Scrambled as a sketch for my own planning of my system from info found in comments on the question:
'Could one construct a Rutt-Etra style scan processor from Cadet modules only? .. '
on the LZX Video Synth Community on Facebook:
A more recent thread on the LZX Video Synth Community on Facebook (that links to this rack) explains stuff a bit further:
Other resources for smaller system configurations and explanations:
also check out this (long and dense) documentation from an event held exploring the Rutt-Etra Scan processing system and its contemporary uses: