KEY OPERATION DETECTOR

PROBLEM TO BE SOLVED: To reduce the manufacturing cost by decreasing the number of elements necessary for the constitution of a key action detector for detecting the action of keys. SOLUTION: A wippen 15 exists normally in a position shown by solid lines and when the key is pushed, the wippen successively passes a first oscillation position shown by an arrow A and a second oscillation position shown by an arrow B. The laser beam L emitted by a light emitting element 33 does not normally fall onto a metallic plate 31 but when the wippen 15 oscillates to the first oscillation position, the light is reflected by the surface of the metallic plate 31 and is received by a light receiving element S1. When the wippen 15 oscillates to the second oscillation position, the light is reflected by the surface of the metallic plate 31 and is received by a light receiving element S2. The key is judged to be pushed when the light receiving elements S1 and S2 successively receive the laser beam L. The number of the light emitting elements necessary for the constitution of the device can therefore be decreased.