atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's New T1 installation question

What you are doing wrong is that for a T1, tip and ring are in the reverse order for the orange pair compared to a 568B cable. A T1 plug should be wired R-T-0-R-T-0-0 from pin 1 to pin 8, where "0" means not used. A 568B plug is wired T-R-T-R-T-R-T-R.

So if you wire the plug 568B, you can reverse the color scheme of the orange pair at the other end and get the same result.

Well I certainly hope he's figured it out by now.

Butch, while you are somewhat correct in the pin assignments, polarity does not matter on a T1 circuit. The only thing that matters is proper placement of the transmit and receive pairs. As long as pins 1,2,4 and 5 are used, that is all that is required.

"A 568B plug is wired T-R-T-R-T-R-T-R. "

Well, sort of on 568B:

Tip 1 is jack position 5
Ring 1 is jack position 4

Tip 2 is jack position 1
Ring 2 is jack position 2

Tip 3 is jack position 3
Ring 3 is jack position 6

Tip 4 is jack position 7
Ring 4 is jack position 8

Yea, I agree that this issue has likely been resolved by now, but it is important to keep even responses to old threads accurate.

Ed you are right. I tested a T1 demark extension in the field, and pins 1 and 2 were crossed. Pin 1 at the near end was connected to pin 2 at the far end, and pin 2 was connected to pin 1. The T1 still worked. So it is OK to just leave it that way?

It's a 4 wire circuit as long as transmit and receive are correct the tip and ring of the pair doesn't matter.

Quote from Ed's post: