With X-10 you need travelers I thought. With INsteon you do not. Or am I missing something?
I am using some low end used X-10 at the moment. They are soooooooooooooooooo cheap and they work (so far) where Insteon was a problem with so few installed.
I cant believe how much money I wasted on Insteon when X-10 may prove more reliable and a hell of a lot cheaper. There are also many more types of X-10 devices compared to Insteon. I bought some 230 V appliance modules new for $10 and they work. Insteon has no such animal.
You may have to use the travellers to establish a hot and/or neutral at one end of your existing 3-way setup - I would expect that to be true for all installations. With the ACT switches you can use multiple single (or multiple) device transmitters at any location that has a hot and neutral. The master dimmer/switch (a receiver) connects directly to the hot/neut/load. Other slave switches (often called multi-way switches) from PCS or Lightolier use similar wiring, but some such as PCS may not be 2-way devices. 2-way devices allow you to verify devices turn on by the receipt of status signals, including when manually turned on by a human :unsure: