We found this circuit in a 1964 Electronic Design. Transistors can be modern general-purpose equivalents. The circuit converts a 1 MHz sinusoidal signal into a rectangular signal.
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...