Abstract:
A monitoring device for passenger transport systems, which systems are designed as elevators, escalators or moving walkways, includes at least one detecting device used to detect an external actuation of an equipment of the passenger transport system, a control device and at least one energy store for storing electrical energy. The energy store is kept in a charged state. The energy store is put into a discharged state when the detecting device detects the external activation of the equipment.

Description:
FIELD 
       [0001]    The invention relates to a monitoring device for transport systems for persons, which systems are designed as elevators, escalators or moving walkways, to such a passenger transport system and to a method for such a passenger transport system. The invention especially relates to the field of elevator systems. 
       BACKGROUND 
       [0002]    A monitoring device for an elevator is known from WO 02/12109 A1. The known monitoring device comprises a number of contactlessly actuable switching devices which are serially connected together to form a safety circuit. The switching devices have to have a specific state in order to be able to safely perform an intended action. In particular, in normal operation it has to be ensured in the case of an elevator system that all doors remain closed and mechanically locked when an elevator car of the elevator system moves. If the elevator car does not move, then a shaft door may be opened only if the elevator car is present at this shaft door. In the case of the known monitoring device each switching devices comprises an active unit and a passive unit, wherein the active unit and the passive unit are so constructed that the passive unit is excited exclusively by a pattern generated by the active unit. The active unit is in this regard constructed as an interrogation unit. The passive unit is constructed as a response unit. The interrogation unit is in that case so constructed that it is in a position of transferring data to the response unit and receiving data from the response unit. A first coil of the interrogation unit and a second coil of the response unit are constructed as antennae. The interrogation unit transmits energy to the response unit by way of an electromagnetic field. This is carried out by an electromagnetic coupling, since the energy transmission functions similarly to a transformer where the energy is transferred from the primary winding to the secondary winding through a narrow coupling. The energy coupled in by way of the electromagnetic field is temporarily stored by the response unit in an energy store. As soon as the response unit has received sufficient energy it is functionally capable and responds in a very specific mode and manner to the pattern generated by the interrogation unit. 
         [0003]    The monitoring unit known from WO 02/012109 A1 has the disadvantage that the interrogation unit has to be permanently supplied with electrical energy by an energy supply, for example a supply mains. If, for example, this energy supply occasionally fails or an energy transmission to the interrogation unit for the monitoring unit is disturbed then the monitoring device is no longer functionally capable, since due to the absence of energy a charging of the energy store of the passive unit then cannot take place by way of the active unit. It thus can no longer be recognized whether a door is open. If the door is closed again during the power failure, such a possible action remains unrecognized. 
       SUMMARY 
       [0004]    An object of the invention is to indicate a monitoring device for transport systems for persons, which systems are designed as elevators, escalators or moving walkways, as well as such a passenger transport system and a method for monitoring such a passenger transport system, which are of improved design. Specifically, it is an object of the invention to indicate a monitoring device for transport systems for persons, which systems are designed as elevators, escalators or moving walkways, as well as such a passenger transport system and a method for monitoring such a passenger transport system in which external actuation of an device of the passenger transport system can be detected even during occasional interruption of an external energy supply. 
         [0005]    The object is fulfilled by a monitoring device for transport systems, which are designed as elevators, escalators or moving walkways, for persons. The monitoring device comprises at least one detecting device, which serves for detection of external actuation of an device of the passenger transport system, and at least one energy store for storage of electrical energy. By “external actuation” there is to be understood actuation of the device which is attributable to an external action and does not take place, for example, due to a control signal of a control device of the passenger transport system. Such external actuations can be, for example, opening of the shaft doors by a person, which by means of a box spanner creates access to the elevator shaft. Other external actuations are also conceivable, for example if a shaft door has been forcibly opened or pushed in. 
         [0006]    The energy store can be kept in a charged state independently of an external energy supply which is present. The detecting device detects external actuation of the device in that the energy store after external actuation of the device is transferred to a discharged state. The state of the energy store can be interrogated by suitable means, for example by the control device of the passenger transport system. A discharged state of the energy store always represents an external actuation and this is so even if the device itself has re-adopted its original start state. The original start state is that physical state which the device has before the external actuation thereof has taken place. In the case of a shaft door this would be, for example, the closed state thereof. Even if the energy store is defective, due to the discharged state an external actuation is assumed and the passenger transport system then has to be checked by an expert. Only an intentional resetting or charging of the energy store erases the information that external actuation has taken place. 
         [0007]    The object is additionally fulfilled by a passenger transport system with at least one monitoring device and by a method for monitoring a passenger transport system with at least one monitoring device. 
         [0008]    It is advantageous that in the case of interruption of the external energy supply the energy store is transferred to a discharged state if the detecting device detects external actuation of the device and that the control device after the interruption switches the external energy supply to the special operating state if the energy store is in the discharged state. The monitoring device is distinguished by a special utilization or circuitry of the energy store for storage of electrical energy. If the external energy supply is available, then the energy store is not absolutely necessary for detection of external actuation of the device of the passenger transport system, since detection of external actuation can be communicated to the control device in conventional manner, for example by way of a bus system. If, thereagainst, the external energy supply is interrupted then the state of the energy store can be manipulated in dependence on detection of external actuation. If during the interruption the external energy supply does not detect external actuation then the energy store remains charged. If on the other hand external actuation of the device of the passenger transport system is detected during interruption of the external energy supply the energy store is then manipulated and transferred to an uncharged state. After the interruption of the external energy supply the state of the energy store can then be interrogated, for example within the scope of an initialization procedure. The state of the energy store now indicates whether or not during interruption of the external energy supply external actuation of the device of the passenger transport system took place. If external actuation did not take place, the control device then switches to the special operating state. 
         [0009]    However, in one possible design of the monitoring device or the transport equipment for persons or the method the energy store can be used, even when the external energy supply is intact, in order to establish that external actuation of the device has taken place. In this case the energy store cannot be transferred, even in the power-free state of the external energy supply, to the discharged state if external actuation of the monitored device is detected. This can also be carried out additionally to a further safety circuit and/or a further safety device. A redundant monitoring and/or interrogation is therefore possible. The energy store can thus also be used in such a case as a status store. In this regard it is advantageous that the control device switches to the special operating state if the energy store is in the discharged state. In addition, the control device can, even when the external energy supply is present, also directly switch to the special operating state if the detecting device detects external actuation of the device. 
         [0010]    By “charged state of the energy store” and “uncharged state of the energy store” there are to be understood two states of the energy store different from one another. A charged state is in that regard not necessarily a fully charged state. In particular, during the interruption of the external energy supply a slight discharging can also occur due to constructional reasons. In addition, a maximum possible charging of the energy store can also vary as a consequence of component tolerances or component ageing. Moreover, the energy store even in the discharged state can still carry a residual charge, since complete discharging is in a given case not necessary for distinction of the states and also in a given case for constructional reasons is too complicated or lasts too long. What is essential is a reliable differentiation of the charged state of the energy store from the discharged state of the energy store. 
         [0011]    It is advantageous that at least one threshold value for the energy store is present, that when an external energy supply is present the energy store can be transferred to a charged state in which the charge of the energy store is greater than the at least one threshold value and that in the case of interruption of the external energy supply the energy store is transferred to a discharged state in which the charge of the energy store is smaller than the at least one threshold value if the detecting device detects external actuation of the device of the passenger transport system. Specifically, an upper threshold value and a lower threshold value for the energy store can be preset, wherein the upper threshold value is greater than the lower threshold value. In this case the energy store is charged above the upper threshold value so that it is in the charged state. In addition, the energy store is discharged to below the lower threshold value so that it is in the discharged state. In that case, a sufficient separation and thus a capability of differentiating the states is guaranteed by way of the spacing between the lower threshold value and the upper threshold value. 
