PURPOSE: To prevent the occurrence of nonconformity such as the switching of a function mode caused by an erroneous touch by selecting the switching of the function mode only when the key signal of a function mode switching key is inputted plural times in prescribed time.

CONSTITUTION: For a bare chip type PCB (PCB) 4, a bare chip 62, a positive electrode terminal 63, and a negative electrode terminal 64 are mounted on a substrate 61, respective keys of a membrane keyboard 5 are connected to the bare chip 62 of the PCB 4 with wiring, and a prescribed key signal can be inputted to the bare chip 62 by touch-operating one key. Further, a function to permit the selection of the switching of the function mode to either an electronic calculator function or an Otello game function is given on condition that the key signal by the operation of a function mode switching key CAL/ OTH is inputted to the bare chip 62 plural times (for example, twice) in the prescribed time (for example, two seconds). Thus, the occurrence of the nonconformity such as the switching of the function mode caused by the erroneous touch can be prevented.