AccuTech™ SMi™ Stepper Motor Memory Tach - Black in Aluminum Panel'Stepper Motor' Memory Tachs The next generation in instrumentation SMi Stepper motor techometers use a small electric motor to drive the pointer. It is more precise than the more common 'aircore' instruments whose accuracy can be affected by the windings. Many professional race teams NASCAR, etc. are switching to this style of tach for the improved accuracy and response (see the in car TV cameras). Maximum RPM recall Just push the Recall button High