This circuit was found in a 1968 General Electric documentation. It has an input impedance of 2 M ohms and excites a load of 16 ohms. The integrated circuit of the time is the PA237.
Found in a 90s Popular Electronics, this touch switch uses a single sensor. PLLs are common today....
We found this circuit in an old documentation from 1979. It is a logic level tester that is...
This ultrasonic insect repellent was found in American documentation from the 1980s. The...