This circuit was originally suggested in a 1968 publication to generate a white mark (frame) on a film at regular intervals to serve as a time reference.
The integrated circuit shown in the figure is nothing more than the LM386 sold by Radio Shack,...
Found in an English publication from the 1980s, this circuit can be built with equivalent...
The transistors of this old circuit from the 60s can be the BC548, in a current version. The...