A wicked project for analog DIY fans is the Lumenoise project developed by Niklas Roy. Lumenoise light pen turns your old CRT-TV into an audiovisual synthesizer.
Unlike modern flat TV’s, old school CRT’s draw the image line by line onto their phosphorescent screen. A photo transistor, placed on a tube TV’s surface, can recognize when the part of the image is drawn underneath it. If this photo transistor is connected with a micro controller which generates the video signal, the controller can localize the exact position of the photo transistor on the screen. That’s the whole trick.
This project in a way goes back directly to the roots of computerization and internet, the Hypertext Editing System (HES) and the File Retrieval and Editing System (FRESS) developed within ARPANET in the 60ies.
The Hypertext Editing System (HES) console at Brown University. Original photo by Greg Lloyd, 1969.
You can find schemes, downloads and information about the Lumenoise project @ http://www.niklasroy.com/project/116