Tom, I know I'm probably beating a dead horse, but card mounting units are designed to provide either RJ48C/X or RJ48S, depending upon the card installed in the slot. I keep asking the question because the chances of a voice-grade circuit running to a wall plate in an office are pretty unlikely. These (ISDN/PRI) circuits likely terminate on a system of some sort, not in someone's office. A DDS circuit (T1) terminating on a wall plate in an office for data use sounds a lot more likely. I agree that either type of RJ48 can be accommodated by a standard 568B extension, but in his description of what's happening, the white/blue pair doesn't appear to be doing anything. Since only the blue and orange pairs have actually been connected, my conspiracy theory may hold some validity.

I keep bringing up the RJ48S scenario because I was called upon to extend one at a check cashing place using what we all assume was a 1,2,4,5 pattern and it turned out that my assumption was wrong. It was mighty embarrassing when I had to be corrected by a Verizon repair technician to use the white/brown pair and not the white/blue.

We haven't heard back from the OP, so we may never know what it turned out to be.

PS: I have a loop back plug that accommodates both RJ48C/X and RJ48S. I got it from a Bell Atlantic technician years ago. It was made by Nevada Western. It loops 1/2 to 4/5 and 7/8 since it's either/or, but never both.

Ed Vaughn, MBSWWYPBX