If your FPV racing quadcopter is equipped with the state-of-the-art Spektrum™ F400 Raceflight Flight Controller (SPMFCF400) and the Spektrum DSMX® Quad Race Receiver with Telemetry (SPM4649T), then all you need to enjoy the benefits the Spektrum Lap Timer System is this little sensor. Like the other connections on the F400 board, this sensor solders into place and operates off the internal power of the RC system. Each time your quad passes by the Lap Timer Base Unit (SPMLTG5000), timing telemetry is sent conveniently to your telemetry-equipped Spektrum transmitter.