Paul,
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And did you discover that by scraping off the black outer coating, the OC71 could actually be used as a crude photo-transistor?
Yes,
I did actually try that in a little light-sesnsitive switch project once.
Oddly enough, when I built my first crystal set, my Dad said instead of using the easy option of a detector diode (then an OA91 germanium diode) he suggested I use a small of coke (No, not the drug or the drink) to fashion a crude cats-whisker detector.
I have heard of razor blades being used as well, how that works I'm not sure.
Chipmunk,
The first "bulbs and batteries" book I ever had used thumb-tacks and paper-clips as switches.
I built a crude oscillator and taught myself Morse Code with the very same sort of switch.
Using a key is a breeze after using a device like that. [Linked Image]