This circuit is from a Radio Electronics magazine from August 1990. The circuit uses components from the time and is suitable for measurements in alternating current.
We found this circuit in a 1967 English magazine, but it can be assembled with minor adaptations, such as...
We found this circuit in an 80's Radio Shack publication. The circuit uses a company buzzer, but...
We found this circuit in a 1992 documentation. When the button is pressed, the circuit produces a...