Well, so much for using a Y-adapter.. X10 strikes again..
None of X10's PTZ cameras have addressable power supplies. They theoretically turn on when selected and off when another camera is selected.. I haven't tried that yet.
According to the VK77A manual, when you select any camera (C1 thru C4), it turns that camera on and turns all the other cameras off.
Well kinda, from what I just confirmed, X10 disables the Video sender module, but not the composite video output. To bad X10 didn't spend the additional 10 cents to disable the composite video signal too. Yet another half-a%$ed attempt at cutting corners and limiting usability!
Now for the real news..
The VA11A video interface uses a Philips SAA7113H video processor. This chip has onboard support for 4 SWITCHABLE composite video inputs and a video output (for monitoring). So if X10 wanted to, they could easily add 3 more video inputs, a video output, 50 lines of code, a new case and sell a 4 input video interface that would resolve all previous issues for less that $100.00. (As a side benefit, it could eliminate the use of all those addressable power supplies)
[come'on, $50 more for 4 more RCA jacks, a dozen SMT resistors, a bigger plastic case, and 2-3 days of programming, not a bad markup] Anyway, as if you can't tell, I'm pretty disappointed by X10 yet again, but I'll keep it in perspective.