While browsing for information on motor control circuits, I found this great site from DC circuitry to PLC's and beyond, and the best of it is it's free. So far, I've found it to be a great help for those maybe that haven't had the priveledge of going through a regular schooling program. Once I find a "reply" button, I will let the author know how much I appreciate his contribution. Check it out. He has 6 volumes with information that a person could spend "forever" on. http://openbookproject.net/electricCircuits/index.htm

Hope it helps someone, Steve...