atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring "Split" CAT5 wire - 2 pair data / 1 pair telco?

"Where did the 4 pair "standard" come from? Remember, there was 4 pair in the CAT zero days. I think you will find the answer if you look at the Bell System/AT&T 568B standard that was probably written for the old Merlin systems. That was the first use of a 4 pair cable."

Actually, it was about a decade before the Merlin systems came out. 568B evolved from WECO's propriety wiring designed for their MET sets that were used on their Dimension PBXs. Later uses came into play on Horizon systems and even for fifth line conversions on ComKey 416 systems. Yes, Western Electric invented it for sure, but someone else managed to get the credit.

Just to keep the archives straight, so that adventurous web surfers from the 24th century will still be able to get their ComKey 416 systems up and running:

The 5th line on a ComKey 416 system requires three-pair wiring.

Ahh yes. That would explain that reel of 3 pair cable that I used to have many years ago.

-Hal

For the record I wasn't trying to say the IT industry invented 4pr cable, merely that it would make no sense for the standards bodies to bother with a 2pr standard when the new Ethernet standards would require 4pr. The point being that the standards bodies need to look forward to compatibility with new technologies, and not create minimalist standards that only work with current technologies.

In the years that I did a lot of SL-1 work we ran nothing but 3 pair cable - voice, data, power. Same for the GTE Omni and, as I recall, the NEC Electra 100.

Sam

For the record I wasn't trying to say the IT industry invented 4pr cable, merely that it would make no sense for the standards bodies to bother with a 2pr standard when the new Ethernet standards would require 4pr.

And I was merely pointing out that at the time the "4 pair standard" was adopted there was no reason to believe ethernet would evolve to more than 2 pair. The "standard guys" just glommed onto 4 pair because there was a 568B WE standard already in use at the time.

Matter of fact the recent use of the other two pair probably came about because somebody said "Hey, lookie here. There's another two pair that isn't being used. Lets use them for something". :idea:

Otherwise you can bet your bippy cable manufacturers would figure out a way to run 10 Gig ethernet on 2 pair just to make UTP a viable alternative to fiber.

-Hal

And they might, yet.

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Ring voltage might actually be more of a problem than what I assumed above. If I have some time to kill one of these days, maybe I'll set this up as an experiment...see what actually happens.

The Fluke certification meters can test for impulse noise, which does not come into play for certification. If transmitting ring voltage down the same cable does cause a significant problem, my guess is that it would show up as impulse noise.

Please let us know the results of your research.