This circuit uses a photo-SCR or LASCR that is not a common component today. The relay depends on the load, and the power is supplied by the power grid.
This two-microphone amplifier was found in a April 1961 Radio Electronics Magazine. The circuit is...
We found this experimental musical instrument in a 1977 Radio Shack brochure. The sound produced...
With this circuit it is possible to modulate the radiation emitted by a laser diode in amplitude. The...