DESCRIPTION TITLE OF THE INVENTION COMMUNICATION SYSTEM AND SUPERIMPOSITION MODULE

TECHNICAL FIELD

[0001] The invention relates to: a communication system, in which a terminal device and a superimposition module are connected to a communication line, the terminal device communicates, using a transmission signal repeatedly transmitted from a transmission unit to the communication line, and the superimposition module communicates, using a superimposed signal superimposed on the transmission signal,' and the superimposition module.

BACKGROUND ART

[0002] Conventionally, a communication system has become widely used, in which a transmission unit (a master unit) and a plurality of terminal devices (slave units) are connected to a transmission path, and communication is performed between each terminal device and the transmission unit. As one example of this type of communication system, there has been provided a system, in which a transmission unit periodically monitors the state of a terminal device (e.g., see Japanese Patent Publication Nos. 1180690, 1195362 and 1144477). In this system, when detecting a change in the state of the terminal device, the transmission unit transmits a signal into other terminal devices to perform a processing corresponding to the change.

[0003] However, in the above communication system, the communication between terminal devices is performed constantly via the transmission unit, and the transmission unit performs polling with respect to terminal devices. Therefore, the transmission speed is slow, and the system is not adequate to transmission of information including relatively large volume of data, such as analog data. Further, in the above communication system, because the whole system stops upon the malfunction of the transmission unit, there is also a problem that the system possesses low reliability.

[0004] Therefore, there has been proposed a communication system (e.g., see Japanese Patent Application Laid-Open No. 2009-225328), in which an existing communication system (in which communication is performed between terminal devices via a transmission unit) is mixed with a communication system (in which communication is directly performed between terminal devices by peer-to-peer (P2P)). In this communication system, a transmission path is shared by terminal devices (first communication terminals) communicating via the transmission unit (a master unit), and superimposition modules (second communication terminals) directly communicating with each other. Therefore, it is possible to easily add superimposition modules to the existing communication system. The terminal devices communicate using a transmission signal (a signal according to a first protocol) repeatedly transmitted from the transmission unit to the transmission path. The superimposition modules communicate using a superimposed signal (a signal according to a second protocol) superimposed on the transmission signal.

[0005] In this case, the transmission signal is a signal according to a time-division system, and each frame in the transmission signal is divided into a plurality of time periods in a direction of a time axis, and a part of the time periods is assigned as a superimposable time period within which the superimposed signal is allowed to be superimposed. That is, the superimposition module communicates using the superimposed signal transmitted into the transmission path shared with the transmission signal, within the superimposable time period assigned to a part of the transmission signal.

[0006] In this configuration, when it is impossible to transmit transmission data within a single superimposable time period due to large volume, a superimposition module divides the transmission data to a plurality of sets of data in order to transmit sequentially for each superimposable time period. That is, the transmission data is transmitted over a plurality of superimposable time periods, and therefore, when the volume of the transmission data is increased, the superimposition module cannot transmit the transmission data with a single frame of a transmission signal, and may transmit the transmission data over a plurality of frames.

[0007] As described above, because a time period within which the superimposition module is allowed to transmit the superimposed signal is limited to a part of the time periods in the transmission signal, data volume that can be transmitted during a single frame of the transmission signal is limited. Therefore, it is difficult to improve the transmission speed between the superimposition modules.

DISCLOSURE OF THE INVENTION

[0008] It is an object of the present invention to provide a communication system and a superimposition module, which can improve communication speed relevant to communication performed with a superimposed signal.

[0009] A communication system of the present invention comprises '• a transmission unit repeatedly transmitting a transmission signal to a communication line," a terminal device communicating using the transmission signal; and a superimposition module communicating using a superimposed signal superimposed on the transmission signal. The transmission unit, the terminal device and the superimposition module are connected to the communication line. The transmission signal is a signal according to a time-division system, in which each of a plurality of frames is divided into a plurality of bands in a direction of a time axis. The plurality of bands includes: a transmission band provided for transmitting data to the terminal device; and a reply band being a time slot provided for receiving a reply signal from the terminal device. The superimposition module comprises a determining unit configured to determine, for each frame in the transmission signal, the presence or absence of the reply signal during a predetermined detection time period after a starting time point of the reply band. The superimposition module is configured to assign the reply band in which the determining unit has determined that the reply signal is present, as an unsuperimposable band within which the superimposed signal is not allowed to be superimposed. The superimposition module is configured to assign the reply band in which the determining unit has determined that the reply signal is absent, as a superimposable band within which the superimposed signal is allowed to be superimposed.

[0010] According to the present invention, because the superimposition module utilizes also the reply band in the transmission signal conditionally, as the superimposable band, for the superimposition of the superimposed signal, it is possible to improve communication speed relevant to the communication performed with the superimposed signal.

[0011] In this communication system, preferably, the plurality of bands in the transmission signal further include an interrupt band provided for receiving an interrupt signal from the terminal device, and the transmission unit is configured to assign, when receiving the interrupt signal in the interrupt band, next reply band to the terminal device that has generated the interrupt signal, and the superimposition module further comprises an interrupt generation unit configured to generate the interrupt signal in the interrupt band, and the superimposition module is configured to assign, when the interrupt generation unit has generated the interrupt signal, the entire region of said next reply band as the superimposable band without making the determining unit determine the presence or absence of the reply signal in said next reply band.

[0012] In this communication system, further preferably, the terminal device comprises a plurality of terminal devices, each of which includes a controlled device that is controlled according to a control command, and the control command is transmitted, from the transmission unit, together with a unique identifier assigned to the controlled device being a controlled object, with the transmission signal, and the transmission unit comprises a setting storage unit configured to store setting information that is information used when controlled devices are collectively controlled, and the setting information includes at least a combination of identifiers of the controlled devices that are targets for the collective control, and a setting device provided for setting the setting information is connected to the communication line, and the setting device is configured to make the transmission unit execute writing the setting information to the setting storage unit, through transmitting the setting information to the transmission unit when the setting information is set, and the superimposition module is located at each of the transmission unit and the setting device, and is configured to transmit, with the superimposed signal, the setting information from the setting device to the transmission unit. Further preferably, the plurality of bands in the transmission signal further include bands capable of being assigned as the superimposable band, in addition to the reply band, and a part of the bands capable of being assigned as the superimposable band is a band for synchronization that is used for only synchronization of the setting information between superimposition modules, each of which is the superimposition module. Further preferably, the setting device is capable of communicating using the transmission signal, and comprises a plurality of setting devices, and when two setting devices of the plurality of setting devices set the setting information simultaneously, one of the two setting devices is configured to transmit the setting information, with the transmission signal, and the other of the two setting devices is configured to transmit the setting information, with the superimposed signal.

