PURPOSE: To reduce the number of required parts and prevent the production of noises due to corse, by connecting a resistor in parallel to a contact which is opened immediatedly before a fixed core comes in contact with a movable core through magnetic attraction of after such a contact is made, and supplying current to an actuating coil through two diodes connected in opposite directions.

CONSTITUTION: When a switch 8 is closed with a contact 13 closed, a large current flow through an actuating coil 11, so that a movable core is attracted to a fixed core. Immediately before the movable core comes in contact with the fixed core through magnetic attraction, the contact 13 is opened, and the actuating coil 11 is supplied with the current limited by a resistor 12, thereby to hold the attracted state of the movable core. When the switch 8 is closed at a time t0, the input voltage of a single-phase AC power source 7 is applied to the actuating coil 11, and a large current, which has been subjected to half-wave rectification by a first diose 14a, flows through the contact 13. While the terminal voltage of the actuating coil 11 is being reversed, the current flowing through the actuating coil 11 recirculates to the actuating coil 11 via a second diode 14b. When the contact 13 is opened, the input current is limited by the resistor 12. After the movable core comes in contact with the fixed core through magnetic attraction, a current substantially close to direct current flows through the actuating coil 11.