LYCOS RETRIEVER 
Switch: Contacts
built 656 days ago
Knife switches are a more or less obsolete type of power switch used in the 1800s. The live (hot) parts of the switch are uncovered and uninsulated, and they are unsuitable for use at shock-risk voltages. Knife switches have a relatively large contact spacing when open, so in the 1800s were often used to control power machinery running at high voltage, a use that can only be considered dangerous.
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Tilt switches contain a conductive liquid and when tilted this bridges the contacts inside, closing the switch. They can be used as a sensor to detect the position of an object. Some tilt switches contain mercury which is poisonous.
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The mercury switch consists of a drop of mercury inside a glass bulb with 2 contacts. The two contacts pass through the glass, and are connected by the mercury when the bulb is tilted to make the mercury roll on to them.
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