MPO111 RTP SLOT Many switches are operated automatically by changes in some environmental condition or by motion of machinery. A limit switch is used, for example, in machine tools to interlock operation with the proper position of tools. In heating or cooling systems a sail switch ensures that air flow is adequate in a duct. Pressure switches respond to fluid pressure. The mercury switch consists of a drop of mercury inside a glass bulb with two or more contacts.|Daftar Episode Amphibia