Thermostats are devices that regulate the temperature of a space by controlling the heating or cooling system. They are used in both residential and commercial buildings to maintain a comfortable temperature range and save energy.
The first thermostat was invented in 1883 by Warren S. Johnson. It was a simple device that used a mercury-filled bulb to sense temperature changes. As the temperature changed, the mercury would expand or contract, causing a lever to move and adjust the heating or cooling system.