This transistor gain test was published in Radio Electronics magazine in July 1959. The transformer used is a special type common at the time. The circuit tests general-purpose transistors.
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...