LYCOS RETRIEVER 
Switch
built 657 days ago
The contacts of a reed switch are closed by bringing a small magnet near the switch. They are used in security circuits, for example to check that doors are closed. Standard reed switches are SPST (simple on-off) but SPDT (changeover) versions are ... available.
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The most basic switch is two pieces of wire coming together. When you touch the wires together, electricity can pass from one to the other, completing the electric circuit. When you pull the wires apart, the circuit is broken.
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Using tools with textured heads, the darkened copper and brass light switch covers are hammered, and the raised surface is sanded. This reveals beautiful highlights of pink copper or gold brass, leaving the recessed hammer blows dark.
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The entire surface of this switch is sensitive because its top is not hinged. (Hinged switches have a large unusable surface area near the hinge.) In addition, this switch has been constructed of heavy aluminum and is very rugged.
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A "snap switch" has an internal pivot mechanism that makes sure that the switch is absolutely on or off. They often make a little "click" noise as the switch. The external actuator might be a little button that is pushed, or a stub that is rotated.
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Unlike standard dimmer switches, which use triacs for switching, these Leviton wall switches use a mechanical relay to switch the load, so they have a much higher load capacity. For ceiling fans, since the electricity is not being modified by the triac in a dimmer, the electricity going to the fan motor is a pure sine-wave and won't cause the fan's motor to make an audible hum.
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