The emergence and changing the oncoming force swift and violent, with numerous and complicated contently of the building trade, the modernized building is in different poses and with different expressions, the model is different, and demonstrate the high, big, the whole, new characteristic progressively. Storey of the modern architecture counts higher and higher, the floor space is larger and larger, inside facilities are more and more perfect, the function is more and more complete, the equipment and material used are newer and newer. It is larger and larger to include the inside flow of horizontal traffic, vertical traffic inside a building. We hope the building (including underground part ) supply power incessantly, and various kinds of calamities have a contingent one in fact. For instance: Such calamities as fire, exploding and earthquake, etc...When these calamities take place, the normal power often breaks down or must disconnect the power, normal illumination all go out at this moment. For the security of support personnel and property, and operate and deal with the production, work that are carried on in time, prevent the calamity or the accident from spreading effectively, should put into and meet an urgent need and light immediately at this moment.