Member Discussion

Stream IP Video Using Only One Twisted Pair?

Hi all! Question for the engineers out there.

Do you think it is possible to stream video via UDP multicast from a camera to a dedicated decoder and monitor using a cable with only the TX pair (camera side) crossed over to the RX pair on the decoder?

So using just one pair of a cat 5 cable, at 10Base-T speeds?

I have a spare pair in a bundle that I could use with my intercom system if it would work...

How is this different than Reusing Existing Twisted Pair Cabling?

Only that it's cheaper (if it can work) I guess, no converters. But ether over twisted is bi-directional and far superior for most all other applications it seems.

And, honestly I never heard of it before. Thanks!

But I did think of something similar:

i.e. was thinking "what if you bought two EOC adapters and then put baluns on those to go on one twisted pair?" I thought it was crazy...

so I'm talking about a unidirectional ethernet cable, which could only work on something without flow control, like UDP.

NVT already takes EOC adapters and puts something like baluns on them. It shows 4 pairs (which is really best for distance and POE) but you can actually use only one pair. I wouldn't count on much POE over 24 awg copper at any large distance. Call them, they'll do the math and tell you what you can get.

NOTE: Others also make competing product, I'm just most familiar with NVT.

Thanks Austin, those are strange indeed!

I don't know if I was clear enough in the OP, but what I was thinking wouldn't need any converters or adapters, that is if it's possible.

I was testing a cable that showed a link light only at the switch, not at the device, which got me thinking whether you could make a transmit only cable from device to switch, by just using one pair. Obviously TCP wouldn't work because of the three-way handshake, but I was thinking maybe multicast datagrams would. Gonna try tomorrow...

10BASE-T uses 2 pairs. The switch won't recognize it without them.

I would agree. The only thing I don't understand is why a cable would show a link light at only one end? Have you ever seen this?

I have not... though I have never needed nor attempted this experiment. Is it a managed switch? If so, try logging into the interface and see if you see anything relevant. It might just be seeing electrical signal that falls within the range to trigger the light.

i.e. was thinking "what if you bought two EOC adapters and then put baluns on those to go on one twisted pair?" I thought it was crazy...

I would have thought so too... but then I did it, completely inadvertently, and it worked.

Had a site with coax connected to the camera and to the DVR, so I put in EoC adapters (Altronix eBridge) and they worked as expected. It was only later I discovered the other end of each piece of coax was connected to a balun that fed the signal over a hundred feet or so of station-Z.

Can't guarantee this will always work... but it definitely MIGHT.


We accidentally did that last year when we were testing EoC adapters. Vigitron provided us with experimental adapters that I believe were just their baluns with the transformers removed or bypassed. On an ~700 ft. run, we were able to get an Axis P3364 to work but it was intermittent.

I noticed that we had inadvertently used Vigitron baluns instead of their sample adapters and after we changed them out, the camera worked flawlessly. I think that the DC resistance of the transformer dropped too much of the PoE voltage.

In our case it was only 100' or so (probably even less) of station-Z, which of course is 22ga. vs. 24 for Cat5e, so yeah, that could be the difference there. Ours were using PoE as well.

This is all at 100Base-T speed at I assume. But only half-duplex, right? Which for cameras is no big deal, also assuming.

Never measured it or checked the link stats, but it worked perfectly and AFAIK continues to work perfectly... at least, I haven't had any calls from the site complaining about cameras dropping out.

Vigitron can also stream power and data over a single pair. We've tested the Vi2401A's with Vi0030 Passive Adapters and were able to provide power and send data at least 1,000 feet on a single pair of 24 gauge CAT5e.