does anyone know how the tach signal is outputted from engine?

is it an increasing voltage from say xx volt - 12 v?

or does the tach get it's reading in another fashion?

thanks

It's a pulsed signal, not a continuous voltage. The pulse frequency will vary with the engine speed. The tach signal is not available directly from the engine but only as an output from the ECU.

ah
i know my conquest w/ msd did a 12v square wave

wasn't sure about how subaru ran... one of my dad's old gms did it in a ramping voltage... aiight thanks