On the bakelite cover of plug a metal ring is installed, and inside of which there are a neon lamp and a current-limiting resistor. When the plug is inserted in the socket, observe the neon lamp whither it is light or not through an inspection hole. If the lamp is light, it means safe. If light is off, it is necessary change over the connections of the plug. For two pins plug, just need to turn 180 deg. For three pins plug, the changing over of connections can be performed quickly by means of a set of mechanizm. This plug plays an active role in simplifying construction of electrical appliance (e.g. omission of transformer) and ensuring safe operation with electricity. |