the my laps transponder is part of AMB on a buy out. as you cross the LOOP as my tack calls it the Computer counts your lap time and lap as you pass over the loop. the loop is a piece of wire in the bround to pck up the singal from the transponder. mount far forward on the rc as you can and flat it works best this way. do not stand it up on it's side it will not count your laps.

AMB personal transponder or Mylaps transponder is the most pouplar serach ebay for one about the best place to get them used and new.