In chapter eight, an efficient derivative of the Trellis sigma-delta modulator, called the Efficient Trellis sigma-delta modulator, is introduced. Instead of exploring 2 N solutions in parallel, only M solutions out of the possible 2 N are tracked. This is possible since only a fraction of all the 2 N solutions contributes to the final output. The selection of which paths to keep is based on the accumulated path cost, i.e. paths with a low cost have a large probability to be part of the output and are selected, whereas more expensive paths are rejected. Compared to the Trellis sigma-delta modulation algorithm, the computational load is reduced by several orders of magnitude, while at the same time improvements in the linearity and stability are obtained.