An overboard alarm system includes a signal device and a receiving station. The signal device includes a water-activated switch, a transmitter controlled by the switch to generate a signal, an antenna for providing the signal from the transmitter, and a floatation aid for keeping an end of the antenna...http://www.google.com.tw/patents/US5886635?utm_source=gb-gplus-share專利 US5886635 - Overboard alarm with localization system interface
