Yes, the whole concept of terminating ("heading up") cables on blocks, and then running cross-connections to interconnect the circuits is so that the ends of the cables are never touched again. Before x-conns were "invented" the ends of the cables were jammed into the KSU cabinet, and just the wires that were needed were extracted and terminated, and subsequent visits would result in shorter and shorter leads, and a real bird's nest of wires.
The x-conns are expendable, moveable, and traceable, as shown in the third photo from Jeff. Every job should look so good, Jeff.
The reason the two left-most (assumed 25-pair) blocks are grey is so that they are distinguishable from the 50-pair white ones.
The grey ones give you three sets of output leads, capable of feeding three telephones, or 6 telephones using bridging clips. (Using bridging clips assumes that 2 telephones, fed by 2 cables terminated on adjacent sides of a single 50-pair block will be receiving the exact same features.) That is a reasonable assumption in your case, but in the real world, the output cables from the KSU would be terminated on a minimum of a 66B25 block, which is longer and wider, and has one "input" clip and five "output" clips per row, allowing up to ten stations (with the bridging clip method) to be fed. In a very large installation, the KSU feed might be multipled on several more 66B25 blocks, so that every x-conn would serve an individual phone, with no bridging clips.
We had a rule that said no bridging clips, everything a home run, and everything a cross-connection, regardless of expedience. That method, applied as a standard in a big place, made every installation harder, but made repair clearing times (the index by which customer satisfaction was rated) very low.
(Of course, a harder installation equated to bigger paychecks, and that was OUR index of satisfaction.)
We had an 8,000 line, 600 trunk PBX with more than 12,000 key sets to maintain, and that method was the only thing that kept the whole place from being chaotic.
30 years from now, we'll have taught you everything there is to know about 1A2.
