This circuit with the LM741 operational amplifier can be applied to other operational amplifiers. We found it in the September 1989 Radio Electronics magazine.
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...