Phase coupling is a necessity in an X-10 based system if you plan to have more than just a few X-10 receivers in your system. A passive coupler does good job of "bridging" 2 or 3 phases of electrical service, but it also attenuates the X-10 signal (not desirable). That is why an amplified coupler/repeater is a much better solution than a passive coupler. I haven't yet experienced a situation where installing an amplified coupler/repeater has not greatly improved X-10 signal reliability. It amplifies the X-10 signal about 50 times when it repeats the signal.
If you are interested in this topic, please review my previous post to this forum with the subject, "Why aren't my X-10 signals getting through?".
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