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 circuit was obtained in a documentation of the 80s, using operational of the time. The...
In the figure we have a third fast adder that we found in an 80's Electronic Engineering. The circuit can...
We found this simple music box circuit that can also be used in a musical bell in a 1991...