This circuit triggers a warning if there is a need to interrupt a process. The circuit has a 1 second delay. The circuit is from old American documentation.
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...