Matt, Put a 200V Full wave Bridge rectifier in the phone line leads before the 3.3 meg resistors on the phone line leads. Then when SWB reverses polarity, it will still work, and you don't have to check polarity when you hook up the circuit! smile It is possible that the additional resistance the FWB introduces will require that you reduce the 3.3 Meg resistors to 3.0 Meg. John C.

When I was young, I was Liberal. As I aged and wised up, I became Conservative. Now that I'm old, I have settled on Curmudgeon.