[0013] In this communication system, further preferably, when receiving control request for the controlled devices and the setting information simultaneously, the transmission unit is configured to temporarily store the control request in a buffer memory and then transmit the control command based on the control request in the buffer memory after writing the setting information to the setting storage unit. Further preferably, the plurality of bands in the transmission signal further include bands capable of being assigned as the superimposable band, in addition to the reply band, and a part of the bands capable of being assigned as the superimposable band is a band for synchronization that is used for only synchronization of the setting information between superimposition modules, each of which is the superimposition module. Further preferably, the setting device is capable of communicating using the transmission signal, and comprises a plurality of setting devices, and when two setting devices of the plurality of setting devices set the setting information simultaneously, one of the two setting devices is configured to transmit the setting information, with the transmission signal, and the other of the two setting devices is configured to transmit the setting information, with the superimposed signal.

[0014] In this communication system, further preferably, the plurality of bands in the transmission signal further include bands capable of being assigned as the superimposable band, in addition to the reply band, and a part of the bands capable of being assigned as the superimposable band is a band for synchronization that is used for only synchronization of the setting information between superimposition modules, each of which is the superimposition module.

[0015] In this communication system, further preferably, the setting device is capable of communicating using the transmission signal, and comprises a plurality of setting devices, and when two setting devices of the plurality of setting devices set the setting information simultaneously, one of the two setting devices is configured to transmit the setting information, with the transmission signal, and the other of the two setting devices is configured to transmit the setting information, with the superimposed signal.

[0016] In this communication system, further preferably, when the plurality of setting devices set, with the superimposed signal, the setting information simultaneously, different superimposable bands are sequentially assigned to the plurality of setting devices respectively.

[0017] A superimposition module of the present invention is used for a communication system comprising: a transmission unit repeatedly transmitting a transmission signal to a communication line; a terminal device communicating using the transmission signal.' and the superimposition module communicating using a superimposed signal superimposed on the transmission signal. The transmission unit, the terminal device and the superimposition module are connected to the communication line. The transmission signal is a signal according to a time-division system, in which each of a plurality of frames is divided into a plurality of bands in a direction of a time axis. The plurality of bands includes* a transmission band provided for transmitting data to the terminal device" and a reply band being a time slot provided for receiving a reply signal from the terminal device. The superimposition module comprises a determining unit configured to determine, for each frame in the transmission signal, the presence or absence of the reply signal during a predetermined detection time period after a starting time point of the reply band. The superimposition module is configured to assign the reply band in which the determining unit has determined that the reply signal is present, as an unsuperimposable band within which the superimposed signal is not allowed to be superimposed. The superimposition module is configured to assign the reply band in which the determining unit has determined that the reply signal is absent, as a superimposable band within which the superimposed signal is allowed to be superimposed.

[0018] In this superimposition module, preferably, the plurality of bands in the transmission signal further include an interrupt band provided for receiving an interrupt signal from the terminal device, and the transmission unit is configured to assign, when receiving the interrupt signal in the interrupt band, next reply band to the terminal device that has generated the interrupt signal, and the superimposition module further comprises an interrupt generation unit configured to generate the interrupt signal in the interrupt band, and the superimposition module is configured to assign, when the interrupt generation unit has generated the interrupt signal, the entire region of said next reply band as the superimposable band without making the determining unit determine the presence or absence of the reply signal in said next reply band.

[0019] In this superimposition module, further preferably, the terminal device comprises a plurality of terminal devices, each of which includes a controlled device that is controlled according to a control command, and the control command is transmitted, from the transmission unit, together with a unique identifier assigned to the controlled device being a controlled object, with the transmission signal, and the transmission unit comprises a setting storage unit configured to store setting information that is information used when controlled devices are collectively controlled, and the setting information includes at least a combination of identifiers of the controlled devices that are targets for the collective control, and a setting device provided for setting the setting information is connected to the communication line, and the setting device is configured to make the transmission unit execute writing the setting information to the setting storage unit, through transmitting the setting information to the transmission unit when the setting information is set, and the superimposition module is located at each of the transmission unit and the setting device, and is configured to transmit, with the superimposed signal, the setting information from the setting device to the transmission unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Preferred embodiments of the invention will now be described in further details. Other features and advantages of the present invention will become better understood with regard to the following detailed description and accompanying drawings where:

Fig. 1A is a system configuration diagram illustrating the whole of a communication system according to First Embodiment;

Fig. IB is a block diagram illustrating a transmission unit of the communication system according to the First Embodiment!

Fig. 2 is a waveform diagram illustrating a transmission signal used in the communication system according to the First Embodiment;

Fig. 3 is a block diagram illustrating a setting device of the communication system according to the First Embodiment;

Fig. 4 is a block diagram illustrating a server unit of the communication system according to the First Embodiment;

Fig. 5 is a waveform diagram illustrating a reply band in the transmission signal used in the communication system according to the First Embodiment;

Fig. 6A is a diagram for explaining data configuration of setting information used in the communication system according to the First Embodiment;

Fig. 6B is a diagram for explaining data configuration of setting information used in the communication system according to the First Embodiment;

Fig. 7 is a block diagram illustrating the transmission unit of the communication system according to the First Embodiment;

Fig. 8 is a diagram for explaining operation of a communication system according to Second Embodiment,' and

Fig. 9 is a diagram for explaining operation of a transmission unit of the communication system according to the Second Embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0021]
(First Embodiment)

As shown in Fig. 1A, a communication system according to the present embodiment includes: a transmission unit 1 as a master unit that is connected to a communication line 2 having a two-wire system; a plurality of terminal devices 3 (in this case, two terminal devices); a plurality of setting devices 4 (in this case, two setting devices); and a server unit 5.

[0022] In this communication system, the communication is performed with two types of signals according to different protocols, including a transmission signal (a signal according to a first protocol) transmitted to the communication line 2 and a superimposed signal (a signal according to a second protocol) superimposed on the transmission signal. The superimposed signal has a higher frequency than the transmission signal.

[0023] The plurality of terminal devices 3 are connected in parallel with respect to the transmission unit 1 via the communication line 2. The transmission unit 1 and the plurality of terminal devices 3 constitute a time-division multiplex transmission system (hereinafter, called "a base system"), in which data transmission from the transmission unit 1 to the plurality of terminal devices 3 and data transmission from the plurality of terminal devices 3 to the transmission unit 1 are performed by time-division.

[0024] In the base system, the plurality of terminal devices 3 are classified into two types of terminal devices including: monitoring terminals provided with switches 31, such as wall switches; and control terminals provided with controlled devices 32, such as relays. Therefore, it is possible to control loads (not shown) connected to the controlled devices 32 in response to monitoring inputs from the switches 31. In this case, each terminal device 3 stores its own address that has been assigned previously in a memory (not shown). Here, things with which the monitoring terminals are provided are not limited to the switches 31. The monitoring terminals may be provided with sensors and the like.

[0025] When receiving a monitoring input, each monitoring terminal transmits, to the transmission unit 1, a control request corresponding to the monitoring input. The transmission unit 1 transmits a control command to a control terminal that is made to correspond to the monitoring terminal by an address, when receiving the control request. The control terminal controls the controlled device 32 according to the control command, when receiving the control command. The load (an electrical apparatus) connected to the controlled device 32 is controlled by, for example, turning on or off a relay as the controlled device 32. The control command reflects the monitoring input that has been inputted from the switch 31, and therefore, operation to the switch 31 is reflected in control for the controlled device 32 in the end.

