Abstract:
A signal transmitter contains at least one first luminous element, at least one second luminous element and an interface for connecting the signal transmitter to a signal box. A drive device is connected between the interface and the at least two luminous elements and the drive device is configured in such a way that, in the case of a switch-on signal coming from the signal box for the second luminous element, the drive device controls the activation of the luminous element depending on the signaling state of the first luminous element.

Description:
BACKGROUND OF THE INVENTION 
     Field Of The Invention 
     The invention relates to a signal transmitter comprising at least one first luminous element and at least one second luminous element and an interface for connecting the signal transmitter to a signal box. The signal box can be a railway signal box but can also be any other facility which enables a signal transmitter to be set or adapted. 
     Signal transmitters of the described type are used in particular in the field of railway technology. With railway technology, signal aspects with varying order ratings are generally assigned to the luminous elements. If one signal aspect is of higher order than another signal aspect, this means that it indicates an unsafe operating state. A signal aspect “proceed” is thus of higher order than a signal aspect “stop”, because a stop signal leads to the railway vehicle or vehicles stopping and thus an accident is less probable than with a “proceed” signal. 
     BRIEF SUMMARY OF THE INVENTION 
     The object underlying the invention is to specify a signal transmitter, which allows for a particularly reliable switchover of the signaling of the signal transmitter. 
     This object is achieved according to the invention by a signal transmitter having the features according to the main claim. Advantageous embodiments of the inventive signal transmitter are specified in the sub claims. 
     Provision is then made in accordance with the invention to connect a drive device between the interface and the at least two luminous elements, and the drive device is embodied such that in the event of a switch-on signal coming from the signal box for the second luminous element, it controls activation of this luminous element as a function of the signaling state of the first luminous element. 
     One significant advantage of the inventive signal transmitter is that the signal transmitter can autonomously decide on the actuation of the luminous elements and can implement a switchover process as a function of order ratings and signaling states, because the drive device is connected between the interface of the signal transmitter and the at least two luminous elements. This is to be clarified with the aid of an example. If for instance a low-order signal aspect and a conversely higher-order signal aspect are assigned to the first and the second luminous elements respectively, in accordance with the invention the switching-on of the higher-order signal aspect would be dependent on the signaling state of the low-order signal aspect. If control commands originate from the signal box for instance in order to switch on both signal aspects, the signal transmitter can autonomously interrupt the activation of the higher-order signal aspect, for instance provided the signal box has switched off the switch-on signal of the low-order signal aspect and only a control signal for switching on the higher-order signal aspect is still present on the signal box side. In this example, therefore, a double signaling of two signal aspects can be prevented and reliability increased, because a misinterpretation of the signal aspect by an observer can be prevented. Nevertheless, the functional efficiency of both luminous elements and/or both signal aspects can be reported to the signal box from the drive device, since in accordance with the invention this is connected between the interface of the signal transmitter and the two luminous elements and a separation thus exists between the luminous elements and the interface. The drive device can therefore report something else to the signal box than is actually indicated by the luminous elements, this not being possible with signal transmitters in which the signal box has a direct effect on the luminous elements. 
     A further significant advantage consists in the luminous color of the two luminous elements possibly being different in the inventive signal transmitter because a double signaling and/or a simultaneous signaling of two colors and a mixed color formation can be prevented on account of the signaling-state-dependent mode of operation of the signal transmitter. Multi-colored signal transmitters can thus also be connected to signal boxes, whereby, in the event of switchover processes, two signal aspects (or the corresponding luminous elements) are activated as standard for a transition time by switching on an operating voltage on the signal box side. An acknowledgement to the signal box such that both signal aspects can be activated can consequently take place by means of the interposed drive device, although only one signal color actually illuminates. The inventive signal transmitter can therefore, without modification, also be connected to signal boxes with temporary double signaling. 
     With a particularly preferred embodiment of the signal transmitter, provision is made for a first signal aspect and a second signal aspect to be assigned to the first luminous element and the second luminous element respectively, wherein the second signal aspect is of higher order than the first signal aspect. 
