This circuit, found in 1993 documentation, is the traditional relaxation oscillator configuration with unijunction transistor. The frequency depends on C and the resistance value R.
This small amplifier was found in Radio Electronics magazine from October 1966. It uses a series of...
This 1969 Philips documentation circuit makes it possible to control an engine through the sound...
This TTL dice was found in an old American 1980s documentation, but can still be easily assembled....