alt Hacker NewsWorth knowing in this context:
Telephones only want a twisted pair. Ethernet, popular with businesses for decades, also wants a twisted pair. Now, that pair must meet much stricter criteria to be suitable, such as Category 5 (for 100Mbit) or Category 5e (1000Mbit ie Gigabit) - but it really is just twisted pair cable, merely a tighter specification than your phone.
Suppose you are a sparky (electrician) and you have some jobs where you are to install telephone connections, some where you put in "Ethernet" (presumably 100baseT would be fine) and some they specifically want you to wire for Gigabit.
You could go to your wholesaler and buy a reel of Cat3 phone cable, a reel of Cat5 100baseT Ethernet, and a third reel of Cat 5e Gigabit cable, and take the right one for each job. So long as you do this flawlessly you can probably save a few pounds every year by using a slightly cheaper cable for some jobs.
Or, you can buy one reel of Cat5e and use that for all these jobs and since it's the same reel you can't have the wrong one and don't need to check paperwork to know you've put the correct cable in a duct etc. Thought that was a phone line but now the client insists it's data? No problem, they're the exact same cable, just smile and agree.
When I bought the place where I live now I wanted GigE to this desk, even though the DSL comes into a different room. I didn't love the idea of cutting holes in walls but I was resigned to maybe needing that, except there's a phone extension in this room (like the author says, we do love phone extensions) and so that room the DSL comes into has a twisted pair to here. I opened up the box, and I'm like huh, that's Cat5e, and sure enough this entire building was wired with Cat5e because like I said, why not, it's basically the same cable, why carry a separate reel?
So I changed the face plates from telephone to Ethernet, and I'm done.
Replies
> Telephones only want a twisted pair. Ethernet, popular with businesses for decades, also wants a twisted pair.
This is why there are two wiring standards, T568A and T568B, with A being compatible with multi-line telephone systems:
> The T568A scheme is based on the older USOC (Universal Service Order Code) standard, which was used for telephone wiring before the advent of high-speed data networks. The USOC standard assigned the green pair to the first line and the orange pair to the second line of a two-line phone system.
* https://www.comms-express.com/infozone/article/t568a-and-t56...
> As of 2018, ANSI/TIA still [recommended] T568A for residential installations for plug-in backward compatibility with old technology like fax machines or a plug-in base station for wireless phone handsets. If you are not using any such devices, or have no intention of plugging ancient RJ11 plugs into RJ45 wall jacks like you would a “phone jack”, then it comes back to personal preference again.
* https://www.truecable.com/blogs/cable-academy/t568a-vs-t568b
* https://www.flukenetworks.com/knowledge-base/application-or-...
As long as both ends of the cable are the same, it does not practically matter which variant is used.
* https://en.wikipedia.org/wiki/ANSI/TIA-568#Wiring
There are also A-B crossover cables (though a lot of NICs can do auto-crossover nowadays):
Gigabit Ethernet require 4 twisted pairs i.e. 8 individual cables. 100Mb Ethernet requires 2 pairs i.e. 4 individual cables. At least in standard configuration
I had the same thing in the house I bought, it was a nice surprise… there were 6 different phone jacks around the house in great locations for Ethernet (WiFi access points or just for a computer), and they all led down to the furnace room where they attached to a punch-down panel (basically they were all spliced into each other.)
To my surprise they were all cat5 cables. With the house being built in 2003 this was surprisingly forward-looking.
I capped all the cables that were on the punchdown panel and put a switch in there instead, and replaced all the wall jacks with RJ45, and bam, working gigabit around the house, including PoE for my WiFi access points. Still haven’t had to punch any holes in the walls.