T. E. Herbert, Telegraphy: a detailed exposition of the telegraph system of the British Post Office (4th edn, 1920)
march 2010 by asfaltics
chapters on the Wheatstone A.B.C., Hughes, Baudot and Murray (automatic and multiplex) systems pp 398-519
printing.telegraphy
telegraphy
donald.murray
BPO
march 2010 by asfaltics