Multiplex transmission system

Abstract: A multiplex transmission system is made up of a master load control unit which is connected to a multiplex transmission network and is capable of executing a multiplexing operation based on control specification information as a master system, slave load control units capables of the multiplexing operation as a slave system, and nonvolatile removable external storage means capable of reading the control specification information as required. Abnormalities associated with the multiplexing operation which arise in the multiplex transmission system are detected, and load control units in an abnormal condition can be restored to a normal condition by resetting.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a multiplex transmission system which processes control specification information relevant to control specifications of loads by multiplexing via a multiplex transmission system, and which is connected to load control units capable of controlling the loads respectively connected thereto. More particularly, the present invention relates to a vehicle multiplex transmission system which is connected to load control units capable of controlling the electric power fed to loads, that is, electrical equipment such as lamps or an air conditioner, aboard the vehicle. Related art Fig. 15 shows an example of a conventional multiplex transmission system of the above described type. Specifically, a multiplex transmission system 5 is made up of one single master load control unit 1, at least one slave load (two slave load control units 2 and 3 shown in Fig. 15), and a multiplex transmission network 4 connecting them together. The master load control unit 1 and the slave load control units 2, 3 are respectively provided with nonvolatile storage sections 1a, 2a, and 3a for holding control specification information. The nonvolatile storage sections 1a, 2a, and 3a of the master load control unit 1 and the slave load control units 2, 3 hold control specification information which are control specifications of loads 2b, 2c, 3b, and 3c in a multiplexed manner through the multiplex transmission network 4. Control status information or control specification information, which are held in the nonvolatile storage sections 1a, 2a, and 3a in a multiplexed manner, are updated by connecting, e.g., an external write terminal to the master load control unit 1, and by writing the control status information or control specification information to be updated into the nonvolatile storage section 1a of the master load control unit 1 from the external write terminal. The control specification information, that is, the control specifications of the loads 2b, 2c, 3b, and 3c, represent the types of loads 2b, 2c, 3b, and 3c (e.g., electrical equipment aboard the vehicle such as lamps and an air conditioner), and controlling methods (e.g., the accurate control of a flashing cycle of the lamps, illuminance of the lamps and lightening actions of a lamp synchronized with door openings, and the control of supply of electrical power such as ON/OFF operations of the air conditioner). The slave load control unit 2 selectively controls either the load (L3)3b or the load (L4)3c by switching between a selective switch (S1)6a and a selective switch (S2)6b, as required. Similarly, the slave load control unit 3 selectively controls either the load (L3)3b or the load (L4)3c by switching between a selective switch (S1)6a or a selective switch (S2)6b, as required. That is, the respective slave load control means 2 and 3, in accordance with the load control information that has been multiplexingly processed, are allowed to selectively control either of the loads (either L1 or L2) respectively connected to the means 2, and either of the loads (either L3 or L4) respectively connected to the means 3. In the multiplex transmission system 5 in normal operation, for example, the master load control unit 1 enters a transmission mode, and the control specification information or the control status information is transmitted during a predetermined period of time (i.e., in a period of "a" sec. in Fig. 16). Each slave load control unit enters a receiving mode during only a predetermined period of time (i.e., in a period of "a + α" sec. in Fig. 16) by use of a built-in timer. It then receives the control specification information or the control status information from the master load control unit, and the thus received information is held in the respective nonvolatile storage sections 2a and 3a. Subsequently, the slave load control unit 2 enters a transmission mode and transmits the control specification information or the control status information during a predetermined period of time (i.e., in a period of "b" sec. in Fig. 16). At this moment, the master load control unit 1 and the slave load control unit 3 enter a receiving mode during only a predetermined period of time (i.e., in a period of "b + α" sec. in Fig. 16) by use of their respective built-in timers. Then, they receive the control specification information or the control status information from the slave load control unit 2. The thus received information is held in the respective nonvolatile storage sections 1a and 3a. Similarly, the slave load control unit 3 enters a transmission mode and sends the control specification information or the control status information during a predetermined period of time (i.e., in a period of "c" sec. in Fig. 16). The master load control unit 1 and the slave load control unit 2 enter a receiving mode during only a predetermined period of time (i.e., in a period of "c + α" sec. in Fig. 16) using their respective built-in timers. Then, they receive the control specification information or the control status information from the slave load control unit 3. The thus received information is held in the respective nonvolatile storage sections 2a and 1a. According to a resetting method and a resetting apparatus used in such a conventional multiplex transmission system 5, the master load control unit 1 enters the transmission mode first to start initial-mode communication at the time of a restoring operation (e.g., a resetting operation) for restoring the system in an abnormal condition to a normal condition. As a result, the control specification information held in the master load control unit 1 is forcibly multiplexed with respect to other load control units (i.e., the slave load control units 2 and 3), and the thus multiplexed information is stored in the respective nonvolatile storage sections 2a and 3a. On the basis of the control specification information or the control status information forcibly multiplexed by the initial-mode communication executed when the system is restored from an abnormal condition to a normal condition (e.g., at the time of a resetting operation), the slave load control unit 2 controls the loads 2b and 2c connected thereto. Similarly, the slave load control unit 3 controls the loads 3b and 3c connected thereto on the basis of the control specification information or the control status information forcibly multiplexed by the initial-mode communication executed when the system is restored from an abnormal condition to a normal condition (e.g., at the time of a resetting operation). The abnormality arising in the multiplex transmission system signifies anomalous communication in a multiplex transmission network or faulty operations of the load control units due to the hit of the power supply. Problems to be Solved by the Invention However, in the above-mentioned conventional multiplex transmission system 5, if any of the respective pieces of load control information respectively held in the storage part 1a of the master load control means 1, the storage part 2a of the slave load control means 2 and the storage part 3a of the slave load control means 3 is multiplexingly processed under such a condition that it is updated in error due to noise or the like, or if the multiplexing processing is executed under such a condition that the load control information is transmitted in error due to noise or the like, there is a fear that the multiplex transmission system 5 fails to operate normally, which raises a problem as to the reliability of the multiplex transmission system 5. Also, in such abnormal operation condition of the multiplex transmission system, there is a fear that the required pieces of load control information (such as the kinds of the loads, the load controlling methods and the like) respectively consisting of the control contents of the loads can be updated in error due to noise or the like to thereby cause the wrong selection and control of the loads that are the objects to be controlled, which also raises a problem as to the reliability of the multiplexing transmission system 5. Further, because there is not provided simple means which, when the load control information of the master load control means 1 is updated, not only can urge the forced transfer of the updated load information to the respective slave load control means 2 and 3 but also allows the thus transferred load control information to be held by the respective storage parts 2a and 3a of the slave load control means 2 and 3, a procedure for updating the load control information is apt to be complicated, which raises a problem that the updating of the load control information cannot be transmitted to the slave load control means with accuracy. Further, if the control status information or the control specification information held in the nonvolatile storage sections 1a, 2a, and 3a is updated in such a conventional multiplex transmission system 5, an external write terminal, or the like, is connected to the master load control unit 1. The control status information or the control specification information to be updated is written into the master load control unit 1 from the external write terminal. This makes it difficult to quickly, accurately, and easily initialize the multiplex transmission system. Further, it is difficult to design a multiplex transmission system using new control specification information at a place located distant away from the multiplex transmission system. Hence, it is difficult to quickly, accurately, and easily update the multiplex transmission system. Further, according to the resetting method and the resetting apparatus used in the conventional multiplex transmission system 5, the master load control unit 1 enters the transmission mode first to start the initial-mode communication when the system is restored from an abnormal condition to a normal condition (e.g., at the time of a resetting operation). Then, the control specification information held in the master load control unit 1 is forcibly multiplexed with respect to other load control units (i.e., the slave load control units 2 and 3). As a result, the load control unit in normal operation is also forcibly subjected to the initial-mode communication carried out to restore the system from an abnormal condition to a normal condition (e.g., to reset the system). As described above, the load control unit being normally operating is also forcibly subjected to the initial-mode communication which uses the control specification information or the control status information of the master load control unit 1. As a result of this, normal load control and multiplexing operations being executed by the normal load control unit is interrupted. In other words, the control and multiplexing operations of the normally operating load are interrupted when the system is restored from an abnormal condition to a normal condition (e.g., at the time of a resetting operation), and the load control and multiplexing operations for the initial-mode communication are executed instead. It is difficult to resume the interrupted load control and multiplexing operations which require a high degree of reliability and accuracy). A similar multiplex transmission system as discussed above is disclosed in DE 43 40 048 A1 and its features common to the present invention are indicated in the precharacterizing part of claim 1. It is the object of the invention to improve such a prior art multiplex transmission system in order to carry out a majority processing on the load control information of the master load control means as well as the load control information of the slave load control means when any inconsistency between the pieces of load control information exists. This object is solved by the features as claimed in claim 1. Further developments of the invention are claimed in sub-claims 2 and 3. In accordance with the invention, the load control information held in the storage part of the master load control means is compared with the load control information respectively held in the storage parts of the slave load control information and, when the reset switch is not pressed down and also when there exists any inconsistency between these three pieces of load control information, a majority processing is performed on the load control information of the master load control means as well as on the load control information of the slave load control means and, in accordance with the results of the majority processing, the above-mentioned multiplexing processing can be executed. The above-mentioned multiplex processing is executed in accordance with the load control information that is included in the above-mentioned three pieces of load control information respectively held in the master load control means and the slave load control means, is consistent with any one or two of them and thus occupies a majority among them, and, when the load control information of the master load control means and the load control information of the slave load control means are all inconsistent with one another, the above-mentioned multiplexing processing can be carried out in accordance with the load control information of the master load control means. In the multiplex transmission system of the present invention, the storage part of the master load control means can be mounted and removed electrically and the reset switch can be used when said load control information of said master load control means is updated and/or when a storage part with said load control information updated is mounted. In short, it is possible to prevent the execution of the control and multiplexing operations of the loads on the basis of the initial-mode communication by interrupting the control and multiplexing operations of the normally operating loads when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Consequently, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads. As a result, it becomes possible to resume the interrupted load control and multiplexing operations which require a high degree of reliability and accuracy. Further, it becomes possible to realize the multiplex transmission system which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a function block diagram of a first embodiment of a multiplex transmission system according to the invention; Fig. 2 is a function block diagram of an embodiment of a multiplex transmission system according to the invention, including master load control means having a removable storage part; Fig. 3 is a time sequence diagram of a multiplexing processing and a majority processing to be performed on load control information employed in an embodiment of a multiplex transmission system according to the invention; Fig. 4 is a flow chart of a multiplexing processing and a majority processing to be performed on the load control information of master load control means employed in an embodiment of a multiplex transmission system according to the invention; Fig. 5 is a flow chart of a multiplexing processing and a majority processing to be performed on the load control information of one slave load control means employed in an embodiment of a multiplex transmission system according to the invention; Fig. 6 is a flow chart of a multiplexing processing and a majority processing to be performed on the load control information of the other slave load control means employed in an embodiment of a multiplex transmission system according to the invention; Fig. 7 is a functional block diagram showing a multiplex transmission system according to a second embodiment of the present invention and a resetting apparatus used together with the multiplex transmission system; Fig. 8A is a schematic representation showing a frame structure of a unit frame of control specification information or control status information according to one embodiment of the invention, and Figs. 8B to 8E are schematic representations showing the structure of data of a header in the frame structure; Fig. 9 is a flowchart which describes abnormal processing occurring in the master load control unit after a resetting operation according to the embodiment of the present invention; Fig. 10 is a flowchart which describes abnormal processing occurring in the slave load control units after the resetting operation according to the embodiment of the present invention; Fig. 11 is a time sequence diagram showing a multiplexing operation executed by the multiplex transmission system and the resetting apparatus during the initial-mode communication which is carried out in a normal condition according to the embodiment of the present invention; Fig. 12 is a time sequence diagram showing a multiplexing operation executed by the multiplex transmission system and the resetting apparatus during the initial-mode communication which is carried out in an abnormal condition according to the embodiment of the present invention; Fig. 13 is a time sequence diagram showing a multiplexing operation executed by the multiplex transmission system and the resetting apparatus during the normal-mode communication which is carried out in a normal mode according to the embodiment of the present invention; Fig. 14 is a time sequence diagram showing a multiplexing operation executed by the multiplex transmission system and the resetting apparatus during the normal-mode communication which is carried out in an abnormal condition according to the embodiment of the present invention; Fig. 15 is a block diagram showing an example of a conventional multiplex transmission system; and Fig. 16 is a time sequence diagram showing a multiplexing operation during an initial-mode communication in a normal condition and a multiplexing operation during the initial-mode communication in an abnormal condition which are executed by the conventional multiplex transmission system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, description will be given below of an embodiment of a multiplex transmission system according to the invention with reference to the accompanying drawings. First embodiment At first, Fig. 1 is a functional block diagram of a first embodiment of a multiplex transmission system 150 according to the