The Inductor Dual Magneto Timer measures the change of magneto coil inductance when the points open or close. Simply shorting leads together will not indicate a point closing, eliminating false readings caused by loss of contact to mag ground terminal. Clip lead pop off or shorting won't cause false indication. Indicator LED's light when the points are closed. On point opening, LED's extinguish and audio tweeter emits a signal. The mag connected to the red lead will emit a rapid beat rate. The mag connected to the green lead will emit a slower beat rate. With both points open a third continuous sound will be emitted. Use also as a relay coil tester. Don't use on battery ignition systems! Solid state construction allows for low battery drain with resultant long battery life! 1 year factory warranty.