We found this circuit that converts a direct voltage into a proportional frequency signal. The circuit is from an Electronics Now from April 1993. The JFET can be of any type.
Using the CMOS 4001 we found this circuit in the October 1974 Radio Electronics magazine. The...
One 4018 is used to divide the frequency of a digital signal by ten as shown here. The maximum...
This 90's project shows how to use an old cassette recorder to practice telegraphy. In position A of the...