The audion-detector and amplifier

Notwithstanding the now wide-spread use of the Audion as a detector in radio telegraph and telephone service few accounts of independent research into the nature of this instrument, or even cursory descriptions of its operation, seem to have been recorded, since the original paper presented before the American Institute of Electrical Engineers in 1906. At that time, pending patent applications prevented the presentation of a detailed description of certain forms and improvements which are to-day common knowledge among radio engineers. It is my purpose herein to outline briefly the subsequent development of the Audion, both as a radio detector and as an amplifier of minute electric impulses. The improved Audion, containing one hot and two independent cold electrodes, is described, and its action as a sensitive detector in radio telegraph and telephone work outlined. Its actiont is shown to be not that of a simple rectifier or valve, but that of a true relay device. The secondary circuit of a radio receiving transformer is connected in shunt between the "grid" electrode and the filament. The telephone receiver and dry battery are connected between the plate electrode and filament. There appears to be no known limit of sensitiveness below which the effect of minute received energy fails to be registered. The device is constant and reliable, requiring only initial adjustments of battery voltages. The Audion is incontestably a "potential operated" device.