Like any modality of perception, the processes of hearing can be divided up into two levels: modular or primary, and symbolic or central. Multiple-canal implantation is rather applied to the former mechanism, single-canal implantation to the latter. A bank of electrical signals recognizable from each other is being built up. It may be utilized in single-canal systems using this vocabulary to form sentences. The proper phonetic feature to be matched will then have to be selected.