This analog frequency meter for low frequencies was found in Radio Electronics magazine from July 1958. The circuit has several scales with the frequencies indicated in the diagram.
This Salen-Key filter can use any operational amplifier and other frequencies can be obtained by...
This circuit can be adapted to be used in a follow the line robot. It was found in the May 1962...
The circuit in the figure uses two of the 4001's four gates to trigger a relay in a timed manner. The...