To reduce the number of signal lines for connecting an current detector and a solenoid electrically.Between solenoids 1-1 and 1-2 and switches SW-1 and SW-2 and on the high sides with respect to the individual solenoids, respectively, there are connected current detectors 4-1 and 4-2. The end portions of the solenoids 1-1 and 1-2 on the individual GND sides are made common. The number of signal lines for connecting a controller and the two solenoids may be “2+1=3”. Therefore, the number of terminals (or the pin number) of a connector 3 may also be “2+1=3” (P1 to P3). The current detectors 4-1 and 4-2 detect the electric currents to flow to the solenoids 1-1 and 1-2. In the case of an incomplete grounding, for example, it is possible to detect an overcurrent to flow to the solenoids.