This circuit supplies 5 V from two AA batteries. The output current is 4 mA, resulting in an 11 mA input current from the batteries. The circuit is from an old EDN.
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...