This circuit can be implemented with other comparators in the same series. The circuit is from a component manual and the supply voltage between 3 and 12 V depends on the application.
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...