This automotive circuit was found in the September 1992 issue of Radio Electronics magazine. The circuit directly drives a relay that must have a coil resistance greater than 65 ohms.
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...