Minimum Cable Cores for RJ45 Plug: Can a LAN Network Function With 2 Wires?

Hello!
I was browsing the Forum but somehow I didn't find the right topic.
Is it possible to connect the LAN network using ONLY 2 wires of the cable?
Basically I found the minimum must be 4 wires and connector pins 1, 2, 3 and 6 are used.
But today I dismantled the plug from the old PCMCIA card, where I can see that ... only pins 3 and 6 are used for transmission on the RJ45 connector!
The others are completely disconnected from anything!

So what's it like in the end?
And I am asking this because I wanted to "experimentally" connect the net to one room, where I have just released a 2-wire twisted pair and I do not care about some super speed of the connection (net from the outside is free anyway).

Greetings!
Marek

Nay rdy, you must have dismantled the modem card.

2 wires for telephone connection. You need 4 for your LAN.

According to the standard, you need two pairs, 4 wires.

Maybe what you took out was a modem, not a LAN card.

bogiebog wrote:

According to the standard, you need two pairs, 4 wires.

Maybe what you took out was a modem, not a LAN card.

For the bank it was a network card that I even used a long time ago.
There is a cable to the card, at the end of which I have an RJ45 and BNC socket and I just took it apart - if you are curious, I can even paste a photo for you.
By the way, it is a 3Com product

hmm, what is the card, what Ethernet standard? Guess there is no Duplex support?

The card is: EtherLink III, LAN PC Card for 10BASE-T and Coax, 3C589D-Combo

And here are the photos of the plug:




I would like to add that the free pins of the RJ45 connector are not even connected to each other.

And there are no connections on the other side of the board?

The tile is multi-layer and the rest of the tracks sit on a different layer

Or maybe it's a modem and not a network card? A lot of old equipment used rj45 sockets not only for Ethernet, they also connected telephone lines (see modems imported some time ago from the west).

Gentlemen - I checked it with a meter and I'm more than sure there are no more ANY connections there.
Only pins 3 and 6 are used.
The PCB is 3-layer and even visually there is nothing else there.
Anyway, if some other pins of the connector were used, I would not ask this question.

So .... how would that work?

How do you have how to start this power cord, check it, then press the plug with only one pair and then we will check ...

According to the standard, it doesn't even make sense to do this, the circuit in the separating trays will not close ...

piterus99 wrote:

How do you have how to start this power cord, check it, then press the plug with only one pair and then we will check ... ...

I will think about it when I find the card itself, but on the other hand, what would it change to make such a cable?
I know that the card worked earlier because I just used it a few years ago.

Out of curiosity, because it's a novelty for me ;)

I know that I used to try to let go of one pair out of curiosity, but it didn't work. I just don't remember after which.

From Wiki: on the TIA-568A, the second pair (orange) connects pins 3 and 6, and the third pair (green) connects pins 1 and 2, and the reverse on the TIA-568B. A 10Base-T hub or switch transmits on pins 1 and 2 and receives on pins 3 and 6, while the nodes transmit on pins 3 and 6 and receive on pins 1 and 2.

From what you can see in the picture, the connections are on pins 3 and 6, so it only transmits or only receives ... This is a strange thing, unless it only works in half duplex ...

Measure the resistance between pins 3-6 and 1-2. Insert a photo of the other side of the tile.

mah111 wrote:

...
From what you can see in the picture, the connections are on pins 3 and 6, so it only transmits or only receives ... This is a strange thing, unless it only works in half duplex ...

Hmmm - that might be a good line of reasoning. :)

tos18 - there is no point in measuring more precisely now, because pins 3 and 6 go through the chokes to the connector, which we connect to the PCMCIA card itself
Between pins 1 and 2 you have "infinity" of resistance because they do not connect either together or with anything else - I wrote about it before.
I learned to use the meter a long time ago, so please do not say that "I must have measured something wrong".

Please, here are some additional pics:

it is impossible in the LAN, there must be 4-wire connections

mayekk wrote:

hmm, what is the card, what Ethernet standard? Guess there is no Duplex support?

on one pair, 100%, there is no full duplex, but how does it work with other network equipment ...

This model of card through the RJ connector can only be connected in pairs with each other. It works like a coaxial connector, only a balun (converter) is plugged in to match the signals. This allows for bypassing the limitations of the cable length (on a coaxial cable it is approximately 180m of the entire network length, on a twisted pair it is practically up to 400m of one section).

Hello!
I am so sorry to everyone - I think I need to see an ophthalmologist
I was looking at the adapter of this card like "magpie on the bone" and ... I did not notice the two paths just going to pins 1 and 2. :(

So I pay you back - you were actually right with those 4 veins. It's just a pity for your wasted time on it.

So the topic is already explained.

On the other side, in the lower part of the plate, you can see two tracks near the inscriptions.

Samuraj wrote:

On the other side, you can see two tracks near the inscriptions at the bottom of the plate.

These two paths somehow "escaped"

I'm going to dig up a corpse. What's it like with this number of cables? I ask because I have a need to use the TV cable to transmit the internet.

There are a lot of different kinds of adapters.
https://a.aliexpress.com/_EJDEcMy

psmanek wrote:

Digging up a dead body. How is it with this amount of cable? I ask because I have a need to use the t.v. cable for internet.

There are a lot of different kinds of adapters.
https://a.aliexpress.com/_EJDEcMy

.

100 Mbps Ethernet needs 2 pairs, or 4 wires.
These adapters will not work.