This circuit was found in a 80s American documentation. The zener diodes determine the points of action of each stage and the transistors can be general purpose types.
The LS4558 integrated circuit is a double 741. The filter response curve is given next to the...
This motor control using transistors was found in a recent English publication. The circuit is for...
This circuit from a 90s Popular Electronics, decodes the old analog TV signal. It works with a...