Found in a 1980s amateur radio QST magazine, this is the conventional circuit of a medium-wave radio. Coils and transformers are commercial types.
This interesting configuration of optical triggering using an oscillator was found in a 90s...
This circuit works with only 1.5 V and can be powered by a solar panel. The circuit is from 1991....
This circuit periodically reverses the rotation of a motor to change the position of eggs in an...