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Electrical switches can make, break or divert an electric current and come in mechanical, electrical or electronic forms. They fall into two categories: power switches and signal switches. Mechanical switches are the most common, while electronic switches use semiconductor devices and have medical applications.
Electrical switches are devices that can make, break or divert an electric current. These can be mechanical, electrical or electronic and consist of two or more contacts, mounted on an insulated structure, which can be moved in and out of contact with each other. As the use of electrical and electronic items has expanded, a wide variety of switches have been developed in numerous styles, including many varieties of toggle, keypad, dial, push button, and rocker configurations.
These switches fall into two basic categories: power switches and signal switches. Power switches are used to power or de-energize an electrical load and are commonly found on light switches, power tools, and appliances. Load disconnectors are used in high voltage power systems that require arc breakers or safety devices that detect the electric arc and interrupt the current, similar to the function of a circuit breaker.
Electrical signal switches are set to react to circumstances that require a preset response and are found in devices such as the thermostat on a heater or air conditioner. When a certain temperature is reached, the thermostat turns another switch on or off. Signal switches are also found in freezers, refrigerators, and sensor-activated security lights. Some security lights are activated by photoelectric light controls which are activated when natural light has dimmed or brightened to a certain level.
The most common are mechanical switches, which make or break an electrical contact when a force, manual or magnetic, is applied to move the switch to an on or off position. Toggle switches have a lever that is pushed or pulled, like the common light switch. Power windows and car locks use rocker switches, which rock back and forth when pressed. Keyboard switches are found on computers, washing machines, stoves, and other devices with push controls.
Electronic switches do not have mechanical contacts, but instead use semiconductor devices. These switches apply electrical control signals to the terminals on the switch which opens and closes the contacts. Touch plate devices, soft-touch controls, and motion detector switches are often electronic. Some electronic safety switches fitted to food processing equipment use radio frequencies which cut off power when a safety door is opened. Electronic switches come in a variety of configurations such as toggle, rocker, pushbutton, rotary, slide and reed switches, and relays.
Electronic electrical switches also have medical applications. Electrical stimulation devices are used to rehabilitate and accelerate the healing of damaged tissue. Transcutaneous electrical nerve stimulation (TENS) devices, neuromuscular electrical stimulation (NMES) devices, and functional neuromuscular stimulation (NSF or ENS) devices use current, controlled by switches, to relieve pain, relax muscles, increase blood circulation and prevent muscle atrophy.
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