There is an MOV, metal-oxide-varistor (MOV), provided with each reader. This device prevents back EMF (high voltage 'spikes') being returned from the electric lock to the unit. High voltage spikes can cause severe damage over a period of time, and erratic operation of the system if not controlled. Failure to fit the MOV at the lock will result in early failure of the unit. It will also invalidate the warranty The MOV should be fitted across the power terminals of the lock
