This configuration with the LM111 was found in your factory manual. The circuit can be implemented with modern operational equivalents. The power supply must be symmetrical.
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...