Abstract:
The invention concerns a method whereby each module is determined from the address of the module located immediately upstream in the networked relative to the central unit, the detected address being transmitted by the upstream module in an attribution message, which triggers off an automatic search phase for the module without address, nearest downstream to a module with an address, during which each downstream module without address receives ( 50 ) the address attribution message, triggers ( 52 ) a delay whereof the duration is so much longer if the received message reception is low, and if at the end ( 54 ) of the delay, no address capture message is detected ( 53 ), it transmits ( 56 ) such a message, stores ( 57 ) the received address, determines the address of the nearest downstream module without address, and triggers ( 30 ) the search phase for the nearest downstream module without address.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns a method and device for the automatic allocation of addresses to a plurality of modules interconnected by a communication network with an arborescent topology. 
     It applies in particular, but not exclusively, to a plurality of modules interconnected by an electric distribution network used both for the electric feeding of the modules and as a communication network for the transmission of digital messages between modules via a modulated carrier current. 
     It is applicable in particular to the remote control and monitoring of urban lamp posts. 
     2. Description of the Prior Art 
     It has been observed that an electric distribution network generally has a complex topology comprising a large number of intersections distributed randomly. In addition, the knowledge of the exact topology of the network has quite often disappeared, said network generally resulting from operations of successive installations carried out over several tens of years. 
     Moreover, if it is desired to be able to communicate with each module separately, it is necessary to allocate one address to each module. 
     In the context of a network of this types the allocation of an address to each module poses a large number of problems. 
     In fact, it is first of all necessary to ensure that the method for addressing the various modules with which it is desired to communicate is able to be applied to any network topology. Next, if it is desired to interconnect a large number of modules, the addressing of the various modules must be able to be carried out with fastidious handlings which might result in significant risks of error. 
     It is also essential to be able to easily add a module in the network without requiring manual interventions on other modules. 
     Furthermore, the range of transmissions by carrier current is relatively small. Thus, it is necessary to repeat the transmitted messages so that they arrive at their destination. Thus, it is essential that the address of each module contains the path by which the message needs to be transited so that it arrives at its destination and so as to be able to determine if a message in a specific path needs to be repeated. 
     The method described in the patent FR 2 734 111 filed by the Applicant is able to partially resolve these problems to the extent where it is necessary to act manually on each module still not having any address and on the module already having an address situated immediately upstream with respect to a central unit situated at the root of the arborescent network, the address of the module with no address being determined according to the address of the upstream module already having an address and according to the number of modules already having an address and connected directly to the module with an address and situated downstream of the latter. 
     Thus, this method does have the drawback of requiring the intervention of operators on the terrain concerned, said operators needing to take action on the control buttons provided on each module. In addition, these modules can be only accessed with difficulty as for example they may be installed several meters from the ground at the top of urban lamp posts. Furthermore, this method is not able to fully eliminate any risk of error as it is possible to initiate the allocation of an address of a module not immediately situated downstream of a module having an address. 
     OBJECT OF THE INVENTION OBJECT OF THE INVENTION 
     The aim of the invention is to resolve these problems. To this effect, it concerns a method for automatically allocating addresses to a multiplicity of modules interconnected by an arborescent topology network connected to a central unit, the address of each module being determined from the address of the module situated immediately upstream in the network with respect to the central unit and already having an allocated address, this address being transmitted onto the network by the upstream module in an address allocation message. 
     SUMMARY OF THE INVENTION 
     According to the invention, this method is characterised in that it includes a phase for automatically searching the module not having any address allocated situated the nearest downstream in the network from a module already having an address allocated, this phase including for each downstream module still not having any allocated address:
         the receiving by the downstream module of the address allocation message and the triggering by the latter of a delay time whose duration is that much longer when the level of reception of the message received is low,   if at the end of the delay time the downstream module does not detect in the network any address capture message, the transmission by the latter of an address capture message containing the address to be allocated, the storing by the latter of the address received as a module address, and the execution by the latter of the phase for the automatic search for the module not having any allocated address situated nearest downstream in the network.       

