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 is from a publication from the 70s. The operational amplifier is from the period. Modern...
We found this circuit in the October 1992 issue of Radio Electronics magazine. The duty cycle can...
This circuit digitally counts input pulses. The circuit from a November 1970 Radio Electronics uses...