Using 3 ports, this rectangular oscillator was found in the March 1996 issue of Electronics Now magazine. The maximum frequency is a few megahertz, determined by R1 and C1.
This circuit for cars with mechanical ignition systems was found in the Electronics Experimenter handbook...
This code practice circuit was found in a 1990s issue of Radio Amaterur Today magazine. It...
The circuit presented was found in the Linear Applications Handbook of the National Semiconductoir of 1994....