     The prioritization of the signal aspects performed by the drive device of the signal transmitter is preferably encoded using hardware, for instance by a corresponding electrical ‘wiring’ (connection-programmed controller’, e.g. by logical circuits (logical gates) which are connected correspondingly to one another). Alternatively, the prioritization can be defined by a corresponding programming of a programmable controller (SPS), which includes a programmable processor for instance. In the latter case, the prioritization is preferably stored in the form of a parameter set, for instance in the form of a priority table, in the memory of the programmable controller. 
     The drive device can therefore include a wire-programmed controller and/or a programmable controller (SPS) in order to be able to execute the described functions. The prioritization or mode of operation of the drive device is in this way preferably a captive ‘component’ or a captive property of the signal transmitter. 
     The luminous color of the two luminous elements is preferably different, but can however also be identical. 
     The drive device is preferably embodied such that in the event of a switch-on signal coming from the signal box for the second luminous element, when the first luminous element is already switched on, it leaves the first luminous element switched on and the second luminous element switched off and generates an acknowledgement (e.g. in the form of acknowledgement signals) on the interface, which indicates the operation (and/or operational readiness) of both luminous elements to the signal box, although the second luminous element is still switched off. 
     In respect of a switchover in another direction, in other words from a higher-order signal aspect to a low-order signal aspect or with a switchover from the second luminous element to the first luminous element, the drive device will preferably perform the switchover directly and switch off the second luminous element and switch on the first luminous element. Such a procedure ensures that the safe signal aspect is immediately realized, if a request is made on the signal box side, independently of the control signals on the signal box side for switching on the second luminous element. 
     The drive device particularly preferably includes a lamp control module and an acknowledgement module connected to the lamp control module, wherein the lamp control module is embodied such that in the event of a switch-on signal coming from the signal box for the second luminous element, when the first luminous element is already switched on, it leaves the first luminous element switched on and the second luminous element switched off, and wherein the acknowledgement module is embodied such that it generates an acknowledgement to the interface in this case, which indicates the operation and/or operational readiness of both luminous elements to the signal box, although the second luminous element (with a switched-on first luminous element) is still switched off. 
     The drive device is preferably embodied such that it only switches on the second luminous element if it receives a signal for switching off the first luminous element from the signal box. 
     Furthermore, it is considered to be advantageous if the drive device is embodied such that in the event of the presence, for longer than a predetermined period of time, of control signals on the signal box side for switching on both luminous elements, it generates an error signal for the signal box (on the interface). 
     The drive device will preferably generate the error signal on the control line on the signal box side (subsequently also abbreviated to signal box line) for the luminous element assigned to the second signal aspect. 
     It is also considered to be advantageous if the signal transmitter has at least one further luminous element for indicating a signal aspect, the quality rating of which lies between that of the second signal aspect and that of the first signal aspect, and the drive device is embodied such that in the event of the presence of switch-on signals on the signal box side for three or more luminous elements, it generates an error signal for the signal box on the interface. 
     In the latter case, the drive device will generate an error signal preferably on all control lines (signal box lines) on the signal box side, on which switch-on signals are present on the signal box side, with the exception of the control line on the signal box side for the luminous element which is assigned to the lowest-order signal aspect. 
     In the event of the presence of switch-on signals (control signals for switching on) on the signal box side for three or more luminous elements, the drive device will preferably only activate the luminous element which is assigned to the lowest-order signal aspect. 
     Furthermore, it is considered to be advantageous if the signal transmitter allows for daytime and nighttime signaling and the drive device generates an error signal if, at the same time, a signaling exists for daytime and nighttime operation. 
     The invention also relates to a railway system with a signal transmitter, as described above, and a railway signal box connected to the signal transmitter. 
     The invention also relates to a method for operating a signal transmitter having at least two luminous elements and an interface which is connected to a signal box. Provision is made in accordance with the invention for a drive device connected between the interface and the at least two luminous elements, in the event of a control signal coming from the signal box for switching on the luminous element assigned to the second signal aspect, to control activation of this luminous element as a function of the respective signaling state of the first luminous element. 
