This circuit was found in an American documentation from the 90s. It consists of a variable with a triac in which the load current can be controlled, monitored by an ammeter.
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...