         [0012]    It is also advantageous that the control device, when the external energy supply is present, transfers the energy store from the discharged state to the charged state only if the detecting device does not detect external actuation of the device. If at this point in time external actuation of the device is still present, then resetting is prevented. This is feasible for, for example, the possibility of automatic resetting which depends on further conditions. 
         [0013]    Additionally or alternatively it is of advantage that the control device, when the external energy supply is present, transfers the energy store from the discharged state to the charged state only if the control device blocks transport of persons by the passenger transport system in the special operating state and manual release takes place. Automatic resetting is not possible in this case. The manual release can in that regard be reserved to, for example, an authorized service operative. For example, it is conceivable with an elevator system that external actuation of an elevator door is monitored at a floor. If during interruption of the external energy supply this floor door has been opened and closed again then a person is possibly still present in the elevator shaft. Thus, the elevator system is blocked at the outset. This applies correspondingly to an escalator or a moving walkway when, for example, a cover to an engine compartment is opened and this cover is monitored by means of a monitoring device according to the invention. 
         [0014]    It is also advantageous that the detecting device comprises a switching element which is mechanically actuable at least indirectly by the device of the passenger transport system and which can be actuated for detecting the external actuation and that in the case of the switching element being actuated a current circuit for discharging the energy store is closed. The mechanically actuable switching element can be constructed as, for example, a button. The components for discharging the energy store, which are present in the current circuit, are in that case so dimensioned that a sufficiently rapid discharging of the energy store is guaranteed. A simple mechanical activation is thus possible. The switching element can thus be designed as, in particular, a passive switching element. It is thereby possible to dispense with a local energy supply. 
         [0015]    In that case, a particular advantage of the invention is that the monitoring device is not capable of simple manual manipulation, for example by jamming the button, as was done impermissibly on rare occasions and has led to serious accidents. The discharged energy store ‘stores’ the actuation of the device permanently and firstly has to be charged again so that the passenger transport system can be returned to the normal operating state. 
         [0016]    However, it is also advantageous that the detecting device comprises an active switching element which is electrically, electronically or electromagnetically actuable at least indirectly by the device of the passenger transport system and which can be actuated for detecting the external actuation, and that when the switching element is actuated a current circuit for discharging the energy store is closed. In that case, in particular, a contactless detection of external actuation of the device of the passenger transport system can also be realized. Moreover, through a circuit construction with the active switching element it is possible to achieve a reliable and substantial discharging of the energy store. For example, the discharging can also take place over a comparatively long period of time even if the activation takes place only briefly. Moreover, the monitoring can thereby be designed to be more complex and, for example, be designed to be insensitive relative to artifacts (an unreal result caused by the method or the effects of a system weakness on a useful signal in measuring, signalling or similar technology) and an external manipulation. 
         [0017]    In that case, the active switching element or an active interrogation unit can be supplied with energy by a switching element at least in part from the energy store. Additionally or alternatively an independent energy source, particularly a battery or an accumulator, can also be provided, which is independent of the external energy supply, wherein the active switching element is supplied with energy at least in part by the independent energy source. In particular, the independent energy source can ensure energy supply of the active switching element only in the case of interruption of the external energy supply. 
