Hi,
I haven't studied this thread in detail but if the idea is to "place a resistance" across the plug then I don't think you can run the same code (if that's what you're doing) with the two different hardware designs. When using the circuit with the opto-isolators you drive the PIC-pin high in order to turn on the opto-isolator and connect the associated resistor across the plug - and if I read your posts correct this works fine.

It's not exactly clear to me how the plug is connected to the circuit in post#1 but it looks to me as if this circuit doesn't work the same way as the one with the opto-isolators. So, if you're trying to run the same code with the two circuits my guess is that's where your problem is.

/Henrik.