PURPOSE: To set the light output of a miniature lamp to an optional level, gradually reduce the light output of the miniature lamp from 100% to a light output level, and easily change the set level to a miniature lamp lighting mode initial state by the switching of a switch.

CONSTITUTION: An astable multivibrator has a variable resistor VR1 for changing a time constant. A capacitor C5 for gradually reducing the light output of a miniature lamp from 100% is provided through a switch SW2. The SW2 is connected to a c-terminal, and the oscillation duty is gradually changed to a set level by the charge of the C5. When the SW2 is connected to a d-terminal, a transistor Q4 is off, the multivibrator is immediately oscillated at the set level. The set level of the light output of the miniature lamp can be regulated by changing the variable resistor VR1.