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"- going"
Input Switch |
The voltage at the output of this module
is +9 volts unless the push to make switch has been pressed. When the
switch has been operated, it is said to have been "made" and
the output voltage immediately falls to 0 volts. The "pull-up" resistor
is there to take the output back up to 9 volts when the switch has been
released. This is essential if you connect to "logic" or PIC devices;
as they have to see a logic1 (+) or a logic 0 (-) signal. Without the resistor the signal would be floating.
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Circuit Diagram
Other examples of switches giving a - going output voltage. |