invention, and Fig. 2 is a function block diagram of a first embodiment of a multiplex transmission system 150 according to the invention, when it includes master load control means 110 which can be mounted and removed. The multiplex transmission system 150 according to the present embodiment is a multiplex transmission system for use in a vehicle, which includes load control means connected thereto in such a manner that they are able to control the supply of power to electric devices carried on board the vehicle as loads such as lights, an air conditioner and the like. That is, as shown in Fig. 1 or 2, the present multiplex transmission system 150 includes load control means which not only can multiplexingly process several pieces of load control information respectively held by their respective storage parts 111, 121 and 131 through a multiplex transmission line 140 but also can control loads 122a, 122b, 132a, 132b respectively connected to the respective load control means in accordance with the load control information that has been multiplexingly processed. The load control means, as shown in Fig. 1 or 2, consists of a single piece of master load control means 110 and one or more pieces of slave load control means 120, 130. Each of the master load control means 110 and slave load control means 120, 130 includes therein a communication I/F circuit for transferring (that is, communicating multiplexingly) the load control information between them through the multiplex transmission line 140, an input I/F circuit to which are connected a plurality of switches and sensors (such as a temperature sensor and the like), an output I/F circuit to which are connected a plurality of loads such as lights, motors, an air conditioner and the like, a ROM (read-only memory) for storing previously determined programs (inclusive of communication protocol for multiplex transmission) and fixed data, a RAM (random access memory) used as a work area when executing a job determined by a control program, a non-volatile memory (in the present embodiment, an EEPROM is used) for recording and holding load control information, and a CPU for carrying out a multiplexing processing and a majority processing. Here, the output I/F circuit includes a diagnostic output which outputs a signal indicating that the load is out of order. A CPU, which is incorporated in the master load control means 110 according to the present embodiment, not only compares load control information held in the storage part (EEPROM) 111 of the master load control means 110 with load control information held in the storage parts (EEPROM) 121, 131 of the slave load control means 120, 130 but also, when the reset switch 112 is not pressed down and also when there exists any inconsistency between the above-mentioned three pieces of load control information, executes a ma jority processing on the respective pieces of load control information of the master load control means 110 and slave load control means 120, 130 and, in accordance with the results of the ma jority processing, carries out a multiplexing processing. Also, the CPU incorporated in the master load control means 110 not only performs a multiplexing processing in accordance with the load control information that is included in the three pieces of load control information respectively held in the master load control means 110 and slave load control means 120, 130, is consistent with any other piece of load control information and thus occupies a majority among them, but also, when the three pieces of load control information of the master load control means 110 and slave load control means 120, 130 are all inconsistent, carries out a multiplexing processing in accordance with the load control information of the master load control means 110. Similarly, CPUs respectively incorporated in the slave load control means 120, 130 according to the present embodiment not only assist the CPU of the master load control means 110 in the multiplexing processing and majority processing in synchronization with the CPU of the master load control means 110, but also individually carry out internal processings such as updating of the storage parts (EEPROMs) 121, 131 and the like within the slave load control means 120, 130. In the present embodiment, the multiplexing processing and majority processing are carried out mainly by the CPU of the master load control means 110, while the CPUs of the slave load control means 120, 130 are used as the assistants of the CPU of the master load control means 110. However, this is not limitative but other arrangements are also possible. For example, it is also possible to provide within the multiplex transmission line 150 a master CPU which can control all of the master load control means 110 and slave load control means 120, 130. That is, the master CPU may be used to play a main role in executing the multiplexing processing and majority processing, while the CPUs of the master load control means 10 and slave load control means 120, 30 may be respectively used as assistants to assist the master CPU in the multiplexing processing and majority processing thereof. In the storage part (EEPROM) 111 provided in the master load control means 110, there are written and held various pieces of load control information consisting of the control contents of switches and loads provided according to vehicle specifications. When assembling the multiplex transfer system, if the storage part (EEPROM) 111 is electrically mounted onto the master load control means 110, then a multiplexing processing is executable so that the load control information corresponding to the specifications (that is, the contents of the loads) of individual vehicles can be transferred to the slave load control means 120 and 130. Here, the load control information consisting of the control contents of the loads means the kinds of the loads, for example, electric devices carried on board the vehicle such as lights, an air conditioner and the like, and load controlling methods such as, a method for controlling the turn-on or turn-off cycles of the lights, a method for controlling the intensity of the turn-on illumination of the lights, a method for controlling the turn-on of the lights in linking with a vehicle door, a method for controlling the supply of electric power to the air conditioner for turning it on/off, and the like. In the present embodiment, alternatively, as shown in Fig. 2, instead of mounting the storage part 111 onto the master load control means 110, a non-volatile memory (for example, EEPROM) serving as the storage part 111 may be arranged in a mountable and removable form (for example, an IC card, an IC connector or the like) and, as the need arises, the non-volatile memory may be inserted into read means provided in the master load control means 110, so that a desired piece of load control information can be read into the master load control means 110. In the present embodiment, as the storage parts 111, 121 and 131, there are used the non-volatile memories. However, the invention is not limited to this but it is also possible to use other means, for example, magnetic recording means (such as a magnetic card, a magnetic disc, a bubble memory or the like), magneto-optic means (such as an MO disc or the like) and the like, provided that it is able to update, store and hold the load control information a given number of times as the need arises. The multiplex transmission line 140 employed in the present embodiment is a signal line through which information is transmitted and received and it is formed of a length of optical fiber cable. According to the present embodiment, as the multiplex transmission line 140, it is also possible to use a wire harness (WH) formed by bundling up a coaxial cable and a pair of twist wires. However, taking it account that the wire harness is greater in diameter and weight, the optical fiber cable is used. The reset switch 112 provided in the master load control means 110 is used not only to urge the forced transfer of the load control information held in the storage part (EEPROM) 111 of the master load control means 110 to the respective slave load control means 120 and 130 but also to allow the thus transferred load control information to be held by the respective storage parts (EEPROM) 121 and 131 of the slave load control means 120 and 130. Here, the forced transfer means that, when the reset switch 112 is pressed down and thus the reset condition is effective, taking priority over the majority processing and multiplexing processing or interrupting these processings temporarily, the load control information held in the storage part ( EEPROM) 111 of the master load control means 10 is transferred to the respective slave load control means 120 and 130. Also, the reset switch 112 employed in the present embodiment is further arranged such that, when external rewrite means is connected to the master load control means 110 and thus the load control information of the master load control means 110 is updated by the rewrite means, it urges the forced transfer of the updated load control information to the respective slave load control means 120 and 130 as well as allows the thus transferred load control information to be held by the respective storage parts (EEPROM) 121 and 131 of the slave load control means 120 and 130. In this case, the forced transfer means that, when the reset switch 112 is pressed down and thus the reset condition is effective, taking priority over the majority processing and multiplexing processing or interrupting these processings temporarily, the new load control information that has been updated and held in the storage part (EEPROM) 111 of the master load control means 110 is transferred to the respective slave load control means 120 and 130. Further, even when the storage part 111 of the master load control means 110 is arranged in the form of an IC card, an IC connector or the like that can be mounted and removed electrically, the reset switch 112 according to the present embodiment can be operated quite similarly to the above cases. That is, when the storage part 111 (such as an IC card, an IC connector or the like) with the load control information thereof updated is newly mounted, the reset switch 112 is used not only to urge the forced transfer of the updated load control information to the respective slave load control means 120 and 130 but also to allow the thus transferred load control information to be held by the respective storage parts (EEPROM) 121 and 131 of the slave load control means 120 and 130. In this case, the term "forced transfer" means that, when the reset switch 112 is pressed down and thus the reset condition is effective, taking priority over the majority processing and multiplexing processing or interrupting these processings temporarily, the new load control information that has been updated and held in the storage part (an IC card, an IC connector or the like) 111 of the master load control means 110 is transferred to the respective slave load control means 120 and 130. In the present embodiment, as shown in Figs. 1 and 2, as the reset switch 112, there can be used various types of switches including a mechanical switch (such as a push-button switch, a slide switch, a toggle switch or the like), an electronic switch (such as an electrostatic capacity detect type switch, an ohm resistance detect type switch or the like), and the like. Next, description will be given below of the operation of the present embodiment. Now, Fig. 3 is a time sequence diagram of the multiplexing processing and majority processing to be performed on the load control information in the multiplex transmission system 150 according to the present embodiment of the invention. Also, Fig. 4 is a flow chart of the multiplexing processing and majority processing on the load control information in the master load control means 110 of the multiplex transmission system 150 according to an embodiment of the present invention, Fig. 5 is a flow chart of the multiplexing processing and majority processing on the load control information in one slave load control means 120 of the multiplex transmission system 150 according to an embodiment of the present invention, and Fig. 6 is a flow chart of the multiplexing processing and majority processing on the load control information in the other slave load control means 130 of the multiplex transmission system 150 according to an embodiment of the present invention. The multiplex transmission system 150 according to the present embodiment includes a single master load control means 110 and at least one slave load control means 120, 130, while the present system 150 is able to perform multiplexing processings on three pieces of load control information respectively held in the storage part (EEPROM) 111 of the master load control means 10 and in the storage parts 121, 131 of the respective slave load control means 120, 130 through a multiplex transmission line (an optical fiber cable) 140. Further, the multiplex transmission system 150 according to the present embodiment not only can compare the load control information held in the storage part (EEPROM) 111 of the master load control means 110 with the two pieces of load control information respectively held in the storage parts (EEPROM) 121, 131 of the slave load control means 120, 130, but also can detect inconsistency between these three pieces of load control information to execute a majority processing on the load control information of the master load control means 110 as well as on the load control information of the respective slave load control means 120, 130 and, in accordance with the results of the majority processing, can carry out a multiplexing processing. In the multiplexing processing, between the single master load control means 110 and one or more slave load control means 120, 130, there is previously established priority in communication. The master load control means 110 is given the highest priority. Also, between the two slave load control means 120 and 130, priority is previously determined in a given order. The load control information, which consists of the control contents of the loads, means the kinds of the loads, for example, electric devices carried on board the vehicle such as lights, an air conditioner and the like, and the controlling methods including a method for controlling the on-off cycles of the lights, a method for controlling the intensity of the turn-on illumination and the turn-on of the lights in linking with a vehicle door, and a method for controlling the supply of power to the air conditioner for turning it on or off. Next, description will be given below of the operation of the multiplexing processing to be performed in the multiplex transmission system 150 according to the present embodiment by use of Figs. 3 to 6. In the multiplexing processing, between the single master load control means 110 and at least one slave load control means 120, 130, there is previously determined the order of communication, so called priority, of the respective load control means. The master load control means 110 is given the highest priority. Also, between the two slave load control means 120 and 130, priority is previously determined in a given order. The CPU mounted in the master load control means 110 according to the present embodiment, as shown in Figs. 3 and 4, after execution of initialization (Step S1-A), at first, transmits the load control information held in its own storage part (EEPROM) 11 (Step S2-A) and, after then, if it completes the transmission of its own load control information (Step S2-A), then it turns into an information reception wait state (Step S3-A). After then, if the CPU completes reception of the load control information held in the storage part 121 of the slave load control means 120, then it turns again into the information reception wait state (Step S4-A). And, if it completes reception of the load control information held in the storage part 131 of the slave load control means 130 (Step S4-A), then it turns into a next state, that is, a majority processing (Steps S5-A to S7-A) wait state. Also, if the majority processing (Steps S5-A to S7-A) is completed, then the CPU executes a normal processing (Step S8-A). Also, the CPU mounted in the slave load control means 120 according to the present embodiment, as shown in Figs. 3 and 5, after execution of initialization (Step S1-B), at first, turns into an information reception wait state (Step S2-B) and, if it completes reception of the load control information from the master load control means 110, then it starts transmission (Step S3-B). After then, if the transmission (Step S3-B) is completed, then the CPU turns again into the information reception wait state (Step S3-B) and, if it completes reception of the load control information from the slave load control means 130 (Step S4-B), then it turns into a next majority processing (Steps S5-B to S7-B) wait state. Also, if the majority processing (Steps S5-B to S7-B) is completed, then the CPU carries out a normal processing (Step S8-B). Similarly, the CPU mounted in the slave load control means 130, as shown in Figs. 3 and 6, after execution of initialization (Step S1-C), at first, turns into an information reception wait state (Step S2-C) and, if it completes reception of the load control information from the master load control means 10, then it turns again into the information reception wait state (Step 53-C). After then, if the CPU completes reception of the load control information from the slave load control means 120, then it starts transmission (Step S4-C) and, if the transmission (Step S4-C) is completed, then it turns into a next majority processing (Steps S5-C to S7-C) wait state. Also, if the majority processing (Steps S5-C to S7-C) is completed, then the CPU executes a normal processing (Step S8-C). The CPU, which is mounted in the master load control means 110 according to the present embodiment, not only compares the load control information held in the storage part (EEPROM) 111 of the master load control means 110 with the respective pieces of load control information respectively held in the storage parts (EEPROM) 121 and 131 of the slave load control means 120 and 130 but also, when the reset switch 112 is pressed down and also when there exists any inconsistency between the above-mentioned three pieces of load control information, executes a majority processing on the load control information of the master load control means 110 as well as on the load control information of the respective slave load control means 120 and 130 and, in accordance with the results of the majority processing, carries out a multiplexing processing. Also, the CPUs respectively mounted in the slave load control means 120 and 130 according to the present embodiment, in