Found in an Electronics Now from the 90s, this circuit appears elsewhere in this section and website. The diodes are for general use and the basic frequency is given by C.
This simple robot or motor control circuit using a photocell as a sensor was found in the magazine...
This circuit uses an operational amplifier to modulate the light emitted by an LED with audio...
Equivalent transistors, such as the BC548, can be used in this circuit that we find in...