We found this circuit in the 1992 special edition of the Electronics Experimenter Handbook. The components used are still current, many admitting equivalents.
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...