         [0018]    For reasons of redundancy a design is also conceivable in which not only a passive switching element, but also an active switching element or an active interrogation unit are provided with a switching element for detecting external actuation of the same device of the passenger transport system. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0019]    Preferred embodiments of the invention are explained in more detail in the following description by way of the accompanying drawings, in which corresponding elements are provided with corresponding reference symbols and in which: 
           [0020]      FIG. 1  shows a passenger transport system with a monitoring device in a schematic illustration, in the manner of a detail, in correspondence with an embodiment of the invention; 
           [0021]      FIG. 2  shows a monitoring device of the passenger transport system illustrated in  FIG. 1  in a schematic illustration, in the manner of a detail, in correspondence with a first possible embodiment of the invention; 
           [0022]      FIG. 3  shows a monitoring device of the passenger transport system illustrated in  FIG. 1  in a schematic illustration, in the manner of a detail, in correspondence with a second possible embodiment of the invention in a non-actuated state of an device of the passenger transport system; and 
           [0023]      FIG. 4  shows the monitoring device illustrated in  FIG. 3  in an externally actuated state of the device of the passenger transport system. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  shows a passenger transport system  1 , which is designed as an elevator (elevator system)  1 , with a monitoring device  2  in a schematic illustration, which is in the manner of a detail, corresponding with an embodiment. In a modified form of embodiment the passenger transport system  1  can also be designed as an escalator or moving walkway. 
         [0025]    The monitoring device  2  comprises a control device  3  and a plurality of detecting devices  4  to  9 . The detecting devices  4  to  9  are connected with the control device  3  by way of a bus system  10 . 
         [0026]    The passenger transport system  1  additionally comprises a plant control  11 , an external energy supply  12 , which is, for example, connected with a current mains, an input device  13  and an output device  14 . The external energy supply  12  can in that regard supply the detecting devices  4  to  9  with energy in parallel with the data transmission by way of the bus system  10 . In addition, the external energy supply  12  supplies the control device  3 , the plant control  11  and optionally the input device  13  and the output device  14  with energy, wherein the lines with respect thereto are, for simplification of the illustration, not shown. By way of example, elevator-relevant data which, for example, are relevant for maintenance can be communicated to the control device  3  by way of the input device  13 . Moreover, the control device  3  can issue data, which are relevant for an operator, particularly a maintenance operative, by way of the output device  14 . The control device  3  can additionally intervene in the elevator control  11 . The control device  3  can thereby switch to a special operating state. In the special operating state transport by the passenger transport system  1  is then blocked. This can take place, for example, by activation of a brake, particularly a safety brake, and/or by deactivation of a drive motor. 
         [0027]    The passenger transport system  1  comprises items of equipment  15 ,  16  which, in this embodiment, are formed as doors  15 ,  16 . Such doors  15 ,  16  can be present at a floor of a building. When the doors  15 ,  16  are closed access to an elevator shaft is excluded. The items of equipment  15 ,  16  can be externally actuated, particularly opened, by persons. In this embodiment a possible external actuation of the device  15  is detected by the detecting device  4 . A possible external actuation of the device  16  is detected by the detecting device  5 . 
         [0028]    The idea of the externally actuable items of equipment  15 ,  16  is in this regard to be understood generally. The items of equipment  15 ,  16  can also be constructed as flaps, locks, particularly three-square locks, of doors, particularly shaft doors, which are monitored. The items of equipment  15 ,  16  are in that case not necessarily a component of the monitoring device  2 . In particular, the monitoring device  2  can also be produced and marketed independently of such items of equipment  15 ,  16 . 
         [0029]    The detecting devices  6  to  9  serve for monitoring further such items of equipment, which, for the sake of simplification, are not illustrated. 
         [0030]    The items of equipment  15 ,  16  serving as shaft doors  15 ,  16  can be monitored by the detecting devices  4 ,  5 . It can thus be established whether anybody could enter the elevator shaft. In particular, it can be monitored in the case of an elevator  1  with reduced shaft head or no shaft head whether anybody could have gone onto the car roof of the elevator car. When an external energy supply  12  is present this information can be communicated to the control device  3  directly by way of the bus system  10 . In the case of interruption of the external energy supply  12  with respect to the detecting devices  4 ,  5  a monitoring is equally possible such as also described on the basis of  FIGS. 2 to 4 . Thus, the passenger transport system  1  can automatically go back to normal operation, for example after a power failure, if no external actuation of the items of equipment  15 ,  16  has taken place. Thus, in this embodiment an automatic return to normal travel is possible if none of the shaft doors  15 ,  16  has been opened in the meantime. 
