Patent GB-463694-A (GB)
Title: Improvements in apparatus for detecting electric impulses
IPC: G01S1/02
Filed: 1935-10-02
Abstract: 463,694. Electric signalling systems. PLESSEY CO., Ltd., and BAILEY, C. E. G., FISH, N. L. YATES-, and THORN, W. A. J. Oct. 2, 1935, Nos. 27224/35 and 19772/36. [Class 40 (i)] [Also in Group XL] Signals such as a succession of dots, or a succession of dashes with spaces equal to the length of a dot, are passed through a transformer to give impulses of opposite sign at the beginning and end of a signal, and are applied to an indicating instrument such as a galvanometer which remains insensitive for a definite period after the arrival of a signal. It thus gives deflections of opposite sign at the beginning of a dot and the end of a dash, respectively, and does not respond to the end of the dot or the beginning of a following dash. Alternatively, the indicating instrument may be normally insensitive and rendered sensitive by the first pulse of a pair so as to respond only to the second pulse of the pair. The invention may also be employed in the reception of more complex signals such as the letters A or N and is particularly applicable to radio systems for guiding aircraft in which differently-directed beams are characterized by different signals. In one receiving arrangement, Fig. 2, the signals are applied through a transformer 10 having secondaries 11, 12 connected oppositely to a double-diode valve 13. At the first pulse of a signal, one of the plates, say the upper one, becomes conducting, the galvanometer 18 is operated in one direction, and the charge on the condenser 14 biasses the other path so that it cannot respond to the next impulse. Another arrangement, Fig. 3 (not shown), employs two opposed triodes with their grids connected to the ends of the transformer secondary and the filaments through a timing element to the midpoint. In a third arrangement, Fig. 5 (not shown), the signals are applied through one secondary winding to the galvanometer and through a second secondary and a further transformer to the grid of a triode valve the anode circuit of which contains a normallyoperated relay which de-energizes in response to the first pulse of a pair to short-circuit the galvanometer during the second pulse. In a fourth arrangement, Fig. 8, the relay 37 controlling a short-circuit around the galvanometer 31 is controlled by a double-diode-triode 43, the grid of which is associated with the timing circuit 44, 45. A rectifier 46 may be connected as shown to limit the potential applied to the grid, whilst the connection of resistance 45 to the potential-divider 49 applies a potential opposite in sign to that by which condenser 44 is charged and makes the discharge curve substantially linear. In another arrangement, Fig. 11, the double-diode-triode is replaced by a triode 53 and two separate rectifiers 52, and the signals are applied through a resistance-capacity network 61, 64. In other arrangements, the short-circuit around the galvanometer is controlled by a relay of slow-release type directly controlled by the signals, Fig. 13 (not shown), or by a relay having a second (hold-on) winding connected to a charged condenser upon operation of the relay, Fig. 14 (not shown), or the galvanometer mechanically closes a short-circuit for itself, Fig. 15 (not shown). Specification 447,707 is referred to.