This Tach Adapter allows users to connect a tachometer, shift light, or RPM activated switch to their distributorless ignition system (Including 1999 and newer Ford Mustangs). The unit senses the current going through the positive coil source wire, then converts that information into a 12-volt square wave signal that can be read by Auto Meter tachometers and accessories. The tach adapter is compact and completely potted with polyurethane for vibration and water protection. The unit wires easily inline on the coil positive 12-volt wire, ground wire, and the tach output wire.