         [0031]      FIG. 2  shows a monitoring device  2  of the passenger transport system  1 , which is illustrated in  FIG. 1 , in a schematic illustration, in the manner of a detail, corresponding with a first possible embodiment of the invention. The detecting device  5  comprises a local control unit  20  and an interface  21 . The local control unit  20  is in that case connected with the bus system  10  by way of the interface  21 . In particular, the local control unit  20  is connected with the control device  3  when the external energy supply  12  is available. The local control unit  20  can then itself be supplied with power from the present external energy supply  12 . 
         [0032]    The detecting device  5  has an energy store  22  for storage of electrical energy. In this embodiment the energy store  22  is formed by a condenser  22 . In addition, a local voltage source  23  serving as a charging source  23  is present. The local voltage source  23  can thus depend on the external energy supply  12 . If the external energy supply  12  is interrupted, then in this case the local voltage source  23  is also without function. The local voltage source  23  can obviously also be a battery or an accumulator. In addition, a resistor  24  and a switching element  25  are provided. The switching element  25  is actuable by the local control unit  20  as is clarified by the dashed-line arrow  26 . When the switching element  25  is closed the energy store  22  is charged by the local voltage source  23  via the resistor  24 . 
         [0033]    After the charging, the switching element  25  can be opened again. The energy store  22  can thereby, when the external energy supply  12  is in fact, be kept in the charged state. In a given case the energy store  22  can also be kept in the charged state in that the switching element  25  is kept closed when the external energy supply  12  is present. A closing, which takes place at a specific spacing, of the switching element  25  is also possible in order to further compensate for a possible loss of charge of the energy store  22  as long as the external energy supply  12  is present. 
         [0034]    If the external energy supply  12  is interrupted and/or an actuating element  27  is actuated then the switching element  25  is opened insofar as the switching element  25  should still not happen to be in an opened state. 
         [0035]    In this embodiment a pin-shaped mechanical actuating element  27  is provided. The pin-shaped mechanical actuating element  27  is in that case actuable by the device  16 , as is indicated by the double arrow  28 . For example, the actuating element  27  can be adjusted by opening of the door  16 . Correspondingly, the actuating element  27  can also be adjusted by opening of a lock, particularly a three-square lock. 
         [0036]    The detecting device  5  further comprises a current circuit  30 , which is formed from the energy store  22 , a resistor  31  and a mechanically actuable switching element  32 . The mechanically actuable switching element  32  can be formed as, in particular, a button  32 . When the actuating element  27  closes the button  32  the energy store is then, if the switching element  25  is open, discharged. In addition, when the actuating element  27  is reset again the energy store  22  remains discharged, since the switching element  25  is open and the voltage source  23  is therefore without function. This principle of functioning is independent of whether the external energy supply  12  is present or interrupted. However, it is a particular advantage of the invention that detection of actuation of the actuating element  27  is possible even when the external energy supply  12  is interrupted. When the interruption of the external energy supply  12  ends, the local voltage source  23  is then indeed again in operation, but the switching element  25  remains open. The energy store  22  is thus kept in the discharged state. 
         [0037]    The local control unit  20  has inputs  33 ,  34 , by way of which the state of the energy store  22  can be detected or read out. If a possible actuation of the actuating element  27  is to be interrogated, for example when the external energy supply  12  is reinstated, the control device  3  then interrogates the state of the energy store  22  from the local control unit  20  by way of the bus system  10 . If the local control unit  20  reports a discharged state of the energy store  22  the control device  3  then blocks, by way of the plant control  11 , possible transport of persons. 
         [0038]    Thus, in the case of interruption of the external energy supply  12  the energy store  22  is transferred to a discharged state if the detecting device  5  detects external actuation of the device  16 . If the energy store  22  after the interruption of the external energy supply  12  is then in the discharged state the control device  3  then subsequently switches to the special operating state. This special operating state can be indicated by way of the output device  14  to an operator, particularly a service engineer. Resetting can then be requested by way of the input device  13 . 
