One of my wife's friends has a KSU 550 and punch-down block in the basement. I am trying to convince her to let me remove the dinosaur from her house (I have a plan to install it in a Don Draper-style office in the house). If I succeed, I will need to know how to remove it and to figure out if the phone system is still going through it. I think it is using some of the 25 pair to connect to sets throughout the house, without using the KSU itself.

Do you have the BSP for the 551? It's available on-line. 518-215-407.

In keeping with my policy not to tell others how to take my work away from me, (or from my friends in the business) I am happy to tell you what to do, but I'm afraid that I can't tell you how to do it.

The quickest way is to pull the line cards out and see if anyone complains about NDT.

Then, you will need to do a visual inspection of the wiring. If you trace any of the 25-pair cables to the ends, and find telephones connected there, then those cables are being used to feed the phones.

Then find the dial tone feed wires at the KSU, and terminate them on a new 66M-50 block. You will find them terminated on the block inside the KSU.

Terminate the existing 25-pair cables on new 66M50 blocks, one cable per left half, and one cable per right half.

Install mushrooms and cross-connect the appropriate dial tone feeds to the appropriate pairs in the 25-pair cables. Use bridging clips on the feed block, so that you can trouble-shoot in the future.

Remove the KSU.

Awesome. This will help convince her to let me have it. I already had a copy of the BSP, and I should have referenced it, as it is a 551. My mistake. Thank you, and I will try to keep you all updated.

The 550 is just a 551 without a power unit. The same BSP applies.