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.
We found this circuit in a 1987 documentation. It is a multi-tester with neon lamp and LEDs...
This two-tone buzzer can be powered by a solar panel. The circuit is from a 1991 documentation. The...
We found this circuit in a Texas Instruments optoelectronics manual. The audio modulator serves for...