The selection of sequences correspond to the OR-divergence. It is used when the aim is to evolve the GRAFCET through one or more sequences, between the several sequences available, starting from a certain step. When the aim is that the GRAFCET evolves just through one sequence, the OR-divergence receptivities must be mutually exclusive. Another way to make shore the GRAFCET evolves just through one sentence is by establishing priorities between the evolution of several sequences. This can be accomplished by changing the receptivities associated with the respective transitions.
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Another example about sequences selection with exclusive receptivities is presented below. By pressing button A sequence 1 is executed, while pressing button B sequence 2 is executed. In the case where both buttons A and B are pressed simultaneously the two sequences are executed in parallel.