magnet 112a and two windings 112c configured to be energized in such direction that the magnetic force of said permanent magnet 112a is reduced when the output signal of the driving circuit is used to energize the power supply the cooperative relation between the star wheel 109 engagement member 108 and the electro magnet 112 etc is the same as that of the first embodiment the electric circuit for use in operating the second embodiment is different from that of the first embodiment only in the ratio between the on off times of the pulse signal for use in operating the electro magnet 112 referring now to fig5 and 6 the operation of the second embodiment of the above described construction will be described fig5 shows a condition before the timer is set and after the operation is finished the power supply switch sw 1 is turned off by the operating member 101 the microswitch sw 2 is turned on or off and the magnetic retraction part 108b of the engagement member is kept in the retracted condition against the iron cores 112b by the permanent magnet 112a of the electro magnet when the knob 107 is rotated in a clockwise direction in order to operate the timer in reference to the above described condition the star wheel 109 is prevented from being rotated by the engagement member 108 being retracted against the electro magnet 112 thus the operating member 101 is rotated to such position as the desired operating time of the timer is made while the frictional engagement between the operating member 101 and the star wheel 109 is slipped when the power supply switch sw 1 is turned on by this operation and the electro magnet 112.