     In respect of the advantages of the inventive method, reference is made to the afore-cited advantages of the inventive signal transmitter, since the advantages of the inventive signal transmitter substantially correspond to those of the inventive method. 
     The invention is described in more detail below with the aid of exemplary embodiments, in which, by way of example 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  shows an exemplary embodiment of a signal transmitter with two luminous elements, 
         FIG. 2  shows the mode of operation of the signal transmitter according to  FIG. 1  in the error-free case, 
         FIG. 3  shows the mode of operation of the signal transmitter according to  FIG. 1  in the event of an excessively long double signaling, 
         FIG. 4  shows the mode of operation of the signal transmitter according to  FIG. 1  in the event of a switchover from daytime to nighttime operation, 
         FIG. 5  shows an exemplary embodiment of a signal transmitter with three luminous elements, 
         FIG. 6  shows the mode of operation of the signal transmitter according to  FIG. 5  in the event of a triple signaling and 
         FIG. 7  shows an exemplary embodiment of a signal transmitter with an acknowledgement module including a switch. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     For the sake of clarity, the same reference characters are always used in the figures for identical or comparable components. 
       FIG. 1  shows an arrangement with a signal transmitter  10 , which is connected to signal box lines L 1  and L 2  by way of an interface  11 . The interface  11  of the signal transmitter  10  and thus the signal transmitter is connected to a signal box  20  by way of these two signal box lines. 
     The signal transmitter  10  includes a luminous arrangement LA, which is equipped with a first (for instance red) luminous element LEU 1  and a second (for instance green) luminous element LEU 2 . A first signal aspect, which is to be indicated by the first luminous element (LEU 1 ), is assigned to the first luminous element LEU 1 . With this and also with the further exemplary embodiments, it is assumed by way of example that the first signal aspect is only to be indicated by a single first luminous element LEU 1 . A plurality of further (“first”) luminous elements, which are actuated in parallel or together with the first luminous element LEU 1  and together herewith indicate the first signal aspect, can naturally be assigned to the first signal aspect. 
     A second signal aspect is assigned to the second luminous element LEU 2 ; the second luminous element LEU 2  is therefore determined so as to indicate this second signal aspect by means of illumination. With this and also with the further exemplary embodiments, it is assumed by way of example that the second signal aspect is only to be indicated by a single second luminous element LEU 2 . A plurality of further (“second”) luminous elements can naturally be assigned to the second signal aspect, which are actuated in parallel or together with the second luminous element LEU 2  and together herewith indicate the second signal aspect. 
     It is then assumed by way of example that the second signal aspect, which is to be indicated by the second luminous element LEU 2 , is of higher order than the first signal aspect, which is indicated by the first luminous element LEU 1 . A higher-order signal aspect is understood here to mean a signal aspect which indicates an un safer signal state than a contrastingly lower-order signal aspect. If there is therefore uncertainty as to whether an even higher-order or a lower-order signal aspect is to be indicated, the arrangement shown in  FIG. 1  will always aim to indicate the lower-order signal aspect since this indicates the un safer state. The priority of the first signal aspect is thus higher than the priority of the second signal aspect, since the first signal aspect is of lower order than the second signal aspect. 
     The first (low-order) signal aspect can be the signal aspect (“stop”) for instance, which is indicated by the first luminous element LEU 1  with a red light. The second (higher-order) signal aspect can be the signal aspect (“proceed”) for instance, which is indicated by the second luminous element LEU 2  with a green light. 
     It is apparent in  FIG. 1  that the luminous arrangement LA is not directly connected to the interface  11  of the signal transmitter  10 . Instead, the luminous arrangement LA is separated from the interface  11  by means of a drive device  12 , which includes a lamp control module  120  and an acknowledgement module  121  for instance. 
