Abstract: A device for protection of a digital multimeter from misinsertion of an input plug. The device prevents misinsertion of the input plug into an input core having no concern with a selected function and generates an alarm sound when a function switch is unconsciously rotated disregarding insertion of the input plug in an input core. The device comprises a plug misinsertion preventing unit for preventing the input plug from being inserted into specified one of the plug inserts when a function except a specified function is selected, the specified function corresponding to the specified plug insert. An alarm generating unit for alarming when the function switch is operated in order to change a function under the condition that the input plug is continuously inserted in the specified plug insert. The plug misinsertion preventing unit comprises a rotating plate and a shielding layer cooperating with the rotating plate. The shielding layer selectively shields the specified plug insert.