I just got finished putting the mounting cord back on an ITT 2564 set. That was the same one from my previous post "Gutted ITT 2564" Enough pairs is an understatement. I can't even begin to imagine a 10 button set or god forbid a call director. I can't wrap my head around 75 or 100 pairs in a single telephone set. That takes more patience than I am currently capable of. That's to say nothing of a main frame in a CO. I watched the videos of the Miracle on 2nd Avenue, after the NY tel. fire. I was in absolute awe. That they restored service in 3 weeks is just beyond my comprehension. Simply amazing.