Based on Texas Instruments documentation, this circuit serves for sensor interfacing. The circuit is based on the LF411, but other operational ones can be used.
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...