Found in older American documentation, this circuit can monitor 3 or more voltages determined by resistors. Components admit equivalents.
This 555-based circuit was found in the August 1976 issue of Radio Electronics magazine. The tone...
This simple 1-transistor receiver has speaker listening. We found it in an article published in...
This circuit was found in an American magazine 73 for radio amateurs of the 80s. It is an...