synchronization with the CPU of the master load control means 110, respectively assist the CPU of the master load control means 110 in the multiplexing processing and majority processing that are carried out mainly by the CPU of the master load control means 110 and, at the same time, they individually carry out their respective internal processings such as updating of the storage parts (EEPROM) 121 and 131 in the slave load control means 120 and 130. Due to this, the CPUs respectively mounted in the slave load control means 120 and 130 are respectively able to control the load 122a or 122b and the load 132a or 132b respectively connected to the slave load control means 120 and 130, in accordance with the load control information that has been multiplexingly processed. Next, description will be given below of the operation of the reset switch 112 provided in the master load control means 110. If the reset switch 112 provided in the master load control means 10 shown in Fig. 1 or 2 is pressed down, then the CPU mounted in the master load control means 110 according to the present embodiment not only can urge the forced transfer of the load control information held in the storage part (EEPROM) 111 of the master load control means 110 to the respective slave load control means 120 and 130 but also allows the thus transferred load control information to be held by the respective storage parts 121 and 131 of the slave load control means 120 and 130. If the forced transfer is executed, then taking priority over the majority processing and multiplexing processing or interrupting these processings provisionally, the load control information held in the storage part (EEPROM) 111 of the master load control means 110 is transferred to the respective slave load control means 120 and 130. Also, when the load control information held in the storage part (EEPROM) 111 of the master load control means 110 is updated, if the reset switch 112 is depressed, then the CPU mounted in the master load control means according to the present embodiment not only can urge the forced transfer of the updated load control information to the respective slave load control means 120 and 130 but also allows the thus transferred load control information to be held by the respective storage parts 121 and 131 of the slave load control means 120 and 130. If the forced transfer is executed, then taking priority over the majority processing and multiplexing processing or interrupting these processings provisionally, new load control information updated and held in the storage part (EEPROM) 111 of the master load control means 110 is transferred to the respective slave load control means 120 and 130. Thanks to this, it is possible to realize a multiplex transmission system 150 which can transmit the updating of the load control information of the master load control means 110 to the respective slave load control means 120 and 130 with accuracy. That is, according to the present multiplex transmission system 150, electric devices carried on board the vehicle such as lights, an air conditioner and the like can be controlled accurately. In particular, the on-off cycles of the lights, the intensity of the turn-on illumination of the lights and the turn-on of the lights in linking with a vehicle door can be controlled accurately. Also, the supply of power to the air conditioner for turning it on or off can be controlled accurately. Next, description will be given below of the operation of the reset switch 112 when an electrically mountable and removable storage part 111 is used. If an IC card or an IC connector incorporating an EEPROM or the like therein is used as the storage part 111 of the master load control means 110, the storage part 111 can be mounted and removed electrically. When the electrically mountable and removable storage part 111 (such as an IC card, an IC connector or the like) is employed, if the reset switch 112 is pressed down when a storage part 111 with the load control information thereof updated is newly mounted, then the CPU mounted in the master load control means 110 according to the present embodiment not only can urge the forced transfer of the updated load control information to the respective slave load control means 120 and 130 but also permits the thus transferred load control information to be held by the respective storage parts 121 and 131 of the slave load control means 120 and 130. If the forced transfer is executed, then taking priority over the majority processing and multiplexing processing or interrupting these proceesings temporarily, the new load control information updated and held in the storage part (an IC card, an IC connector or the like) 111 of the master load control means 110 is transferred to the respective slave load control means 120 and 130. This facilitates the updating of the load control information, which makes it possible to realize a multiplex transmission system 150 which, when a new storage part 111 with the load control information updated is mounted electrically, is able to transmit the updating of the load control information of the master load control means 110 to the respective slave load control means 120 and 130 accurately. Therefore, according to the present multiplex transmission system 150, electric devices carried on board the vehicle such as lights, an air conditioner and the like can be controlled accurately. In particular, the on-off cycles of the lights, the intensity of the turn-on illumination of the lights and the turn-on of the lights in linking with a vehicle door can be controlled accurately. Also, the supply of power to the air conditioner for turning it on or off can be controlled accurately. Next, description will be given below of the operation of the majority processing to be performed in the multiplex transmission system 150. In Figs. 4 to 6, reference character A designates the load control information that is held in the storage part (EEPROM) 111 of the master load control means 110, B stands for the load control information held in the storage part 121 of the slave load control means 120, C expresses the load control information held in the storage part 131 of the slave load control means 130, and S3 represents the reset switch 112. At first, description will be given below of the operation of the majority processing to be executed in the master load control means 110. The CPU mounted in the master load control means 110 according to the present embodiment, as shown in Fig. 4, not only compares the load control information A that has been multiplexingly processed (Steps S2-A to Steps S4-A), the load control information B and the load control information C (Step S5-A) but also, when the reset switch 112 is not depressed (in Step S6-A, off) and also when there exists any inconsistency between these three pieces of load control information, carries out a majority processing on the load control information A of the master load control means 110 as well as the load control information B and C of the slave load control means 120 and 130, when A ≠ B = C as the result of the majority processing, rewrites the load control information A of the master load control means 110 into the load control information B of the slave load control means 120, and then executes a normal processing (Step SB-A) in accordance with the rewritten load control information. When the reset switch 112 is depressed (in Step S6-A, on) or when any of (A=B=C, A≠B≠C, A=B≠C, or A=C≠B) holds good, the data are not rewritten but the normal processing (Step S8-A) is executed. Next, description will be given below of the operation of the majority processing to be executed in the slave load control means 120. The CPU mounted in the slave load control means 120 according to the present embodiment, as shown in Fig. 5, not only compares the load control information A that has been multiplexing processed (Step S2-B to Step S4-B) with the two pieces of load control information B and C (Step S5-B) but also, when A=B=C or A=B≠C holds good in Step S5-B, or when the reset switch 112 is not depressed (in Step S6-B, off), the data are not rewritten but a normal processing (Step S8-B) is carried out. When A=C≠B or A≠B≠C holds good in Step S5-B, then the load control information B is rewritten into the load control information A (Step S7-B) and, after then, the normal processing (Step S8-A) is performed. Also, when A≠B=C holds good in Step S5-B and the reset switch 112 is pressed down (in Step S6-B, on), then the load control information B is rewritten into the load control information A (Step S7-B) and, after then, the normal processing (Step S8-A) is executed. Next, description will be given below of the operation of the majority processing to be executed in the slave load control means 130. The CPU mounted in the slave load control means 130 according to the present embodiment, as shown in Fig. 6, not only compares the load control information A that has been multiplexing processed (Step S2-C to Step S4-C) with the two pieces of load control information B and C (Step S5-C) but also, when A=B=C or A=C≠B holds good in Step S5-C, or when the reset switch 112 is not depressed (in Step S6-C, off), the data are not rewritten but a normal processing (Step S8-C) is carried out. When A=B≠C or A≠B≠C holds good in Step S5-C, then the load control information C is rewritten into the load control information A (Step S7-C) and, after then, a normal processing (Step S8-C) is executed. Also, when A≠C=B holds good in Step S5-C and the reset switch 112 is depressed (in Step S6-C, on), the load control information C is rewritten into the load control information A (Step S7-C) and, after then, a normal processing (Step S8-C) is carried out. Due to this, when a new storage part 111 with the load control information thereof updated is mounted electrically, the updating of the load control information of the master load control means 110 can be transmitted to the respective slave load control means 120 and 130 accurately and also it is possible to realize a multiplex transmission system 150 which can carry out a highly reliable multiplexing processing. In other words, according to the present multiplex transmission system 150, electric devices carried on board the vehicle such as lights, an air conditioner and the like can be controlled accurately. In particular, the on-off cycles of the lights, the intensity of the turn-on illumination of the lights and the turn-on of the lights in linking with a vehicle door can be controlled accurately. Also, the supply of power to the air conditioner for turning it on or off can be controlled accurately. Also, when the electrically mountable and removable storage part 111 (such as an IC card, an IC connector or the like) is employed, if the reset switch 112 is pressed down when a storage part 111 with the load control information thereof updated is newly mounted, then the CPU mounted in the master load control means 110 according to the present embodiment not only can urge the forced transfer of the updated load control information to the respective slave load control means 120 and 130 but also permits the thus transferred load control information to be held by the respective storage parts 121 and 131 of the slave load control means 120 and 130. This prevents the newly updated load control information of the master load control means 110 from being multiplexingly processed in accordance with the two pieces of load control information of the slave load control means 120 and 130 that are consistent with each other and occupy a majority in the three pieces of the load control information, while the forced transfer of the updated load control information to the respective slave load control means 120 and 130 can be urged, thereby being able to realize a multiplex transmission system 150 which can carry out a highly reliable multiplexing processing. That is, according to the present multiplex transmission system 150, electric devices carried on board the vehicle such as lights, an air conditioner and the like can be controlled accurately. In particular, the on-off cycles of the lights, the intensity of the turn-on illumination of the lights and the turn-on of the lights in linking with a vehicle door can be controlled accurately. Also, the supply of power to the air conditioner for turning it on or off can be controlled accurately. Second embodiment Fig. 7 is a functional block diagram showing a multiplex transmission system (50) according to second embodiment of the present invention and a resetting apparatus (60) used together with the multiplex transmission system. Fig. 8A shows a frame structure (43) of a unit frame (44) of control specification information (42) or control status information (41) according to second embodiment of the invention. Figs. 8B to 8E show the structure of data of a header (45) in the frame structure (43). To begin with, the multiplex transmission system (50) according to the embodiment of the present invention will be described. As shown in Fig. 7, the multiplex transmission system (50) according to one embodiment of the present invention comprises a removable external storage means (11), a multiplex transmission network (40), and a plurality of load control units (51, ..., 51) connected to the multiplex transmission network (40). The multiplex transmission network (40) of the present embodiment is a signal line for exchanging information, and the signal line is made up of one optical fiber cable. A coaxial cable or a wire harness which is made by tying twisted pair lines in a bundle may also be used as the multiplex transmission network (40) of the present embodiment. However, the optical fiber cable is used in the embodiment in order to prevent an increase in size and weight of the network. The removable external storage means (11) can update and hold the control specification information (42), as required. The removable external storage means (11) is electrically removable with respect to the master load control unit (10), and is nonvolatile storage means capable of reading the control specification information (42) while it is attached to the master load control unit. The removable storage means (EEPROM) (11) holds the control specification information (42) relevant to control specification of switches (S1 and S2) and loads (L1, L2, L3, and L4) corresponding to vehicle specifications. The external storage means (11) can update and hold the control specification information (42), as necessary. Further, the external storage means (11) is electrically removable with respect to the master load control unit (10) and is capable of reading the control specification information (42), as necessary, while it is attached to the master load control unit. The control specification information (42) relevant to the control specifications of the loads signifies the type of load, e.g. , electrical equipment aboard a vehicle such as lamps and an air conditioner, a controlling method, e.g., control related to a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, and the control of the electrical power supply such as ON/OFF operations of the air conditioner. The term "electrical attachment" used herein signifies the state in which signals can be processed via metal electrode connectors of the reading means. However, attachment is not particularly limited to this meaning, and various connecting methods, such as a connecting method which uses applications of an electromagnetic force (e.g., radiowaves or electrostatic induction), or optical connecting techniques which use applications of infrared rays or visible rays, may be also used to realize attachment. Nonvolatile memory (e.g., EEPROM) used as the removable external storage means (11) is made in a removable form (e.g., an IC card or IC connector), and it is inserted into reading means disposed in the master load control unit (10), as required. As a result, it becomes possible for the master load control unit (10) to read desired control specification information (42). Although nonvolatile memory is used as the removable external storage means (11), the removable external storage means is not particularly limited to the nonvolatile memory. Magnetic storage means (e.g., a magnetic card, a magnetic disk, and bubble memory) or magneto-optical means (e.g., an MO disk) may also used as the removable external storage means so long as it is externally removable and is capable of updating and holding the control specification information (42) a predetermined number of times, as required. The load control units (51, ..., 51) multiplex the control specification information (42) relevant to control specifications of the loads (22a, 22b, 32a, and 32b) or the control status information (41) relevant to the results of control of the loads (22a, 22b, 32a, and 32b) through the multiplex transmission network (40) which is an information communications network. Based on the thus multiplexed control specification information (42), the load control units can control the loads (22a, 22b, 32a, and 32b) respectively connected thereto. A plurality of load control units are connected to the multiplex transmission network (40). The load control units (51, ..., 51) comprise the single master load control unit (10) and at least one slave load control unit (20, 30). The single master load control unit (10) is connected to the multiplex transmission network (40) and is made up of one of the load control units (51,..., 51) capable of executing a multiplexing operation based on the control specification information (42) as the master system. The slave load control units (20, 30) hold the control specification information (42) and is connected to the multiplex transmission network (40). The slave load control units (20, 30) are made up of the load control units (51,...51) capable of carrying out the multiplexing operation as a slave system. Next, the configuration of the master load control unit (10) of the present embodiment will be described. As illustrated in Fig. 7, the master load control unit (10) is provided with nonvolatile storage sections (21, 31) which are capable of updating, holding, and reading the control status information (41) relevant to the master load control unit, as necessary. The master load control unit (10) made up of one of the load control units (51, ..., 51) divides the control specification information (42), which is acquired from the removable external storage means (11) during the course of the initial-mode communication (45a-2), into a predetermined number of unit frames (44), as shown in Fig. 7. When sequentially multiplexing the thus divided unit frames (44) with respect to the slave load control units (20, 30), the master load control unit (10) is capable of multiplexing the unit frame in synchronism with an acknowledgement ACK (46) which is sent from the slave load control units (20, 