Patent GB-581919-A (GB)
Title: Phase correction circuit
IPC: H04L7/00
Filed: 1944-05-26
Abstract: 581,919. Synchronous movements ; synchronism indicators. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. May 26, 1944, No. 10251. Convention date, May 29, 1943. [Classes 40 (iii) and 40 (v)] Phase-corrections are applied to a motor 31 driving a synchronizing distributer or kicker 30 more promptly for large than for small phase errors. The device, which is suitable for use when marking signals are lengthened and distorted, may act on the beginning or end of a marking impulse or on both. Negative marking signals, which may be derived from rectified tone impulses, pass through a filter 1 to the input of a double triode 4. The triode has a thresholding action, the grid 5 being positively biassed by a battery 82 and by a resistance 84 for that purpose and the level of the negative signals is designed to exceed the level required for cut-off in order that the marking condition going out from anode 7 shall consist in a full cut-off. The valve 4 has a push-pull connection; the second grid 9 is biassed to cut-off through resistance 13 so long as anode 7 is conducting, but permits anode 8 to conduct so long as anode 7 is cut off, those two situations constituting the marking and spacing conditions respectively. If switch 17 is closed, the cutting off of anode 7 on a change from spacing to marking causes a negative pulse to pass through condenser 19 and diode 15 to the grids of the double triode 22. A pulse is consequently applied through anode 24 and transformer 27 to a gas-discharge lamp 29 which is mounted on a rotating part and serves as a stroboscope. At the same time a correcting pulse is applied through anode 23 to the kicker or synchronizing distributer 30. A threshold bias is provided for the grids of valve 22 by battery 82 and resistance 21. When switch 18 is closed, a similar pulse is applied to lamp 29 and kicker 30 at the change from marking to spacing, when anode 8 of valve 4 cuts off. The kicker 30 is driven by the shaft 32 of the motor 31 which drives the multiplex distributer of the telegraph system. The phase of the motor 31 is corrected by an auxiliary motor 38 turning the housing of motor 31 in either direction through gearing 36. The correcting motor 38 is connected through the armature of a relay 41 to one or other or neither of the sources of voltage +120 V. and - 120 V. and is thus caused to apply corrections in one direction or the other, or to remain stationary, under the control of the double triode 43 whose anodes feed the two opposed windings of the relay and are themselves cut off or rendered conductive according to the charges accumulated on the grid condensers 63, 64 in response to correcting impulses derived from the kicker 30. The correcting impulses on the grid of valve 22 cause positive impulses from anode 23 to be applied to all the conducting segments (shown in white) of the kicker 30 and during perfect synchronism the impulses get no further, but when the distributer is fast they pass through one of the brushes 56 to condenser 63, the positive charge stored on that condenser for grid 44 being greater for large errors of synchronism than for small, owing to the way in which the brushes 56 are connected to the resistances 60. When the distributor is slow, impulses are similarly stored on condenser 64 through one or other of the brushes 49. When sufficient charge has accumulated to raise the corresponding grid above cut-off, current flows through the corresponding winding of relay 41 and a correction is consequently applied by motor 38. If, as a result of distortion the marking signals are so lengthened or shortened that condensers 63, 64 are both charged, the windings of relay 41 will be equally excited in opposition and no correction will be applied so long as synchronism obtains, but if through an error of synchronism one condenser becomes more heavily charged than the other, the windings will be unequally excited and the armature will move so as to apply a correction. If, however, only one of the switches 17, 18 is closed, corrections are applied only on the leading or the trailing edge of the marking impulses, as the case may be, and the sharper edge may be selected for use. Instead of the condensers 19, 20, and double triodes 4, 22, a transformer may be used, Fig. 2 (not shown), in conjunction with ordinary triodes for deriving the correcting impulses wich are applied to the kicker 30.