Bell System Technical Journal 26(3),395–409 (1947), DOI 10.1002/j.1538-7305.1947.tb00902.x. Page395 abstract/introduction: coded PAM samples, binary-level count, experimental speech encoder/decoder. Publisher ieeexplore.ieee.org/document/6773095/ ; original scan vtda.org/pubs/BSTJ/vol26-1947/articles/bstj26-3-395.pdf .