We found this circuit in an American publication from 1977. The circuit drives two LEDs according to the control of the inputs. The technology is TTL requiring 5 V to power supply.
Taken from a 1956 Raytheon transistor manual, this circuit uses varistors to obtain modulation of a signal...
This circuit was found in a 1980s American documentation. The circuit is based on integrated CMOS 4001...
In the figure we have the original version of an amplifier with high input impedance, 1.2 M ohms....