Switches
1) Switches are the simplest kind of sensor, giving data in the form of
an open or closed connection.
2) Mechanical switches such as buttons are used to measure user input.
3) Microswitches are small switches with an extended arm to increase sensitivity.
Typical uses include collision detection and conveyer belts.

4) Tilt switches turn on/off through gravity acting on mercury or "ball
in cage" design. Mercury is no longer used for health reasons.

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