ITT/WE 636 Key Differences

[Babybearjs]

I was working on a 564 phone last week and was having some issues with the 636 key assembly, so... I decided to switch it out... thinking the unit bad, which it was... (broken Wire) I noted a difference between the 2 636 units and was wondering why the difference? on 1 unit, its wired with a ORG/BLK wire on the hold key which is attached to the "N" terminal. on the other unit, the Org/Blk wire is missing. based on the schematic, the wire is used as a signal wire, optional. so, why did they omit it from the newer designs? was this a option that was never used? or did it cause problems with the KTS?  (Reference: ITT TIMM-2 manual Pg. 258.23 636 key.) was there ever a BSP that showed the same thing, or did ma Bell use the ITT paperwork?