Working with the previous circuits, this circuit resets after 1 second. The circuit is from Radio Electronics magazine, August 1984. The time can be changed.
Carbon microphones are no longer used in most projects. However, finding one in the scrap metal, it...
This circuit produces a strong tone of audio or ultrasound, depending on the values of components C1 and...
This alarm from an old 1978 publication uses PNP transistors and driver and output transformers that are...