     By means of these arrangements, the invention exploits the attenuation which occurs in transmissions by carrier current so as to define a delay time whose period depends on the distance between the transmitting module and the receiving module, this delay time being triggered so as to decide which module needs to be allocated with the transmitted address. In this way, the module which is allocated with the transmitted address is the one which has the shortest delay time and thus the one closest to the transmitting module of the message. The invention also makes it possible to by degrees fully automatically allocate a respective address to all the modules of a given branch of the network connected to the central unit without involving any risk of error. 
     By repeating this operation for all the branches of the network, it is possible to fully automatically allocate an address to all the modules connected to the network. 
     Advantageously, the address of a module is determined according to that of the module immediately upstream and the possible presence of other modules already having an address and situated at the same level with respect to the central unit. As a result, the address of each module solely indicates the position of the module with respect to the other modules in the network. 
     According to one characteristic of the invention, the address of a given module includes an order number obtained by successively numbering all the modules situated on a path directly connecting the given module to the central unit by starting by one for the first module connected on the path to the central unit, as well as one linking address for determining the various line sections constituting the path connecting the module to the central unit. As a result, if all the allocated addresses are retransmitted to the central unit, the list of the allocated addresses makes it possible to restore the topology of the network. 
     According to another characteristic of the invention, the method of the invention includes a prior phase for automatically looking for a module having an address situated closest upstream in the network to a module not having any address, this module transmitting on the network a message seeking a module having an address, this phase including for each module already having an address:
         the receiving by the module of the message seeking a module having an address and the triggering by the latter of a delay time whose period is that much longer when the level of reception of the message received is short,   if at the end of the delay time the nodule does not detect on the network any address capture message containing the address with the predetermined value, the transmission by the latter of an address capture message, the determination by the latter of the address of the module not having any address situated immediately downstream in the network, and the transmission of an address allocation message containing the determined address.       

     Again, according to another characteristic of the invention, the method of the invention further includes a prior phase for the automatic search for a module not having any allocated address and situated immediately downstream of a module already having an allocated address, this phase being triggered by the central unit or by a module already having an allocated address which transmits on the network a message seeking a module without an address, this phase including for each module not having any address:
         the receiving by the module of the message seeking the module without any address and the triggering by the later of a delay time whose period is that much longer when the level of reception of the message received is low.   if at the end of the delay time the module does not detect on the network any module search message, the transmission by the latter of a module search message to the central unit which has the effect of triggering the phase for the automatic search for a module having an address situated closest upstream in the network to a module not having any address.       

