PURPOSE: To prevent hazard such as electricity receiving shock to a human body at the time of opening a cover by shutting electric power source which receives A.C. current and sends stabilized D.C. current and shutting the electric power source output at the time a box cover which covers a load circuit part which is operated by the output of the electric power source.

CONSTITUTION: A pair of contact parts 28 having spring properties and condutivity are installed in a box which covers a D.C. current stabilizing electric power source part 2 and a theory part 17 which is operated by the output of the power source. An insulating body 41 to be inserted between contacts at the time of closing the cover is installed in the cover 40 and ON/OFF control of the output of the electric power source is carried out corresponding to the separation of or contact between the contacts.