This circuit was found in a 80’s American documentation. The adjustment trimpot is from 47k to 100k. The diodes are general-purpose types use and the supply voltage depends on the relay.
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...