The Nasa MOBi is a state of the art fail-safe transponder man overboard system. It consists of a base unit and up to eight active transponders for crew or valuable equipment. In operation the base station sequentially interrogates each transponder which then broadcasts its presence. In the event of a crew member falling overboard the drop in signal level is detected by the base unit which sounds a high intensity audible alarm. To aid identification of the missing crew member the base station continually displays the names of all the crew currently logged on the signal levels of their transponder fob and their current status. Three AAA cells power each transponder for several weeks of continuous use. Should the base station be turned off the transponders will go to sleep with a life of several years. So if you are sailing with Tom Dick and Harry don't forget to take MOBi with you!.