A thermostat is a component of which senses the temperature of a system so that the system's temperature is maintained near a desired setpoint. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer fluid as needed, to maintain the correct temperature. Thermostats are used in any device or system that heats or cools to a setpoint temperature, examples include building heating, central heating, air conditioner, HVAC system, as well as kitchen equipment including ovens and refrigerators and medical and scientific incubators.