[en] The additional information about nature of S energy levels in forbidden gap of silicon has been received. The spectral dependences of IR extinguishing of photoconductivity (PC) in Si< S> samples with a various degree of compensation are investigated. In the samples three sites of IR extinguishing of PC in the spectral regions of (0.27-0.35); (0.37-0.4) and (0.42-0.6) eV are found out. It is shown that observable PC IR extinguishing in Si< S> cannot be interpreted on the basis of two-level model of Rouz. In our opinion, sulphur, as well as oxygen, introduces donor levels in the silicon forbidden gap. Other deep power levels are connected with the sensitized centers beginning from the E_c-0.27 eV. Such centre in silicon can be the multiply charged 'quasi-molecules' consisting of two or four sulphur atoms located in the neighbour units of a crystal lattice. (authors)