GB192090A - Improvements in electrical amplifying apparatus - Google Patents

Abstract

192,090. Westinghouse Electric & Manufacturing Co., (Assignees of Slepian, J.). Jan. 20, 1922, [Convention date]. Thermionic amplifiers and detectors; audible reception of unmodulated continuous waves.- Relates to receiving-apparatus for wireless and like signals employing a back-coupled valve which is set into oscillation by a received impulse and is choked into quiescence immediately afterwards by a negative charge accumulating on its grid; and consists in providing means for controlling the choking effect in accordance with the intensity of the received impulses. Fig. 1 shows one arrangement in which the aerial inductance 25 is coupled to a tuned circuit 14, 15 in the plate circuit of the valve 1 and to a coil 7 in the grid circuit. The grid circuit is completed through a grid leak 9 shunted by a condenser 8, and the plate circuit includes a battery 12 and telephones 11. When continuous wave telegraph signals are received on the aerial, the valve oscillates intermittently, being choked periodically owing to a negative charge accumulated on its grid being unable to escape rapidly through the leak resistance. The oscillations may be of audible group frequency and will then give rise to an audible note in the telephones. The invention provides another coil 16 coupled to the coils 15, 25 and connected in circuit with the grid leak 8, 9 and a rectifying-valve 17. By this means the received signals are caused to apply a biassing voltage to the grid, with the result that the amplitude reached by the intermittent oscillations before they are choked varies with the intensity of the received signals. The apparatus may thus be used for reception of telephone signals, but in this case the grid leak 9 should be adjusted so that the group frequency of the intermittent oscillations is above the audible limit. In a modification shown in Fig. 2, the two valves are combined in one tube 27, the function of the anode of the rectifying valve being performed by an extra grid 31 placed between the usual grid 32 and plate 28. The rectifying- grid 31 is connected to one end of the coil 33, the other end of which is connected through the grid leak 9 to the cathode 29, while the grid 32 is connected to a tapping on the coil 33.