Based on NXP 74HC logic, this circuit can be adapted for various uses. The circuit can also be used with 12V power, and the circuit replaced with a common 4046 PLL.
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...