     It is possible to provide a message transmitted by the central unit for initialising the module addresses stored by all or part of the modules connected to the network so as to be able to then allocate new addresses to the reinitialised modules. In this way, it is possible to easily take into account the connection of a new module between two modules already configured. 
     It is also possible to ensure that the module search with no address messages are repeated by the other modules so that they can be transmitted to the extremities of the branches of the network. 
     The present invention also concerns a device for implementing the method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       There follows hereafter a non-restrictive example of one embodiment of the method and device of the invention with reference to the accompanying drawings on which: 
         FIG. 1  diagrammatically represents a multiplicity of modules connected by a star network to which the addressing method of the invention can be applied; 
         FIG. 2  shows the structure of a module address; 
         FIG. 3  shows the structure of the messages transmitted by the network; 
         FIGS. 4 and 5  represent flowcharts showing the sequence of the stages of the method of the invention; 
         FIG. 6  represents a module according to the invention. 
         FIG. 7  shows the electronic diagram of an electronic circuit of the module used by the method of the invention. 
         FIG. 8  shows in the form of time controlled curves the functioning of the electronic circuit shown on  FIG. 6 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  represents a star network making it possible to connect a central unit UC to a plurality of electronic modules M 1  to M 15 , the various elements connected by the network communicating with one another by messages, for example transmitted on the network, via the modulation of a carrier wave. 
     In this network, the method of the invention seeks to automatically allocate a respective single address to each module according to the position of the latter in the network. To this effect, the invention exploits the attenuation phenomenon according to the distance which occurs, especially when a signal is transmitted on an electric energy feed line. In this case, the transmissions by the network are preferably carried out by a bidirectional carrier current via the phase modulation of a carrier wave. 
     Each module Mi connected to the network is marked with respect to the central unit UC by an address constituted by an order number  43  and a linking address  44  ( FIG. 2 ). 
     The order number  43  of each module Mi, for example on one octet is obtained by successively numbering all the modules situated on the path of the network connecting the module Mi to the central unit by starting by the number one for the module connected directly to the central unit and situated on the path in question. 
     Thus, on  FIG. 1 , the central unit UC is connected to three main lines  1 ,  2 ,  3  and the modules M 0 , M 12  and M 14  connected directly to the central unit bear an order number equal to 1, the following modules M 1 , M 13 , M 15  bearing an order number equal to 2, and so on until reaching the extremity of each main line. 
     When a secondary line is encountered, such as  4  on the main line  1 , the module M 5 , situated on the secondary line  4  and connected directly to the main line, bears the same order number, namely 3 in the example of  FIG. 1 , as that of the module M 2  situated at the same level on the main line. The following modules M 6 , M 7  on the secondary line  4  are numbered on the basis of this order number  3 . Thus, the order number  43  of a module corresponds to the number of modules plus 1 situated between the module in question and the central unit UC. 
     The linking address  44  of a module Mi makes it possible to mark the line section (between two intersections or between one intersection and one line extremity) to which the module is connected and to determine the path connecting the module to the central unit, this number taking account of all the intersections located between the module and the central unit. Thus, this address  44  is constituted for example by three fields  45  to  47  or levels of two octets each, the first octet indicating a line number L and the second an intersection number  1 . 
     The first level  45  gives the number of the main line  1  to  3  to which the module is connected and the number of intersections on the main line between the central unit UC and the module. If the line L and intersection I numbers of the second level  46  are different from zero, they respectively indicate the secondary line number  4 ,  5  to which the module is connected and the number of intersections encountered on the secondary line in the direction of the central unit. Similarly, the line number of the third level  47  makes it possible to number the second row secondary lines  6  which start from a first row secondary line  4 ,  5 . 
     Thus, for example, the module M 11  bearing the address “4-11-21-10” is the fourth module by leaving the central unit on the path which connects it to the latter. The field  47  indicates that it is connected to the secondary line  6 , second row no  1 . The field  46  indicates that this secondary line is connected to the intersection no  1  of the secondary line  5 , first row no  2 , and the field  45  indicates that this secondary line  5  is connected to the intersection no  12  of the main line  1  no  1 . 
     This method for addressing a module thus makes it possible to localise any module connected to the network and determine the path which connects it to the central unit. 
     On  FIG. 3 , each message transiting on the network includes the following fields: 
     a transmitter order number  32  of the last retransmitting module on one octet, 
     a transfer direction  33  on one octet, namely 0 for the messages intended for the modules Mi, and 1 for those messages intended for the central unit UC, 
     an address  34  on 7 octets of the transmitting module or receiver of the message according to the direction  33 , 
     instructions  35  or information to be transmitted on 3 octets, and 
     a control sum word  36  on 2 octets making it possible to ensure that the 
     contents of the message have been correctly transmitted. 
     Each module Mi which receives a message starts by determining if it is the intended addressee of the message by reading the “direction” field and if the direction is equal to 0′ the “address” field of the destination module. If it is not the intended recipient of the message, the module examines the fields  32  to  34  so as to determine if it is located on the transmission path of the message and at a sufficient distance from the transmitter. If this is the case, it repeats the message by inserting its order number in the field  32 . 
     By means of this structure, a message transiting on the network can be repeated by the various modules Mi of the network so as to go beyond the limited range (several hundreds of meters) of transmissions by a carrier current. 
     So as to avoid complex handlings and sources of error, the address of the modules is determined automatically. In the following, the address of a module shall be noted N-(I,i) 1 .(I,i) 2 .(I,i) 3  or more generally N- . . . (I,i) n , n being the last positive level  45  to  47  of the linking address  44 . 
     According to the flowchart shown on  FIG. 3 , the central unit UC executes a procedure  20  for the automatic allocation of addresses starting by a phase for finding the next address to be allocated (stages  21  to  29 ) on the basis of the address 
     A=“N- . . . (I,i) n ” passed as a parameter of the procedure. 
     On initialisation of the network, the first address to be allocated to the first module encountered on the network from the central unit is equal to A=“1-10”. 
     This phase commences by interrogating the modules Mi so as to determine if the address A=“N- . . . (I,i+1) n ” has not already been allocated (stage  21 ). This interrogation consists of transmitting a first interrogation message containing this address and of awaiting the response for a period Tmax. 
     If the central unit does not receive any response (stage  22 ), this means that the address A transmitted has not been already allocated. In the present case, this also means that an intersection has still not been detected on the line  1 . In this case, it transmits a new interrogation message containing the address A=“N- . . . (I,i) n ” passed as a parameter of the procedure  20  (stage  25 ). If no reply is received, this address can therefore be allocated (stage  29 ) and the central unit transmits an address allocation message containing this address, in this case “1-10” (stage  30 ). 
     All the modules Mi which receive this message execute the procedure  50  shown on  FIG. 5 . In this procedure, if the module Mi still does not have an allocated address (stage  51 ), it measures the voltage level N of the carrier wave received and converts this level into a time Ti, knowing that the received voltage level decreases according to the transmission distance. (stage  52 ). Thus, the time Ti can be calculated by the following formula: 
     
