This circuit is from a factory manual from the 80s. The circuit can be implemented with modern operationals. The supply must be symmetrical, and the diode is general-purpose.
This circuit generates the busy tone of ordinary telephones. The transistors can be the BC548 and...
This small 1 W amplifier uses a Motorola integrated circuit from the 1970s. The integrated circuit...
This is a configuration widely used for oscillators with crystal from 1 to 20 MHz typically. The...