Does anyone know the signal to the tach at 6500 to 6600rpm? Does the tach read it just by how many volts, or signal length or something else? Sorry I am not electronic engineer as you can tell ha.

Also, does anyone happen to know the signal at 4900rpm?

Thanks in advance for help. If all else I can pull my dash apart and test myself, but is there more to it than just volts?