       
         
           
             Ti 
             = 
             
               
                 ( 
                 
                   N 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   max 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   N 
                 
                 ) 
               
               
                 
                     
                 
                 ⁢ 
                 N 
               
             
           
         
       
     
     where Nmax is die maximum level likely to be received. 
     In this way, the higher is the voltage level of the signal received, the shorter is the time Ti. Moreover, if Ti is greater than a value Tmax, it is considered that the module is too distant and the procedure is abandoned. 
     In stages  53  and  54 , the module Mi awaits a message for capturing the address A contained in the address allocation message. If this message is not received during the time Ti, this means that the module Mi is situated closest to the transmitter of the address allocation message. If this is not die case, the procedure  50  is terminated. 
     If the module Mi is closest to the transmitter of the address allocation message, it transmits an address capture message (stage  56 ) and is allocated the address A which it stores in a memory location provided for this purpose (stage  57 ). The transmission of the capture message in stage  56  has the effect of interrupting the procedure  50  being executed by the other modules on stand by in stages  53  and  54 . 
     After stage  57 , the module Mi executes the previously described procedure  20  with the address A=“((N+1)- . . . (I,i) n , that is in this case “2-10” for allocating an address to the closest non-programmed module in the network, that is to the module M 1 . 
     According to  FIG. 1 , the main line  1  is divided into three branches  1 ,  4 ,  5  after the module M 1  which is directly connected to the modules M 2 , M 5  and M 8  situated downstream in the network with respect to the central unit UC. 
     When the module M 1  is about to allocate an address to the next module by transmitting the address “3-10”, this is the closest module, for example the module M 2  which is going to allocate this address. On the next iteration, the module M 2  shall allocate the address “4-10” to the closest module, namely the module M 3 . 
     When the module M 4  having received the address “5-10” situated at the extremity of a branch of the network is to execute the procedure  20  with the address “6-10”, no module shall respond to the address allocation message transmitted in stage  27  and no module carries out any processing. 
     As a result, at the end of this first sequence of iterations, only the modules M 0  to M 4  connected on a given branch of the network have an address. 
     During this sequence, the central unit UC remains available to pick up the messages from the network so as to capture all the address capture messages and store all the addresses which have been allocated. 
     At the end of this sequence, the central unit UC transmits a module search message with no address, possibly constituted by an address allocation message whose “address” field  34  is equal to a predetermined value, for example 0, the direction indicated in the message in the field  33  being at 0 (towards the modules). All the modules which receive this message trigger the procedure  50  shown on  FIG. 5  and go on stand by for receiving a message during the time Ti (stages  52  to  54 ). 
     Each module which does not have an address yet awaits for a module search message with an address transmitted in the direction of the central unit this message able to be constituted by an address allocation message whose “address” field  3 ′ is equal to 0 and the “direction” field  33  equal to 1 for a time Ti corresponding to the level of the signal received (stage  61 ). If during this time no other module has transmitted such a message, it transmits in stage  62  an address allocation message with the address “field” A equal to 0 and the “direction” field equal to 1 (towards the central unit). In this way, only the module not having any allocated address situated closest to the module or central unit responds and is the transmitter of the address allocation message whose “address” field is equal to 0. 
     All the modules Mi which receive this address allocation message again initiate the procedure  50  (stages  51  to  54 ) and the first module with no address, namely M 12  or M 14 , receiving the message then transmits in turn an address allocation message with the “address” field  34  at zero (stages  55 ,  58 ,  61  and  62 ). The central unit UC and all the modules with an address receive this message (stages  51  to  54 ) and the central unit which is situated closest to the module M 12  or M 14  shall transmit an address allocation message with the “address” field  34  equal to “1-20” knowing that the address “1-10” has already been allocated (stages  58  to  60  and procedure  20 ). 
     In this way, at the end of the second and third sequences of iterations, the modules M 12  to M 14  of the two main lines  2 ,  3  shall respectively receive the addresses “1-20”, “2-20”, “1-30” and “2-30”. 
