This receiver was found in an article in Electronics Now magazine in March 1994. The coils are critical, as shown in the figure. Listening is through headphones.
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...