The LightBridge uses IR light sources centered over each lane to illuminate the IR detector mounted in the track below.
http://www.pinewood-derby-timer.com/cat ... 144436.htm
There are also 3 new DerbyPaks that combine our DerbyStick, LightBridge, and Race Software into complete race packages.
http://www.pinewood-derby-timer.com/der ... talog.html