This memory saver retains all automotive pre-sets and computer memory when disconnecting or changing automotive batteries. A 12 VDC sealed lead acid battery inside the unit provides enough power to keep the pre-sets and memory intact while you disconnect or remove a vehicle's battery. It's as simple as plugging the memory saver into the vehicle with the attached OBDII 16-pin DLPL connector. Then flip the on/off switch and the memory is retained. It includes a 120 VAC charge cord with overcharge protection built-in, to recharge the memory saver battery when it gets low. Made in USA.