Generally, the camera control PLC commands are not long-distance, since all the camera power supplies are located back near the monitor.
OK I'm confused again. If your camera power supplies are at one location near the monitor then your video breakouts are located there also and all your CAT 5cables. Otherwise you can't be turning on your wired cameras individually. You are controlling your cameras individually right?
I'm confused at your confusion...
Maybe I'm misunderstanding the term, "video breakouts", but let me try to clarify what I
think you are asking: The camera power supplies are all located near the same physical spot where all the "local" camera cables
and the "near end" of the Cat-5 extension cables for the "remote" groups of cameras come together and are merged -via several "breakout boxes"(*)- into a single video and single audio output feed to the TV monitor. So,
most of the signal joining takes place at this "central office". However, the Cat-5 extension cables serve three to five remote cameras each, and so the signals from the remote cameras in each group are joined together at the remote location (i.e. - at the other end of the respective Cat-5 cable) via "breakout boxes"(*) into single video and audio lines coming back over the Cat-5 cables. And yes, all individual cameras are controlled individually.
(*) Note: "Breakout boxes" would more correctly be called "merging boxes" as they function in this layout.
Going back to my original question, I'm wondering whether there is a simple, "passive" way to provide enough impedance matching to suppress the reflections, "ringing", etc.
Going back to my original answer. No. No amount of impedance matching will address the fact that you have the outputs of all 16 cameras wired in parallel through all your "Y"s.
You have 16, 75 ohm resistors in all in parallel. Your monitor is looking at a whats left of a video signal across 5 ohms instead of 75 ohms. You need to isolate those 16 lines OR seriously boost the signal.
OK, I'm no RF engineer (hence all my questions about impedance matching). But, I'm not sure we're talking about the same issue here. My understanding -such as it is- is that video "ringing" is caused by "standing waves" on "transmission lines", that occur as a result of portions of the video signal being reflected (perhaps repeatedly) due to the incomplete transfer of signal from the transmission line to the load - which, in turn, is caused by the load impedance not matching the "characteristic impedance" of the transmission line. This is the impedance mismatch that I'm seeking to address. I understand that traditonally this matching is accomplished by balun devices at one or both ends of the transmission line (and at each merged input, in the case of signal-joining). Because I'm not finding any suitable balun devices, and the "active" Cat-5 matching chips or compensator chips would require some sort of power supply, I'm hoping there might be some other passive component(s) that would work instead.
That said, I want to emphasize that the problem I'm seeing is with video "ringing"; I don't see any other overt evidence of signal
loss - such as weak/"snowy" pictues - that would indicate any need for signal
boosting, per se, because the images with all cameras merged is comparable to the image from any camera when it is directly connected by itself -
except for the presence of the "ringing". That's why I'm uncertain that there is any need for signal multiplexing with the intent of avoiding direct signal loss.
So, that's my "take" on the situation, FWIW...