30) upon successful receipt of the unit frame (44). Thus, the master load control unit (10) is connected to the multiplex transmission network (40) so as to be able to effect the above described operations. As shown in Fig. 8 (a) to (e), in the case where the master load control unit (10) executes a multiplexing operation during the course of the initial-mode communication (45a-2), each of the slave load control uni ts (20, 30) sends the acknowledgement ACK (46) to the master load control unit (10) upon successful receipt of the unit frame (44) of the control specification information (42) from the master load control unit. The master load control unit (10) is connected to the multiplex transmission network (40) so as to be possible to resend the unit frame (44) once transmitted until it receives the acknowledgement ACK (46). Further, the master load control unit (10) sequentially sends new unit frames (44) subsequent to the currently sent unit frame (44) upon receipt of the acknowledgement ACK (46). The master load control unit is connected to the multiplex transmission network (40) so as to be able to effect the above described operations. The master load control unit (10) of the present embodiment comprises a communications I/F circuit for transferring the control specification information (42) among units (i.e., for exchanging the information between the units through multiplex communication); an input I/F circuit connected to a plurality of switches, i.e., S1 and S2; ROM (read only memory) for holding predetermined control programs (including a communications protocol for multiplex transmission) and fixed data; a temporary storage section (RAM) (14) which is programmable read memory used as a work area in which the control specification information (42) is expanded when a job defined by the control program is executed; a metal electrode connector which is electrically connected to the removable external storage means (11) and reads the control specification information (42) held therein; a built-in timer used to execute a multiplexing operation in the event of abnormalities arising in the communication mode; and an MPU for executing the multiplexing operation. The output I/F circuit is provided with a diagnostic output from which signals representing problems in the loads are output. In the case where the control specification information (42) held in the removable external storage means (11) is read by electrically attaching the removable external storage means (EEPROM) (11) to the master load control unit (10), the MPU implemented in the master load control unit (10) of the embodiment reads the control specification information (42) retained in the removable external storage means (11). If collation between the thus read control specification information items (42) arises several times, the MPU acquires the control specification information items (42) which match with each other, as well as executing a multiplexing operation based on the thus acquired control specification information (42) with respect to the slave load control units (20, 30). The MPU implemented in the master load control unit (10) of the present embodiment di vides the thus acquired control specification information (42) into a predetermined number of unit frames (44). When carrying out a multiplexing operation for each unit frame (44), the MPU sequentially carries out multiplexing operation for each unit frame (44) between the MPU and the load control units (20, 30) in synchronism with the signal of the acknowledgement ACK 46 which is generated by the slave load control units (20, 30) upon successful receipt of the unit frame (44). Further, the MPU implemented in the master load control unit (10) of the present embodiment collates the checksum information of the control specification information (42), sent from the master load control unit and a verification ACK (48) received from each of the slave load control units (20, 30). If there is collation between them, the multiplexing of the control specification information (42) is completed, and the communication shifts to normal-mode communication. On the other hand, if no collation arises between them, the multiplexing operation for each unit frame (44) on the basis of the control specification information (42) can be executed again. The configuration of the slave load control units (20, 30) of the present embodiment will now be described. At least one slave load control unit (the two slave load control units 20 and 30 in the present embodiment) is capable of controlling the electrical power supply fed to electrical equipment such as lamps and an air conditioner disposed as loads in a vehicle. The slave load control units are connected to the multiplex transmission network (40) and are provided with the nonvolatile storage sections (21, 31) for holding the control specification information (42), respectively. The slave load control units are capable of executing a multiplexing operation, as slave units, with respect to the master load control unit (10) through the multiplex transmission network (40). The slave load control units (20, 30), which are respectively made up of the load control units (51, ... 51), respectively generate the verification ACK (48) which is checksum information with respect to the control specification information (42) received from the master load control unit (10). The slave load control units also collate the verification ACK (48) and the confirmation ACK (48) received from the master load control unit (10). If no collation arises between these verification ACK (48) codes, the multiplexing processing is executed again for each unit frame (44) on the basis of the control specification information (42) of the master load control unit (10). If there is collation between the verification ACK (48) codes, the slave load control units further collate the control specification information (42) held in the nonvolatile storage sections (21, 31) of the slave load control units (20, 30) and the control specification information (42) received from the master load control unit (10). If no collation arises between these control specification information items (42), the contents of the storage sections of the slave load control units (20, 30) are updated so as to be replaced with the control specification information (42) received from the master load control unit (10), and the multiplexing operation in the initial-mode communication (45a-2) is completed. The communication then shifts to the normal-mode communication (45a-1). The slave load control units are connected to the multiplex communication network (40) so as to effect the above described operations. Each of the slave load control units (20, 30) comprises a communications I/F circuit for transferring the control specification information (42) among units (i.e., for exchanging the information between the units through multiplex communication); an input I/F circuit connected to a plurality of sensors (e.g., temperature sensors); an output I/F circuit connected to a plurality of loads (L1 or L2), (L3 or L4) such as lamps, motors, and an air conditioner; ROM (read only memory) for holding predetermined control programs (including a communications protocol for multiplex transmission) and fixed data; a temporary storage section (RAM) (24, 34) which is programmable read memory used as a work area in which the control specification information (42) is expanded when a job defined by the control program is executed; nonvolatile memory (EEPROM is used in the present embodiment) which serves as the nonvolatile storage section (21, 31) for recording the control specification information (42); a built-in timer used to execute a multiplexing operation in the event of abnormalities arising in the communication mode; and an MPU for executing the multiplexing operation. Nonvolatile memory is used as the nonvolatile storage sections (21, 31) in the present embodiment. However, the nonvolatile storage sections are not limited to the nonvolatile memory. Magnetic storage means (e.g., a magnetic card, a magnetic disk, and bubble memory) or magneto-optical means (e.g., an MO disk) may also used as the nonvolatile storage sections so long as it is externally removable and is capable of updating and holding the control specification information (42) a predetermined number of times, as necessary. The MPU implemented in each of the slave load control units (20, 30) of the present embodiment calculates checksum information with respect to the control specification information (42) which is sent from the master load control unit (10) while being divided into the unit frames (44). The MPU also executes the multiplexing operation so as to send the thus calculated checksum information to the master load control unit (10) as the verification ACK (48). The MPU implemented in each of the slave load control units (20, 30) executes the multiplexing operation, which the MPU of the master load control unit (10) executes as the master system, in synchronism with the MPU of the master load control unit (10) as a slave system. The MPUs also individually execute internal processing of the nonvolatile storage sections (EEPROM) 21 and 31 in the slave load control units (20, 30), such as the updating of the storage sections. The MPU implemented in each of the slave load control units (20, 30) generates the verification ACK (48) which is the checksum information with respect to the control specification information (42) received from the master load control unit (10). The MPU collates the verification ACK (48) and the confirmation ACK (48) received from the master load control unit (10). If no collation arises between these verification ACK (48) codes, the multiplexing operation is executed again for each unit frame (44) on the basis of the control specification information (42) of the master load control unit (10). If there is collation between the verification ACK (48) codes, the MPUs further collate the control specification information (42) held in the nonvolatile storage sections (21, 31) of the slave load control units (20, 30) and the control specification information (42) received from the master load control unit (10). If no collation arises between these control specification information items (42), the contents of the nonvolatile storage sections (21, 31) of the slave load control units (20, 30) are updated so as to be replaced with the control specification information (42) received from the master load control unit (10), and the multiplexing operation of the control specification information (42) is completed. The communication then shifts to the normal-mode communication. The configuration of the frame structure (43) of the unit frame (44) of the present embodiment will now be described. The control specification information (42) or the control status information (41) is transmitted on a unit frame basis. Such a unit frame (44) is divided into a predetermined number of subdivisions, as shown in Fig. 8 (a) to (e), and is transmitted (i.e., multiplexed) through the multiplex transmission network (40). The frame structure (43) of the unit frame (44) comprises a header (45) in which a communications protocol used for executing a multiplexing operation through the multiplex transmission system (40) is described, and a data sequence (44a) in which the contents of the control specification information (42) or the control status information (41) are described. The frame structure may be provided with BCC (Block Checksum Character) which signifies the checksum of the transmitted/received unit frame, as shown in Fig. 8 (a) to (e). The configuration of the header (45) of the unit frame (44) of the present embodiment will now be described. The header (45) comprises the communication mode information (45a), the recognition information (45b), and the frame type information (45c), as shown in Fig. 8 (a) to (e). The header (45) of the present embodiment is 8 bits long and comprises communication mode information (45a), (B7), recognition code information (45b), (B6, B5), frame type information (45c), (B4), and frame numbers (B3 - B0). The communication mode information (45a) is described by the subject of communication when it carries out the initial-mode communication (45a-2) signifying the execution of the multiplexing of the control specification information (42) held in the removable external storage means (11) or the normal-mode communication (45a-1) signifying the execution of the multiplexing of the control status information (41). The recognition code information (45b) is described by one of the load control units (51, ..., 51) when it sends the control specification information (42) or the control status information (41) while it is divided into the unit frames (44). The recognition code information describes whether the sender is the master load control unit (10) or one of the slave load control units (20, 30). The frame type information (45c) shows whether the unit frame (44) to be sent is an ACK frame (45c-1), signifying the unit frame (44) of the control specification information (42) multiplexed in the environment in which the initial-mode communication (45a-2) is executed, or a normal frame (45c-2) signifying the unit frame (44) of the control status information (41) multiplexed in the environment in which the normal-mode communication (45a-1) is executed. The configuration of the resetting apparatus (60) of the present embodiment will be described. Abnormalities used herein signify communication failures in the multiplex transmission network (40) or operation failures of the load control units (51, ... 51) due to the hit of the electrical power source. According to a resetting method for use in the resetting apparatus (60) capable of detecting abnormalities associated with the multiplexing operation carried out in the multiplex transmission system (50) as well as resetting the load control units (51,...,51) so as to restore them from an abnormal condition to a normal condition, if the master load control unit (10) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the normal-mode communication (45a-1) is described in the communication mode information (45a), the master load control unit (10) is restored to a normal condition by executing the multiplexing operation with respect to the master load control unit (10) by use of the control status information (41) held in the slave load control unit (20 or 30) which is normally executing the normal-mode communication. On the other hand, if the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the normal-mode communication (45a-1) is described in the communication mode information (45a), the slave load control unit (20 or 30) is restored to a normal condition by executing the multiplexing operation with respect to the abnormal slave load control unit (20 or 30) by use of the control status information (41) held in the other slave load control unit (30 or 20) or the master load control unit (10) which is normally executing the normal-mode communication (45a-1). Further, if the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the initial-mode communication (45a-2) is described in the communication mode information (45a), the slave load control unit (20 or 30) is restored to a normal condition by executing the multiplexing operation with respect to the abnormal slave load control unit (20 or 30) by use of the control specification information (42) held in the master load control unit (10). As shown in Fig. 7, the resetting apparatus (60) of the present embodiment is provided with abnormality detecting means (62) and recovery control means (64) so as to cope with the following situations. If the master load control unit (10) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if abnormal load control unit information (62a) is generated based on the fact that the normal-mode communication (45a-1) is described in the communication mode information (45a), recovery control means (64) restores the master load control unit (10) to a normal condition by executing a multiplexing operation with respect to the master load control unit (10), using the control status information (41) held in the slave load control unit (20 or 30) which is normally executing the normal-mode communication (45a-1). On the other hand, if the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the abnormal load control unit information (62a) is generated based on the fact that the normal-mode communication (45a-1) is described in the communication mode information (45a), the recovery control means (64) restores the slave load control unit (20 or 30) to a normal condition by executing a multiplexing operation with respect to the slave load control unit (20 or 30), using the control status information (41) held in the other slave load control unit (30 or 20) or the master load control unit (10) which is normally executing the normal-mode communication (45a-1). Further, if the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the abnormal load control unit information (62a) is generated based on the fact that the initial-mode communication (45a-2) is described in the communication mode information (45a), the recovery control means (64) restores the slave load control unit (20 or 30) to a normal condition by executing a multiplexing operation with respect to the slave load control unit (20 or 30), using the control specification information (42) held in the master load control unit (10). More specifically, the configuration of the resetting apparatus (60) of the present embodiment will be described. The abnormality detecting means (62) is connected to the recovery control means (64) and the multiplex transmission network (40), as shown in Fig. 7. With this arrangement, the abnormality detecting means (62) detects an abnormal multiplexing operation arising in the load control units (51, ... 51) which carry out the multiplex operation on the multiplex transmission network (40). Further, the abnormality detecting means (62) generates the abnormal load control unit information (62a) on the basis of the recognition code described in the header (45) by specifying the abnormal load control unit from the load control units (51,..., 51). The recovery control means (64) is connected to the abnormality detecting means (62) and the multiplex transmission network (40), as shown in Fig. 7. With this arrangement, the recovery control means (64) selects either the initial-mode communication (45a-1) or the normal-mode communication (45a-1) as a restoring operation to be executed according to the abnormal load control unit information (62a). The recovery control means (64) describes the communication mode information (45a) in the header (45) when executing the thus selected restoring operation. Further, the recovery control means (64) restores the load control unit of the load control units (51, ... 