File DF-296 ‘’Communications equipment in the USSR - Part A: Wireless communications equipment’’ is a translation of a German document written in July 1941. It describes several radio sets used by the SU at that time. I have to thank Randy Rezabek of TICOM Archive for sending me the NARA aid which mentioned this file.
Now I’m not a technician so I can’t be sure if/how this equipment is connected to the Russian Fish story but two references stick out since they mention teleprinters:
Notes : A1: Undamped unmodulated telegraphy , A3: Telephony .
As always I have uploaded the file. If you have more information please share!