The Inertial Sense Module or ISM is a solid-state electronic device developed for use with the interVOLT DCC Pro.In simple terms the ISM detects movement (from both engine vibration and acceleration) when attached to the vehicle chassis or body. Once the input voltage is within operating range this movement will provide a trigger signal to the DCC Pro and initiate the charging cycle.This enables the DCC Pro to be operated in Ignition Mode without having to tap into the vehicle manufacturer’s wiring system to obtain a signal. As a result, the whole DCC Pro install becomes totally independent of the vehicle’s electrical system, aside from the common connection of the main battery terminals.