We found this circuit in the October 1994 issue of Electronics Now magazine. The circuit uses a now-uncommon 4046 PLL and the gates of a CMOS 4001.
The basis of this circuit is the 723, an old integrated circuit not easier to find these days. The...
This circuit was found in a May 1981 Radio Electronics magazine article. The circuit is offset...
The circuit presented was found in a Japanese magazine in 1973. The circuit uses transistors of...