What signal does the distributor send to the tach in a normal car? I assume that it sends at least one signal per revolution but possibly up to four then the circuitry in the tach counts the number of pulses over a short amount of time a calculates the number of revolutions per minute??

Its a weird question but if any body knows how it works I would be very interested in hearing it!!!

 

sends one pulse for each plug that fires. So you get 2 pulses per revoultion of the crankshaft.

Been that way for about 100 years.