[0026] The transmission unit 1 stores, in a storage unit 12 (see Fig. IB), a control table in which the switches 31 and the controlled devices 32 are made to correspond to each other by addresses. Here, for example, in a case where a terminal device 3 has a switch 31 with poles, a unique terminal address assigned to the terminal device 3 corresponds to all poles of the switch 31 of the terminal device 3. Therefore, by only the unique terminal address, it is impossible to specify a pole of the switch 31 that has been actually operated. Accordingly, in the operating terminal, a load number is assigned to each of the poles of the switch 31 in order to specify the actually operated pole. Then, an address, in which a load number is added after the unique terminal address of the terminal device 3, is used as a unique address (identifier) assigned to a switch 31. Similarly, in the control terminal, a load number is assigned to each of the relay circuits of the controlled device 32. Then, an address, in which a load number is added after the unique terminal address of the terminal device 3, is used as a unique address (identifier) assigned to a controlled device 32.

[0027] As shown in Fig. IB, the transmission unit 1 includes a transmission processing unit 11, the storage unit 12, a communication module 9 that communicates using the transmission signal, a superimposition module 8 and a setting storage unit 13 as described below. The communication module 9 includes a transmission-reception unit 92, a transmission data analysis unit 93 and a transmission data generation unit 94 that are connected to the transmission-reception unit 92.

[0028] The transmission-reception unit 92 generates a waveform of a transmission signal and then transmits the generated signal via the communication line 2, or extracts a reply signal from a transmission signal transmitted via the communication line 2. The transmission data analysis unit 93 analyzes a content of the reply signal received by the transmission-reception unit 92. The transmission data generation unit 94 generates data to be transmitted with the transmission signal, and then transmits the data to the terminal devices 3 via the transmission-reception unit 92. The transmission processing unit 11 refers to the control table stored in the storage unit 12, and then performs monitoring of the switches 31 and control of the controlled devices 32, with the transmission signal. Here, the transmission unit 1 also has functions of periodically monitoring operating states of the terminal devices 3 and storing the operating states in the storage unit 12.

[0029] Next, operation of the base system will be explained below.

[0030] The transmission unit 1 served as the master unit transmits, to the communication line 2, a transmission signal according to a time-division system, as shown in Fig. 2. The transmission signal includes a voltage waveform having a form to be divided into a plurality of bands in a direction of a time axis. That is, the transmission signal is a time-division multiplexing signal with bipolar (+-24V), which includes seven bands: a preliminary interrupt band 21; a preliminary band 22," a transmission band 23; a reply band 24; an interrupt band 25; a shunt detection band 26; and an inactive band 27. The preliminary interrupt band 21 is a time period provided for detecting a secondary interrupt. The preliminary band 22 is a time period that is set in accordance with the interrupt band 25 and the shunt detection band 26. The transmission band 23 is a time period provided for transmitting data to the terminal devices 3. The reply band 24 is a time slot provided for receiving a reply signal returned from the terminal device 3. The interrupt band 25 is a time period provided for detecting an interrupt signal as described below. The shunt detection band 26 is a time period provided for detecting short circuit. The inactive band 27 is a time period provided for when processing is not on time.

[0031] In each terminal device 3, when an address stored in its own memory (not shown) corresponds to address data included in the transmission band 23 of a transmission signal that has been received via the communication line 2, the terminal device 3 extracts a control command for controlling the controlled device 32 from the transmission signal. Further, the terminal device 3 returns the control result, as a signal with a current mode (a signal transmitted by shunting the communication line 2 through proper low impedance), in synchronization with the reply band 24 in the transmission signal. Here, power to internal circuits in each terminal device 3 is supplied through rectifying and stabilizing the transmission signal transmitted via the communication line 2.

[0032] The transmission unit 1 normally performs continuously polling to have sequential access to each terminal device 3, with periodically changing address data included in a transmission signal. Upon continuously polling, when an address of a terminal device 3 corresponds to address data included in a transmission signal, the terminal device 3 with the corresponding address extracts a control command to operate if the control command is included in the transmission signal. Then, the terminal device 3 with the corresponding address returns its own operating state, as the control result, to the transmission unit 1.

[0033] When receiving an interrupt signal that has been generated in response to a monitoring input from a switch 31 provided in any monitoring terminal (terminal device 3), the transmission unit 1 searches for the terminal device 3 that has generated the interrupt signal, and then has access to the terminal device 3 and performs also interrupt polling.

[0034] That is, the transmission unit 1 normally transmits a transmission signal according to a normal mode as the mode data. Then, when detecting an interrupt signal that has been generated in a monitoring terminal (terminal device 3) in synchronization with the interrupt band 25 in the transmission signal, the transmission unit 1 transmits a transmission signal according to an interrupt polling mode as the mode data.

[0035] The terminal device 3 that has generated the interrupt signal returns, as reply data, a low-order bit of its own address in synchronization with the reply band 24 in the transmission signal, if a high-order bit of its own address corresponds to a high-order bit of address data included in the transmission signal according to the interrupt polling mode. Therefore, the transmission unit 1 can acquire the address of the terminal device 3 that has generated the interrupt signal.

[0036] When acquiring the address of the terminal device 3 that has generated the interrupt signal, the transmission unit 1 transmits a transmission signal for demanding that the terminal device 3 returns a
control request. Then, the terminal device 3 returns, to the transmission unit 1, the control request corresponding to the monitoring input from the switch 31. When receiving the control request, the transmission unit 1 transmits, to the terminal device 3, an instruction for clearing the monitoring input. The terminal device 3 then clears the monitoring input.

[0037] The transmission unit 1 that has received the control request generates a control command to transmit to a terminal device 3 (a control terminal) made to correspond to the terminal device 3 (the monitoring terminal), which is a source of the control request, by a correspondence relation between addresses. Then, the transmission unit 1 transmits, to the communication line 2, a transmission signal including the control command, to control a controlled device 32 that is provided at the terminal device 3 (the control terminal).

[0038] As described above, in the base system, the terminal devices 3 (the monitoring terminal, the control terminal) communicate with each other through the transmission unit 1 according to Polling/Selecting protocol (the first protocol).

[0039] In the control table of the transmission unit 1, the switches 31 are made to correspond to the controlled devices 32 one-to-one, however, the switches can be also made to correspond to the controlled devices one-to-many. For example, in a case where turning on or off power to a lighting apparatus, as a load, using a controlled device 32, the transmission unit 1 can perform an individual control in which a lighting apparatus with 1-pole is controlled by a switch 31 with 1-pole, or a collective control in which a lighting apparatus with a plurality of poles is collectively controlled by a switch 31 with 1-pole. The collective control includes a group control and a pattern control. The group control is a control in which a plurality of relays to be controlled is made to correspond to a switch 31 with 1-pole and the plurality of relays is collectively turned on or off by operation to the switch 31. The pattern control is a control in which control states (ON or OFF) corresponding to a plurality of relays and each relay to be controlled are made to correspond to a switch 31 with 1-pole and the plurality of relays is turned on or off by operation to the switch 31.

