A model and an algorithm are proposed to reconstruct ancestral regulatory signals, mostly of protein-DNA interaction, at inner nodes of the transcription factor phylogeny on the basis of contemporary signal distribution. The algorithm also infers an evolutionary scenario, i.e. a set of edges in the tree, along which the signal diverged the most. The model and algorithm were tested with artificial data and biological evidence on signals NrdR, MntR and factor LacI (for the last two cases data are not shown).