This document discusses various types of power plugs and sockets. It describes special purpose plugs and sockets used for electric car charging and other industrial, commercial, or institutional systems. It also covers important safety features of plugs and sockets like polarization, earthing or grounding to protect against insulation failures, and interchange hazards when plugs and sockets are not compatible. Most car drivers only need relatively quick topping up of electric cars as they usually drive less than 40 miles per day.