This is a long shot, but perhaps someone has some old paperwork squirreled away....

I acquired a batch of interesting vintage Frederick Electronics TTY signal gear recently, but without manuals - any info or documentation at all would be GREATLY appreciated.

The basic functions of each of these is fairly evident, but some of the connections are mysterious, and troubleshooting will be difficult!

660 Baudot to Morse Code Converter
CV/A-19 Baudot to Morse Converter
671 Morse to Baudot Converter