Found in a customer's garage by 209Diamondhander, this might be a build of Don Lancaster's TV Typewriter.
KBD.news Published October 8, 2021
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Found this gem in a customer's garage. Any thoughts on what it could be? […] Late husband's build from about 40 years ago – 209Diamondhander.
As DZP points out, the owner may have built one of Don Lancaster's TV Typewriters from the 1973 Radio-Electronics magazine plans.
The project documentation is available in this PDF.
This is not a computer, not really a terminal either. Rather a simple character generator ("Build this TV Typewriter and display messages on your set's screen").
This construction project started out as a very low-cost computer terminal for home use, but as it went together, we became aware of the many possible noncomputer uses for such a device, particularly since it is priced right – Don Lancaster (1973).
A machine that puts letters and numbers on an ordinary unmodified TV set.
What can you do with such a thing?
According to the designer: "Obviously, it's a computer terminal for timesharing services, schools, and experimental use. It's a ham radio teletype terminal. Coupled to the right services, it can also display news, stock quotations, time, and weather. It's a communication aide for the deaf. It's a teaching machine, particularly good for helping preschoolers learn the alphabet and words. It also keeps them busy for hours as an educational toy."