         [0039]    However, the control device  3  transfers the energy store  22 , when the external energy supply  12  is present, from the discharged state to the charged state only if the detecting device  5  no longer detects the external actuation of the device  16 . This means that the door  16  is closed again or a lock associated with the door  16  is locked again. In addition, a manual release has to be carried out by the service engineer so that the control device  3  transfers the energy store  22  from the discharged state to the charged state. 
         [0040]    In this embodiment manual release takes place by means of the input device  13 . The manual release is communicated by the control device  3  to the local control unit  20 . In addition, in this embodiment the energy store  22  can, for reasons of construction, be transferred to the charged state only if the current circuit  30  is opened again. If the switching element  32  is opened and at the same time the local control unit  20  closes the switching element  25 , then the energy store  22  is charged by the local voltage source  23 . Logically, charging of the energy store  22  takes place only when the passenger transport system  1 , when the external energy supply  12  is present and after predetermined checks have been carried out, is transferred by authorized personnel from the special operating state to a normal operating state. 
         [0041]    The local control unit  20  can additionally monitor charging of the energy store  22  by way of the inputs  33 ,  34 . In that case, it is possible to predetermine for the energy store  22  a threshold value above which the energy store  22  is charged. 
         [0042]    In this embodiment the mechanically actuable switching element  32  designed as a button  32  is a passive switching element  32 . 
         [0043]      FIG. 3  shows a monitoring device  2  of the passenger transport system  1 , which is illustrated in  FIG. 1 , in a schematic illustration in the manner of a detail corresponding with a second possible embodiment, in a non-actuated state of the device  15  of the passenger transport system  1 . The detecting device  4  of the monitoring device  2  in this embodiment comprises an active unit  42  constructed as an interrogation unit  42  and a passive unit  43  constructed as a response unit  43 . The response unit  43  can be, for example, a transponder, a tag, a smart card or a chip card. The interrogation unit  42  comprises a first coil  44 . The response unit  43  comprises a second coil  45 . The interrogation unit  42  and the response unit  43  are in a rest state when the device  15  is not actuated. In the rest state the interrogation unit  42  and the response unit  43  are so far apart from one another that no interaction takes place. In this embodiment a possible interaction takes place by way of an electromagnetic coupling. Thus, in the rest state there is an insufficient electromagnetic coupling between the coils  44 ,  45 . 
         [0044]    The operation mode of the monitoring device  2  in correspondence with the second possible embodiment is described in the following also with reference to  FIG. 4 . 
         [0045]      FIG. 4  shows the monitoring device  2 , which is illustrated in  FIG. 3 , in an externally actuated state of the device  15  of the passenger transport system  1 . Since the device  15  is in an externally actuated state an adjustment of the response unit  43  relative to the state illustrated in  FIG. 3  takes place. Specifically, the response unit  43  can be adjusted in a direction  46  towards the interrogation unit  42 . As a result, the first coil  44  of the interrogation unit  42  and the second coil  45  of the response unit  43  are disposed so close to one another that an interaction is possible. An electromagnetic coupling between the coils  44 ,  45  is thus present. 
         [0046]    In this embodiment the interrogation unit  42  comprises a first modulator  47  and a first demodulator  48 . In addition, a generator  41  is provided, which can be designed as, for example, a high-frequency generator  41  or a radio-frequency generator  41 . The response unit  43  comprises a second modulator  49  and a second demodulator  50 . In addition, the response unit  43  comprises an energy store  51 , which is formed by, for example, a condenser  51 . The response unit  43  therefore preferably manages without an individual energy supply, such as a battery. 