     The lamp control module  120  is connected to the interface  11  and thus to the two signal box lines L 1  and L 2  so that it can receive control signals ST 1  and/or ST 2  from the signal box  20  by way of the signal box lines. The lamp control module  120  has the task of evaluating the control signals transmitted by way of the signal box lines L 1  and L 2  and actuating the two luminous elements LEU 1  and LEU 2  by way of the lamp control lines LS 1  and LS 2 . The luminous elements are actuated here as a function of the respective signaling state which the luminous arrangement LA assumes. The mode of operation of the lamp control module  120  is explained in more detail below. 
     The acknowledgement module  121  is connected to the lamp control module  120  and is actuated hereby by way of one or more control lines, of which only one is shown in  FIG. 1  for the sake of clarity and is identified with the reference character LO. 
     The acknowledgement module  121  has the task of generating acknowledgement signals SR 1  and SR 2  and transmitting these via the signal box lines L 1  and L 2  to the signal box  20 . The signal box  20  receives an acknowledgement message about the respective state of the signal transmitter  10  by way of the acknowledgement signals SR 1  and SR 2 , wherein the state signaled by the signal transmitter  10  and/or by the acknowledgement module  121  to the signal box  20  need not necessarily correspond to the luminous state of the luminous arrangement LA, as explained in more detail below. 
       FIG. 2  shows by way of example the mode of operation of the signal transmitter  10  and the acknowledgement signals sent back to the signal box  20  by the signal transmitter  10 , if a switchover from the first luminous element LEU 1  to the second luminous element LEU 2  takes place in an error free manner. 
     An upper section “a)” in  FIG. 2  shows how control signals are transmitted by way of the signal box lines L 1  and L 2  from the signal box  20 . At time instant t 0 , the signal box thus begins to transmit a control signal with the control command “Prio_ 1 _Day” to the signal transmitter  20  by way of the signal box line L 1 . No control command is transmitted at this time instant by way of the signal box line L 2 . 
     Section “b)” in  FIG. 2  shows how the drive device of the signal transmitter  10  actuates the luminous arrangement LAQ such that according to the control command “Prio_ 1 _Day” the first luminous element LEU 1  illuminates. The first signal aspect is indicated with the luminous element LEU 1 . 
     At a subsequent time instant t 1 , the signal box additionally transmits a control signal with the control command “Prio_ 2 _Day” on the signal box line L 2 , with which the second luminous element LEU 2  of the luminous arrangement LA is to be activated. From time instant t 1  to time instant t 2 , two control commands “Prio_ 1 _Day” and “Prio_ 2 _Day” are thus present on the signal transmitter  10 , with which the signal box would like to activate both luminous elements LEU 1  and LEU 2  at the same time. 
     As apparent in section “b)” of  FIG. 2 , only the first luminous element LEU 1  is however still activated by the luminous arrangement LA in the time interval between the time instants t 2  and t 1 , this being indicated in  FIG. 2  by specifying the corresponding control command “Prio_ 1 _Day”. Although activation of both luminous elements LEU 1  and LEU 2  is therefore desired on the signal box side, only the first luminous element LEU 1  is activated by the drive device of the signal transmitter  10 , because namely the first luminous element LEU 1  is used to indicate the lower-order signal aspect. If control commands for indicating two signal aspects exist, the signal transmitter  10  will indicate only the lower-order signal aspect. The higher-order signal aspect is not indicated. 
       FIG. 2  furthermore shows in section “c” how the acknowledgement to the signal box is performed by way of the signal box lines L 1  and L 2 . It is apparent that both an acknowledgement signal with the acknowledgement information “Prio_ 1 _Day_ok” and also an acknowledgement signal with the acknowledgement information “Prio_ 2 _Day_ok” is transmitted by way of the signal box line L 1 . 