[0040] In order to achieve the group control and the pattern control, the transmission unit 1 further includes a setting storage unit 13 that stores setting information used for collectively controlling a plurality of controlled devices 32. The setting information includes at least a combination of unique addresses (hereinafter, called "individual addresses") assigned to the controlled devices 32 that are targets for the collective control. In the present embodiment, the setting information includes information in which the combination of the individual addresses is made to correspond to a group address or a pattern address. The group address is made to correspond to, in the control table, an address of a switch 31 operated upon the group control. The pattern address is made to correspond to, in the control table, an address of a switch 31 operated upon the pattern control.

[0041] Therefore, when a switch 31 corresponding to the group address or the pattern address is operated, the transmission unit 1 expands the addresses of the controlled devices 32 to be controlled by collating the setting information, and then transmits the control command to those controlled devices 32.

[0042] That is, in order to perform the group control or the pattern control, previously setting of the setting information representing that which group (or which pattern) each controlled device 32 belongs to is needed. The setting device 4 is a device used for setting such setting information. When the transfer processing of the setting information is performed, the setting device makes the transmission unit 1 execute writing the setting information to the setting storage unit 13 by transmitting (transferring) the setting information to the transmission unit 1.

[0043] As shown in Fig. 3, the setting device 4 includes a communication module 9, as the case of the transmission unit 1. The setting device 4 further includes a setting processing unit 41 that performs setting of the setting information, an input unit 42, a display unit 43, and a storage unit 44. Therefore, a user can input the setting information through the input unit 42 while checking the setting content at the display unit 43. Then, the inputted setting information is temporarily stored in the storage unit 44 through the setting processing unit 41. The setting device 4 performs registration of the setting information (writing to the setting storage unit 13) by transferring, to the transmission unit 1, the setting information in the storage unit 44.

[0044] The server unit 5 is configured to be capable of monitoring and controlling information relevant to the terminal devices 3 (the operating states or the like of the switches 31 and the controlled devices 32), by a web browser function in a client terminal 7 via a network 6. The client terminal 7 is not limited in particular, as long as the client terminal 7 includes a user interface, such as a web browser function, a display unit and an operating unit. In this case, a personal computer is used as the client terminal 7.

[0045] As shown in Fig. 4, the server unit 5 includes a communication module 9, as the case of the transmission unit 1. The server unit 5 further includes a storage unit 51 that stores the setting information, and a web screen constituting unit 52 that is connected to the setting processing unit 41 and provides web contents to the client terminal 7. The server unit 5 also functions as a setting device. Therefore, a user can perform setting of the setting information, using the client terminal 7, even from a remote place. Then, the inputted setting information is stored in the storage unit 51 of the server unit 5. Here, the storage unit 51 of the server unit 5 stores also schedule data for performing the scheduling control for the terminal devices 3 according to a schedule.

[0046] Here, in a conventional communication system, generally, the setting information as above is transferred, with a transmission signal, from the setting device 4 or the server unit 5 to the transmission unit 1. As a specific method, there are a first method in which the setting information is transferred while all of monitoring of the switches 31 and controlling of the controlled devices 32 are interrupted, and a second method in which the setting information is transferred while all of monitoring of the switches 31 and controlling of the controlled devices 32 are continued.

[0047] In the first method, the setting device 4 or the server unit 5 transfers the setting information, with the transmission signal exclusively, while monitoring of the switches 31 and controlling of the controlled devices 32 are interrupted. In the second method, the setting device 4 or the server unit 5 generates an interrupt signal, and then transfers the setting information after receiving the interrupt polling from the transmission unit 1.

[0048] However, in the first method, during the transmission of the setting information, the transmission unit 1 can perform neither monitoring of the switches 31 nor controlling of the controlled devices 32, and therefore, there is a problem that the operation of the base system is substantively stopped. In particular, when the setting number of the group addresses or the pattern addresses is large (e.g., the setting number of the pattern addresses is 72 and the setting number of the group addresses is 128), a relatively long time (e.g., about 30 minutes) is required for the transmission of the setting information. As a result, a time during which the operation of the base system is substantively stopped is increased.

[0049] Further, in the second method, because the setting device 4 or the server unit 5 transfers the setting information by the interrupt, delay occurs in the monitoring of the switches 31 and the controlling of the controlled devices 32 performed by the transmission unit 1, and therefore, delay occurs in the operation of the base system. In addition, for the transmission of the setting information, the second method requires a longer time than the first method. As a result, a time required for the registration of the setting information is increased. [0050] In order to resolve those problems, the communication system

according to the present embodiment transfers, with not the transmission signal but the superimposed signal, data for the registration of the setting information for the group control or the pattern control as described above, the synchronization, or the like.
[0051] Specifically, in the communication system according to the present embodiment, the transmission unit 1 that registers the setting information, the setting device 4 and the server unit 5 that have functions of setting the setting information are respectively provided with superimposition modules 8 (see Fig. IB, Fig. 3 and Fig. 4). The superimposition modules 8 are communication interfaces that communicates with each other, using the superimposed signal superimposed on the transmission signal, while sharing the base system and the communication line 2. The superimposition modules 8 transfer, with the superimposed signal, the setting information from the setting device 4 or the server unit 5 to the transmission unit 1. Hereinafter, the communication performed with the superimposed signal will be explained in detail.
[0052] Each superimposition module 8 directly transfers transmission data (the setting information) to the other superimposition modules 8, according to a protocol (a second protocol) different from the above-mentioned first protocol, by peer-to-peer (P2P), without via the transmission unit 1. [0053] As shown in Fig. IB, each superimposition module 8 includes: a superimposition unit 81 that is connected to the communication line 2; a superimposition transmission-reception unit 82 that is connected to the superimposition unit 81; a superimposition data analysis unit 83," and a

superimposition data generation unit 84. The superimposition data analysis unit 83 and the superimposition data generation unit 84 are connected to the superimposition transmission-reception unit 82. [0054] The superimposition unit 81 superimposes a superimposed signal on a transmission signal to transmit via the communication line 2, or separates a transmission signal and a superimposed signal from a signal transmitted via the communication line 2. The superimposition transmission-reception unit 82 transmits a superimposed signal to the other superimposition modules 8, or receives a superimposed signal from the other superimposition modules 8, via the superimposition unit 81. The superimposition data analysis unit 83 analyzes the content of a superimposed signal that has been received by the superimposition transmission-reception unit 82. The superimposition data generation unit 84 generates a superimposed signal to be transmitted by the superimposition transmission-reception unit 82. [0055] By this configuration, each superimposition module 8 superimposes, on a transmission signal, a packet including data to be transmitted to the other superimposition modules 8, according to the second protocol and then transmits the signal to the communication line 2, or receives a packet according to the second protocol that has been transmitted from the other superimposition modules 8. That is, the communication according to the first protocol between the terminal devices 3 is performed via the transmission unit 1 as above, and on the other hand, the communication according to the second protocol between the superimposition modules 8 is performed directly without dependence on the transmission unit 1. As a

