This is the MYLAPS RC4 "3-Wire" Direct Powered Personal Transponder. In R/C racing, details matter. The slightest change or modification can be the difference between making the box, or being a back marker. So MYLAPS developed the next generation RC4 3-Wire transponder to do more than just count your laps. The RC4 3-Wire provides the user with telemetry data such as lap times, connected voltage and ambient car temperature, information that can be used to shave seconds off your overall times. RC4 transponders are compatible with RC4 timing systems can be used for both indoor and outdoor on-road and off-road racing and will perform on just about any surface.