Abstract: An object is to provide a key protection structure for an electronic apparatus which can prevent a preset value of a switch from being intentionally changed by the user or the like. When setting of a first switch 21 is ended, a tool shutter operation portion 72 of a lock key 70 is inserted into a first shutter operation hole 61. The tool shutter operation portion 72 is then engaged with an engaging recess 45 of a first shutter 40. Thereafter, the lock key 70 is rotated, so that the first shutter 40 is rotated. A covering portion 44 of the shutter is therefore moved immediately above the first switch 21 to close a first switch operation hole 58, whereby the first switch 21 can be locked (key-protected) so as not to be externally operated.

Abstract: A numerical value setting device which accomplishes a numberical value setting or registering operation whether a power supply is interrupted or restored during its operation has a set value registering timer. The set value registering timer defines a period at the end of which the set value is registered. The set value registering timer counts different period clock pulses depending on the states of the power supply to assure that the correct numerical value is registered.