1.This linguist was the founder of the phoneme theory and analyzed the phoneme from the point of view of the morphemic structure of words and sound interchange within which he distinguished synchronic and diachronic types of alternation. Later on he tried psychological approach to the phoneme regarding the latter as a complex perception of the articulatory movements and of the muscular sensations connected with them together with the resulting acoustic impressions, all of which react on mind simultaneously. Though his views were not widely spread and were rather obscure he had some followers who developed both of his theories.
2.This linguist began his research work investigating the phoneme from the morphological point of view but later changed his opinion fundamentally under the influence of the Copenhagen school of linguistics. He considered the phoneme to be an abstraction which can not be observed or perceived and distinguished between general phonology which studies the structure of a concrete language and theoretical phonology which produces for the former the conceptual apparatus. In his theory he used terms borrowed from cybernetics which makes his approach original but rather obscure.