     It is therefore indicated to the signal box by way of the acknowledgement signals having both acknowledgement information “Prio_ 1 _Day_ok” and “Prio_ 2 _Day_ok” that both the first luminous element LEU 1  and also the second luminous element LEU 2  are ready for operation. After receiving the corresponding acknowledgment signals or after receiving the corresponding acknowledgement information “Prio_ 1 _Day_ok” or “Prio_ 2 _Day_ok”, the signal box  20  will shut off the first luminous element LEU 1  by way of the signal box line L by shutting off the signal command “Prio_ 1 _Day” at time instant t 2 . Only the control command “Prio_ 2 _Day” thus still exists at the signal transmitter  10 , said control command being transmitted via the control signal ST 2  from the signal box line L 2 . As soon as the control command “Prio_ 1 _Day” has been switched off on the signal box side, the drive device  12  according to  FIG. 1  will switch off the first luminous element LEU 1  and switch on the second luminous element, in other words the control command “Prio_ 2 _Day”, which is transmitted by way of the signal box line L 2 . The corresponding switchover from the first luminous element LEU 1  to the second luminous element LEU 2  is shown in section “b)” in  FIG. 2 . 
     After switching over from the first luminous element LEU 1  to the second luminous element LEU 2 , the acknowledgement signal SR 1 , which is transmitted by way of the signal box line L 1  to the signal box, is switched off, by the transmission of the acknowledgement information “Prio_ 1 _Day_ok” being switched off. 
     From time instant t 2 , only the second luminous element LEU 2  according to the control command “Prio_ 2 _Day” is thus indicated on the luminous arrangement LA. 
     Here  FIG. 3  shows the mode of operation of the signal transmitter  10  according to  FIG. 1  in the event of an error; it is assumed here by way of example that the time span, during which diverging and/or deviating control commands are transmitted on the two signal box lines L 1  and L 2 , exceeds a predetermined maximum duration dtmax. 
     It is apparent in  FIG. 3  that at time instant t 0  the control command “Prio_ 1 _Day” is transmitted from the signal box by way of the signal box line L 1 , with which control command the first luminous element LEU 1  of the luminous arrangement LA is to be switched on. Accordingly, the signal transmitter  10  according to  FIG. 1  will also perform the signaling and switch the first luminous element LEU 1  on on the luminous arrangement LA. The corresponding switching-on is visualized in section “b)” of  FIG. 3  by specifying the control command “Prio_ 1 _Day”. 
     The signal transmitter  10  will furthermore send an acknowledgement signal SR 1  with the acknowledgement information “Prio_ 1 _Day_ok” to the signal box  20  on the signal box line L 1 , so that a correct mode of operation of the signal transmitter  10  is indicated to the signal box  20 . 
     If now at time instant t 1  the control signal ST 2  with the control command “Prio_ 2 _Day” is also transmitted via the signal box line L 2  to the signal transmitter  10 , it will, as already mentioned in connection with  FIG. 2 , initially remain in a signaling of the first signal aspect by the first luminous element LEU 1 . This is indicated in section “b)” of  FIG. 3  by specifying the control command “Prio_ 1 _Day”. 
     The signal transmitter  10  will accordingly acknowledge receipt of the control command “Prio_ 2 _Day”, by transmitting the acknowledgement information “Prio_ 2 _Day_ok” to the signal box on the signal box line L 2 . Positive acknowledgement information “Prio_ 1 _Day_ok” and “Prior_ 2 _Day_ok” thus exists at the signal box  20 . 
     The drive device  12  of the signal transmitter  10  will monitor the time span in which two different control commands “Prio_ 1 _Day” and “Prio_ 2 _Day” exist at the interface  11  and will generate an error signal if a predetermined maximum time span dtmax is exceeded. It is then assumed that this maximum time duration dtmax is exceeded at time instant t 2 . Accordingly, the drive device  12  of the signal transmitter  10  will transmit acknowledgement information “Prio_ 2 _Error” on the signal box line L 2 , with which the error of excessively long double signaling which has occurred is indicated to the signal box  20 . Positive acknowledgement information “Prio_ 1 _Day_ok” is still conversely indicated on the signal box line L 1  since the luminous arrangement LA still correctly indicates the first signal aspect by means of the first luminous element LEU 1 . 
     The transmission of the acknowledgement information “Prio_ 2 _Error” may ensue for instance because the acknowledgement information “Prio_ 2 _Day_ok” is switched off. The signal box  20  namely expects, when transmitting the signal aspect “Prio_ 2 _Day” via the signal box line L 2 , that the acknowledgement information “Prio_ 2 _Day_ok” is sent back by the signal transmitter  10  as acknowledgement information. If this does not happen, the signal box knows that an error has occurred. 
