Phil Kingery has written several in depth articles about X10:
Before we can choose the right X-10 device, however, we need to know a little more about the load we are wanting to control and how the circuit is wired.
Complex Residential Coupling with Considerations for Dim/Bright
There is an interesting and often confusing aspect of home automation, and that is, "speed" control. I am constantly amazed by just how easily we all associate "dimming" with "speed control".
Dim/Bright Commands and Coupler-Repeaters ...plus some other information about new stuff in the world of X-10
120/240v Residential Coupling
Three-Way Switch Circuits
More Three-Way and Four-Way Switch Circuits
Troubleshooting Three-Way and Four-Way Switch Circuits
Noise and Filtering, but let’s just define noise first.
Noise and Filtering, So Let’s Look at Filters.
Noise and Filtering, Troubleshooting
More Noise, Filtering and Troubleshooting (and let’s get this one done, already)
In more complex installations, a capacitor across the two legs will both help and hurt.
Two-Way and Extended Code
Two-Way Receivers with Direct Dimming and Scenes.
A Better X-10 Interface
What is Extended Code - Part 2