1. An encoder for converting a plurality of first digital signals into a plurality of second digital signals, each said first digital signal representing a bit of a thermometer code and each said second digital signal representing a bit of a corresponding adjacent binary code, said encoder comprising: a plurality of first regenerating means, one corresponding to each of said first signals, for regenerating said first digital signals, thereby to produce a set of third digital signals, said third digital signals being grouped into signal subsets, one said signal subset corresponding to each of said second digital signals, and each of said third digital signals being grouped into only one of said signal subsets; means associated with each said digital signal subset for generating a corresponding fourth digital signal, the state of each said fourth digital signal being determined by the collective states of said corresponding signal subset such that said fourth digital signals in combination represent an adjacent binary code corresponding to the thermometer code represented by said first digital signals; and second regenerating means for regenerating said fourth digital signals, thereby to produce said second digital signals, said second regenerating means comprising a plurality of regeneration stages, each stage producing a set of output signals by regenerating a set of input signals, the stages being serially connected to form a pipeline such that the input signals to each stage other than a first stage of said pipeline comprise the output signals produced by a preceding stage of the pipeline, the fourth digital signals being applied as input signals to said first stage, the second digital signals being generated by a last stage of said pipeline.