     If the transmission of the control command “Prio_ 1 _Day” is now terminated at time instant t 3 , only the control command “Prio_ 2 _Day” on the signal box line L 2  still exists on the signal transmitter  10 . This control command can be realized immediately by the first luminous element LEU 1  being switched off and the second luminous element LEU 2  being switched on. A switchover is thus carried out from the first (lower-order) signal aspect to the second (even higher-order) signal aspect. This is visualized in  FIG. 3  in section “b)” by specifying the signal aspect “Prio_ 2 _Day”. 
     Once the first signal aspect or the first luminous element LEU 1  have been switched off, corresponding acknowledgment information is transmitted via the signal box line L 1  to the signal box, by the acknowledgement information “Prio_ 1 _Day_ok” being switched off at time instant t 3 . 
     Since, on account of the switching off of the first signal aspect, double signaling also no longer exists, an error signal no longer needs to be transmitted to the signal box by way of the signal box line L 2 . The signal transmitter  10  at time instant t 3  will accordingly transmit positive acknowledgement information “Prio_ 2 _Day_ok” to the signal box line L 2 , with which a correct display of the second signal aspect is indicated with the aid of the second luminous element LEU 2 . 
       FIG. 4  shows by way of example the mode of operation of the signal transmitter  10  according to  FIG. 1 , if the control command “Prio_ 2 _Day” for setting the second signal aspect is transmitted by way of the signal box line L 2  from the signal box  20  in the time span between time instants t 1  and t 0 . It is apparent that the signal transmitter  10  executes the control command “Prio_ 2 _Day” by correspondingly actuating the luminous arrangement LA, by switching on the second luminous element LEU 2  of the luminous arrangement LA. A positive acknowledgement by displaying the second signal aspect takes place by way of the second signal box line L 2  with the aid of the acknowledgement signal SR 2 , with which the acknowledgment information “Prio_ 2 _Day_ok” is transmitted to the signal box. 
     If at time instant t 1  transmission of not only the control command “Prio_ 2 _Day” on the signal box line L 2  but also of the control command “Prio_ 1 _Night” on the signal box line L 1  is started on the signal box side, the signal transmitter  10  will immediately, in other words already at time instant t 1 , switch over from the second signal aspect to the first signal aspect, since the first signal aspect has a higher priority because it has a lower order and defines a safer state. 
     At the same time the signal transmitter  10  will transmit an error signal to the signal box  20 , by transmitting the acknowledgement information “Prio_ 2 _Error” on the signal box line L 2 . The signal box  20  is thus notified by the signal transmitter  10  that the display of the first lower-order signal aspect takes place in “night mode”, although transmission of the second signal aspect has previously taken place in “day mode”. This acknowledgement message enables the signal box  20  to check whether a daytime signaling or a nighttime signaling is to take place. 
     The acknowledgement on the signal box line L 2  takes place by sending the acknowledgement information “Prio_ 1 _Night_ok”, because the first signal aspect is actually shown in night mode on the luminous arrangement LA, such as corresponds to the control command “Prio_ 1 _Night”. 
     Once the transmission of the control command “Prio_ 2 _Day” on the signal box line L 2  is terminated at time instant t 2  and only a transmission of the control command “Prio_ 1 _Night” still takes place, the transmission of the acknowledgement information “Prio_ 2 _Error” is stopped and only the acknowledgement information “Prio_ 1 _Night_ok” is still transmitted, with which a correct display of the first signal aspect is signaled in night mode. 
       FIG. 5  shows an exemplary embodiment of an arrangement, in which the signal transmitter  10  is connected to three signal box lines L 1 , L 2 , and L 3  by way of its interface  11  and is thus connected to a signal box  20  by way of three signal box lines. 