result, the communication speed in the communication according to the second protocol can be further increased, compared with that in the communication according to the first protocol. Then, the communication according to the second protocol can be used for transmitting information including large data volume, such as the setting information for the group control or the pattern control, compared with the control request or the control command.
[0056] Further, each superimposition module 8 includes a determining unit 85 that monitors the transmission signal transmitted between the transmission unit 1 and the terminal devices 3 in the base system. The determining unit 85 analyzes a transmission state of data (hereinafter, called "a state") based on the transmission signal. The superimposition module 8 determines whether or not the state analyzed by the determining unit 85 is a state suitable to the superimposition of the superimposed signal. Then, the superimposition unit 81 superimposes the superimposed signal on the transmission signal at a timing when the superimposition module 8 has determined that the state is suitable to the transmission. [0057] Here, the adopted transmission signal has a signal format as shown in Fig. 2. Even if superimposed within the preliminary interrupt band 21, the preliminary band 22 or the inactive band 27, the superimposed signal hardly influences communication according to the first protocol. Also, the transmission signal hardly influences the superimposed signal. Therefore, the preliminary interrupt band 21, preliminary band 22 and inactive band 27 are bands (hereinafter, called "superimposable bands") within which the

superimposed signal is allowed to be superimposed. Further, in the present embodiment, although described below in detail, the superimposition module 8 utilizes also the reply band 24 conditionally, as a superimposable band, in addition to those three bands.
[0058] In the other bands (the transmission band 23, interrupt band 25 and shunt detection band 26), a time during which the transmission signal is stable at a high level or low level is relatively short, and therefore, when superimposed within the other bands, the superimposed signal easily influences the communication according to the first protocol. When the superimposed signal is superimposed within the other bands as described above, a signal (an interrupt signal or reply data) transmitted and received between the transmission unit 1 and the terminal devices 3 also easily influences the superimposed signal. Accordingly, the other bands as described above are bands (hereinafter, called "unsuperimposable bands") within which the superimposed signal is not allowed to be superimposed. [0059] Also, rise and fall times in the transmission signal are not adequate to time periods within which the superimposed signal is superimposed, due to influence of high-harmonic noise, influence of a transient response with a voltage inversion in a signal, or the like. Accordingly, even in the preliminary interrupt band 21, preliminary band 22 or inactive band 27, a predetermined time period (e.g., 300us) after the band is changed (rising or falling) is defined as an unsuperimposable band.
[0060] Here, the determining unit 85 is configured to determine whether the band is a superimposable band or an unsuperimposable band, based on an

analysis result of the state of a transmission signal, and the superimposition unit 81 is then configured to transmit a superimposed signal only when the determining unit determines that the band is the superimposable band. As above, the superimposition module 8 superimposes the superimposed signal only within the superimposable band in the transmission signal so as to synchronize with the transmission signal, and therefore, it is possible to prevent that the communication according to the first protocol and the communication according to the second protocol, sharing the communication line 2, influence each other.
[0061] Here, when the superimposition module 8 could not transmit data only within a single superimposable band due to large volume of the data, the superimposition module 8 interrupts the communication at the end of the superimposable band, and transmits the remaining data within next superimposable band. That is, when receiving a transmitted superimposed signal as divided sets of data, the superimposition transmission-reception unit 82 couples the divided sets of data to make the original data, and when transmitting a superimposed signal, the unit 82 divides data into sets of data so that each of the sets has a size capable of being superimposed on a superimposable band.
[0062] Power to each unit in the superimposition module 8 is supplied, using a system (a centralized power supply system), as the case of the terminal devices 3, in which the power is supplied by rectifying and stabilizing the transmission signal transmitted from the transmission unit 1 via the communication line 2. However, the power supply system is not limited to

such a configuration. The power to each unit in the superimposition module 8 may be supplied, using a system (a local power supply system) in which the power is supplied by rectifying and stabilizing a commercial power. [0063] Here, generally, in a transmission signal, only the preliminary interrupt band 21, preliminary band 22 and inactive band 27 are utilized, as superimposable bands, for the superimposition of the superimposed signal. On the other hand, the superimposition module 8 of the present embodiment utilizes also the reply band 24 conditionally, as a superimposable band, for the superimposition of the superimposed signal, in addition to three bands of the preliminary interrupt band 21, preliminary band 22 and inactive band 27.
[0064] That is, the determining unit 85 determines, for each frame in a transmission signal, the presence or absence of the reply signal during a predetermined detection time period after a starting time point of the reply band 24, and then, the superimposition module 8 assigns the reply band 24 in which the determining unit 85 determines that the reply signal is absent, as a superimposable band within which the superimposed signal is allowed to be superimposed. On the other hand, the superimposition module 8 assigns the reply band 24 in which the determining unit 85 determines that the reply signal is present, as an unsuperimposable band. [0065] More specifically, the reply band 24 includes five blocks: "Bl" to "B5", as shown in Fig. 5. When the reply signal is generated at a terminal device 3, a pulse occurs, in the first block Bl, during a prescribed time (e.g., 900us) after a starting time point of the reply band 24. Here, the determining unit

85 defines, as a detection time period Tl, a predetermined time period after the starting time point of the reply band 24. Then, when no pulse occurs within the detection time period Tl, the determining unit 85 determines that the reply signal is absent, and assigns, as a superimposable band, a time period T2 from the second block B2 in the reply band 24. In the example of Fig. 5, the reply band 24 has a length of 6400us, and the detection time period Tl has a length of 1900us after the starting time point of the reply band 24. When no pulse occurs within this detection time period Tl, the time period T2 having a length of the remaining 4500us is assigned as the superimposable band. On the other hand, when a pulse occurs within this detection time period Tl, the determining unit 85 determines that the reply signal is present in the reply band 24, and assigns, as the unsuperimposable band, the reply band.
[0066] If even a part of the reply band 24 other than the detection time period Tl can be used as a superimposable band, as shown in the following Table 1, data volume of superimposable bands per frame in the transmission signal is increased significantly, compared with a case where the entire region of the reply band 24 is assigned as an unsuperimposable band. Table 1 represents volumes of data capable of being respectively transmitted within bands, a total of the volumes, and a transmission speed, with respect to each of a case where the reply band 24 is not used for the superimposition of the superimposed signal and a case where a part of the reply band 24 (a part other than the detection time period) is used for the superimposition of the superimposed signal. Here, those values are calculated by assuming

that data of 40bit can be transmitted within 1ms. [0067] [Table 1]
As above, the data volume of the superimposed signal allowed to be superimposed per frame in the transmission signal is increased significantly, through using even a part of the reply band 24 for the superimposition of the superimposed signal, and the communication speed is improved. In the example of Table 1, the communication speed is 6.3kbps in the case where the reply band 24 is not used for the superimposition of the superimposed signal. On the other hand, the communication speed is improved to 15.7 kbps in the case where the reply band 24 is used for the superimposition of the superimposed signal.
[0068] Here, as one example, the setting information transferred with the superimposed signal has a signal configuration as shown in Fig. 6A or Fig. 6B. That is, the setting information relevant to the pattern control is configured by a type 61, an address 62, a fade 63, component information 64, a checksum 65 and a termination 66, as shown in Fig. 6A for example. In the example of Fig. 6A, the type 61 has 16-bit data, the address 62 has 12-bit data, the fade 63 has 4-bit data, the component information 64 has 4288-bit data, the checksum 65 has 8-bit data, and the termination 66 has 8-bit data.

