with regard to the explanation of fig1 through 3 , reference is made to the background information section . fig4 shows a regulating system for regulating output voltage u out of a vehicle generator 2 , using an external voltage regulator 1 . the regulating system includes a generator unit 8 in which generator 2 is integrated as a structural unit together with a rectifier 3 , a power output stage 11 , and an auxiliary regulator 13 . the generator unit also contains an excitation coil l and a freewheeling diode d . power output stage 11 includes a transistor 12 which is controlled by a control unit 4 using a predetermined pulse duty factor . main regulator 1 is implemented as software , structurally separated from generator unit 8 . control unit 4 may be a control unit for managing electrical power and consumption , an engine control unit , or a central computer , for example . in normal operation the generator is regulated by main regulator 1 , which generates an appropriate manipulated variable as a function of the instantaneous actual voltage , taking into account the available engine power . the manipulated variable may be supplied to power output stage 11 , either via a pwm interface 10 or a digital interface 6 . the manipulated variable is converted by auxiliary regulator 13 into a corresponding control signal for switching transistor 12 ( optionally , the control signal could also be transmitted directly to transistor 12 ). the pulse duty factor ( on time / off time ) determines the magnitude of excitation current i err flowing through excitation coil l , and thus the magnitude of the phase voltages induced in the stator windings of generator 2 . rectifier 3 is used for rectifying the phase voltages from generator 2 , and produces generator output voltage u out at its output . the manipulated variable output by main regulator 1 is checked for plausibility by a suitable device which is integrated into auxiliary regulator 13 , for example . one criterion for the plausibility of the manipulated variable may be the rate of change or the absolute value thereof , for example . as long as the manipulated variable is in a specified range within predetermined limiting values ( normal operation ), auxiliary regulator 13 does not perform a regulating function . however , if a malfunction or a breakdown of main regulator 1 is detected , auxiliary regulator 13 becomes active and takes over emergency regulation , or at least emergency control , of generator 2 . it is thus possible for auxiliary regulator 13 to regulate the regulating variable to a fixed setpoint value , for example , or to use the last plausible control signal obtained or an average value of the control signal , for example , as an auxiliary manipulated variable . furthermore , defined data from generator unit 8 may be transmitted to control unit 4 via digital interface 6 . such data may be diagnostic parameters , the instantaneous df signal , the instantaneous excitation current i err , a generator temperature , or error messages , for example . the generator system also includes a temperature sensor 15 for measuring the generator temperature or a proportional variable . the generator temperature is preferably transmitted to both main regulator 1 and auxiliary regulator 13 . when generator 2 overheats it is thus possible to reduce the excitation of , and thus the load on , the generator . main regulator 1 according to the present invention is preferably set up so that it is able to receive various types of sensor information and operating state information via digital interfaces , for example , for the purpose of ensuring a stable onboard electrical system with consideration for the generator state of health , the state of health of the engine , of the electrical consumers in the onboard electrical system , and / or the state of the battery . to this end , the main regulator is preferably connected to engine control unit 5 , battery state detector ( integrated into control unit 4 ), and terminal b + of the onboard electrical system . the supply to the onboard electrical system may be optimized as a function of the information obtained about the state of health of the internal combustion engine ( engine torque ), the state of the battery , etc ., by adapted regulation of generator 8 . fig5 shows a second embodiment of a regulating system according to the present invention in which , in contrast to fig4 , a pwm interface 10 is provided between control unit 4 and generator unit 8 . in this embodiment , diagnostic data and other information may be transmitted during an initialization phase from generator unit 8 to control unit 4 , before the regulation begins . the regulation then occurs with a time delay in the opposite direction . fig6 shows the method steps of redundant voltage regulation in the form of a flow diagram . in step 20 , normal operation is carried out in which the regulation is performed by main regulator 1 . in step 21 , manipulated variable k transmitted by main regulator 1 is checked for plausibility by a logic system contained in generator unit 8 which may be integrated into auxiliary regulator 13 , for example , a threshold value , for example , being monitored . if manipulated variable k or a function of manipulated variable k , such as a df signal or the rate of change thereof , for example , is within predetermined threshold values sw ( case j ), normal operation nb is maintained . when a predetermined threshold value sw ( case n ) is exceeded , in step 22 auxiliary regulator 13 runs in non - operational mode hb which ensures operation of generator 2 , even if main regulator 1 fails . an additional aspect of the present invention , which results in more rapid availability of electrical power in the onboard electrical system , is illustrated in fig7 . in normal operation ( step 20 ) a check is continuously performed as to whether there is sufficient power in the onboard electrical system . this may be achieved by monitoring the system voltage or evaluating start - up requirements of consumers ( step 25 ), for example . when the supply is sufficient ( case j ), normal operation continues . when there is an undersupply of electrical power or an undersupply is imminent ( because of start - up requirements for multiple large consumers , for example ), control unit 4 directs engine control 5 to bring the internal combustion engine to an operating point featuring higher engine torque . it is thus possible to increase the excitation ( df signal ) of generator 2 much more quickly without overloading the engine . it is also possible to take into account additional operating information such as the generator temperature , state of the vehicle battery , etc ., in the voltage regulation .