Good day Gentlemen,
on the topic of mechanical TV and mechanical color TV see French engineer Roger Dupouy's wonderful site. Over the past 10 years, Roger has entirely built from scratch 30 line cameras and receivers, ditto in 60 lines, and now color. Most of the site is available in english:
http://la-radiovision.fr/
60 line mirror-screw TV & color demo:
http://la-radiovision.fr/projetmirror-suite.htm
Best Regards
jhalphen
Paris/France