Therefore, the setting information has 4336-bit data per pattern. [0069] The type 61 represents a type of the setting information (a distinction of the group control and the pattern control). The address 62 represents a pattern address (here, 72 addresses of "01" to "72") or a group address (here, 128 addresses of "001" to "128"). The fade 63 represents, in a case where the present control state is gradually moved to a control state that has been set after performing of the pattern control, a time period until the movement to the control state is completed. The time period of the fade 63 is selected from an instant, 3sec, 6sec and lmin. The component information 64 represents sets of individual addresses (here, 256 addresses of "00-1" to "63-4") to be collectively controlled. The checksum 65 is an error detection code of data. The termination 66 is a code representing a termination of the setting information.
[0070] In the component information 64, a control content, a setting time of a timer, a dimming level (in a case where a load is a lighting apparatus) and the like are set with respect to each individual address. The control content is alternatively selected from "ON", "OFF' and "Exclusion". In the case where the load is the lighting apparatus, the setting time is alternatively selected from "Nothing", "Temporarily turning on a light for 30sec", "Temporarily turning on a light for lmin", "Temporarily turning on a light for 5min", "Temporarily turning on a light for 60min", "Temporarily turning on a light for 120min", "Turning off a light 30sec late", "Turning off a light lmin late", and "Turning off a light 5min late". The dimming level is alternatively selected from values "0" to "128" that represent in stages

brightness from a lighting-off state to a fulHighting-on state. [0071] The setting information relevant to the group control, as shown in Fig. 6B for example, is configured by a type 61, an address 62, component information 64, a checksum 65 and a termination 66. In the example of Fig. 6B, the type 61 has 16-bit data, the address 62 has 12-bit data, the component information 64 has 2048-bit data, the checksum 65 has 8-bit data, and the termination 66 has 8"bit data. Therefore, the setting information has 2284-bit data per group.
[0072] Here, a time required for transferring the setting information is obtained as the following Table 2, based on the data volume of the above setting information per pattern or per group and the communication speed shown in the above Table 1. Table 2 shows times required for transferring the respective setting information for 1 pattern, 72 patterns, 1 group and 128 groups, with respect to each of a case where the reply band 24 is not used for the superimposition of the superimposed signal and a case where a part of the reply band 24 is used for the superimposition of the superimposed signal. [0073] [Table 2]
According to the communication system of the present embodiment as explained above, because the superimposed signal is used for transferring the setting information, the system can prevent delay from occurring in the

operation of the base system even while continuing to monitor the switches 31, to control the controlled devices 32 and to further transfer the setting information. Further, because the communication system of the present embodiment utilizes also the reply band 24 in the transmission signal conditionally for the superimposition of the superimposed signal, the data volume of superimposable bands per frame in the transmission signal is increased significantly, compared with a case where the reply band 24 is not utilized. Accordingly, it is possible to shorten a time required for transferring the setting information from the setting device 4 or the server unit 5 to the transmission unit 1, and to shorten a time required for registration of the setting information. In particular, when the setting number of the group addresses or the pattern addresses is large (e.g., the setting number of the pattern addresses is 72 and the setting number of the group addresses is 128), a time required for the transmission of the setting information is shortened significantly.
[0074] In the present embodiment, because each of the setting device 4 and server unit 5 includes not only the superimposition module 8 but also the communication module 9, it is also possible to transfer the setting information to the transmission unit 1, with the transmission signal. The transmission signal and the superimposed signal can be arbitrarily switched, as a signal used for transferring the setting information, by operation to the setting device 4 or the server unit 5 for example.
[0075] In the present embodiment, the superimposition module 8 uses the predetermined time period after the starting time point of the reply band 24,

as the detection time period for determining the presence or absence of the reply signal in the determining unit 85. However, the entire region of the reply band 24 including this detection time period can be also used as a superimposable band.
[0076] That is, in this case, the superimposition module 8 includes an interrupt generation unit (not shown) that actively generates an interrupt signal in the interrupt band 25 (see Fig. 2). The interrupt generation unit provides an interruption, and accordingly, it becomes possible to use the entire region of the next reply band 24 as a superimposable band. When the interrupt generation unit generates an interrupt signal, the superimposition module 8 can superimpose a superimposed signal within the entire region of the next reply band 24 without making the determining unit 85 determine the presence or absence of the reply signal in the next reply band 24. [0077] When the entire region of the reply band 24 is used as a superimposable band, the detection time period Tl having the length of 1900us after the starting time point of the reply band 24 is added as a superimposable band, in the example of Fig. 5, and therefore, the superimposition module 8 can superimpose a superimposed signal within the entire region of the reply band 24 having the length of 6400us in total. Under the same conditions as Table 1, the superimposition module 8 uses the entire region of the reply band 24 as a superimposable band, and accordingly, the superimposition module 8 can transmit data that is larger by 76-bit data, in the reply band 24. As a result, it becomes possible to transmit, with the superimposed signal, data that is larger by 4k-bit data per sec. That is, the

communication speed is improved by 4kbps.
[0078] As shown in Fig. 7, the transmission unit 1 may further includes a buffer memory 14 and a confliction detecting unit 15, and may be configured to store, when receiving the control request for the controlled device 32 and the setting information simultaneously, temporarily the control request in the buffer memory 14. The confliction detecting unit 15 detects confliction between^ the control request transmitted from the terminal device 3, with the transmission signal; and the setting information transferred from the setting device 4 or the server unit 5, with the superimposed signal. That is, the confliction detecting unit 15 determines that the control request and the setting information have conflicted with each other, when a timing when the communication module 9 has received the control request matches a timing when the superimposition module 8 has received the setting information. [0079] In this configuration, when the confliction detecting unit 15 detects the confliction, the transmission unit 1 stores the control request received at that time temporarily in the buffer memory 14. In this case, when writing of the setting information to the setting storage unit 13 is completed, the transmission processing unit 11 reads out the control request stored in the buffer memory 14 and then transmits, to the terminal device 3, the control command based on the control request.
[0080] In the configuration including the buffer memory 14 and confliction detecting unit 15 as explained above, when the control request and the setting information to the transmission unit 1 conflict with each other, the control request is temporarily stored in the buffer memory 14 by the

