Is this color scheme another standard for RJ45 cable?

Question

I'm trying to add a RJ45 connector to a Ethernet cable for a NVR system (Surveillance Cameras).

The cameras comes with ethernet cables and I see that the only have 4 cables used and in different positions than RJ45 color coding T568A or T568B (image below)

Seeing from bottom, the order is White Orange,Orange, Blue White, None, None, Blue, None, None.

I know that some question should be answered by the manufacturer, but in theory, the cameras should work with standard T568A/B?

Is this another standard?

since I tried this ethernet cable connecting a laptop with a router and internet connection it works. So, it seems the missing cable colors are not needed for the cameras nor internet connection.

Thanks in advance.

Answer 1

This was how Cat3 (voice grade) cables were sometimes wired for 10BASE-T (old 10 Mbps Ethernet from the 80's and 90's). It only has the two pairs necessary for 10BASE-T. It's probably not Cat5 quality cable or better, but if it were, it would meet the requirements for 100BASE-T (100 Mbps "Fast Ethernet" from the late 90's), because that used just two pairs in these two locations, but it required Cat5 or better. These cables will not work for 1000BASE-T (1Gbps "gigabit Ethernet"), because gigabit Ethernet requires all 4 pairs.

You can replace these cables with proper 4-pair Cat5e T568A or B cables and your cameras will work fine; the placement of the two necessary pairs is the same on a modern cable as they are in the cables you got with your cameras.

Answer 2

You're focusing on the colour - instead consider the signal on that wire.

Minimum RJ45 Pinout for a 10/100 Mbit LAN Cable
Pin 1 → Transmit +
Pin 2 → Transmit -
Pin 3 → Receive +
Pin 4 → 
Pin 5 → 
Pin 6 → Receive -
Pin 7 → 
Pin 8 → 

The electrons don't care what the colour of their wire insulation is.

The only reason we have specific pairs allocated is because this reduces cross-talk between adjacent pairs. By twisting both legs of Transmit together, any stray noise induced in one wire is likely to be induced in the other wire the same way, raising/lowering both voltages by the same amount and leaving the same nett difference.

For short runs it is possible to use flat cable without any twists, though that's often well under a metre before the signal becomes degraded.

There's also a very small minor advantage that the Blue pair is in the middle, which is where Telco wiring would expect to find an analogue voice pair, and Telecom-types would number the Blue/white pair as the "first line" so having it not used by 10/100 Mbit could prevent damage if something was misplugged.

And yes, this means it is totally possible to run two separate 100 Mbit links over a single 4-pair cable - in the early 2000's I did it where there was only one run of wiring installed but we needed exactly two hosts, and a small desktop switch was not justified.

Answer 3

In the Bell color scheme that 568A and 568B both use a subset of, pair 1 is blue/white, and pair 2 is orange/white. So the diagram illustrates the correct way to wire the connector for any cable that only has two pairs. Or, really, any cable that has at least two pairs, since the colors don't matter, so long as pairs are paired up correctly.

Answer 4

It's a case of "penny pinching" on the cable and then using the available conductors to make the cable work for the application in question.

In many four pair telecoms cables*, the pairs are color coded as follows.

1. White/Blue
2. White/Orange
3. White/Green
4. White/Brown

The cables typically used for base-T ethernet follow this code, with the white wires additionally having a "tracer" of their partner colour so they can be identified individually.

Similarly a two pair cable will normally have the pairs coded as

1. White/Blue
2. White/Orange

On an RJ series connector, traditionally the pairs straddled each other, with the centre pair being pair 1, then pair 2 straddled pair 1, pair 3 straddled pair 2 and so-on. This, along with the design of the connectors meant plugging a smaller plug into a larger socket would mate in a sensible manner, but it wasn't a great design from a signal integrity point of view.

T568A modifies the traditional telco layout for better performance in high bandwidth applications. The first two pairs remain in the centre, providing backwards compatibility with one and two line voice systems, but the third and fourth pairs are moved to the side. T568B further swaps the second and third pairs, it's not clear to my why this swap happened.

10BASE-T and 100BASE-TX require two pairs, but instead of using the first and second pairs, they conventionally use the second and third pairs. I presume the original intent of this was to allow voice and Ethernet to co-exist on the same cable (though in practice, many Ethernet controllers short out the unused pairs, so you would still need a special cable or adapter to do this). It also has the interesting effect that a cable wired with T568A on one end and T568B on the other acts as a crossover cable.

So someone is trying to pinch pennies, they pick up some cheap two pair cable. Ethernet requires the second and third pairs, but their cable only has the first and second pairs. So they use a non-standard wiring to make it work.

* This is consistent with the "25 pair code" used in the USA, but also consistent with the "20 pair code" used in australia and the "30 pair code" used in the UK. I dunno about other countries.