     A luminous arrangement LA of the signal transmitter  10  has three luminous elements LEU 1 , LEU 2  and LEU 3 , which are assigned in each instance to a predetermined signal aspect. In this case it is assumed for instance that the first luminous element LEU 1  illuminates red and is assigned to the lowest-order signal aspect, the second luminous element LEU 2  illuminates yellow and is assigned to an average-order signal aspect and the third luminous element LEU 3  illuminates green and is assigned to the highest-order signal aspect. The first luminous element LEU 1  thus signals a particularly safe state, the second luminous element LEU 2  signals an average state in respect of safety and the third luminous element LEU 3  signals a particularly unsafe state, compared with the two other signal aspects. 
     The mode of operation of the arrangement according to  FIG. 5  is shown by way of example in  FIG. 6 . It is apparent that at time instant t 1 , a control command “Prio_ 1 _Day” is transmitted via the signal box line L 1  from the signal box to the signal transmitter  10 . With this control command, the signal transmitter  10  is requested to switch on the first luminous element LEU 1  on the luminous arrangement LA in order to display the first signal aspect. 
     It is apparent in  FIG. 6  that the signal transmitter  10  immediately executes the control command “Prio_ 1 _Day”. It is thus apparent in section “b)” of  FIG. 6  that the control command “Prio_ 1 _Day” is executed on the luminous arrangement LA. 
     Section “c)” in  FIG. 6  shows the acknowledgement which is transmitted from the signal transmitter  10  to the signal box  20 . It is apparent that the acknowledgment information “Prio_ 1 _Day_ok”, with which the signal transmitter  10  indicates that the luminous arrangement LA or the first luminous element LEU 1  correctly indicates the first signal aspect, is transmitted on the signal box line L 1 . 
     If at time instant t 2  a simultaneous transmission of the control command “Prio_ 1 _Day” and “Prio_ 2 _Day” takes place, the signal transmitter  10  will further execute the control command “Prio_ 1 _Day” on the luminous arrangement LA and will address the first luminous element LEU 1 , as a result of which the first signal aspect is indicated. The second signal aspect, which is called up by the control command “Prio_ 2 _Day”, is not executed, since the priority of the second signal aspect is less than the priority of the first signal aspect, since namely the second signal aspect is even higher-order than the first signal aspect. 
     The acknowledgment information, which is transmitted to the signal box  20 , is shown in section “c)” of  FIG. 6 . It is clear in the time period between t 2  and t 3  on the signal box line L 2  that acknowledgement information “Prio_ 2 _Day_ok” is transmitted to the signal box  20 . It is thus indicated to the signal box  20  that the control command “Prio_ 2 _Day” exists for indicating the second signal aspect and could be executed if the first signal aspect was switched off. 
     It is now assumed by way of example in  FIG. 6  that at time instant t 3 , a third control command “Prio_ 3 _Day” is transmitted from the signal box  20  via the signal box line L 3 . Thus a total of three control commands exists at the signal transmitter  10 , namely “Prio_ 1 _Day”, “Prio_ 2 _Day” and “Prio_ 3 _Day”. In this case the drive device  12  of the signal transmitter  10  according to  FIG. 5  will continue the display of the first signal aspect, which defines the safest state, and will switch on the first luminous element LEU 1 . The display of the first signal aspect is transmitted to the signal box  20  via the first signal box line L 1  by transmitting the acknowledgement information “Prio_ 1 _Day_ok”. 
     In respect of the two other control commands “Prio_ 2 _Day” and “Prio_ 3 _Day”, the signal transmitter  10  will generate error signals and transmit the same to the signal box  20 , by, with the aid of the acknowledgment module  121  according to  FIG. 5 , the acknowledgment information “Prio_ 2 _Error” and “Prio_ 3 _Error” being transmitted to the signal box  20  by way of the two signal box lines L 2  and L 3 . Information thus exists in the signal box  20  such that the first signal aspect is correctly indicated by the first luminous element LEU 1 . Furthermore, the information exists that two further control commands exist on the signal transmitter  10 , which may actually not be the case. In order to eliminate the error, a warning signal can be generated for instance on the signal box side, which allows the operating personnel to examine the signal transmitter  10  or the signal box lines L 1  to L 3  for an error. 