transmission unit 1, and the registration of the setting information to the setting storage unit 13 is performed preferentially. Accordingly, it is possible to rapidly complete the registration processing of the setting information by the setting device 4 or the server unit 5. Further, even when the switch 31 for the collective control is operated at the same time as modification of the setting information, the transmission unit 1 can perform the collective control, using new setting information that has been modified. [0081] Here, in the transmission signal, a part of bands capable of being assigned as the superimposable band may be a band for synchronization that is used for only synchronization of the setting information between superimposition modules 8. That is, in the communication system of the present embodiment, the setting information for the group control or the pattern control is stored not only in the transmission unit 1, as master data, but also in the setting storage unit 13 of the setting device 4 or the server unit 5. Accordingly, if the setting device 4 or the server unit 5 is exchanged or added during the operation of the communication system, inconsistency (mismatch) of the setting information may occur between the transmission unit 1, the setting device 4 and the server unit 5. In such a case, it is required that the setting information stored as the master data in the transmission unit 1 is synchronized with the setting information stored in the setting device 4 and the server unit 5, in order to ensure the consistency of the setting information in the whole of the communication system. [0082] Therefore, the transmission unit 1 fixedly sets the part of bands in the transmission signal as the band for the synchronization. Then, the

transmission unit 1 transmits the setting information as the master data to the setting device 4 and the server unit 5 with the superimposed signal, using the band for the synchronization, to order to synchronize the setting information. When receiving the setting information from the transmission unit 1, each of the setting device 4 and the server unit 5 compares the received setting information with the setting information stored in its own setting storage unit 13, and then writes the received setting information to the own setting storage unit 13 if there is a mismatch between those setting information. Therefore, it is possible to synchronize the setting information for each frame in the transmission signal, and to constantly ensure the consistency of the setting information in the whole of the communication system.
[0083] Although the configuration that the respective superimposition modules 8 are housed in the transmission unit 1, setting device 4 and server unit 5 was illustrated in the present embodiment, the communication system is not limited to such a configuration. For example, the superimposition modules 8 may be provided separately from the transmission unit 1, setting device 4 and server unit 5, and may be directly connected to the transmission unit 1, setting device 4 and server unit 5. [0084] (Second Embodiment)
The communication system of the present embodiment is different from that of the First Embodiment in that the system is configured to be capable of responding to even a case where a plurality of setting devices 4 or

server units 5 set the setting information simultaneously. Hereinafter, when the setting device 4 and the server unit 5 are not distinguished in particular, those are called "setting units" as a whole. The present embodiment will be explained on the assumption that each setting unit includes the communication module 9 and is capable of communicating, using the transmission signal.
[0085] For example, it is assumed that while a certain setting unit transfers the setting information, a user sets the setting information using another setting unit. In this case, because the superimposed signal is already used exclusively by the certain setting unit transferring the setting information, it is impossible to transfer the setting information set by the user with the superimposed signal. Accordingly, in the present embodiment, when two setting units set the setting information simultaneously, one setting unit transfers the setting information, with the transmission signal, and the other setting unit transfers the setting information, with the superimposed signal. Specifically, each setting unit has an arbitration function of assigning the transmission signal and the superimposed signal so that a method for transferring the setting information does not match methods used by other setting units, through communicating with other setting units. [0086] When receiving different setting information with the transmission signal and the superimposed signal from two setting units as described above, the transmission unit 1 has the following configuration so as not to write those different setting information to the setting storage unit 13 simultaneously. That is, the transmission unit 1 alternately switches the

communication module 9 and the superimposition module 8, as a destination of reading the setting information, so as to alternately write the setting information received with the transmission signal and the setting information received with the superimposed signal to the setting storage unit 13. Specifically, the transmission unit 1 makes a semaphore perform exclusive control for each registration of the setting information per pattern or per group (per group address or per pattern address), and alternately switches the communication module 9 and the superimposition module 8. [0087] According to the above-mentioned configuration, when two setting units set the setting information simultaneously, one setting unit switches a method for transferring the setting information in response to a trend of the other setting unit, and accordingly, it is possible to effectively transfer the setting information to the transmission unit 1.
[0088] Further, when three or more setting units set the setting information simultaneously, one setting unit transfers the setting information, with the transmission signal, and the remaining setting units transfer the setting information, with the superimposed signal. In this case, because a plurality of setting units set the setting information, with the superimposed signal, it is preferred that different superimposable bands are respectively assigned to the plurality of setting units sequentially.
[0089] For example, when three setting units set the setting information simultaneously, one setting unit transfers the setting information, with the transmission signal, and two setting units transfer the setting information, with the superimposed signal. Here, different superimposable bands are

respectively assigned to the two setting units that transfer with the superimposed signal, and each setting unit transfers the setting information to the transmission unit 1, with the assigned superimposable band. At this time, the two setting units that transfer the setting information with the superimposed signal are periodically configured to switch bands within which the superimposed signal are superimposed, according to the data volume of the setting information.

[0090] Specifically, as shown in Fig. 8, the two setting units that transfer the setting information with the superimposed signal first notify the transmission unit 1 of addresses to be set (the group addresses or the pattern addresses). The transmission unit 1 calculates the data volume of the setting information (the communication data volume) based on the received addresses, and assigns superimposable bands used for the transmission of the setting information to the two setting units, and notifies the two setting units of the superimposable bands. Here, when it is impossible to use the reply band 24 as a superimposable band, the transmission unit 1 divides other superimposable bands into two groups^ the preliminary interrupt band 21 and preliminary band 22; and the inactive band 27, and then assigns the preliminary interrupt band 21 and preliminary band 22 to one of the two setting units that transmits data having larger volume, and assigns the inactive band 27 to the other of the two setting units that transmits data having smaller volume. On the other hand, when it is possible to use the reply band 24 as a superimposable band, the transmission unit 1 periodically checks the remaining data volume of the setting information, with respect to the two setting units that transfer the setting information with the superimposed signal, and assigns the superimposable bands according to a flow chart of Fig. 9.

[0091] That is, as shown in Fig. 9, the transmission unit 1 periodically checks the remaining data volume (SO), and calculates a difference between the remaining data volumes in both setting units. If the difference between the remaining data volumes is less than 40bit (Si: NO), the transmission unit 1 assigns the reply band 24 to one of the two setting units that has larger remaining data volume, and assigns the set of the preliminary interrupt band 21 and preliminary band 22, or the inactive band 27 to the other of the two setting units that has smaller remaining data volume (S2). Then, if the difference between the remaining data volumes is equal to or more than 40bit (Si: YES) and further is less than 140bit (S3: NO), the transmission unit 1 assigns the inactive band 27 or the reply band 24 to one of the two setting units that has larger remaining data volume, and assigns the set of the preliminary interrupt band 21 and preliminary band 22 to the other of the two setting units that has smaller remaining data volume (S4). Then, if the difference between the remaining data volumes is equal to or more than 140bit (S3: YES) and further is less than 220bit (S5-" NO), the transmission unit 1 assigns the set of the preliminary interrupt band 21 and preliminary band 22, or the reply band 24 to one of the two setting units that has larger remaining data volume, and assigns the inactive band 27 to the other of the two setting units that has smaller remaining data volume (S6). Then, if the difference between the remaining data volumes is equal to or more than 220bit (S5: YES), the transmission unit 1 assigns the set of the preliminary interrupt band 21 and preliminary band 22, the reply band 24, and the inactive band 27 to one of the two setting units that has larger remaining data volume, and assigns no superimposable band to the other of the two setting units that has smaller remaining data volume (S7).