         [0047]    The interrogation unit  42  is in a position of transmitting information to the response unit  43  and obtaining information from the response unit  43 . The coils  44 ,  45  in that case serve as antennae  44 ,  45 . The interrogation unit  42  transmits energy to the response unit  43  by way of an electromagnetic field. This takes place via an electromagnetic coupling, which functions similarly to a transformer, in which the energy is transmitted from a primary winding through a narrow coupling to a secondary winding. The response unit  43  temporarily stores the energy, which is coupled in by way of the electric magnetic field, in the energy store  51 . As soon as the response unit  43  has received sufficient energy it is functionally capable and responds in specific manner to a pattern M generated by the interrogation unit  42 . 
         [0048]    The pattern M, which is generated by the interrogation unit  42 , as well as an answer M′ can be, for example, numbers, which are illustrated by a pattern. The pattern M exciting the response unit  43  does not in this case have to be very complex, since it primarily serves for transmission of energy and thus for triggering the answer M′. In one possible embodiment the pattern M can be a phase-modulated high-frequency signal. The pattern M is preferably used by the response unit  43  merely for obtaining energy and for synchronization of an answer. Thus, the pattern M can be understood as an instruction to the response unit  43  to generate a corresponding answer M′. 
         [0049]    A causal link of the answer M′ and the question M can thus be ensured. 
         [0050]    The response unit  43  can change the pattern M in such a manner that it is ensured that the change takes place through the response unit  43  itself and not through another element. For example, the response unit  43  can answer a question M by the transmission of a unique number M′. A unique identification of the response unit  43  is thus possible. 
         [0051]    Thus, it is possible to unambiguously distinguish between an unactuated state of the device  15  and an externally actuated state of the device  15 . 
         [0052]    In one possible embodiment the interrogation unit  42  of the detecting device  4  comprises an independent energy source  55  which is independent of the external energy supply  12 . The independent energy source  55  can therefore supply the interrogation unit  42 , which is designed as an active unit  42 , with energy even in the case of interruption of the external supply  12 . In particular, the generator  41 , first modulator  47  and first demodulator  48  can thus be supplied with energy. 
         [0053]    The response unit  43 , which is designed as a passive unit  4 , thereagainst does not need any independent energy source. The independent energy source  55  can be formed by, for example, a battery  55  or an accumulator  55 . Thus, in a given case charging of the independent energy source  55  by way of the external energy supply  12  is possible in usual operation. 
         [0054]    The interrogation unit  42  comprises a local control unit  20 ′ and an active switching element  56 . The active switching element  56  can comprise at least one transistor. If the external energy supply  12  is interrupted then the local control unit  20 ′ and the active switching element  56  can be supplied by the independent energy source  55 . 
         [0055]    If an externally actuated adjustment of the device  15  takes place then the coils  44 ,  45  go into a spacing in which an electromagnetic coupling is possible, as is illustrated in  FIG. 4 . Through the exchange of the patterns M, M′ it is detected that an external actuation of the device  15  has taken place. The local control unit  20 ′ thereupon switches the active switching element  56  so as to discharge the energy store  22 ′. 
         [0056]    After the interruption of the external energy supply  12  the control device  3  reads out the state of the energy store  22 ′ by way of the local control unit  20 ′. The control device  3  can thus establish whether or not external actuation of the device  15  took place during the interruption of the external energy supply  12 . 
         [0057]    Subsequently, the energy store  22 ′ can under specific conditions be shifted back into the charged state as is described on the basis of  FIG. 2 . For that purpose the local control unit  20 ′ can switch the switching element  25 ′. Charging of the energy store  22 ′ can take place at least indirectly by way of the external energy supply  12 . 
         [0058]    In a modified embodiment it is also possible to eliminate the independent energy source  55  of the interrogation unit  42 . The energy supply of the interrogation unit  42 , which is an active unit  42 , can in that case be taken over by the energy store  22 ′. For that purpose the energy store  22 ′ can, for example, be discharged to below a threshold value, wherein this threshold value is selected to be of such a height that even under the threshold value a sufficient energy supply of the interrogation unit  42  is still guaranteed. The discharged state of the energy store  22 ′ is then to be understood as discharged only with respect to the threshold value and not with respect to a possible energy supply of the interrogation unit  42 . 
