A mutual convertibility relationship between 50% duty cycle duobinary and minimum bandwidth (MB) dicode signals is identified through the spectral inversion of either signal by means of multiplication by a sinusoidal waveform of frequency equal to half the data bit rate and sharp bandlimiting at the Nyquist frequency. A signalling technique is described in which the mutual convertibility principle is used in order to convert a transmitted MB dicode signal into nonminimum bandwidth (NMB) dicode form at the signal destination for data recovery purposes.Drawings of relevant waveforms and spectra obtained from a special-purpose computer simulation verify the basic concept. The evidence obtained from a practical implementation of the MB dicode signalling technique shows that both MB dicode signals and their duobinary counterparts can be converted to NMB dicode form having an error performance within 1.5 dB of the optimum obtainable for Class 1 partial response (PR) signals, without recourse to decision feedback equalization (DFE) at the signal destination.