Ethernet over unused twisted pair?

[Tom Metro]

Scott R. Ehrlich wrote:
> I'm trying to find a way to get an Ethernet connection from a second floor 
> room diagonally across the house to the first floor.    There is no plenum 
> - no dropped ceiling...

Often your best bet is to go vertical, first. Up to the attic, or down
to the basement. Then move horizontally, and finally vertical again to
the destination.

CAT5 is pretty easily concealed, if you care to get creative in how you
route it. You can blend it into baseboard molding, remove baseboard and
route a channel for it, use surface-mount raceways, or hide it behind
things like downspouts on the exterior of the building.


> Is there any device that could convert the Ethernet signal from my 
> Linksys box to something I could plug into a phone jack...

There was a product on the market for doing this, but I haven't seen it
recently. It it used boxes similar to the power line adapters.


> Could using two DSL boxes on the wire do the job?

I've never heard of ADSL modems being used in a peer-to-peer fashion.
I'd tend to think that would require a firmware tweak, but I don't know.
Besides, what does an ADSL modem cost these days? Aren't they around
$100? So this is likely to be more expensive than other options.


> ...what are my options...

What are your reasons for preferring to avoid wireless?


jay-R5TnC2l8y5lBDgjK7y7TUQ at public.gmane.org wrote:
> As long as its a 4 wire phone line and not 2 wire you can run
> standard 10/100 over it.

Ethernet is pretty tolerant. There are stories of it working over barbed
wire. :-)  But technically, as Bill Horne mentioned, home phone wiring
is typically CAT3 at best, and likely even worse. The twists per inch
and other characteristics don't compare to CAT5 wiring, so you can't
achieve 100 Mbps speeds. If you went this route without the phone line
adapters mentioned above, I'd recommend connecting only one device over
the link, and manually setting the speed to 10 Mbps, rather than letting
it negotiate. (Probably half duplex would be a good idea, too.)

As for using a single pair of wires, I didn't look at the link Bill
Horne posted, but in addition to the active phone line adapters I
mentioned above, there are passive devices meant to carry signals over a
single twisted pair. The keyword you want to search on is "balun."
PImfg.com is one company that sells a variety of baluns, though the vast
majority are for sending high-bandwidth signals (typically video) over
CAT5 wiring. It looks like they do have a few for single twisted pair.


Bill Horne wrote:
> Alternatively, you could make use of your cable TV cables for 10Base2
> Ethernet...

If I recall correctly, 10-Base-2 used 50 Ohm impedance cable, while
cable TV wiring is 75 Ohm. For a short run it may still work fine.


Gregory Boyce wrote:
> Rather than the phone lines, you could use ethernet over the powerlines in 
> your house.  A fried of mine has been using it without any issues, 
> although he was more concerned about latency than bandwith.

I've read that the modern version of this technology works pretty good,
so I'd also recommend considering it. Though I wouldn't look at it as
being as secure as wired Ethernet. It's sort of a hybrid between a wired
technology and wireless. In the same way that your neighbors might pick
up X10 signals from your home automation devices, neighbors attached to
the same transformer as you might be able to pick up your power line
signals. It narrows the scope compared to wireless, where you might have
a drive-by hacker, but you're still leaking signal outside of your
house. I presume modern power line adapters incorporate encryption, but
I'd read up on how good it is first.

 -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/