PURPOSE: To reduce the number of components, improve characteristics and economical efficiency, and save space.

CONSTITUTION: A switching circuit 2 in which three sets of two sets of switching functions connected in series are connected in parallel is formed, and an intermediate connecting point of switching functions 2a and 2b which constitute a first switching circuit is connected to a first terminal of a coil 3a of a first electromagnet 3, and the intermediate connecting point of switching functions 2c and 2d which constitute a second switching circuit is connected to the second terminal of the coil 3a of the first electromagnet 3 and the first terminal of the coil 4a of the second electromagnet 4, respectively. Also the intermediate connecting point of switching functions 2e and 2f which constitute a third switching circuit is connected to the second terminal of the coil 4a of the second electromagnet 4. Thus six switching functions can be operated by one set of control function so that a current value supplied to the coils 3a and 4a of the pair of electromagnets 3 and 4 can be maintained at specified current values.