[0092] According to the configuration as explained above, even when three or more setting units set the setting information simultaneously, each setting unit can transfer the setting information to the transmission unit 1, parallel to the other setting units. Accordingly, even when a plurality of setting units set the setting information simultaneously, in the transmission unit 1, the registration of the setting information is completed during the same period, and therefore, it is possible to shorten a period during which the consistency of the setting information is not kept in the whole of the communication system.

[0093] The other configurations and functions are the same as those of the First Embodiment.

[0094] Although the present invention has been described with reference to certain preferred embodiments, numerous modifications and variations can be made by those skilled in the art without departing from the true spirit and scope of this invention, namely claims.

CLAIMS

1. A communication system, comprising:

a transmission unit repeatedly transmitting a transmission signal to a communication line!
a terminal device communicating using the transmission signal; and

a superimposition module communicating using a superimposed signal superimposed on the transmission signal,

wherein the transmission unit, the terminal device and the superimposition module are connected to the communication line,

wherein the transmission signal is a signal according to a time-division system, in which each of a plurality of frames is divided into a plurality of bands in a direction of a time axis, the plurality of bands including a transmission band provided for transmitting data to the terminal device! and

a reply band being a time slot provided for receiving a reply signal from the terminal device,

wherein the superimposition module comprises a determining unit configured to determine, for each frame in the transmission signal, the presence or absence of the reply signal during a predetermined detection time period after a starting time point of the reply band, and

wherein the superimposition module is configured to assign the reply band in which the determining unit has determined that the reply signal is present, as an unsuperimposable band within which the superimposed signal is not allowed to be superimposed,

the superimposition module being configured to assign the reply band in which the determining unit has determined that the reply signal is absent, as a superimposable band within which the superimposed signal is allowed to be superimposed.

2. The communication system according to claim 1,

wherein the plurality of bands in the transmission signal further include an interrupt band provided for receiving an interrupt signal from the terminal device,

wherein the transmission unit is configured to assign, when receiving the interrupt signal in the interrupt band, next reply band to the terminal device that has generated the interrupt signal, and

wherein the superimposition module further comprises an interrupt generation unit configured to generate the interrupt signal in the interrupt band,

the superimposition module being configured to assign, when the interrupt generation unit has generated the interrupt signal, the entire region of said next reply band as the superimposable band without making the determining unit determine the presence or absence of the reply signal in said next reply band.

3. The communication system according to claim 1 or 2,

wherein the terminal device comprises a plurality of terminal devices,

each of which includes a controlled device that is controlled according to a control command,

the control command being transmitted, from the transmission unit, together with a unique identifier assigned to the controlled device being a controlled object, with the transmission signal,

wherein the transmission unit comprises a setting storage unit configured to store setting information that is information used when controlled devices are collectively controlled,

the setting information including at least a combination of identifiers of the controlled devices that are targets for the collective control,

wherein a setting device provided for setting the setting information is connected to the communication line, the setting device being configured to make the transmission unit execute writing the setting information to the setting storage unit, through transmitting the setting information to the transmission unit when the setting information is set, and

wherein the superimposition module is located at each of the transmission unit and the setting device, and is configured to transmit, with the superimposed signal, the setting information from the setting device to the transmission unit.

4. The communication system according to claim 3, wherein when receiving control request for the controlled devices and the setting information simultaneously, the transmission unit is configured to temporarily store the control request in a buffer memory and then transmit the control command based on the control request in the buffer memory after writing the setting information to the setting storage unit.

5. The communication system according to claim 3,

wherein the plurality of bands in the transmission signal further include bands capable of being assigned as the superimposable band, in addition to the reply band, and

wherein a part of the bands capable of being assigned as the superimposable band is a band for synchronization that is used for only synchronization of the setting information between superimposition modules, each of which is the superimposition module.

6. The communication system according to claim 3,

wherein the setting device is capable of communicating using the transmission signal, and comprises a plurality of setting devices,

wherein when two setting devices of the plurality of setting devices set the setting information simultaneously, one of the two setting devices is configured to transmit the setting information, with the transmission signal, and the other of the two setting devices is configured to transmit the setting information, with the superimposed signal.

7. The communication system according to claim 6,

wherein when the plurality of setting devices set, with the superimposed signal, the setting information simultaneously, different superimposable bands are sequentially assigned to the plurality of setting devices respectively.

8. A superimposition module, used for a communication system comprising:

a transmission unit repeatedly transmitting a transmission signal to a communication line,

a terminal device communicating using the transmission signal," and

the superimposition module communicating using a superimposed signal superimposed on the transmission signal,

wherein the transmission unit, the terminal device and the superimposition module are connected to the communication line,

wherein the transmission signal is a signal according to a time-division system, in which each of a plurality of frames is divided into a plurality of bands in a direction of a time axis, the plurality of bands including:

a transmission band provided for transmitting data to the terminal device! and

a reply band being a time slot provided for receiving a reply signal from the terminal device,

wherein the superimposition module comprises a determining unit configured to determine, for each frame in the transmission signal, the presence or absence of the reply signal during a predetermined detection time period after a starting time point of the reply band, and

wherein the super-imposition module is configured to assign the reply band in which the determining unit has determined that the reply signal is present, as an unsuperimposable band within which the superimposed signal is not allowed to be superimposed,

the superimposition module being configured to assign the reply band in which the determining unit has determined that the reply signal is absent, as a superimposable band within which the superimposed signal is allowed to be superimposed.

9. The superimposition module according to claim 8,

wherein the plurality of bands' in the transmission signal further include an interrupt band provided for receiving an interrupt signal from the terminal device,

wherein the transmission unit is configured to assign, when receiving the interrupt signal in the interrupt band, next reply band to the terminal device that has generated the interrupt signal, and

wherein the superimposition module further comprises an interrupt generation unit configured to generate the interrupt signal in the interrupt band,

the superimposition module being configured to assign, when the interrupt generation unit has generated the interrupt signal, the entire region of said next reply band as the superimposable band without making the determining unit determine the presence or absence of the reply signal in said next reply band.

10. The superimposition module according to claim 8 or 9, wherein the terminal device comprises a plurality of terminal devices, each of which includes a controlled device that is controlled according to a control command,

the control command being transmitted, from the transmission unit, together with a unique identifier assigned to the controlled device being a controlled object, with the transmission signal,

wherein the transmission unit comprises a setting storage unit configured to store setting information that is information used when controlled devices are collectively controlled,

the setting information including at least a combination of identifiers of the controlled devices that are targets for the collective control,

wherein a setting device provided for setting the setting information is connected to the communication line, the setting device being configured to make the transmission unit execute writing the setting information to the setting storage unit, through transmitting the setting information to the transmission unit when the setting information is set, and

wherein the superimposition module is located at each of the transmission unit and the setting device, and is configured to transmit, with the superimposed signal, the setting information from the setting device to the transmission unit.