[garaetjjte]

>If you've got two pair, you can probably run 100BaseTx

Well, 100BASE-TX will also run on single pair in half-duplex mode.

Alternatively you can also use powerline adapters over any cabling (twisted pair/coax/whatever). Just instead of connecting adapter prongs to power socket, connect to your cable and feed there enough power to supply the adapters. Around 50V DC (as commonly used by PoE supplies) will probably be enough.

[toast0]

> Well, 100BASE-TX will also run on single pair in half-duplex mode.

I mean, kind of, but I don't know how you get network cards to run on a single pair? I'm actually interested, because if it works for 100BaseTx, it probably also works for 10BaseT, and I've got 10BaseT half duplex device I'd like to network, but only one pair available (there's a 3-pair cable run, but two are used for voice communication). I've tried a commercial product (ETSLAN Monoline Balun), but while I can get it to work a bit when testing on parts of the line, it doesn't work across the whole line; if I can just wire something more simple, that'd be worth a try too.

[garaetjjte]

You just connect single pair, it should auto-negotiate if other device supports it, otherwise you need to set mode in network card settings manually. https://i.imgur.com/xIsJJiN.png

[toast0]

So just connect pin one and three to the white wire and two and six to the solid color wire on both ends and it should work as long as both ends are half-duplex?

I would think the NICs would sense their own transmissions and declare a local collision?

[garaetjjte]

I'm sorry, I got things mixed up. You're right there would a collision with their own transmission. So there needs to be circuit that cuts offs their RX port while it is transmitting.