This circuit for multiple sound inputs was found in a Radio Electronics from January 1992. It consists of a Bargraph connected to a multi-input mixer.
This commercial circuit, sold under the designation H531 in Japan in the 1960s, used three...
This circuit is from the manual of the components used, from the 80s. The circuit is valid for...
Found in a 1980s American documentation, this circuit appears with variations elsewhere in this...