These little devices are a pair of balance Balance means, uh, balance to unbalanced. It's a little conversion unit, usually with a Transformer inside and here's what they do: if you've got a remote camera some considerable distance away and You' got a monitor um, that you want to connect to that camera you can use instead of running separate power cables and uh, coaxial video cables, you can use standard data cable and you plug it in to one unit, plug it into the other unit, and that lets you send power over the cable. Plus, it also gives you the video signal over the cable and the way it achieves. this is it.

Uh, usually is a Transformer not for the power, but just for the video that couples onto the cable so they're electrically separate, but they still get the signal through. Let me show you what I mean by that and then we'll open these up and see what's inside. A really good way of demonstrating this is probably with a problem that we've all come across at some point. It's connecting laptops to amplifiers.

so if you've got a laptop and most laptops don't have a ground, they often have the uh, the mains plug going to the little power supply and the laptop itself is isolated from ground and sometimes you get a slight tingle off them just because of electrical leakage to the power supply. So if you take your audio cable, I'm just showing one channel in this instance uh, as opposed to like left and right and you connect to an amplifier with a standard, safer, a standard headphone socket to a line in connector. Then it connects the General Chass with one core and it connects the audio signal with the other. The amplifier might be grounded, or it might just be on a different sort of Uh power supply that they both have different interactions with each other.

And what can happen is that in the case of a grounded amplifier and the laptop, it's not just sending the audio, but it's also sending that electrical noise produced by power supply along that cable and you end up with lots of sort of strange buzzing, hissing noises from the activity of the laptop. and also, uh, the mains reference the slight Main's leakage through that. The way to solve that in the case of the audio application is to put in a audio isolation. Transformer What this does is it presents a winding on a Transformer to the laptop that looks just like a set headphones and it has another winding which has matched the amplifier that looks like a line in and that couples the audio signal across.

But because there's no direct electrical connection, because it's a Transformer with two separate windings, it isolates the two and that noise can't travel along between them and cause problems. This is also useful even if you have a grounded piece of equipment because if you have a long run of cable and you've got two separate grounds in different areas of the building, they can carry a lot of electrical noise just through interference suppression equipment coupling that noise onto the the Earth or ground connection. The other advantage of a Um balanced circuit because this is the balanced aspect that it can U if it's connected to the input, then the balance type uh Arrangement because the signal is basically going that direction and that direction and then vice versa for the AC It uh means that if you have an adjacent cable that's radiating a lot of noise onto that and it ju induces a current uh in both directions in those wires, then they cancel each other out because one is effectively pushing, one is pulling, and it just results in an easy way of connecting equipment without that electrical noise. I Use a audio isolation Transformer on my laptop to connect to the Uh speakers because uh, without it, it is very noisy, right? Tell you what, let's open these up.

The other option for these, you can get uh the audio and video version I Thought that that's what I was getting here. It doesn't really matter I did kind of list that but I don't think they knew what they were selling. That's fine. These look as other glued together so I'm going to give them a reassuring squeeze with the nice Vice of knowledge and see if this makes crunchy noises.

I Don't know how easy these are going to get into. They strike me as being that horrible chewy plastic. This is where I'd normally give them a sharp tap with a pair of pliers or Hammer as we know it in the trade, but if this doesn't work, Um, then I shall pause the video which I think I'm going to do because I just know these are those chewy plastic ones are very hard to open and I shall smash the living beas out of them and then I'll come back once I've done that one moment, please. The cases have been smashed off.

It is now time to explore and I was completely wrong. I Honestly thought the little Transformers in these were going to be used to galvanically separate it, but they're not. They are purely impedance matching, which is a horrific science in its own right. So let's explore the circuitry and then I'll show you the schematic of these.

We have the connector here. Got the two modules side by side here, one up the other way and the power wires come in and they go to two of those pairs. They don't try and treat them as Twisted pairs, just basically one full twisted pair is positive and one is negative. There is the facility to have the audio signal sent across another of those Twisted pairs but not uh given the Transformer treatment, but the video uh signal which is a very high frequency signal this is probably why they've done it goes to this little Transformer but I it's A it's a dark science.

It's almost like radio science. Uh, the wireless technology. It's a cable science is ridiculous. Uh I'll I'll provide a link to Cable impedance on Wikipedia It doesn't make good reading.

it's not enjoyable reading at all unless you're really geeky and into that. But the BNC connector basically goes to one side of it, goes to um, one of the windings and the other goes to the other, passes through this little impedance matching. Transformer looks at a little toid like this and then goes to the connector and then the other end does exactly the same thing. Anything else Worth showing on this not really I shall show you the schematic which will not make sense of anything at all because it's super high frequency signals being propagated along cables.

which is just an nightmare. Let the scientists do that. So we just need to plug the cables in. So here's the uh.

Well, there's the power for a start. Positive is going across the blue twisted pair. negative is going across the brown twisted pair. The audio is going across the green twisted pair before the video signal goes across the orange twisted pair.

it. uh, goes through the Transformer So the each connection to the BNC connector is going through one winding. but why are they actually kind of opposing each other? That is tricky. I'm not sure the science behind that, perhaps perhaps you could elaborate on that on that for me in the comments, but it's going along the cable and then the same treatment other end.

It must be to do with the fact is such a high frequency signal that would may maybe actually caused complications of Ganic Separation Um, but that is what's in these units. I Can't really go much further. I Mean that it looks so simple. but really, the science behind it is absolutely not simple.

The same with uh, the balanced Uh cables that we get for Data Networks, Rs485, and the termination resistors. That's all down to Cable impedance and creating infinite, uh, apparent infinite length to avoid signal Reflections your at the frequencies we're talking about here. uh, reflections of signals from the cable ends actually become an issue and you do have to match the characteristic impedance of the cable. Um, but this is it.

It's interesting as I say I'll let the true experts on this technology in in the comments, but there we have it. That's the inside of two generic video balance units.