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 circuit, which uses components still common today, was found in a 1997 documentation. It...
This circuit with its light source was found in American documentation two years 70. Or...
This circuit was found in a Philips documentation from 1966. The circuit provides 1 mW with a...