It serves as a reference, since today we can have simpler and more compact solutions. This circuit is from an Electronics Experimenter Handbook from 1992. The integrated circuits are from that time.
This shield circuit can serve as a basis for a digital mixer or simply for a switch without noise...
This shield or interface makes it possible to control power loads connected to the power grid from...
Based on an LM36000 OTA this circuit was found in the July 1988 issue of Radio Electronics...