Jim:
I do not recommend the capacitor approach. I have seen the capacitor blow-up in an electrical panel and make a mess at the very least. If you are in front of it and it blows up, it would be even worse. The passive coupler does the same thing as the capacitor, but it does it safely. It is also "tuned" to only pass an X-10 signal from one phase to another.
The only difference between the passive coupler and the amplified coupler is that the amplified coupler amplifies the X-10 signal more than 50 times. This is a big difference however and that is what makes it worth the money. It can turn an unreliable X-10 system into a very reliable system.
Robert
RCI Automation
rciautomation@csi.com[Link: ourworld.compuserve.com]