There are basically two types, the association in series and the association in parallel (2.6b). When dealing with a contact association, it is normal to set up a table containing all possible combinations of contacts. It is known as Truth Table.
It is possible to notice that in the combination in series the load will only be activated only when these two contacts are activated, thus being called function E. In the combination in parallel any one of the connected contacts connects the load and for this reason it is called the OR function.
In the case of association of normally closed contacts, the NF contacts in the same way can be found in series and parallel. In the same way, the parallel association is called a non-E function. Just as to change a wheel in an automobile, when the tire sticks, it is necessary to know the tools themselves, their electrical commands, to really understand the operation of a circuit and later To draw the same, you need to know the appropriate elements.
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