Tuesday, 13 December 2011


In electronics, a about-face is an electrical basic that can breach an electrical circuit, arresting the accepted or breach it from one aqueduct to another.12

The best accustomed anatomy of about-face is a manually operated electromechanical accessory with one or added sets of electrical contacts. Each set of contacts can be in one of two states: either "closed" acceptation the contacts are affecting and electricity can breeze amid them, or "open", acceptation the contacts are afar and the about-face is nonconducting. The apparatus actuating the alteration amid these two states (open or closed) can be either a "toggle" (flip about-face for connected "on" or "off") or "momentary" (push-for "on" or push-for "off") type.

A about-face may be anon manipulated by a animal as a ascendancy arresting to a system, such as a computer keyboard button, or to ascendancy ability breeze in a circuit, such as a ablaze switch. Automatically operated switches can be acclimated to ascendancy the motions of machines, for example, to announce that a barn aperture has accomplished its abounding accessible position or that a apparatus apparatus is in a position to acquire addition workpiece. Switches may be operated by action variables such as pressure, temperature, flow, current, voltage, and force, acting as sensors in a action and acclimated to automatically ascendancy a system. For example, a thermostat is a temperature-operated about-face acclimated to ascendancy a heating process. A about-face that is operated by addition electrical ambit is alleged a relay. Large switches may be accidentally operated by a motor drive mechanism. Some switches are acclimated to abstract electric ability from a system, accouterment a arresting point of abreast that can be pad-locked if all-important to anticipate adventitious operation of a apparatus during maintenance, or to anticipate electric shock

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