Re: electronic equivalent works just fine with the amateurs
Actually that's derived from Fax, First experimental Fax on wire was in 1851. SSTV is to Fax, what RTTY is to Telex/Teleprinters (from 1928, but also Victorian experimenters). Radio Fax was also in 1930s, at same time as Baird, and transmitted in the USA after radio program close down. Add on printers for existing ordinary radios were sold in USA. The Mechanical TV was also done in USA too as a novelty after normal progam close down, but the radio fax was more practical.
SSTV doesn't do moving images, it's basically Fax.