Thanks to the USS Iowa teletype gang, I have just scanned a Navy manual that covers all the 28 Compact units including the AN/UGC-77 TEMPEST KSR (the one with photocells) I have been looking for a UGC-77 manual for years - now I can see if my homebrew schematics match Teletype's official ones!

This manual refers to high-level (UGC-20, UGC-25, etc.) and low-level (UGC-77, etc.) in the parts list and schematics.

I have also pulled out the wiring diagrams for the low-level units here -

Cheers,