     In the fourth sequence of iterations, the central unit again transmits an address allocation message whose “address” field  3 ′ is at zero and the module M 5  closest to the central unit and still not having any address shall in its turn transmit an address allocation message whose “address” field is at zero (stages  51  to  55 ,  58 ,  61  and  62 ). Only the module M 1  already having an address and situated closest upstream of the transmitting module M 5  responds to this message by transmitting an address capture message with A=0 (stages  51  to  55  and  58  to  60 ) and triggers the address allocation procedure  20  by using its address whose order number  43  is increased by 1, that is A=“(N+1)- . . . (I,i) n ”, namely in the example describes “3-10”. 
     According to this procedure, the module M 1  first of all transmits an interrogation message concerning the address A=“(N+1)- . . . (I,i+1) n ”=“3-11” (stage  21 ) and awaits a response (stage  22 ). During this time, all the modules Mi receiving this interrogation message compare the address A received with the address to which they are allocated. As this address has still not been allocated, no module replies (stage  22 ). As a result, the module M 1  passes to the stage  25  consisting of interrogating the modules to know if the address A=“(N+1)- . . . (I,i+1) n ”=“3-10” has been allocated. The module having this address transmits a message indicating that this address is allocated. 
     This message is received by the module M 1  which then executes the stages  27 ,  28  designed to create a new intersection. Thus in stage  27 , the module M 1  triggers modification of the addresses of the modules M 2  to M 4  of the branch so as to replace each address A=“(N)- . . . (I,i) n ” by “(N)- . . . (I,i+1) n ”, that is replace the addresses “3-10”, “4-10” and “5-10” by “3-11”, “4-11” and “5-11”. To this effect, it sends the module M 2  an address modification message containing the new address “3-11” of the module M 2 . On receiving this message, the module M 2  modifies its address with the new address received and sends the next module, namely M 3 , an address modification message. The modules M 2  to M 4  of the branch are thus renumbered as far as the extremity of the branch. 
     At the same time, the central unit receives this address modification messages and in turn updates the list of module addresses allocated in the network. 
     In stage  28 , the module M 1  determines the address to be allocated to the module M 5 , having regard to the detection of a new intersection by adding to it an additional level  45 ,  46 ,  47 , this address being equal to “N- . . . (I,i+1) n , (1,0) n−1 ”, that is “3-11-10”. 
     The module M 1  then transmits an address allocation message containing the determined address (stage  30 ). 
     The module M 5 , which is the module closest downstream from the module M 1  and which still does not have any address, is allocated this address (stages  51  to  57 ) and triggers the procedure  20  for allocating an address to the closest module, that is the module M 6 . 
     At the end of this fourth sequence of iterations, all the modules M 5  to M 7  of the branch  4  shall thus receive an address. 
     At the end of this sequence, the central unit initiates a new sequence of iterations by transmitting a “no address” module search message so as to determine if there are still modules without any address. By executing the previously described procedures, only the module M 8  still not having any address and situated closest to the central unit answers this message by transmitting an address allocation message whose “address” field is at zero (stages  51  to  55 ,  58 ,  61  and  62 ). Only the module M 1  with an address closest to the module M 8  takes this message into account by executing the stages  51  to  55 ,  58  to  60  and seeks to allocate the address 3-10 to the module M 8  by triggering the procedure  20  with this address. 
     In stage  21 , it transmits an interrogation message containing the address 3-11. As this address is already allocated to the module M 2  (stage  22 ), which in reply transmits an allocated address message, the module M 1  determines in stage  23  the address to be allocated to the module M 8 . This stage consists of seeking the value k so that the address N- . . . (I,i+1) n (k,0) is free. In the present example, thus an interrogation message shall be transmitted containing the address “3-11-10” which triggers a response from the module M 5  to which this address has already been allocated. Then it transmits an interrogation message containing the address “3-11-20”. As this address has not been allocated, no module answers and the module M 1  deduces from this that this address is free. Thus, it transmits an address allocation message containing this address (stage  30 ). As previously described, this message triggers the address allocation to the modules M 8  to M 10  which shall successively receive the addresses “3-11-20”, “4-11-20” and “5-11-20”. 
     At the end of this fifth sequence of iterations, only the module M 11  still does not have any address. 
     In the sixth sequence of iterations, still initiated by the central unit via the transmission of an address allocation message whose “address” field is at zero, the module M 11  answers that it still does not have an address. As previously described, the module M 8 , which is the closest module upstream with an address, triggers the address allocation procedure  20  and determines the address to be allocated to this module by transmitting address interrogation messages. Thus, it shall detect the presence of an intersection and create this intersection by renumbering the downstream modules M 9  and M 10  which shall therefore receive the addresses “4-11-21” and “5-11-21”. Then the module M 8  transmits an address allocation message containing the address “4-11-21-10”, this address being received and accepted by the module M 11  (stages  51  to  57 ) which shall attempt to allocate the address “5-11-21-10” to the next module. If the module M 11  is the last module of the network branch to which it is connected, this sequence ends. 
     The central unit initiates a seventh sequence to see if there are still modules having no address in the network. If all the modules of the network have an address, no module will answer the address allocation message transmitted by the central unit and the address allocation procedure of the invention ends. 
     So as to be able to establish the relation between the allocated addresses and the geographical position of the modules Mi, it is possible to ensure that the address capture message transmitted in stage  56  by each module which is allocated with an address contains a module identification code, for example a series number. 
     It is also possible to provide on each module a control button for manually triggering the transmission of a module search message with a view to allocating an address to those modules which still do not have one. If the module in question still has no allocated address, it transmits an address allocation message to the central unit (“address” field  3 ′ equal to 0 and “direction” field  33  equal to 1), which makes it possible to look for the closest upstream module having an allocated address (stages  50  to  56 ,  58  to  60 ). If this module already has an address, it transmits an address allocation message whose fields “address” and “direction” are equal to 0 so as to look for the module situated closest downstream still not having any address. 
       FIG. 6  shows a module example Mi in which the method of the invention can be implemented, this module being designed so as to use an electric energy distribution network as a communication network. On this figure, the module Mi  10  includes at least two stages, namely: 
     a first stage for feeding the module  10 , coupling of the latter to the electricity distribution network and the generation of a synchronisation signal on the basis of the voltage Us provided by the electric network, and 
     a second stage organised around a processor  9  (for example a microprocessor) ensuring control of the entire module and in particular executing the previously described procedures  20  and  50 . 
     The first stage includes: 
     a feed circuit  11  which, on the basis of the voltage Us between the phase  18  and the neutral  19 , provides the power voltages required for the various elements of the module  10 , 
     a coupling circuit  5  connected between the phase  18  and the neutral  19  and designed to ensure the exchange of information between the processor  9  and the electric network, and 
     a synchronisation circuit  8 , also connected between the phase  18  and the neutral  19  and designed to generate a synchronous logic signal SS of the electric voltage Us provided by the electric network, this logic signal SS being applied to an input of the processor  9 . 
     The coupling circuit  5  can be embodied with the aid of a transformer or a LC type resonating circuit adjusted to the frequency of the transmission carrier of the messages via a carrier current. 
     The second stage, or control stage, includes around the processor  9 : 
     a non-volatile memory (for example an EEPROM type memory) for saving information, especially the information linked to the configuration of the module  10  and its address, and 
     a transmission/receiving circuit  12  designed to modulate the information to be transmitted and provided by the processor  9 , and to send the signal obtained to the coupling circuit  5  and for demodulating and amplifying the information signals transmitted by the coupling circuit  5  and delivering the processor  9  with the information obtained. 
     Moreover, the processor  9  is connected to two indicator lights, a red indicator light  14  for signalling faults, and a green indicator light  15  for signalling operating states. It is also connected to a stop/start button  16 , and a button  17  able to trigger the transmission of an address allocation message whose “address” field  34  is at zero, especially at the time of installation and connection of the module to the network. When the transmission of this message is triggered in this way, the processor  9  shall read in the memory t 3  the address allocated to the module  10 , this address being able to be nil if no address has previously been allocated to the module. 
     As previously mentioned, the processor  9  communicates with the central unit UC an the other modules Mi by messages transmitted via carrier current, these messages being transmitted for example by the phase modulation of a frequency of 132 kHz via the electric distribution network. 
