Abstract: A film with a first circuit printed on a lower surface, a film insulator and a film with a second circuit printed on an upper surface are mounted on the keyboard. Each of the first and second circuits includes a plurality of contacts. The film insulator defines a plurality of apertures. One of the contacts of the first circuit will be engaged with one of the contacts of the second circuit through one of the apertures defined in the film insulator if a key switch is pressed. The key switch includes a frame defining two vertical slots. A slidable member includes a plate, two hooks projecting downwardly from the plate and each including a barb for engaging with one of the vertical slots and a hollow cylinder projecting downwardly from the plate and defining two vertical slots. A cup includes two barbs projecting radially inwardly therefrom. The hollow cylinder is insertable in the cup. The barbs formed on the cup are engageable in the slots defined in the hollow cylinder.