This circuit produces the sound of percussion such as blocks, drum, bell, etc. The frequency depends on the marked capacitors, which can have a wide range of values depending on the desired sound.
The figure shows three circuits for using headphones in amplifiers with speakers that do not have...
In this charger, the charging current is basically limited by the LEDs. The transformer is a low...
This configuration is from an old integrated circuit manual. The circuit can be applied to modern...