How would you do this?

[ERMEGM]

I want to thank everyone for their help on explaining a few things. There are a lot of things to consider when putting circuits in these types of environments and some of us have more experience than others, so I'm sure I speak for most of us when I say that I appreciate everyone's input especially when someone is sharing their trial and errors with the rest of us. I hope Charles didn't take my questions as questioning his formulation. I am merely trying to understand and also make sure that I am clearly describing what I am trying to do.

With that said, I'd like to share what I have found myself about what I was asking to do. This setup can obviously be modified to do what you need it to do, but this is something that works for my application, so I'd like to share it with you.

The red input is what activates the routine. The pic is already running and pin 5 is pulled low. Pin 5 sees 5 volts through the zener when 12 volts is applied to the red input. When the positive input goes high with 12 volts, the transistor is turned on and diverts the 12 volts from the red wire to ground so pin 5 sees nothing and is pulled low again.

The circuit on the right is a negative trigger. Pin 4 sees 12 volts through the two resistors above. When ground is applied to the negative input, pin 4 is pulled low to trigger another routine on the pic.

My question is this though, why the RC parallel filter? I know I can simply use the same setup, but I'd like to understand what value this has. I know the cap is for smoothing out the input to prevent the pic from seeing multiple inputs when there is only one (debouncing), but what's the parallel resistor for? I see how it's part of a voltage divider on the right side circuit, but what about on the left side? Is that just to discharge the cap?

Thanks,
Tony