Abstract: Signalling means for enhancing the performance of automatic fingerprint identification systems by reducing system response to non-fingerprint-like regions within an image field pattern of interest. A two dimensional generalized sequency analyzer, such as a fast Fourier transform machine, responsive to a binary coded image signal identifies discrete frequency terms occurring within a selected bandwidth corresponding to a spatial frequency region of interest, associated with a fingerprint image. Logic means, responsive to the sequency analyzer, further identifies the relative energy levels of the bandwidth-limited spectral content of the binary coded image signal to signal the identity of a non-fingerprint-like region within the scanned image.