This circuit was found in a 1966’s American publication. What it does is to receive a pulse and keep it for intervals of up to 1 minute at the output.
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...