Patent GB-590261-A (GB)
Title: Improvements in or relating to arrangements for repeating oscillograph indications at a distance
IPC: G01R13/20
Filed: 1945-04-14
Abstract: 590,261. Cathode-ray oscillographs. STANDARD TELEPHONES & CABLES, Ltd and CLEAVER, R. F. April 14, 1945, No. 9385. [Class 37] An arrangement for repeating the indications of a local cathode-ray oscillograph operated by electrostatic deflection, on a remote cathoderay oscillograph, comprises a cathode follower thermionic valve stage connecting a deflecting plate of the remote oscillograph with the corresponding plate of the local oscillograph. Indications of a local oscillograph 1 are repeated on a second or remote oscillograph 2 connected thereto by cable or other transmission line conductors. The deflecting plates 3, 4, 5, 6 of the oscillograph 1 are supplied with steady deflecting potentials from terminals 7, 8, 9, 10 through resistances 11, 12, 13, 14. The four plates are connected to a conductor 19 of fixed negative potential by four condensers 15, 16, 17, 18. The conductor 19 is connected to the negative terminal 20 of the high-tension supply source and its potential is determined by two resistances 22, 23 connected in series between the negative terminal 20 and the positive hightension terminal 21. The junction of the resistances 22, 23 is earthed at 24. Four similar triode valves 25, 26, 27, 28 have their cathodes connected to the conductor 19 and their anodes to the terminals of the condensers 15, 16, 17, 18 which are connected to the corresponding oscillograph plates. These valves serve as electronic short-circuiting switches for the respective condensers and are controlled by rectangular pulses applied simultaneously to the four control grids from a source connected between terminals 20, 29. As explained in Specification 590,260, in the periods when the valves are blocked the condensers charge, causing the spot to trace a line on the oscillograph screen. When the four valves are unblocked the condensers discharge rapidly and the spot returns to the starting point. If the deflecting plates of the two oscillographs 1, 2 were directly connected, the capacitance to earth of the connecting leads would shunt the condensers 15, 16, 17, 18 and affect the indications of the local oscillograph 1. To prevent this, four buffer valves 30, 31, 32, 33 are interposed in the connections between the corresponding plates of the two oscillographs. These valves are arranged as cathode followers with their anodes connected to the high-tension terminal 21 and their cathodes through resistances 34, 35, 36, 37 to the common conductor 19. The control grids are connected to the plates 3, 4, 5, 6 of the local oscillograph 1 and the cathodes are also connected to the corresponding deflecting plates 38, 39, 40, 41 of the oscillograph 2 through long conductors 42, 43, 44, 45. In order to discharge these conductors during the discharge periods of the condensers 15, 16, 17, 18, discharger valves 46, 47, 48, 49 are shunted across the cathode resistances 34, 35, 36, 37, their anodes being connected to the cathodes of the corresponding valves 30, 31, 32, 33. The discharger valves are indirectly controlled by the pulses used to control the switching valves 25, 26, 27, 28 and are arranged to be cut off during the charging period and to conduct during the discharging period so that the conductors 42, 43, 44, 45 are rapidly discharged. The discharger valves are controlled by a switching valve 50 with its cathode connected to the conductor 19 and its control grid to the terminal 29 to which the switching pulses are applied. The anode is connected to the earth terminal 24 through a potentiometer 51, the movable contact of which is connected to the grid of an inverter valve 52 having its anode connected to the terminal 21 through a resistance 53 and to the control grids of the discharger valves 46, 47, 48, 49 through a blocking condenser 54. The control grids are connected to the conductor 19 through a high resistance 55. The discharger valves 46, 47, 48, 49 may alternatively be grid-controlled gas-filled tubes, or mechanical commutators or electromagnetic relays may be used for short-circuiting the cathode resistances 34, 35, 36, 37. The conductors 42, 43, 44, 45 may be the conductors of a cable, which may contain additional earthed conductors serving as screens. The screen conductors need not be directly earthed, so that they can be used at the same time for a telephone circuit. Two quadded cables may be employed, each having one pair of conductors connecting one pair of plates of the oscillograph 2 to the cathodes of the corresponding cathode follower valves, the other pair of conductors being earthed.