Here's a British tumbler switch, 1940s/early 1950s style (Britmac "Little Briton" rated 250V 5A AC/DC). Note the spring linkage between the operating handle and the contacts below:
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Starting from the "on" position, thus:
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Moving the handle upwards toward "off" moves the top of the tumbler assembly downward (foreground of photo), but all it does initially is to start tensioning the spring:
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Handle moved over the greater part of its travel, but contacts still firmly closed:
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Almost there now, note the position of the spring with the top of the tumbler almost at the "point of no return":
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Until finally, on the very last portion of the travel the spring snaps the contacts open quickly:
[This message has been edited by pauluk (edited 05-02-2006).]