I posted this in mechanical forums but i think this belongs here..
So you all know that MSD has there Selectable rpm pills for use with there shiftlights and stuff..
Basically the pills are just a two prong pill that has a certain resistor in it to activate msd shift light..
so my question is does anyone know how those rpm pills work..

ie: if i hook the pill up to my tach wire and say the pill is set to 6000, once i rev to 6000rpm will voltage pass through the pill or.......????

Thanx