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All of the logic in the first examples of this section has been accomplished with relay contacts and other input switches. When sets of contacts are wired in series with each other as in Fig. 1 (below), their logic function is called an AND function because switch 1 AND switch 2 AND switch 3 must all be closed to pass power to CR1, the relay coil for the circuit. If any of the switches is opened, the series circuit is broken, and no power will be sent to the coil. |
Above: Fig. 1: AND and OR logic functions
executed by input switches and a relay coil.
The second circuit in Fig. 1 shows three sets of contacts that are wired in parallel with each other. This type of circuit is called an OR circuit because either switch 1 OR switch 2 OR switch 3 can close and energize the relay coil CR2.
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