This circuit makes use of a 741 single source operational amplifier to measure resistors on a linear scale. The circuit may use as an indicator a common multimeter on a low current range.
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...