S7 surgace boxes  short circuit and overload protection functions, and is used in industrial, commercial and residential lighting distribution system. They also have the advantages of high protection level (up to IP20), high breaking capacity, reliable and sensitive action, convenience, multi pole installation, long service life, etc. Single pole is mainly suitable for the circuit of 50Hz and 240V AC; two, three and four poles are suitable for the circuit of 50Hz and 415V to protect overload and short circuit. They are also used to turn electrical equipment and lighting circuits on or off under normal conditions.