rf 34 stop 34 signal which actuates audio tone generator 60 to produce an audio tone which stops the runner after he has made a false start i e started before the 34 start 34 tone is generated circuit 38 includes a plurality of switches 64 66 and 68 which respectively actuate coder circuits 70 72 and 74 to produce a coded rf 34 call 34 signal a coded rf 34 start 34 signal and a coded rf 34 stop 34 signal these coded rf signals are supplied to rf transmitter 73 for transmission to audio box 30 remote start control 46 includes manually actuatable switches 76 and 78 which respectively actuate coder 80 to produce a coded rf 34 start 34 signal and coder 82 to produce a coded rf 34 stop 34 signal these rf signals are transmitted by transmitter 84 circuit 38 also includes an rf receiver 86 for receiving either a coded rf 34 start 34 signal from remote start 46 or a coded rf detection signal from detector 14 these signals are decoded by decoder circuits 88 and 90 start mode select circuit 91 in response to the respective signals decoded by decoders 88 and 90 sends a signal to electronic timer circuit 40 to indicate whether a runner is started by an audio tone or is self started referring now to fig4 there is shown in greater detail a block diagram of ultrasonic detectors 14 16 18 and 20 as shown transmitter one shot multivibrator 92 produces a a.