One of the promoters that we work with in the summer runs Mountain Cross events and uses the popular Cartessa NBL gate controller for the start. The DIN plug on the front can be used to get a start impulse for qualifying. Pin out is 3 12+ and pin 4 12-. A small project box and a 12v relay coil with a reverse biased diode will complete. The circuit is live when the gate drops for about 2 seconds. You can also rig a light with this circuit for deaf riders (or ones with ipods blasting).

Picture1.jpg (42 Kb, 58 downloads) schematic of the unit