GB318989A - Improvements in receivers for telegraphic and like signals - Google Patents

Abstract

318,989. Electrical Research Products, Inc., (Assignees of Curtis, A. M., and Burton, E. T.). Sept. 15, 1928, [Convention date]. Addition to 312,338. Eliminating effects of disturbing currents.- Wandering zero is corrected by means of saturation effects in a transformer having a core of high permeability, features disclosed in Specifications 270,354 and 315,821 being adopted. The primary coils 14, 15, Fig. 1, have their cores polarized in opposite directions by the coils 19, 20, which are energized by a battery 21 through a resistance r and choke c. Owing to saturation effects in the cores, the transformers 14, 17 and 15, 18 are effective over only a narrow range of current strength in positive and negative signals respectively. When the signals A, Fig. 7, passing from the input pair 12, 13, Fig. 1, to the receiving circuit 16, exhibit zero wander so that their peak voltage cross the narrow voltage bands x or y for which the coils 17, 18 are respectively effective, voltage-impulses B, C are applied to the grids of the valves 22, 23. The resistances 24, 25 and condensers 26, 27 are so arranged that unidirectional impulses D, E of plate current pass through the primaries of the transformers 29 so as momentarily to energize the polarized relay 30. Voltage impulses smoothed to the form I are consequently admitted from the batteries 30a through the impedance network 33 to the grid of the valve 38, so as to correct the zero wander. In a modification (Fig. 2, not shown) the grids of the valves 22, 23 are positively biassed, with the result that the plate-current impulses are of unequal magnitude as at F, G, and only one in each pair is able to actuate the relay 30 so as to send on impulses H. In another modification (Fig. 3, not shown) a negative grid-bias is applied to the valves 22, 28 and the resistances and condensers 24 - - 27 are omitted. Single impulses of plate current (corresponding to the rising portions of the excess signals) are produced in this case as at J, K; impulses L are input to the network 33, and a grid-voltage correction M is applied to the valve 38. Figs. 4, 5 show two alternative networks which may be used instead of the network 33; and according to Fig. 4 (part not shown) a transformer-coupled amplifier is inserted between the transformer 29 and relay 30. The relay 30 shown in Figs. 4, 5 is provided with an additional winding 55b which prolongs the effects of the impulses applied to the winding 55<a>; the charging current to the condenser 31, Fig. 4, or 6 Fig. 5, prolongs the impulses N (winding 55a) to the form 0 (winding 55b). In Fig. 5 the locking network 61, 62 can be adjusted independently of the shaping network 33. In a simplified arrangement (Fig. 6, not shown) the push-pull pair of valves 22, 23 is replaced by a single valve and the signals as well as correcting impulses are applied to the correcting relay 30, a corrected - signal curve of the type shown at P being obtained. Specifications 270,354 and 315,821 are referred to.