that, when pressed, causes the touch screen  114  to once again display the settings screen  2347  ( FIG. 24H ). 
     The “Events” button  2312  of the main menu screen  2307  ( FIG. 24B ) is configured to, responsive to a touch by the user, cause the touch screen  114  to display an events history screen  2359  ( FIG. 24J ), the events history screen  2359  displaying event data stored in memory including the first memory resource  1402  and/or the second memory resource  1418  ( FIGS. 14A and 14B ). The event data comprises, for each stored event, an event type  2360 , a time  2361  at which the event occurred, and a date  2362  on which the event occurred. The events history screen  2359  is provided with a “Back” button  2357  that, when pressed, causes the touch screen  114  to once again display the main menu screen  2307  ( FIG. 24B ). It should be understood that some events that can be summarized in the events history screen  2359  can be not merely change of state of a monitored signal, but instead events that are the result of certainty combinations of signals as determined by an algorithm ran by the MCU  1400  ( FIG. 15 ). One such event, for example, is associated with faulty door contacts. If both the DFO and DFC signals are true at the same time, a Door Failure event is triggered (an example of a failure message screen shown in  FIG. 24L ), since a door cannot be both fully open and fully closed at the same time. In this case, events showing when the DFO and DFC changed are displayed in the events history screen  2359 , in addition to the event that represents failure. In that case, the event representing the failure will have the same time stamp as the DFO or DFC event that actually triggered the door failure event. There could also be warning events corresponding to internal state of the device, like an undesirably high temperature, or loss of communication with the second memory resource  1418  ( FIG. 14B ) or with the RTC  1502  ( FIGS. 15 and 17 ) or with low main power voltage, etc. 
     The “Information” button  2314  of the main menu screen  2307  ( FIG. 24B ) is configured to, responsive to a touch by the user, cause the touch screen  114  to display an information screen  2365  ( FIG. 24K ), which can display manufacturer/supplier information  2366  and device/hardware/firmware information  2367 . The information screen  2365  is provided with a “Back” button  2368  that, when pressed, causes the touch screen  114  to once again display the main menu screen  2307  ( FIG. 24C ). 
       FIG. 25  is a block diagram depicting an elevator door monitor  100  operating in an exemplary interactive environment  2400  according to aspects of the present disclosure. Wireless module  118  ( FIG. 1 ) permits two-way communication between the elevator door monitor  100  and a cloud  2404  via a communication link  2402   a . Cloud  2404  can represent, for example, be a remote monitoring system, but it is to be understood that cloud  2404  is not necessarily limited to such a system. As explained with regard to cloud computing generally in U.S. Patent Application Publication No. 2014/0379910 to Saxena et al., cloud  2404  can include “a collection of hardware and software that forms a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, services, etc.), which can be suitably provisioned to provide on-demand self-service, network access, resource pooling, elasticity and measured service, among other features.” Cloud  2402  may be deployed as a private cloud (e.g., infrastructure operated by a single enterprise/organization), community cloud (e.g., infrastructure shared by several organizations to support a specific community that has shared concerns), public cloud (e.g., infrastructure made available to the general public, such as the Internet), or a suitable combination of two or more disparate types of clouds. In this description, “cloud computing” is defined as a model for enabling on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services). As stated in U.S. Patent Application Publication No. 2014/0075431 to Kumar et al: “Generally, a cloud computing model enables some of those responsibilities which previously may have been provided by an organization&#39;s own information technology department, to instead be delivered as service layers within a cloud environment, for use by consumers (either within or external to the organization, according to the cloud&#39;s public/private nature).” As further explained in the aforementioned Kumar et al. patent application, a cloud computing model can take the form of various service models such as, for example, Software as a Service (“SaaS”), “in which consumers use software applications that are running upon a cloud infrastructure, while a SaaS provider manages or controls the underlying cloud infrastructure and applications,” and Platform as a Service (“PaaS”), “in which consumers can use software programming languages and development tools supported by a PaaS provider to develop, deploy, and otherwise control their own applications, while the PaaS provider manages or controls other aspects of the cloud environment (i.e., everything below the run-time execution environment).” The definition of “cloud computing” is not limited to any of the other numerous advantages that can be obtained from such models when properly deployed. Given such functionality of cloud  2404 , a remote user  2406  can access services provided in the cloud  2404  via a remote device such as cell phone (smartphone)  2408  for purposes of remotely communicating with the elevator door monitor  100 . 
     Still referring to  FIG. 25 , elevator door monitor  100  can also, in some implementations, be configured to communicate directly, via a communication link  2402   c , to the cell phone  2408  of the remote user  2406 . Using either or both of the aforementioned methods of remote communication, the remote user  2406  is able to exchange various kinds of data with the elevator door monitor  100 . For example, via the cell phone  2408 , a text communication from the remote user  2406  to the elevator door monitor  100  may state: “Send me a history of events.” See the above discussion of event history with regard to  FIG. 24J . In response to that text communication, the elevator door monitor  100  can access the stored events history and reply with the history information, sending it as a text reply to the cell phone  2408 . As another example, remote user  2406  could send a text: “Activate 3rd contact.” As previously explained with regarding to  FIG. 1 , a third set of output contacts could comprise controls for LEDs or an alarm. Thus in response to the quoted text, the elevator door monitor can activate (or de-activate) a light indicator or an alarm. However, it is presently contemplated that the elevator door monitor  100  would preferably be configured so that no command sent remotely would change any configuration settings of the types described above with regard to  FIGS. 24A-24L . 
     The communication links  2402  shown in  FIG. 25  represent a network or networks that may comprise hardware components and computers interconnected by communications channels that enable sharing of resources and information. The network may comprise one or more of a wired, wireless, fiber optic, or remote connection via a telecommunication link, an infrared link, a radio frequency link, a cellular link, a Bluetooth® link, or any other suitable connectors or systems that provide electronic communication. The network may comprise intermediate proxies, routers, switches, load balancers, and the like. The paths followed by the network between the devices as depicted in  FIG. 25  represent the logical communication links between those devices, not necessarily the physical paths or links between and among the devices. 
     Although several aspects have been disclosed in the foregoing specification, it is understood by those skilled in the art that many modifications and other aspects will come to mind to which this disclosure pertains, having the benefit of the teaching presented in the foregoing description and associated drawings. For example, regarding the entry of numeric setting information through GUIs, instead of choosing from a preselected list of values as discussed with regard to display regions  2326  and  2328  of the signal configuration screen  2322   FIGS. 24D and 24E ), a user could navigate to a numeric keypad screen ( FIG. 24I ) and enter specific values directly into those display regions  2326  and  2328 . It is thus understood that the disclosure is not limited to the specific aspects disclosed hereinabove, and that many modifications and other aspects are intended to be included within the scope of any claims that can recite the disclosed subject matter. 
     One should note that conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain aspects include, while other aspects do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more particular aspects or that one or more particular aspects necessarily comprise logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular aspect. 
     It should be emphasized that the above-described aspects are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the present disclosure. Any process descriptions or blocks in flow diagrams should be understood as representing modules, segments, or portions of code which comprise one or more executable instructions for implementing specific logical functions or steps in the process, and alternate implementations are included in which functions may not be included or executed at all, can be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present disclosure. Many variations and modifications can be made to the above-described aspect(s) without departing substantially from the spirit and principles of the present disclosure. Further, the scope of the present disclosure is intended to cover any and all combinations and sub-combinations of all elements, features, and aspects discussed above. All such modifications and variations are intended to be included herein within the scope of the present disclosure, and all possible claims to individual aspects or combinations of elements or steps are intended to be supported by the present disclosure.