Dave:

Sorry for the late chime-in. You mentioned polarity issues, but not specifically what they are. Is this a case of just that particular line not being able to dial out or all of the lines on just one particular set?

If the issue applies to all sets that share that line, just reverse the polarity as it enters the KSU, test and be done with it. Granted, this is not a true fix, but it will solve the problem instead of spending hours chasing gremlins.

If it's station-specific, then everyone here who has replied is on the same bandwagon. Something is hidden and will need to be found. Reversing polarity on a per-line basis can be done within some 6-button sets by butchering the terminal strips on the line cord pairs, but it's nearly-impossible on 10/20/30 button ones.

On a side note: What is the exact model of KSU we are talking about? I don't immediately recall any that have two 25 pair connectors for output except San/Bar's pre-packaged units.

Ed Vaughn, MBSWWYPBX