Quick question...does anyone know if an "engine-driven electrical system" is defined anywhere by the FAA? I ask because I know that many two-stroke engines have a "lighting coil" that does provide enough power for some anti-collision lights and a few instruments but I don't think they are required to have a transponder. I am also wondering about a closed circuit system with an alternator or generator and battery used only for ignition and possibly electric start but independent from a battery-powered system used for the radio. Cheers, Matthew