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.
Delayed Pulse Generator This can be considered an "advanced" application where two 555 integrated...
We found this circuit in a 1994 publication. It makes use of a divider for 16 384 CMOS type 4060. By...
This buffered version of the previous circuit appeared in an article in the September 1989 Radio...