Abstract: An airborne system for automatically and electronically recognizing and dcting the relative presence of invariant features of a transient submarine signal occurring in the presence of signal-like noise. A plurality of comb filters receive MAD signal information in the amplitude-time domain and filter it to provide amplitude-time-frequency domain information. The primary features (positive and negative slopes) of this latter information are then abstracted, the abstracted information being utilized in a signal processor to detect and recognize the relative presence of invariant, submarine recognition features. Upon recognition, a decision thereof is routed to a visual display.