Jettison the Crew, Assertion of Command, Free Digital Command, and Free Analog Command were all realized using simple push-buttons. Jettison the Crew involved throwing a life ring “overboard”, but the sensing was simply a push-button in the life ring holder to feel whether the life ring was sitting in the holder. Assertion of Command and Free Digital shared an actual push-button, since in any given software state only one of those commands was possible to send. Additionally, upon a successful Assertion of Command, the song “Mississippi Queen” was played through two speakers sitting on the COACH. The music player was a pre-wired board from RadioShack, so all our circuitry had to handle was shorting to leads together whenever the music was to play; thus, those leads were literally connected via a MOSFET whose gate was under software control. The Free Analog Command was activated using a third push-button. All three push-button circuits provided basic hardware debouncing and then connected directly to the E128 input pins.
The Free Analog Command also required a magnitude for its parameter, so a second potentiometer was provided. This potentiometer had the same range of variable resistance, so the exact same circuit was used as for the throttle potentiometer.