     In the exemplary embodiment according to  FIG. 6 , it is now assumed that at time instant t 4 , the transmission of the control command “Prio_ 1 _Day” is terminated. Only control commands “Prio_ 2 _Day” and “Prio_ 3 _Day” thus still exist. 
     Since a lower-order signal aspect is transmitted with the control command “Prio_ 2 _Day” than with the control command “Prio_ 3 _Day”, the signal transmitter  10  will execute the signal aspect, which is assigned to the control command “Prio_ 2 _Day” and arrange the luminous arrangement LA accordingly. Section “b)” of  FIG. 6  shows the corresponding visualization of the control command “Prio_ 2 _Day”. 
     The signal transmitter  10  will signal the correct display of the second signal aspect by sending back the acknowledgment information “Prio_ 2 _Day_ok” via the signal box line L 2  to the signal box  20 . 
     Since the third signal aspect with the third luminous element LEU 3  could also be indicated, the signal transmitter  10  will also additionally generate acknowledgement information “Prio_ 3 _Day_ok” and transmit the same via the third signal box line L 3  to the signal box  20 . 
     If now at a subsequent time instant t 5 , the transmission of the control command “Prio_ 2 _Day” is determined, only the control command “Prio_ 3 _Day” for indicating the third signal aspect is still present at the signal transmitter  10 . 
     The third signal aspect is indicated by the signal transmitter  10 , by the third luminous element LEU 3  being activated. The corresponding signaling is shown in section “b)” of  FIG. 6  by specifying the control command “Prio_ 3 _Day”. The correct display of the signal aspect is transmitted by acknowledgement information “Prio_ 3 _Day_ok” on the signal box line L 3  to the signal box  20 . 
       FIG. 7  shows by way of example an exemplary embodiment of a signal transmitter  10 , in which generation of the acknowledgment information takes place by opening or closing switches  200 ,  201 , and  202  using the lamp control module  120  of the signal transmitter  10 . The three switches  200 ,  201  and  202  can form the acknowledgement module  121  according to  FIG. 5 . 
     The generation of acknowledgement information on the signal box lines L 1 , L 2  and L 3 , which each include a forward conductor and a return conductor, takes place in this case as follows: if a control command in the form of a control voltage U 1 , U 2  and U 3  is transmitted from the signal box  20 , this is evaluated by the lamp control module  120 . A positive acknowledgement (cf. acknowledgement signals “Prio_ 1 _Day_ok”, “Prio_ 2 _Day_ok” and “Prio_ 3 _Day_ok” in  FIG. 6 ) or execution of the corresponding control command is indicated by the lamp control module  120 , by it closing the associated switch  200 ,  201  or  202 . By closing the respective switch, a current flow I 1 , I 2  and I 3  is produced, which indicates to the signal box  20  that the respectively requested signal aspect or the associated luminous element or elements is/are or would be ready for operation. A current flow I 1 , I 2  or I 3  thus corresponds to an acknowledgment signal “Prio_ 1 _Day_ok”, “Prio_ 2 _Day_ok” or “Prio_ 3 _Day_ok” in  FIG. 6 . 
     By opening the respective switch, a current flow I 1 , I 2  or I 3  is interrupted so that in the event of a control voltage U 1 , U 2  or U 3  switched on by the signal box  20  being signaled thereto, the respectively requested signal aspect is not available or the associated luminous element or elements are not ready for operation or another error has occurred. An erroneous current flow I 1 , I 2  or I 3  with a switched-on control voltage U 1 , U 2  or U 3  thus corresponds to an acknowledgment signal “Prio_ 1 _Error”, “Prio_ 2 _Error” or “Prio_ 3 _Error” (cf.  FIG. 6 ) on the respective signal box line L 1 , L 2  or L 3 . 
     Actuation of the luminous elements LEU 1  to LEU 3  takes place immediately, namely by the lamp control module  120  by way of the lamp control lines LS 1  to LS 3 . 
     Although the invention was illustrated and described in more detail by the preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived herefrom by the person skilled in the art, without departing from the protective scope of the invention.