I want to thank Bob Bartizek for his kindness and electrical expertise. Awhile back I was looking for a way to use 3 inputs to control the aspect of a PRR signal. He designed a circuit to make this happen and today we got it to work. I have known Bob for a number of years and first met him in person at a 2007 Pittsburgh area NMRA event (Model Train Jamboree) sponsored by my division. As far as I'm concerned, Bob is the first and last word on TMCC. Some of you might recall his December 2006 article on the subject. If TMCC required a book to make it work (which it doesn't), he'd be my choice to write it. Bob has always been willing to share his knowledge and help out a fellow modeler.
This is the circuit he designed. The top of the diagram shows the track plan and the problem we needed to solve. If any of the 3 inputs (2 switches and 1 block) are activated, the signal should indicate STOP. Direction of travel is right to left.
I even made a little movie of the circuit in action.
Once again Bob - thank you very much!!! You are a prince!!