Survey Sez - I'm not sure what you want explained - The one camera at-a-time setup, or the 4-camera setup.

X10's approach to a 4 camera video surveillance system centers around their remote modules. They have one video receiver and one video capture device imported into the computer, and use the X10 remote-capable power supplies on their cameras to turn them on and off, so only one camera was on at a time.
Although I like their inexpensive, weather-resistant camera design, this idea of turning all cameras off (or more accurately the wireless transmitters) except one wasn't appealing to me.
There are several 4-input computer video capture PCI cards on the market, so I bought one that allows 4 video inputs at 30 Frames Per Second (full-motion) video on each input, or 120 FPS total. Conveniently, they come with their own video capture/record software, which has all the nice features of email, alarming, etc. It does not interact with the X10 modules, as it is not made by X10.
My setup uses only one wireless channel, and 3 wired cameras. I get full motion video from all 4 cameras on my quad-screen view 24/7. I also use another X10 channel separately for wireless TV sending. Admittedly, the channel choice was a matter of trial and error, but dbemowsk's explanation of channel choice is about the best I've seen. There is NO getting away from the microwave oven interference on 2.4 GHz, as that is where they transmit as well.
I hope this helps.