51) which caused the abnormal multiplexing operation by executing the selected restoring operation with respect to that load control unit on the basis of the abnormal load control unit information (62a) and the communication mode information (45a). Still more specifically, the configurations of the recovery control means (64) and the abnormality detecting means (62) of the present embodiment will be described. Each of the recovery control means (64) and the abnormality detecting means (62) of the present embodiment comprises a communications I/F circuit for transferring the control specification information (42) among units (i.e., for exchanging the information between the units through multiplex communication); ROM (read only memory) for holding control programs relevant to a predetermined restoring operation (including a communications protocol for multiplex transmission) and fixed data; a temporary storage section (RAM) which is programmable read memory used as a work area in which the control specification information (42) or the control status information (41) is expanded when a job defined by the control program is executed; a built-in timer used to execute the restoring operation in the event of abnormalities arising in the communication mode; and an MPU for executing the restoring operation. The MPUs implemented in the recovery control means (64) and the abnormality detecting means (62) of the present embodiment can collectively carry out the resetting method for use in the resetting apparatus (60) capable of detecting abnormalities associated with the multiplexing operation carried out in the multiplex transmission system (50) as well as resetting the load control units (51,...,51) so as to restore them from an abnormal condition to a normal condition. The MPUs are connected to the slave load control units (20, 30) and the master load control unit (10) through the multiplex transmission network (40) so as to make it possible to monitor the multiplexing operation for each unit frame (44) in synchronism with the acknowledgement ACX (46) which are generated by the slave load control units (20, 30) upon successful receipt of the unit frame (44), when the multiplexing operation is executed for each unit frame (44). The MPUs are also capable of monitoring the following operations. The checksum information of the control specification information (42) sent by the MPUs and the verification ACK (48) received from the slave load control units (20, 30) are collated with each other. If there is collation between them, the multiplexing of the control specification information (42) is completed, and the communication shifts to the normal-mode communication. If no collation arises between them, the multiplexing operation is executed again for each unit frame (44) on the basis of the control specification information (42). The MPUs implemented in the recovery control means (64) and the abnormality detecting means (62) restore the load control unit from an abnormal condition to a normal condition in the following manner: [1] If the master load control unit (10) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the normal-mode communication (45a-1) is described in the communication mode information (45a), the master load control unit (10) is restored to a normal condition by executing the multiplexing operation with respect to the master load control unit (10) by use of the control status information (41) held in the slave load control unit (20 or 30) which is normally executing the normal-mode communication. [2] If the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the normal-mode communication (45a-1) is described in the communication mode information (45a), the slave load control unit (20 or 30) is restored to a normal condition by executing the multiplexing operation with respect to the abnormal slave load control unit (20 or 30) by use of the control status information (41) held in the other slave load control unit (30 or 20) or the master load control unit (10) which is normally executing the normal-mode communication (45a-1). [3] If the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the initial-mode communication (45a-2) is described in the communication mode information (45a), the slave load control unit (20 or 30) is restored to a normal condition by executing the multiplexing operation with respect to the abnormal slave load control unit (20 or 30) by use of the control specification information (42) held in the master load control unit (10). The operation of the embodiment of the present invention will be described. Fig. 9 is a flowchart which describes abnormal processing occurring in the master load control unit (10) after a resetting operation according to the embodiment of the present invention. Fig. 10 is a flowchart which describes abnormal processing occurring in the slave load control units (20, 30) after the resetting operation according to the embodiment of the present invention. Fig. 11 is a time sequence diagram showing a multiplexing operation executed by the multiplex transmission system (50) and the resetting apparatus (60) during the initial-mode communication (45a-2) which is carried out in a normal condition according to the embodiment of the present invention. Fig. 12 is a time sequence diagram showing a multiplexing operation executed by the multiplex transmission system (50) and the resetting apparatus (60) during the initial-mode communication (45a-2) which is carried out in an abnormal condition according to the embodiment of the present invention. Fig. 13 is a time sequence diagram showing a multiplexing operation executed by the multiplex transmission system (50) and the resetting apparatus (60) during the normal-mode communication (45a-1) which is carried out in a normal mode according to the embodiment of the present invention. Fig. 14 is a time sequence diagram showing a multiplexing operation executed by the multiplex transmission system (50) and the resetting apparatus (60) during the normal-mode communication (45a-1) which is carried out in an abnormal condition according to the embodiment of the present invention. To begin with, the operation of the multiplex transmission system (50) according to the embodiment of the present invention will be described. The removable external storage means (11) is capable of updating and holding the control specification information (42), as necessary. The removable external storage means is electrically attachable to the master load control unit (10), and it is also capable of reading the control specification information (42), as required, while being attached to the same. Nonvolatile memory (e.g., EEPROM) used as the removable external storage means (11) is made in a removable form (e.g., an IC card or IC connector), and it is inserted into reading means disposed in the master load control unit (10), as required. As a result, it becomes possible for the master load control unit (10) to read desired control specification information (42). The load control units (51, ..., 51) multiplex the control specification information (42) relevant to control specifications of the loads (22a, 22b, 32a, and 32b) or the control status information (41) relevant to the results of control of the loads (22a, 22b, 32a, and 32b) through the multiplex transmission network (40) which is an information communications network. Based on the thus multiplexed control specification information (42), the load control units can control the loads (22a, 22b, 32a, and 32b) respectively connected thereto. The single master load control unit (10), which is made up of one of the load control units (51,..., 51) and is connected to the multiplex transmission network (40), is capable of executing a multiplexing operation based on the control specification information (42) as the master system. Similarly, the slave load control units (20, 30), which are made up of the load control units (51,...51) and are connected to the multiplex transmission network (40), hold the control specification information (42) . The slave load control units (20, 30) are connected to the multiplex transmission network (40) and are capable of carrying out the multiplexing operation as a slave system between the salve load units and the master load control unit (10) through the multiplex transmission network (40). Next, the operation of the master load control unit (10) of the embodiment of the present invention will be described. The nonvolatile storage sections (21, 31) connected to the master load control unit (10) are capable of updating and holding the control status information (41) which is relevant to the load control unit and is to be multiplexed, as well as being capable of reading the control status information (41), as necessary. As shown in Fig. 11 or 13, the master load control unit (10) made up of one of the load control units (51, ..., 51) divides the control specification information (42), which is acquired from the removable external storage means (11) during the course of the initial-mode communication (45a-2), into a predetermined number of unit frames (44). When a multiplexing operation is executed for each unit frame (44) between the master load control unit and the slave load control units (20, 30), the master load control unit (10) multiplexes the unit frame in synchronism with an acknowledgement ACK (46) which is sent from the slave load control units ( 20, 30) upon successful receipt of the unit frame (44). As shown in Figs. 11 - 14, in the case where the master load control unit (10) executes a multiplexing operation during the course of the initial-mode communication (45a-2), the master load control unit (10) sends the acknowledgement ACK (46) to each of the slave load control units (20, 30) upon successful receipt of the unit frame (44) of the control specification information (42) from the slave load control units (20, 30). The slave load control units (20, 30) resend the unit frame (44) once sent until they receive the acknowledgement ACK (46). Further, upon receipt of the acknowledgement ACK (46), the slave load control units (20, 30) are capable of sequentially sending new unit frames (44) subsequent to the currently sent unit frame (44). As shown in Figs. 11 - 14, in the case where the slave load control units (20, 30) execute a multiplexing operation during the course of the initial-mode communication (45a-2), the slave load control units (20, 30) send the acknowledgement ACK (46) to the master load control unit (10) upon successful receipt of the unit frame (44) of the control specification information (42) from the master load control unit (10). The master load control unit (10) resends the unit frame (44) once sent until it receives the acknowledgement ACK (46). Further, upon receipt of the acknowledgement ACK (46), the master load control unit (10) is capable of sequentially sending new unit frames (44) subsequent to the currently sent unit frame (44). In the master load control unit (10) of the present embodiment, the communications I/F circuit is capable of transferring the control specification information (42) or the control status information (41) among units through the multiplex transmission network (40) (i.e., it exchanges the information between the units through multiplex communication). The input I/F circuit is capable of receiving signals from a plurality of switches S1 and S2. The ROM is read only memory for holding predetermined control programs (including a communications protocol for multiplex transmission) and fixed data. The temporary storage section (RAM) (14) is programmable read memory used as a work area in which the control specification information (42) or the control status information is expanded when a job defined by the control program is executed. The metal electrode connector is electrically connected to the removable external storage means (11) and is capable of reading the control specification information (42) held in the same. The built-in timer is capable of generating a trigger signal for the purposes of restoring processing by executing a predetermined count-up operation or count-down operation if the communication mode is in an abnormal condition. The MPU is capable of collectively executing the multiplexing operation. The built-in timer may be shared between the resetting apparatus (60) and the multiplex transmission system (50). Similarly, the count-up or count-down information of the built-in timer may be multiplexed, and the thus multiplexed information may be shared between the resetting apparatus (60) and the multiplex transmission system (50). In the case where the control specification information (42) held in the removable external storage means (11) is read by electrically attaching the removable external storage means (EEPROM) (11) to the master load control unit (10), the MPU implemented in the master load control unit (10) of the embodiment reads the control specification information (42) ratained in the removable external storage means (11). If collation between the thus read control specification information items (42) arises several times, the MPU acquires the control specification information items (42) which match with each other, as well as executing a multiplexing operation based on the thus acquired control specification information (42) between the MPU and the slave load control units (20, 30). The MPU implemented in the master load control unit (10) of the present embodiment divides the thus acquired control specification information (42) or control status information (41) into a predetermined number of unit frames (44), as shown in Figs. 11 - 14. When carrying out a multiplexing operation for each unit frame (44), the MPU sequentially executes the multiplexing operations for each the unit frame (44) between the MPU and the load control units (20, 30) in synchronism with the signal of the acknowledgement ACK (46) which is generated by the slave load control units (20, 30) upon successful receipt of the unit frame (44). Further, the MPU implemented in the master load control unit (10) of the present embodiment collates the checksum information of the control specification information (42), sent from the master load control unit, and the verification ACK (48) received from each of the slave load control units (20, 30), as shown in Figs. 12 to 14. If there is collation between them, the multiplexing of the control specification information (42) is completed, and the communication shifts to normal-mode communication. On the other hand, if no collation arises between them, the multiplexing operation for each unit frame (44) on the basis of the control specification information (42) can be executed again. The operation of the slave load control units (20, 30) of the present embodiment will now be described. At least one slave load control unit (the two slave load control units 20 and 30 in the present embodiment) is capable of controlling the electrical power supply fed to electrical equipment such as lamps and an air conditioner disposed as loads in a vehicle, as shown in Fig. 8 (a) to (e). The slave load control units are connected to the multiplex transmission network (40) and are provided with the nonvolatile storage sections (21, 31) for holding the control specification information (42), respectively. The slave load control units are capable of executing a multiplexing operation, as slave units, between the slave load control units and the master load control unit (10) through the multiplex transmission network (40). The slave load control units (20, 30), which are respectively made up of the load control units (51, ... 51), respectively generate the verification ACK (48) which is checksum information with respect to the control specification information (42) received from the master load control unit (10), as shown in Figs. 11 to 14. The slave load control units also collate the verification ACK (48) and the confirmation ACK (48) received from the master load control unit (10). If no collation arises between these verification ACK (48) codes, the multiplexing processing is executed again for each unit frame (44) on the basis of the control specification information (42) of the master load control unit (10). If there is collation between the verification ACK (48) codes, the slave load control units further collate the control specification information (42) held in the nonvolatile storage sections (21, 31) of the slave load control units (20, 30) and the control specification information (42) received from the master load control unit (10). It no collation arises between these control specification information items (42), the contents uf the storage sections of the slave load control units (20, 30) are updated so as to be replaced with the control specification information (42) received from the master load control unit (10), and the multiplexing operation in the initial-mode communication (45a-2) is completed. The communication then becomes possible to shitt to the normal-mode communication (45a-1). In the slave load control units (20, 30), the communications I/F circuit is capable of transterring the control specification information (42) among units (i.e., it is capable of exchanging the information between the units through multiplex communication). The input I/F circuit is capable of receiving signals from a plurality of sensors (e.g., temperature sensors), and it transfors the thus received signals to the MPU. The output I/F circuit is capable of receiving signals from a plurality of loads (L1 or L2), (L3 or L4) such as lamps, motors, and an air conditioner, and it transfers the thus received signals to the MPU. The ROM is read only memory for holding predetermined control programs (including a communications protocol for multiplex transmission) and fixed data. The temporary storage section (RAM) (24, 34) is programmable read memory used as a work area in which the control specification information (42) or the control status information (41) is expanded when a job defined by the control program is executed. The nonvolatile memory (EEPROM is used in the present embodiment) serves as the nonvolatile storage section (21, 31) for recording the control specification information (42) or the control status information (41). The built-in timer is capable of generating a trigger signal for the purposes of restoring processing by executing a predetermined count-up operation or count-down operation if the communication mode is in an abnormal condition. The MPU is capable of collectively executing the multiplexing operation. The built-in timer may be shared between the resetting apparatus (60) and the multiplex transmission system (50). Similarly, the count-up or count-down information of the built-in timer may be multiplexed, and the thus multiplexed information may be shared between the resetting apparatus (60) and the multiplex transmission system (50). The MPU implemented in each of the slave load control units (20, 30) of the present embodiment calculates checksum information with respect to the control specification information (42) or the control status information (41) which is sent from the master load control unit (10) while being divided into the unit frames (44), as shown in Fig. 11 or Fig. 12. The MPU also executes the multiplexing operation so as to send the thus calculated checksum information to the master load control unit (10) as the verification ACK (48). The MPU implemented in each of the slave load control units (20, 30) executes the multiplexing operation, which the MPU of the master load control unit (10) executes as the master system, in synchronism with the MPU of the master load control unit (10) as a slave system. The MPUs also individually execute internal processing of the nonvolatile storage sections (EEPROM) 21 and 31 in the slave load control units (20, 30), such as the updating of the contents of the storage sections. The MPU implemented in each of the slave load control units (20, 30) generates the verification ACK (48) which is the checksum information with respect to the control specification information (42) received from the master load control unit (10), as shown in Figs. 11 to 14. The MPU collatco the verification ACK (48) and the confirmation ACK (48) received from the master load control unit (10). If no collation arises between these verification ACK (48) codes, the multiplexing operation is executed again for each unit frame (44) on the basis of the control specification information (42) of the master load control unit (10). If there is collation between the verification ACK (48) codes, the MPUs further collate the control specification information (42) hold in the nonvolatile storage sections (21, 31) of the slave load control units (20, 30) and the control specification information (42) received from the master load control unit (10). If no collation arises between these control specification information items (42), the contents of the nonvolatile storage sections (21, 31) of the slave load control units (20, 30) are updated so as to be replaced with the control specification information (42) received from the master load control unit (10), and the multiplexing operation of the control specification information (42) is completed. The communication is capable of shifting to the normal-mode communication. As described above, by means of the multiplex transmission system (50) of the embodiment of the present invention, it becomes possible to transfer the control specification information, which is held in the removable external storage means (11) electrically attachable to the master load control unit (10), to each of the slave load control units (20, 30). Further, it becomes possible to hold the thus transferred control specification information (42) in each of the nonvolatile storage sections (21, 31) of the slave load control units (20, 30). As a result, it becomes possible to easily, quickly, accurately initialize the multiplex transmission system (50). As a result of the use of the electrically removable external storage means (11), it becomes easy, quick, accurate to design the multiplex transmission system (50) which uses new control specification information (42) at a place spaced apart from the current multiplex transmission system (50). In short, it is possible to easily, quickly, accurately transfer the control specification information (42) of the master load control unit (10) to the slave load control units (20, 30), which in turn makes it possible to easily, quickly, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner (e.g., the accurate control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, and the control of supply of electrical power such as ON/OFF operations of the air conditioner). According to the multiplex transmission system (50), and the resetting method and the resetting apparatus for use therewith, when the updated control specification information (42) is described into (i.e., transferred to) the slave load control units (20, 30), the master load control unit (10) transmits a frame in synchronism with the acknowledgement ACK (46). The checksum information with respect to the control specification information (42) which has been sent while having divided into the unit frames (44) can be sent to each of the slave load control units (20, 30) as the verification ACK (48). In consequence, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. The configuration of the frame structure (43) of the unit frame (44) of the present embodiment will now be described. The control specification information (42) or the control status information (41) is transmitted on a unit frame basis. Such a unit frame (44) is divided into a predetermined number of subdivisions by the master load control unit (10) or the slave load control units (20, 30), as shown in Fig. 8 (a) to (e). The thus divided unit frames are transmitted (i.e., multiplexed) through the multiplex transmission network (40). A communications protocol used for executing a multiplexing operation is described in the header (45) which constitutes the frame structure (43) of the unit frame (44) by the resetting apparatus (60), the master load control unit (10), or each of the slave load control units (20, 30) through the multiplex transmission system (40), as shown in Fig. 7 or Fig. 8 (a) to (e). Similarly, the contents of the control specification information (42) or the control status information (41) are described in the data sequence (44a) by the master load control unit (10) or each of the slave load control units (20, 30). As with the BCC shown in Fig. 8 (a) to (e), BCC is a block checksum character described by the master load control unit (10) or each of the slave load control units (20, 30), as well as signifying the checksum of the transmitted/received unit frame. As a result of the use of the frame structure (43) of this unit frame (44), the master load control unit (10) becomes possible to selectively enter a transmission mode according to a predetermined rule so as to start the initial-mode communication (45a-2) when restoring (e.g., resetting) the load control unit from an abnormal condition. The multiplexing of the control specification information (42) held in the master load control unit (10) can be selectively executed with respect to other load control units (51,...,51) (i.e., the slave load control units ( 20, 30) 2, 3) according to a predetermined rule . Accordingly, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Further, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) which uses the control specification information (42) or control status information (41) of the master load control unit (10). In consequence, the control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b) executed by the normally operating load control units (51,..., 51) are not interrupted. Therefore, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). In short, it is possible to prevent the execution of the control and multiplexing operations of the loads ( 22a, 22b, 32a, and 32b) on the basis of the initial-mode communication (45a-2) by interrupting the control and multiplexing operations of the normally operating loads (22a, 22b, 32a, and 32b) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Consequently, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). As a result, it becomes possible to resume the interrupted load control and multiplexing operations which require a high degree of reliability and accuracy. Further, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. The operation of the header (45) of the unit frame (46) according to the embodiment of the present invention will now be described. The header (45) of the present embodiment is 8 bits long, as shown in Fig. 8 (a) to (e). The resetting apparatus (60), the master load control unit (10), or each of the slave load control units (20, 30) can describe communication mode information (45a), (B7), recognition code information (45b), (B6, B5), frame type information (45c), (B4), and frame numbers (B3 - B0) into the header. The communication mode information (45a) is described by the subject of communication (i.e., the resetting apparatus (60), the master load control unit (10), or each of the slave load control units (20, 30)) when it carries out the initial-mode communication (45a-2) signifying the execution of the multiplexing of the control specification information (42) held in the removable external storage means (11) or the normal-mode communication (45a-1) signifying the execution of the multiplexing of the control status information (41). The recognition code information (45b) is described by one of the load control units (51, ..., 51) when it sends the control specification information (42) or the control status information (41) while it is divided into the unit frames (44). The subject of communication (i.e., the master load control unit (10) or each of the slave load control units (20, 30)) can describe whether the sender is the master load control unit (10) or one of the slave load control units (20, 30). The subject of communication (i.e., the master load control unit (10) or each of the slave load control units (20, 30)) can describe the frame type information (45c) so as to show whether the unit frame (44) to be sent is an ACK frame (45c-1), signifying the unit frame (44) of the control specification information (42) multiplexed in the environment in which the initial-mode communication (45a-2) is executed, or a normal frame (45c-2) signifying the unit frame (44) of the control status information (41) multiplexed in the environment in which the normal-mode communication (45a-1) is executed. As a result of the use of the header (45) having such a data structure, the master load control unit (10) becomes possible to selectively enter a transmission mode according to a predetermined rule so as to start the initial-mode communication (45a-2) when returning (e.g., when it is reset) from an abnormal condition. The multiplexing of the control specification information (42) held in the master load control unit (10) can be selectively executed with respect to other load control units (51,...,51) (i.e., the slave load control units (20, 30) 2, 3) according to a predetermined rule. Accordingly, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Further, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) which uses the control specification information (42) or control status information (41) of the master load control unit (10). In consequence, the control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b) executed by the normally operating load control units (51,..., 51) are not interrupted. Therefore, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). In short, it is possible to prevent the execution of the control and multiplexing operations of the loads ( 22a, 22b, 32a, and 32b) on the basis of the initial-mode communication (45a-2) by interrupting the control and multiplexing operations of the normally operating loads (22a, 22b, 32a, and 32b) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Consequently, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). As a result, it becomes possible to resume the interrupted load control and multiplexing operations which require a high degree of reliability and accuracy. Further, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. The operation of the initial-mode communication (for a normal condition) of the control specification information (42) in a normal condition will now be described. The multiplex transmission system (50) of the present embodiment executes a multiplexing operation for a normal condition according to the following procedures. [Step 1] After power has been turned on as a result of a resetting operation, the slave load control unit (20) and the slave load control unit (30) fetch the control specification information (42) stored in the respective nonvolatile storage sections (EEPROM) (21, 31) and hold the thus fetched information in the respective temporary storage sections (RAM) (24, 34) of the slave load control units. Simultaneously, the master load control means electrically attaches the removable external storage means (EEPROM) (11) to the master load control unit (10) after the power has been turned on as result of resetting, whereby the control specification information (42) held in the removable external storage means (11) is read. In this event, the master load control unit (10) reads the control specification information (42) held in the removable external storage means (EEPROM) (11). In the present embodiment, the reading of the information is continuously carried out so as to continuously read the same control specification information (42) several times. In the case where the master load control unit (10) continuously reads the information several times (three times in the present embodiment), the true control specification information (42) is recognized when all of the read control specification information items (42) match with each other, that is, at the time of a 100% match between the read control specification information items (three times). The thus recognized control specification information (42) is read in the temporary storage section (RAM) (14). A multiplexing operation based on the thus fetched control specification information (42) can be executed between the master load control unit and the slave load control units (20, 30). As a result, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. [Step 2] In the multiplexing operation based on the thus fetched control specif ication information (42), the master load control unit (10) divides the thus fetched control specification information (42) into a predetermined number of unit frames 44 (16 unit frames (one frame is 8 bytes long) in the present embodiment. The master load control unit sequentially executes the mutliplexing operation for each unit frame (44) between the master load control unit and the slave load control units (20, 30). The sequential execution of the multiplexing operation for each unit frame 44 signifies the execution of the multiplexing operation for each unit frame (44) in a constant order, e.g., the execution of the multiplexing of the first unit frame (44), the execution of the multiplexing of the second frame (44), ... , the execution of the multiplexing of a unit frame (44) of the last number (i.e., the last unit frame). In short, as a result of the execution of the multiplexing operation for each unit frame (44), it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. [Step 3] When the multiplexing operation is sequentially executed for each unit frame (4) between the master load control unit and the slave load control units (20, 30), the master load control unit (10) executes the multiplexing operation in synchronism with the acknowledgement ACK (46) which is generated by the slave load control units (20, 30) upon successful receipt of the unit frame (44). In the multiplexing operation in synchronism with the acknowledgement ACK (46), the acknowledgement ACK (46) functions as a transmission start instruction (i.e., a synchronizing signal) which is sent to the slave load control units (20, 30) of the unit frame (44). [Step 4] In the case where the multiplexing operation in synchronism with the acknowledgement ACK (46)is executed, each of the slave load control units (20, 30) sends the acknowledgement ACK (46) to the master load control unit (10) upon successful receipt of the unit frame (44) from the master load control unit (10). The master load control unit (10) resends the unit frame (44) once sent until it receives the acknowledgement ACK (46). Upon receipt of the acknowledgement ACK (46), the master load control unit (10) sequentially sends new unit frames (44) subsequent to the currently sent unit frame (44) (Fig. 9 or Fig. 8 (a) to (e)). Specifically, the master load control unit sequentially sends subsequent unit frames in order: namely, a first unit frame (44) -> a second unit frame (44) ->, ..., a fifteenth unit frame (44) -> a sixteenth unit frame (44). In short, as a result of the execution of the multiplexing operation in synchronism with the acknowledgement ACK (46), it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. [Step 5] After the completion of the sequential transmission of a predetermined number (16 in the present embodiment) of unit frames (44) (i.e., the completion of the transmission of the control specification information (42) from the master load control unit (10) while it is divided into the unit frames (44)), the slave load control units (20, 30) respectively calculate checksum information with respect to the control specification information (42) which is sent from the master load control unit (10) while it is divided into the unit frames (44). The thus calculated checksum information is sent to the master load control unit (10) as the verification ACK (48). The completion of the sequential transmission of a predetermined number (16 in the present embodiment) of unit frames (44) signifies the receipt of the acknowledgement ACK (46) codes, which are the same as the transmitted unit frames (i.e., a predetermined number is 16), from the slave load control units (20, 30) as a result of the transmission of all the unit frames (44). [Step 6] If no collation arises between the verification ACK (48) codes (i.e., between the verification ACK (48) sent from the slave load control unit (20) to the master load control unit (10) and the verification ACK (48) received from the master load control unit (10) or between the verification ACK (48) sent from the slave load control unit (30) to the master load control unit (10) and the verification ACK (48) received from the master load control unit (10)), the master load control unit (10) judges that the control specification information (42) of the master load control unit (10) has not been successfully sent. Then, the multiplexing operation based on the control specification information is executed again for each unit frame (44). In this event, if there is collation between the verification ACK (48) codes (i.e., between the verification ACK (48) of the slave load control unit (20) and the verification ACK (48) of the master load control unit (10) or between the verification ACK (48) of the slave load control unit (30) and the verification ACK (48) of the master load control unit (10)), the control specification information (42) held in the nonvolatile storage sections (21, 31) of the slave load control units (20, 30) and the control specification information (42) received from the master load control unit (10) are further collated with each other. If no collation arises between these control specification information items (42) (i.e., between the control specification information (42) hold in the nonvolatile storage section (21) of the slave load control unit (20) and the control specification information (42) received from the master load control unit (10) or between the control specification information held in the nonvolatile storage section (31) of the slave load control unit (30) and the control specification information received from the master load control unit (10)), the contents of the nonvolatile storage sections (21, 31) of the slave load control units (20, 30) are updated so as to be replaced with the control specification information (42) received from the master load control unit (10), and the multiplexing operation of the control specification information (42) is completed. It is judged that the communication mode of the control specification information (44) has been normally completed, and hence the communication shifts to the normal-mode communication. In short, as a result of the execution of the multiplexing operation which involves the collation of the acknowledgement ACK (46) codes, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. [Step 7] The master load control unit (10) collates the checksum information of the control specification information (42), sent from the master load control unit, and the verification ACK (48) received from each of the slave load control units (20, 30). If there is collation between them, the master load control unit (10) judges that the communication mode of the control specification information (44) has been normally completed. Then, the multiplexing of the control specification information (42) is completed, and the communication shifts to normal-mode communication. On the other hand, if no collation arises between them, the master load control unit (10) executes again the multiplexing operation for each unit frame (44) based on the control specification information (42). In short, as a result of the execution of the multiplexing operation which involves the collation of the verification ACK (48) codes, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. Specific examples of multiplexing operation in an abnormal condition will now be described below. First example of multiplexing operation in an abnormal condition The two slave load control means (20, 30) are waiting for the control specification information (42) from the master load control unit (10) in the communication mode of the control specification information (42). Hence, if the master load control unit (10) is in an abnormal condition, all of the functions become inoperative (Fig. 12 (a)). Second example of multiplexing operation in an abnormal condition The slave load control means (20, 30) start their built-in timers after the receipt of the control specification information (42) from the master load control unit (10). By means of the built-in timers, the acknowledgement ACK (46) can be sent after the lapse of a predetermined period (by the built-in timers) even if the master load control unit fails to receive the acknowledgement ACK from the salve load control units (20, 30) (Fig. 12(b)). Third example of multiplexing operation in an abnormal condition The master load control unit (10) starts its built-in timer after the receipt of the acknowledgement ACK from the slave load control units (20, 30). By means of the built-in timer, the control specification information (42) can be sent again after the lapse of a predetermined period (by the built-in timer) even if the master load control unit fails to receive the acknowledgement ACK from the salve load control units (20, 30) (Fig. 12(c)). Fourth exemple of multiplexing operation in an abnormal condition The master load control unit (10) starts its built-in timer after having sent the control specification information (42). By means of the built-in timer, the control specification information (42) can be sent again after the lapse of a predetermined period (as a result of a counting operation of the built-in timer) even if the master load control unit fails to receive the acknowledgement ACK from the salve load control units (20, 30) (Fig. 12(d)). As described above, according to the embodiment of the present invention, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. Next, the operation of the resetting method according to the embodiment of the present invention will be described. Abnormalities used herein signify communication failures in the multiplex transmission network (40) or operation failures of the load control units (51, ... 51) due to the hit of the electrical power source. A resetting method according to the embodiment of the present invention makes it possible to detect abnormalities associated with the multiplexing operation carried out in the multiplex transmission system (50) as well as to reset the load control units (51,...,51) so as to restore them from an abnormal condition to a normal condition. As shown in Fig. 12 (a) to (d) or Fig. 14, the resetting method makes it possible to restore the abnormal load control units to a normal condition through the execution of the following restoring operations ([Restoring Operation 1] to [Restoring Operation 3]). Restoring Operation 1 If the master load control unit (10) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the normal-mode communication (45a-1) is described in the communication mode information (45a), the master load control unit (10) is restored to a normal condition by executing the multiplexing operation with respect to the master load control unit (10) by use of the control status information (41) held in the slave load control unit (20 or 30) which is normally executing the normal-mode communication. Restoring Operation 2 If the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the normal-mode communication (45a-1) is described in the communication mode information (45a), the slave load control unit (20 or 30) is restored to a normal condition by executing the multiplexing operation with respect to the abnormal slave load control unit (20 or 30) by use of the control status information (41) held in the other slave load control unit (30 or 20) or the master load control unit (10) which is normally executing the normal-mode communication (45a-1). Restoring Operation 3 If the slave load control unit (20 or 30) becomes abnormal during the course of the execution ot the normal-mode communication (45a-1), and if the initial-mode communication (45a-2) is described in the communication mode information (45a), the slave load control unit (20 or 30) is restored to a normal condition by executing the multiplexing operation with respect to the abnormal slave load control unit (20 or 30) by use of the control specification information (42) held in the master load control unit (10). With reference to the flowchart shown in Fig. 9, a restoring operation for the master load control unit (10) using the resetting method of the embodiment will now be described. As shown in Fig. 14, the resetting apparatus (60) of the embodiment can restore the master load control unit to a normal condition by executing the ([Restoring Operation 1]) which will be described below. Restoring Operation 1 If the master load control unit (10) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the abnormal load control unit. information (62a) is generated based on the fact that the normal-mode communication (45a-1) is described in the communication mode information (45a) (step S2 -> step S3) as a result of the detection of B7 of the header 45 (step S1 -> step S2), recovery control means (64) restores the master load control unit (10) to a normal condition by executing a multiplexing operation with respect to the master load control unit (10), using the control status information (41) held in the slave load control unit (20 or 30) which is normally executing the normal-mode communication (45a-1) (step S3 -> S4). If the master load control unit (10) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if it is judged that the initial-mode communication (45a-2) is described in the communication mode information (45a) (step S1 -> Y in step S2 or N in step 2 -> N in step S3) as a result of the detection of B7 of the header 45 (step S1 -> step S2), the master load control unit can return to a normal condition (the normal-mode communication (45a-1)) after the initial-mode communication (45a-2) based on the communication mode of the control specification information (42) in an abnormal condition shown in Fig. 12 (a) to (d) has been executed (Y in step S2 -> step S5 -> step S6 -> step S7) (step S4). As a result, the master load control unit (10) becomes possible to selectively enter a transmission mode according to a predetermined rule so as to start the initial-mode communication (45a-2) when returning (e.g., when it is reset) from an abnormal condition. The multiplexing of the control specification information (42) held in the master load control unit (10) can be selectively executed with respect to other load control units (51,...,51) (i.e., the slave load control units (20, 30) 2, 3) according to a predetermined rule. Accordingly, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Further, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) which uses the control specification information (42) or control status information (41) of the master load control unit (10). In consequence, the control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b) executed by the normally operating load control units (51,..., 51) are not interrupted. Therefore, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). In short, it is possible to prevent the execution of the control and multiplexing operations of the loads ( 22a, 22b, 32a, and 32b) on the basis of the initial-mode communication (45a-2) by interrupting the control and multiplexing operations of the normally operating loads (22a, 22b, 32a, and 32b) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Consequently, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). As a result, it becomes possible to resume the interrupted load control and multiplexing operations which require a high degree of reliability and accuracy. Further, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. With reference to the flowchart shown in Fig. 10, a restoring operation for the slave load control units (20, 30) using the resetting method of the embodiment will now be described. As shown in Fig. 14, the resetting apparatus (60) of the embodiment can restore the slave load control units to a normal condition by executing the ([Restoring Operation 2] and [Restoring Operation 3]) which will be described below. In the processing for restoring the slave load control units (20, 30) to a normal condition, the initial-mode communication (45a-2) of the master load control unit (10) or the normal-mode communication (45a-1) (i.e., the communication mode) is constantly monitored. If a request for the initial-mode communication (45a-2) in the header (45) is detected, the initial-mode communication (45a-2) designated by steps S15 to S17 can be immediately executed. Restoring Operation 2 If the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), if it is detected (Y in step S13) that the normal-mode communication (45a-1) is described in the communication mode information (45a) as a result of the detection of B7 of the header 45 (step S11 -> step S12), and if the abnormal load control unit information (62a) is generated on the basis of the normal-mode communication (45a-1) (Y in step S12 -> Y in step S13), the recovery control means (64) restores the slave load control unit (20 or 30) to a normal condition (the normal-mode communication (45a-1)) by executing a multiplexing operation with respect to the slave load control unit (20 or 30) (Y in step S13 -> step S14), using the control status information (41) held in the other slave load control unit (30 or 20) or the master load control unit (10) which is normally executing the normal-mode communication (45a-1). Restoring Operation 3 If the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), if it is detected (N in step S13) that the initial-mode communication (45a-2) is described in the communication mode information (45a) as a result of the detection of B7 of the header 45 (step S11 -> step S12), and if the abnormal load control unit information (62a) is generated based on the initial-mode communication (45a-2) (N in step S13), the recovery control means (64) restores the slave load control unit (20 or 30) to a normal condition (the normal-mode communication (45a-1)) by executing a multiplexing operation with respect to the slave load control unit (20 or 30) (Y in step S13 -> step S15 -> step S16 -> step S17), using the control specification information (42) held in the master load control unit (10). As a result, the master load control unit (10) becomes possible to selectively enter a transmission mode according to a predetermined rule so as to start the initial-mode communication (45a-2) when returning (e.g., when it is reset) from an abnormal condition. The multiplexing of the control specification information (42) held in the master load control unit (10) can be selectively executed with respect to other load control units (51,...,51) (i.e., the slave load control units (20, 30) 2, 3) according to a predetermined rule. Accordingly, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Further, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) which uses the control specification information (42) or control status information (41) of the master load control unit (10). In consequence, the control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b) executed by the normally operating load control units (51,..., 51) are not interrupted. Therefore, the multiplex transmission system becomes possible to ensure uninterrupled execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). In short, it is possible to prevent the execution of the control and multiplexing operations of the loads (22a, 22b, 32a, and 32b) on the basis of the initial-mode communication (45a-2) by interrupting the control and multiplexing operations of the normally operating loads (22a, 22b, 32a, and 32b) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Consequently, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). As a result, it becomes possible to resume the interrupted load control and multiplexing operations which require a high degree of reliability and accuracy. Further, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. The operation of the resetting apparatus (60) using the resetting method of the embodiment will now be described. As shown in Fig. 12 (a) to (d) or Fig. 14, the resetting apparatus (60) of the embodiment can restore the load control unit to a normal condition by executing the ([Restoring Operation 1] to [Restoring Operation 3]) which will be described below. Restoring Operation 1 If the master load control unit (10) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if abnormal load control unit information (62a) is generated based on the fact that the normal-mode communication (45a-1) is described in the communication mode information (45a), the recovery control means (64) restores the master load control unit (10) to a normal condition by executing a multiplexing operation with respect to the master load control unit (10), using the control status information (41) held in the slave load control unit (20 or 30) which is normally executing the normal-mode communication (45a-1). Restoring Operation 2 If the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the abnormal load control unit information (62a) is generated based on the fact that the normal-mode communication (45a-1) is described in the communication mode information (45a), the recovery control means (64) restores the slave load control unit (20 or 30) to a normal condition by executing a multiplexing operation with respect to the slave load control unit (20 or 30), using the control status information (41) held in the other slave load control unit (30 or 20) or the master load control unit (10) which is normally executing the normal-mode communication (45a-1). Restoring Operation 3 If the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the abnormal load control unit information (62a) is generated based on the fact that the initial-mode communication (45a-2) is described in the communication mode information (45a), the recovery control means (64) restores the slave load control unit (20 or 30) to a normal condition by executing a multiplexing operation with respect to the slave load control unit (20 or 30), using the control specification information (42) held in the master load control unit (10). More specifically, the operation of the resetting apparatus (60) of the present embodiment will be described. As shown in Fig. 7, the abnormality detecting means (62) is capable of detecting an abnormal multiplexing operation arising in the load control units (51, ... 51) which carry out the multiplex operation on the multiplex transmission network (40). Further, the abnormality detecting means (62) is capable of generating the abnormal load control unit information (62a) on the basis of the recognition code described in the header (45) by specifying the abnormal load control unit from the load control units (51,..., 51). As shown in Fig. 7, the recovery control means (64) is capable of selecting either the initial-mode communication (45a-1) or the normal-mode communication (45a-1) as a restoring operation to be executed according to the abnormal load control unit information (62a). The recovery control means (64) describes the communication mode information (45a) in the header (45) when executing the thus selected restoring operation. Further, the recovery control means (64) is capable of restoring the load control unit of the load control units (51, ... 