True. However, in the context of much of the equipment that many of us are dealing with, these older forms of logic are most relevant. This is why I read and try to understand posts, such as Eric’s. So the historical part is nice to know. But understanding how the early forms work is essential to the understanding of the later versions. That is why I enjoy herring from people, such as yourself, and others on this forum who have a better understanding of the subject.