Development and fixation occur in the same solution. So there is essentially one processing step (with a wash after).
It is quite complex, but to (over)generalize, basically a high pH developing solution which also contains the fixing agent (silver halide solvent). The high pH is required so that development takes place very fast, before the thiosulfate dissolves the undeveloped silver halides.
Last edited by Michael R 1974; 10-09-2013 at 12:21 PM. Click to view previous post history.