A keyboard having a sensor layer below a chassis layer is described. The magnetic field signal includes data information transmitted from the base station to a movable remote station. The present invention also provides uses thereof. Incident light passed through the photoelectric conversion layer further passes through the optical absorption layer and, after that, is reflected by the reflecting electrode layer. A leg supporting part is provided on the bottom of the housing, into which the leg of the second electric contact is press-fitted from the rear, to prevent deformation of the leg.