Electrical Switches
Every device that makes use of electricity must be controlled by an electrical switch of some kind. This is true for the simplest of all electronic devices, such as light bulbs, as well as the most complex machines, such as computers. Both kinds of devices are used by people to achieve some purpose, and in order to control those machines, their users require interface tools that give them control over their devices.
Toggles,
rotaries,
push-buttons and
rockers are all examples of such controls. Two of the most common types of
electric switches are
single-pole and
double-pole switches. The simplest type of electrical switch is a single-pole (SP) switch. SP switches have two points, called contacts, that connect to make a circuit and separate to break the circuit. Double-pole (DP) switches, in comparison, have two "on" positions and one "off" position. For example, the fan button on kitchen range hoods has a high-off-low configuration where the two "on" positions provide different voltages.
All electrical switches control whether the circuits to which they are connected are closed or open. An electrical circuit is so named because when it is complete it forms a closed circuit through which electricity passes without interruption. When a circuit is opened, electricity cannot pass without interruption, which ceases the operation of the device involved in the circuit. When a circuit is opened, the switch controlling that circuit can be said to be in the "off" position. When switched to the "on" position, the switch closes the circuit, allowing again for the continuous flow of electricity through the circuit. Because there are so many different kinds of electronic devices, an equally wide variety of different circuitry options is necessary to accommodate them. In a simple electric light, nothing more than wires, a switch and a power source is necessary for the light's operation. In a computer keyboard, a complex web of circuits embedded on a circuit board is necessary to send signals to an attached processor. In both cases though, switches are used to control the circuitry.
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