The feed material is dispersed by the classifying wheel and transported through the same by the classifying air. The dust entrained in the air is transported through the support wheel and discharged via the fines discharge. The coarse product is rejected by the classifying wheel and conveyed to the coarse material discharge. The product routing is designed such that no back-mixing can occur and a high quality of dust removal is ensured. The special configuration with the support wheel is patented; it permits optimum access for quick and thorough cleaning at minimum downtime. Protected by additional patents, the TTSP classifier is a refinement of the TSP classifier, primarily with the aim of improving the precision of cut even further by means of two consecutive classifying stages. At the same product loading of the classifying air, the TTSP classifier achieves a much higher precision of cut than the TSP, or at a constant coarse product quality, achieves a higher loading factor. This makes it possible to almost treble the throughput in comparison with the TSP.