This oscillator for frequencies up to a few tens of kilohertz was found in a 1970s documentation. The transistor can be of general use. For the component values used, the frequency is 250 Hz.
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...