Compu-Fire 20550 Elite 1 Digital Electronic Ignition - HDE-2 Single Fire All circuits are contained on the timing plate There is no module or anything else to mount The HDE-1 and HDE-2 have fixed advance curves and 6500 RPM rev-limiters to protect the engine Model HDE-3 has eight advance curves and an eight-stage rev-limiter adjustable from 6000 to 7500 RPM or off. All models have the Accu-Ray timing LED for precise timing and system check