Patent GB-538214-A (GB)
Title: Improvements in or relating to the successive indication of a plurality of conditions
IPC: G01S1/02
Filed: 1940-03-30
Abstract: 538,214. Electric indicating systems; thermionic distributers. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. March 30, 1940, No. 5766. Convention date, March 31, 1939. [Class 40 (v)] [Also in Group XXXVIII] An arrangement for indicating in succession on a single instrument a plurality of conditions, such as those relating to the flight of an aeroplane, comprises a modulator associated with each of the conditions and adapted to be rendered temporarily operative by an impulse, a source of alternating voltage impressed on the modulator, and means for deriving a direct voltage from the alternating voltage and varying its amplitude in accordance with the condition to be indicated. In Fig. 3, the indications from a turn bar gyro and an artificial horizon gyro are exhibited in rapid succession on a cathode ray tube 31 so as to be simultaneously observable. A pair of valves 6, 8 together with inductances 9, 11 and differential condenser 13, 15 operate as a balanced modulator, the output from which is coupled by transformer 41 to a pair of rectifiers 37, 39 whose cathodes are connected by a centre-tapped resistance 43. A voltage of frequency f<SP>1</SP> is injected into the grid circuits of valves 6, 8 while a voltage of frequency f<SP>2</SP> is injected into the common grid return and also by means of transformer 45 between centre taps of resistance 43 and secondary of transformer 41. A similar circuit for the artificial horizon gyro is shown with the references distinguished by subscripts. The cathode of detector 37 is connected to a horizontal deflecting plate of tube 31 while cathode of 37<SP>1</SP> is connected to a vertical deflecting plate. The other two plates are earthed. An amplifier 49 is connected between the common grid return of modulators 6, 8 and cathode of 391 and an amplifier 491 similarly cross connected. In operation, valves 6, 8, 61, 8<SP>1</SP> are biased to cut off. On receipt of impulse A valves 6, 8 conduct and a direct voltage appears on the horizontal deflecting plate of tube 31 which is proportional to the degree of unbalance of the modulator system due to movement of condenser 13, 15 in accordance with the indication of the turn bar gyro. During this period valves 61, 81 are still blocked but valve 491 supplies a vertical line drawing voltage at frequency f<SP>2</SP> for the turn bar gyro. Impulse B now follows and the vertical deflecting plate of tube 31 is energized in accordance with the indication of the artificial horizon gyro while valve 49 supplies a horizontal line drawing voltage. Any number of horizontal deflecting modulators may be connected at X, X and any number of vertical deflecting modulators at Y, Y successive control impulses being used to operate them in rapid succession so that all the indications may be observed together on tube 31. The two pairs of rectifiers 37, 39 and 371, 39<SP>1</SP> are respectively common to all horizontal and vertical modulators. A modification is described using pentodes for which the indications include the deviations from a glide path. Reference has been directed by the Comptroller to Specification 536,090.