Abstract: A decoding and display mechanism that may be integrated with avionics, navigation and communications equipment whose encoded audio output is normally monitored directly through the pilot's headset. The encoded audio signal is coupled through a programmable bandpass filter to remove potentially contaminating noise signals, particularly human voice signals, that might otherwise prevent successful decoding of the superimposed (e.g. Morse) code. The filtered encoded audio signal is then coupled to a (microprocessor-based) decoder which decodes the symbols of the encoded tone and generates a set of output signals representative of the alpha-numeric abbreviation of the source of the channel being monitored. This set of output signals is then used to drive a digital display (or other humanly perceptible indicator, such as a synthesized voice enunciator), so that the pilot may be provided with the identification of the source of the monitored channel.