         [0059]    In a further possible embodiment the energy store  22 ′ can equally serve for energy supply of the interrogation unit  42 . However, the active switching element  56  is in that case designed so that when the active switching element  56  is closed a progressive discharging of the energy store  22 ′ takes place. The energy store  22 ′ can then also be discharged to such an extent that when the external energy supply  12  is interrupted the interrogation unit  42  is no longer functionally capable as a consequence of a lack of sufficient energy supply. If the external energy supply  12  is then reinstated then the discharged state of the energy store  22 ′ can nevertheless be read out. 
         [0060]    In a further possible embodiment the energy supply of the interrogation unit  42  of the detecting device  4  can also be ensured partly by way of the energy store  22 ′ and partly by way of the independent energy source  55 . 
         [0061]    The active switching element  56  can thus be electromagnetically actuated at least indirectly. The electromagnetic actuation takes place, in the case of the embodiments described on the basis of  FIGS. 3 and 4 , by the electromagnetic coupling. In corresponding manner, an electrical or electronic actuation of the active switching element  56  of the detecting device  4  can also take place at least indirectly when an external actuation of the device  15  takes place with the external energy supply  12  interrupted. 
         [0062]    The manner of functioning of a bistable switch can thus be realized by way of the energy store  22 ,  22 ′ locally at every detecting device  4  to  9 . After an interruption of the external supply  12  a central interrogation by the control unit  3  is possible by way of the bus system  10 . The control device  3  can thus guarantee central monitoring. As soon as at least one of the detecting devices  4  to  9  detects external actuation this—represented by a discharged energy store  22 ,  22 ′—is initially stored locally at the respective detecting device  4  to  9  and then reported to the central control device  3 . There can thus be intervention in the operation depending on the respective situation. Independently of that, monitoring by the detecting device  4  to  9  can be guaranteed even when the external energy supply  12  is present. The control device  3  can, for example, decide in situation-dependent manner that stopping does not take place, that a safety brake is activated or that a rapid stop is required. 
         [0063]    Resetting of the respective local energy store  22 ,  22 ′ can be possible only in specific circumstances. For example, it can be required that all doors  15 ,  16  are closed. In addition, it can be required that an inspection is not ongoing. The control device  3  can centrally command resetting by way of the bus system  10 . A central control by way of the input device  13  and the output device  14  and yet a local monitoring are thus possible. 
         [0064]    In addition, a function test routine can be started by way of the input device  13 . Charging and discharging operations during operating pauses or maintenance operations can, for example, be carried in such a function test routine. The energy stores  22 ,  22 ′ can thereby be checked for sufficient functional capability, particularly a sufficient capacity. Also possible are a charge measurement, a charge time measurement, a voltage loss measurement and the like so as to estimate a life of the individual energy stores  22 ,  22 ′. This enables preventative maintenance. 
         [0065]    In the case of a further possible modification the discharging of the energy store  22  can also take place by way of a resistor  31 , which is designed as a warning light  31 . Moreover, it is advantageous for the resistance  31  to be so dimensioned that the energy in the case of external actuation is rapidly diminished. 
         [0066]    In the method for monitoring the passenger transport system  1  it is advantageous that in the event of interruption of the external energy supply  12  the energy store  22 ,  22 ′ is transferred to a discharged state if external actuation of the device  15 ,  16  is detected and that after the interruption the external energy supply  12  is switched to the special operating state if the energy store  22 ,  22 ′ is in the discharged state. 
         [0067]    The invention is not restricted to the described embodiments. Thus, the most diverse safety-relevant switches of the passenger transport system, for example also car doors, access doors of engine compartments and the like, can be supplemented or monitored by the monitoring device according to the invention. 
         [0068]    In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.