This circuit with a bargraph scale was found in a 90s Popular Electronics. The circuit measures the intensity of a sound in three scales. R14 works as a sensitivity adjustment.
This circuit was published in an Italian magazine Radio Elettronica in February 1976. The...
Found in a Popular Electronics from the 90's, this circuit converts a 40 V symmetrical source to a 5...
This high selectivity circuit for single tone decoding was found in 1970s documentation. The coil...