An expansion unit 50, 60 or 70 is connected to a controller body 10 including an analog direction key 12, a digital direction key 14, command buttons 20a-20z, command levers 22l, 22r, etc. An expansion unit 50 including a photo emitting unit 52 is connected to thereby make the controller cordless. An...http://www.google.com.hk/patents/US20050233808?utm_source=gb-gplus-share專利 US20050233808 - Controller and expansion unit for controller
