This adapter was designed to overcome one of the main problems i found in trying to read the pulse off the negative Ignition terminal on a older style cars. This is for cars that have ether ignition coil or igniters. Its also compatible with the "high voltage" tach signals for older pre 2003 cars, were a high voltage pulse are required for the tach.

On the coil end all is needed is Ground (chassis) and the Neg-coil/igniter.

On the Micro controller side, all is needed is Ground, Vcc (Power), Signal out.

Its compatible with 3.3v, 5v, 12v. Signal out will swing between Vcc (HIGH), ground (LOW).

OPTICAL ISOLATION! (to prevent any high voltage signal to send to your microController).