A keyboard includes a plurality of keys thereon, each of which is capable of three different switching actions for entry of data or commands into a word processor, typewriter, computer or the like. Each key includes a first inclined surface for generating a first switching action responsive to finger...http://www.google.com.hk/patents/US4769516?utm_source=gb-gplus-share專利 US4769516 - Finger operated switching apparatus
