Selective or Individual Signals
Thomas D. Lockwood · Transactions of the American Institute of Electrical Engineers · 1892
Amnong the mairiy subordinate branches of invention in auxiliarv appliances which surround and form a suitable setting for that grand central figure, the Electric SpeaLing Telephone, none represents inore painstaking, thouight, has been more tlhor- oughly ransacked, or has constituted a more attractive pursuit than the study of selective signaling.