Switching between 2 digital over analog cable CCTV camera feeds

Thread Starter


Joined Jun 22, 2019
Here's what I'm trying to do: I have a Q-See QT View camera system with 8 inputs. The system is designed to run 4K cameras over the old coax/12V dual cable from old analog camera systems, and works well. It saves having to re-run cables when upgrading from an old analog camera system to a new digital system. I believe it's now sending a digital signal over the coax cable. Various manufacturers have the same setup, although I doubt they use a standard (interchangeable) protocol.

What I'd like to do is be able to take 1 input and electronically switch between 2 camera feeds. Switching would be infrequent, but would need to be done remotely (no human activated switch). If it was just a straight digital signal, I could probably just use a relay. But given that the signal is being sent over coax and has got to be a fairly high frequency signal, I'm guessing that a relay wouldn't work.

Any suggestions on how to accomplish this would be appreciated. I have no problem providing the control signal to drive the switching circuit, just have no idea what would be involved to build a circuit that would electronically pass one feed or the other feed. When it comes to transmission lines (which I'm guessing the 50 or 75 ohm coax is) I'm out of my depth.

Thank you.


Joined Aug 1, 2013
Without knowing more about the amplitude and bandwidth of the coax signal, it's hard to recommend a chio=p or circuit. There are coax relays, a normal-type relay coil with BNC connectors as signal contacts and better than average but not perfect impedance control through the armature and contacts. probably expensive.

Digi-Key has "high-frequency relays" that could work.

Or, try this:

Near-perfect signal integrity, stupidly expensive:

What voltages are available to power the relay and control circuit?

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Thread Starter


Joined Jun 22, 2019
What voltages are available to power the relay and control circuit?
The overall control circuit has a 12V supply, and I'm using an ESP32 for the web interface so I have 12V, 5V and 3.3V to work with. I'm looking at the HF relays on digikey you referenced and it's worth mocking something up to see if one will work.

Finding the bandwidth has been a good question. Numerous searches and camera datasheets have not yielded any useful information.



Joined Mar 14, 2008
A coax (BNC) type relay should work, but they appear to be rather expensive (several hundred US dollars).
You might be able to find a used one for a reasonable price.