I found this pdf version of "The Complete Handbook of Slow-Scan Television" by Dave Ingram, April 1977, at the Internet Archive.
Although I have a copy of the printed version a pdf back-up is always a good idea. Useful reference for those that don't have a copy at all.
The pdf version doesn't have the complete scans of the fold-out circuit diagrams (pp193-208), they are quite wide. I'll scan them and add them to this posting soon.
Steve A.
Damn, it's too large to upload here (35MB), if you want a copy let me know via PM (along with your e-mail address), make sure your in-box can take a single file of that size and has enough remaining space. (Mine doesn't - must have a weed-out).