Found in the 1969 neon lamp documentation, using neon lamps this circuit provides 18 V regulated with 0 to 4 mA current. The lamps are types of the time.
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...