1. In a digital decoder for decoding encoded digital data words which have been encoded using a code comprising a plurality of different length code words, said decoder comprising a plurality of logic gates connected in the form of a binary decoding tree having branches and interior and leaf nodes, means for supplying bits of encoded digital data words to gates of the tree, said bits being supplied to gates at different levels of the tree dependent upon the position of the bit in the encoded word, a plurality of gate enable lines coupled to gates at different levels of the tree for selectively enabling said gates, different gate enable lines being connected to different gates of the tree, means for sequentially supplying said gate enable lines with gate enable signals for sequentially enabling gates of the tree, an increasing number of gate enable lines being simultaneously supplied with gate enable signals as gate enable signals are sequentially supplied to said gate enable lines, outputs from gates associated with leaf nodes of the binary decoding tree being indicative of the digital data word.