Okay, a few thoughts ...
I use an old 1983
Tandy Model 102 computer with a FireCracker unit and a "TempTrax" Model F probe reader to control a swimming pool pump, and to control X-10 cameras and lights around the house. A friend helped me write a BASIC program to send the correct X-10 signals to the modules and cameras via the FireCracker unit!
Here are a few things you should know:
1. If ONE x-10 camera is on and transmitting, you cannot turn on another camera on the same channel and unit settings (1,2,3,4 or A,B,C,D on the camera
and receiver) at the same time. This will give you the zig-zag screen as both cameras fight to display a picture on the same frequency.
2. Assume your cameras are set to unit codes 1,2,3 and 4. When you turn on unit 1, it will display a picture. When you turn on unit 2, unit 1 will turn itself off, and unit 2's picture will be displayed. The same goes for 3 and 4. The EXCEPTION is when you set your camera units to numbers above '4.' If your cameras are set to 5,6,7 and 8 (or 9,10,11 and 12) for example, you must turn OFF whatever camera you are viewing BEFORE you turn another camera on, or the images will clash. I tried to rotate through my cameras with the computer, sending "A-9, ON ... A-10,ON ... A-11, ON ..." and so forth and found that they would not display. When I sent "A-9,ON ... A-9, OFF ... A-10, ON ... A-10, OFF ... A-11,ON ... A-11,OFF ..." and so forth, the cameras numbered above '4' worked properly. I do not know why this is the case, but that is what you must do to sequence through cameras with a unit code above '4.'
3. Your house has TWO feeds for current. Each feed is 120 volts AC, and when you use both, you get your 240 volt AC current for air compressors and welders, etc. If your cameras are on the same circuits (breakers that are all fed by ONE of the two feeds) the X-10 signals will all work, but if you plug cameras into circuits fed by the OTHER side of your breaker box, the X-10 signal won't reach them unless you hook up a "signal bridge" which will send the X-10 signals to both feeds.
4. Not to be insulting, but have you checked to see that you have removed any LENS CAP from the "black" cameras?
5. If you are using a TV to view your cameras, you must make sure that your cameras are being fed to one of the
AUXiliary inputs, and that your TV is set to VIEW that input.
6. The paddles on the camera and receiver must basically FACE each other in order for the signal to work, and you can forget about the "100-foot range!" They're good for about 25 feet, on a GOOD day. Less, if the signal is going through walls.
If you live in the San Diego area, I'd be glad to help you with this stuff, but if you are elsewhere, you'll have to go find a techno-geek who can help you out.