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An early switch operating by this principle was invented by Chester I. Hall of the General Electric Company, with a patent filed in 1921 and approved in 1924.Like the modern infinite switch, Hall's invention used a bi-metallic strip, heated by a constant current, to break a connection after a given period of time.
A limit switch with a roller-lever operator; this is installed on a gate on a canal lock, and indicates the position of a gate to a control system A limit switch mounted on a moving part of a bridge In electrical engineering , a limit switch is a switch operated by the motion of a machine part or the presence of an object.
A thermal switch (sometimes thermal reset or thermal cutout (TCO)) is a device which normally opens at a high temperature (often with a faint "plink" sound) and re-closes when the temperature drops. The thermal switch may be a bimetallic strip , often encased in a tubular glass bulb to protect it from dust or short circuit .
Knob-and-tube wiring (sometimes abbreviated K&T) is an early standardized method of electrical wiring in buildings, in common use in North America from about 1880 to the 1930s.
In adjustable thermostats another contact is positioned with a regulating knob or lever. The position so set controls the regulated temperature, called the set point. Some thermostats use a mercury switch connected to both electrical leads. The angle of the entire mechanism is adjustable to control the set point of the thermostat.
A hot plate or hotplate is a heated flat surface on a stove or electric cooker on which food may be cooked. [3] It comprises a heated top which is flat and usually circular, and may be made of metal, ceramic, or heat-resistant glass, with resistive wire forming a heating element fitted underneath and a thermostat to control the temperature.
Switches may be operated by process variables such as pressure, temperature, flow, current, voltage, and force, acting as sensors in a process and used to automatically control a system. For example, a thermostat is a temperature-operated switch used to control a heating process.
Two control knobs for a heating/cooling system. The left knob controls the temperature while the right controls the fan speed. A control knob is a rotary device used to provide manual input adjustments to a mechanical/electrical system when grasped and turned by a human operator, so that differing extent of knob rotation corresponds to different desired input.