Stan, thank you for the explanation.
As to sensor (safety) control, it turns out that going thru my many purchases from ebay, I bought a number of rotary switches (I have 2 ZW Transformers and used them to switch tracks & throttles). One of the switches is a 4-pole/5 pos. switch and is perfect for the job. I am not only turning safety functions on/off, I am also selecting a specific track section, illuminating a lamp on the selected track section, and changing ZW throttles based on where the engine is coming from/going to.
And Adriatic, I used the (~) symbol to indicate approximate. I need to fiddle with the regulator output to make sure I have enough 'juice' to drive the servos on the TT without overdriving the optics.