     The stages  52  to  54  can be implemented by a delay line outside the processor  9 , for example integrated in the receiving/transmission circuit  12 . 
     As shown on  FIG. 7 , this delay line includes a first stage  41  for detecting the receiving of a message, and a second delay stage  42 , these two stages being connected by a reciprocal mounted diode D 3 . 
     The first stage  41  is in fact designed to detect the negative portion of the envelope of the received modulated carrier wave. To this effect, it comprises an input EI receiving the modulated signal received by the network, said input being connected by means of a resistor R 1  to the inverter gate input of an operational amplifier whose non inverter gate input is connected to the ground. At the same time between the inverter gate input and the output of the amplifier  11 , this circuit includes a resistor R 2  connected in series to two diodes D 1 , D 2  mounted head-to-tail, the joining point between the output of the comparator I 1  and the diodes D 1 , D 2  being connected to the diode D 3 . 
     The second stage  42  comprises a first capacitor discharge circuit including a capacitor C 1  and a resistor R 3  both mounted in parallel between the diode D 3  and the ground, the joining point between the diode D 3 , the capacitor C 1  and the resistor R 3  being connected to the inverter gate input of a comparator I 2 . This stage also includes a second capacitor discharge circuit including a capacitor C 2  and a resistor R 4  mounted in parallel between the ground of the circuit and the non-inverter input of the comparator I 2 , the latter being connected to the transmitter of a transistor Ti, for example an npn type, whose collector is connected to a reference voltage, for example the negative supply terminal of the circuit (−5 volts). The delay line further comprises an output S constituted by the output of the comparator I 2  and a control input E 2  connected to the base of the transistor T 1  by means of a resistor R 5 , the output S and the input E 2  being connected to the processor  9 . 
     The first stage provides at its output a nil voltage signal when no message is currently being received and a signal approximately at a constant to voltage corresponding to the level of the negative envelope of the modulated carrier wave received by the module  10 . As a result, during the receiving of a message, the capacitor C 1  is charged with the measured voltage. At the same time, the capacitor C 2  is charged with the maximum negative voltage delivered via the feeding of the circuit as long as the transistor T 1  is operating, that is as is long as a control voltage is applied to the input E 2  by the processor  9 . 
     Of course, this circuit can be designed to carry out a detection of the positive envelope of the transmission carrier. In this case, the collector of the transistor T 1  is connected to the positive supply terminal of the circuit and the transmitter of the transistor to the comparator I 2 . 
       FIG. 7  illustrates the functioning of the delay line shown on  FIG. 6 . This figure shows two curves  71 ,  72  representing the time-controlled evolution of the voltages at the inputs of the comparator I 2 , the curve  71  corresponding to the voltage at the terminals of the capacitor C 1 , and the curve  72 , the voltage at the terminals of the capacitor C 2 . 
     These two curves first of all exhibit a constant level which for the curve  71  corresponds to the receiving period of a message and for the curve  72  in the period during which the capacitor C 2  remains charged, the transistor T 1  being conductive. At the instant to, the transmission of the message currently being received ends and the voltage at the output of the stage  41  moves to 0. The capacitor C 1  thus starts to be discharged in the resistor R 3 . 
     As soon as the processor  9  detects the end of the arrival of a message (address allocation message) at to on  FIG. 7 , it restores the control voltage applied to the input E 2  which has the effect of triggering the discharging of the capacitor C 2 . When the two curves  71  and  72  meet at the point I corresponding to the instant t 1 , the voltages applied to the input terminals of the comparator I 2  are equal and thus the comparator delivers at the output S a pulse  73  which is received by the processor  9 . In this way, the voltage level received at E 1  has been transformed into a wait time which is compared with the time corresponding to the maximum voltage level. 
     The advantage obtained by using this circuit resides in the fact that a comparison is made of two exponential curves so that the weaker the signals are, the more expanded is the difference between the two curves. 
     It is to be noted that if a message is received before the instant t 1 , the outgoing signal from the stage  41  reverts to a lower level and the capacitor C 1  is recharged, this having the effect of moving forward the instant t 1  where the two curves cross. Thus, it is essential that on receipt of the pulse  73 , the processor  9  sees if a message is being received. If no message is being received, the processor  9  considers that the time Ti=t 1 −t 0  has elapsed and that it is the first stage to have received the message which has triggered the delay time Ti. In this case, it executes the stage  55 . If this is not the case, execution of the procedure  50  ends.