51) which caused the abnormal multiplexing operation by executing the selected restoring operation with respect to that load control unit on the basis of the abnormal load control unit information (62a) and the communication mode information (45a). Still more specifically, the operation of the recovery control means (64) and the abnormality detecting means (62) of the present embodiment will be described. In the recovery control means (64) and the abnormality detecting means (62) of the present embodiment, the communications I/F circuit is capable of transferring the control specification information (42) among units (i.e., for exchanging the information between the units through multiplex communication). The ROM is read only memory for holding control programs relevant to a predetermined restoring operation (including a communications protocol for multiplex transmission) and fixed data. The temporary storage section (RAM) is programmable read memory used as a work area in which the control specification information (42) or the control status information (41) is expanded when a job defined by the control program is executed. The built-in timer is capable of generating a trigger signal for the purposes of restoring processing by executing a predetermined count-up operation or count-down operation if the communication mode is in an abnormal condition. The MPU is capable of collectively executing the multiplexing operation. The built-in timer may be shared between the resetting apparatus (60) and the multiplex transmission system (50). Similarly, the count-up or count-down information of the built-in timer may be multiplexed, and the thus multiplexed information may be shared between the resetting apparatus (60) and the multiplex transmission system (50). The MPUs implemented in the recovery control means (64) and the abnormality detecting means (62) of the present embodiment can collectively carry out the resetting method for use in the resetting apparatus (60) capable of detecting abnormalities associated with the multiplexing operation carried out in the multiplex transmission system (50) as well as resetting the load control units (51,...,51) so as to restore them from an abnormal condition to a normal condition. The MPUs are connected to the slave load control units (20, 30) and the master load control unit (10) through the multiplex transmission network (40) so as to make it possible to monitor the multiplexing operation for each unit frame (44) in synchronism with the acknowledgement ACK (46) which are generated by the slave load control units (20, 30) upon successful receipt of the unit frame (44), when the multiplexing operation is executed for each unit frame (44). The MPUs are also capable of monitoring the following operations. The checksum information of the control specification information (42) sent by the MPUs and the verification ACK (48) received from the slave load control units (20, 30) are collated with each other. If there is collation between them, the multiplexing of the control specification information (42) is completed, and the communication shifts to the normal-mode communication. If no collation arises between them, the multiplexing operation is executed again for each unit frame (44) on the basis of the control specification information (42). The MPUs implemented in the recovery control means (64) and the abnormality detecting means (62) restore the load control unit from an abnormal condition to a normal condition by executing the following restoring operations ([Restoring Operation 1] to [Restoring Operation 3]). Restoring Operation 1 If the master load control unit (10) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the normal-mode communication (45a-1) is described in the communication mode information (45a), the master load control unit (10) is restored to a normal condition by executing the multiplexing operation with respect to the master load control unit (10) by use of the control status information (41) held in the slave load control unit ( 20 or 30) which is normally executing the normal-mode communication. Restoring Operation 2 If the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the normal-mode communication (45a-1) is described in the communication mode information (45a), the slave load control unit (20 or 30) is restored to a normal condition by executing the multiplexing operation with respect to the abnormal slave load control unit (20 or 30) by use of the control status information (41) held in the other slave load control unit (30 or 20) or the master load control unit (10) which is normally executing the normal-mode communication (45a-1). Restoring Operation 3 If the slave load control unit (20 or 30) becomes abnormal during the course of the execution of the normal-mode communication (45a-1), and if the initial-mode communication (45a-2) is described in the communication mode information (45a), the slave load control unit (20 or 30) is restored to a normal condition by executing the multiplexing operation with respect to the abnormal slave load control unit (20 or 30) by use of the control specification information (42) held in the master load control unit (10). As described above, according to the multiplex transmission system (50) of the embodiment of the present invention, it becomes possible to transfer the control specification information (42), which is held in the removable external storage means (11) electrically attachable to the master load control unit (10), to each of the slave load control units (20, 30). Further, it becomes possible to hold the thus transferred control specification information (42) in each of the nonvolatile storage sections (21, 31) of the slave load control units (20, 30). As a result, it becomes possible to easily, quickly, accurately initialize the multiplex transmission system (50). As a result of the use of the electrically removable external storage means (11), it becomes easy, quick, accurate to design the multiplex transmission system (50) which uses new control specification information (42) at a place spaced apart from the current multiplex transmission system (50). In short, it is possible to easily, quickly, accurately transfer the control specification information (42) of the master load control unit (10) to the slave load control units (20, 30), which in turn makes it possible to easily, quickly, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner (e.g., the accurate control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, and the control of supply of electrical power such as ON/OFF operations of the air conditioner). According to the multiplex transmission system (50), and the resetting method and the resetting apparatus (60) for use therewith, when the updated control specification information (42) is described into (i.e., transferred to) the slave load control units (20, 30), the master load control unit (10) transmits a frame in synchronism with the acknowledgement ACK (46). The checksum information with respect to the control specification information (42) which has been sent while having divided into the unit frames (44) can be sent to each of the slave load control units (20, 30) as the verification ACK (48). In consequence, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. According to the multiplex transmission system (50) of the present embodiment and the resetting method and the resetting apparatus (60) for use therewith, the master load control unit (10) becomes possible to selectively enter a transmission mode according to a predetermined rule so as to start the initial-mode communication (45a-2) when restoring (e.g., resetting) the load control unit from an abnormal condition. The multiplexing of the control specification information (42) held in the master load control unit (10) can be selectively executed with respect to other load control units (51,...,51) (i.e., the slave load control units (20, 30) 2, 3) according to a predetermined rule. Accordingly, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Further, it is possible to prevent the normally operating load control units (51,..., 51) from being forcibly subjected to the initial-mode communication (45a-2) which uses the control specification information (42) or control status information (41) of the master load control unit (10). In consequence, the control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b) executed by the normally operating load control units (51,..., 51) are not interrupted . Therefore, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). In short, it is possible to prevent the execution of the control and multiplexing operations of the loads ( 22a, 22b, 32a, and 32b) on the basis of the initial-mode communication (45a-2) by interrupting the control and multiplexing operations of the normally operating loads (22a, 22b, 32a, and 32b) when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Consequently, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads (22a, 22b, 32a, and 32b). As a result, it becomes possible to resume the interrupted load control and multiplexing operations which require a high degree of reliability and accuracy. Further, it becomes possible to realize the multiplex transmission system (50) which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. According to the multiplex transmission system of the invention, due to provision of simple means or the reset switch which not only makes it possible to urge the forced transfer of the load control information held in the storage part of the mater load control means to the respective slave load control means but also permits the thus transferred load control information to be held by the respective storage parts of the slave load control means, the updating of the load control information of the master load control means can be transmitted to the respective slave load control means accurately. Also, due to use of a storage part which can be mounted and removed electrically, the updating of the load control information can be carried out easily. Further, in the updating operation, if the reset switch is pressed down, then the newly updated load control information of the master load control means can be prevented from being processed multiplexingly in accordance with the load control information of the slave load control means that is consistent with other one or two of the three pieces of load control information and thus occupies a majority among them, which makes it possible to urge the forced transfer of the updated load control information to the respective slave load control means. That is, when a new storage part with the load control information updated is mounted electrically, the updating of the load control information of the master load control means can be transmitted to the respective slave load control means accurately. Due to this, electric devices carried on board the vehicle, such as lights, an air conditioner and the like can be controlled with accuracy. That is, the on-off cycles of the lights, the intensity of the turn-on illumination of the lights, and the turn-on of the lights in linking with the opening or closing operation of the door of the vehicle can be controlled accurately. Also, the accurate control of power supply to the air conditioner for turn-on or turn-off thereof can be realized. Also, the multiplex transmission system according to the invention not only compares the load control information held in the storage part of the master load control means with the load control information held in the storage part(s) of the slave load control means but also, when there exists any inconsistency between the load control information, executes a majority processing on the load control information of the master load control means as well as on the load control information of the slave load control means and, in accordance with the results of the majority processing, carries out a multiplexing processing, thereby being able to realize a highly reliable multiplexing processing. Thanks to this, according to the present invention, electric devices carried on board the vehicle, such as lights, an air conditioner and the like can be controlled with accuracy. That is, the on-off cycles of the lights, the intensity of the turn-on illumination of the lights, and the turn-on of the lights in linking with the opening or closing operation of the door of the vehicle can be controlled accurately. Also, the accurate control of power supply to the air conditioner for turn-on or turn-off thereof can be realized. According to the multiplex transmission system of the embodiment and the resetting method and the resetting apparatus for use therewith, it becomes possible to transfer the control specification information, which is held in the removable external storage means electrically attachable to the master load control unit, to each of the slave load control units. Further, it becomes possible to hold the thus transferred control specification information in each of the nonvolatile storage sections of the slave load control units. As a result, it becomes possible to easily, quickly, accurately initialize the multiplex transmission system. As a result of the use of the electrically removable external storage means, it becomes easy, quick, accurate to design the multiplex transmission system which uses new control specification information at a place spaced apart from the current multiplex transmission system. In short, it is possible to easily, quickly, accurately transfer the control specification information of the master load control unit to the slave load control units, which in turn makes it possible to easily, quickly, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner (e.g., the accurate control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, and the control of supply of electrical power such as ON/OFF operations of the air conditioner). According to the multiplex transmission system of the present embodiment, and the resetting method and the resetting apparatus for use therewith, when the updated control specification information is described into (i.e., transferred to) the slave load control units, the master load control unit transmits a frame in synchronism with the acknowledgement ACK. The checksum information with respect to the control specification information which has been sent while having divided into the unit frames can be sent to each of the slave load control units as the verification ACK. In consequence, it becomes possible to realize the multiplex transmission system which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like. According to the multiplex transmission system of the present embodiment and the resetting method and the resetting apparatus for use therewith, the master load control unit becomes possible to selectively enter a transmission mode according to a predetermined rule so as to start the initial-mode communication when restoring (e.g., resetting) the load control unit from an abnormal condition. The multiplexing of the control specification information held in the master load control unit can be selectively executed with respect to other load control units (i.e., the slave load control units) according to a predetermined rule. Accordingly, it is possible to prevent the normally operating load control units from being forcibly subjected to the initial-mode communication when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Further, it is possible to prevent the normally operating load control units from being forcibly subjected to the initial-mode communication which uses the control specification information of control status information of the master load control unit. In consequence, the control and multiplexing operations of the normal loads executed by the normally operating load control units are not interrupted. Therefore, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads. In short, it is possible to prevent the execution of the control and multiplexing operations of the loads on the basis of the initial-mode communication by interrupting the control and multiplexing operations of the normally operating loads when the load control unit is restored (e.g., reset) from an abnormal condition to a normal condition. Consequently, the multiplex transmission system becomes possible to ensure uninterrupted execution of control and multiplexing operations of the normal loads. As a result, it becomes possible to resume the interrupted load control and multiplexing operations which require a high degree of reliability and accuracy. Further, it becomes possible to realize the multiplex transmission system which is highly resistant to disturbance such as noise as well as is highly reliable. Moreover, the multiplex transmission system can highly reliably, accurately control electrical equipment aboard a vehicle such as lamps and an air conditioner, more specifically, the control of a flashing cycle of the lamps, the illuminance of the lamps and lightening actions of a lamp synchronized with door openings, ON/OFF operations of the air conditioner, or the like.

Claims: A multiplex transmission system comprising: multiplexing processing means (150) performing a multiplexing processing on load control information held in a storage part (111, 121, 131) through a multiplex transmission line (140); load control means (120, 130) for controlling loads connected to the respective load control means; a single piece of master load control means (110) for controlling a load; one or more pieces of slave load control means (120, 130) for controlling a load (122a, 122b, 132a, 132b); wherein said master load control means (110) includes a reset switch (112) which can be used not only to urge the forced transfer of said load control information held in said storage (111) of said master load control means (110) to said respective slave load control means (120, 130) but also to allow said transferred load control information to be held by the respective storage parts (121, 131) of said slave load control means (120, 130); characterized in that load control information held in said storage part (111) of said master load control means (110) is compared with load control information held in the storage parts (121, 131) of said slave control means (120, 130) and, when said reset switch (112) is not depressed and also when there exists any inconsistency between said load control information, a majority processing on said load control information of said master load control means (110) as well as on said load control information of said slave load control means (120, 130) is executed; and in that said multiplexing processing is executed in accordance with the load control information included in said load control information of said master load control means (110) and said load control information of said slave control means (120, 130), when said load control information is consistent with any other one or two of them and thus occupies a majority among them, and when said load control information of said master load control means (110) and said load control information of said slave control means (120, 130) are all inconsistent with one another, said multiplexing processing is executed in accordance with said load control information of said master load control means (110). A multiplex transmission system as set forth in claim 1, wherein said reset switch (112) is used, when said load control information of said master load control means (110) is updated. A multiplex transmission as set forth is claim 1 or 2, wherein said reset switch (112) is used, when a storage part (111, 121, 131) with said load control information updated is mounted.

Inventors: IMAIZUMI NOBUHIRO, ONIISHI TATSUAKI, IMAIZUMI, NOBUHIRO, ONIISHI, TATSUAKI
Applicants: YAZAKI CORP, YAZAKI CORPORATION
Application year: 1996
Main classification: B60R16
IPC codes: B60R16