Using 555 integrated circuits, this alarm circuit was found in a 90s American documentation. The signal must be applied to a good audio amplifier.
This circuit was found in old documentation. It can be made based on modern components. The time...
This small two-transistor AM radio was sold in the 1960s in Japan. The circuit was powered by two...
I found this circuit in an old English magazine from 1979, but it can be easily assembled with...