US1940161A - Synchronizing system - Google Patents

Synchronizing system Download PDF

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US1940161A
US1940161A US531794A US53179431A US1940161A US 1940161 A US1940161 A US 1940161A US 531794 A US531794 A US 531794A US 53179431 A US53179431 A US 53179431A US 1940161 A US1940161 A US 1940161A
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United States
Prior art keywords
signals
synchronizing
current
television
circuit
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US531794A
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Barthelemy Rene
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Compteurs Schlumberger SA
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Cfcmug
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00Details of television systems
    • H04N5/04Synchronising
    • H04N5/08Separation of synchronising signals from picture signals
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00Details of television systems
    • H04N5/14Picture signal circuitry for video frequency region
    • H04N5/16Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00Details of television systems
    • H04N5/14Picture signal circuitry for video frequency region
    • H04N5/16Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level
    • H04N5/165Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level to maintain the black level constant

Description

Dec. 19, 1933. BARTHELEMY 1,940,161

SYNCHRONIZ ING SYSTEM Filed April 2l, 1931 3 Sheets-Sheet l 1933- R. BARTHELEMY V SYNCHHONIZING SYSTEM Filed April 21. 1931 a Sheets-Sheet 2 IHI WU Q3 ip A 1616 Patented Dec. 19, 1933 PATENT OFFICE SYNCHRONIZING SYSTEM Rene Barthelemy, Fontenay-aux-Roses, France, minor to Compagnie Pour La Fabrication Des Compteurs Et Materiel DUsines A Gas,

Montrouge, France, a. joint-stock company of France- Application April 21, 1931, Serial No. 531,794, and in France May 21, 1930 11 Claims. (Cl. 178-495) Several of applicant's previous patents disclose a remotely controlled synchronizing device to which is transmitted a current of very short duration termed top repeated at equal intervals of the order of 1 of a second inthe case of telecinematography and which sets up an appropriate local oscillation.

The present invention has reference to a method and means enabling the local oscillation to be started solely through the agency of the synchronizing top, to the exclusion of the other signals emitted by the sending apparatus and which are generally transmitted on the same carrier wave as the synchronizing signal.

The principle oi the invention consists in produclng by means of the synchronizing top a modulation of the carrier wave which corresponds to a variation 01! the virtual value of said wave of opposite sign to that which would be produced by the television signals. To these two modulations correspond two variations of opposite sign of the mean current detected in the receiver and with this difference of signs it is easy to eliminate the effects of the television signals on the synchronizing system. I

A simple means for enabling the two sorts of signals to be diiierentiated at the sending end consists in causing the top to modulate by momentarily raising the plate voltage of the oscillating valve, whereas the modulated television signals are applied to the grid circuit of said lamp through the medium of a suitable impedance between the time intervals which separate two successive tops; this kind of modulation generally lowers the virtual current in the aerial.

A further object of the invention is to increase the security of selection by mounting in the deteeter circuit a stopper" circuit tuned to the frequency of the synchronizing top and from the ends of said circuit is tapped the synchronizing voltage of suitable frequency, phase and am.- plitude, which may then be applied, amplified or not, to the motor to be synchronized or any other equivalent system.

Several embodiments of the invention have been illustrated in the accompanying drawings wherein:

Fig. 1 illustrates a transmitting device modulated according to the invention.

Fig. 2 illustrates a suitable receiver for use with the transmitting device of Fig. 1.

Fig. 3 illustrates a modified circuit arrangement for the receiving device of Fig. 3.

Fig. 4 illustrates a further modification of the receiving device of Fig. 3.

Fig. 5 is a graph of the oscillations received by the device of Fig. 4.

Fig. 6 is a graph of the oscillations after selection effected by the device of Fig. 4.

Fig. 7 is a circuit arrangement of an automatic device for regulating the grid bias of the receiver of Fig. 4, and

Fig. 8 illustrates a modification of the device of Fig. 7, and Fig. 9 a modification of the device of Fig. 8.

In the device of Fig. 1, an oscillating valve 0 (which may be replaced by a bank of valves and may be followed by a high frequency amplifier if high powers are to be obtained) produces the continuous wave of suitable frequency by means of conventional reaction couplings, for example the electromagnet coupling of an oscillating cir cult constituted by the coil B and the condenser K with an inductance Ci mounted in the grid circuit. Another suitable inductance A coupled to the coil B transmits the energy to the aerial, an earth having been featured at T. The modu-- lation of the apparatus by the television oscillations is accomplished by applying the modulating voltage coming in at M and N to the resistance R which may also be an inductance. A very small capacity C lets through the high frequency carrier current. Modulation is thus effected by variation of the grid potential and it is observed that the virtual current in the aerial decreases when the strength of said. modulation is increased.

Said modulation is discontinued at each complete scanning of the image. for a very short interval of time, during which time interval the synchronizing top" is transmitted. To this end, a switch Z, rotating synchronously with the spindle of the scanning disc, breaks the current fed by a direct current source E to the primary P of a transformer, at the exact moment when the television modulation is interrupted. The connec tions being suitably established, an additional voltage, lasting a very short length of time, for example 1/10,000th of a second, is introduced by the secondary S into the plate circuit of the oscillating valve and is added to the normal direct voltage. The virtual current in the aerial is suddenly increased and such excess current easily attains a value equal to the ordinary current. The current resumes its normal value when the energy stored up in the transformer is practically dissipated by the valve. Then the grid modulation starts again arid the direct current source E again feeds the primary P, the time for establishing the Bill necessary current being calculated so as to be of the order of of a second.

The excess voltage may be introduced into the plate circuit in any other manner without departing from the present invention. Thus, the drawbacks attendant on a switch breaking a certain current may be avoided by substituting therefor the filament-plate circuit of a three electrode valve and by using the synchronous commutator to vary considerably the grid bias without breaking the current.

At the receiving end, the signals will be selected by using the detected current, or a current proportional thereto, after amplification. Said current 2' generally flows through the plate of a valve and an anode resistance or impedance p (Fig. 2). A fraction r of said resistance will be used to start the local oscillation derived from the neon tube L, the condenser Y, the resistance D and the source P, which device was disclosed in applicants U. S. application Serial No. 415,537 filed December 20th, 1929.

The potential difference used will he ran, it will dwindle to a very small value at the moment when the top" is received, it will be higher in the absence of any modulation and its mean value will increase again when the television modulation is applied. Thus if said voltage ri mounted in series with the discharge tube be opposed to the voltage supplied by the local source P, the latter may be adjusted so that the tube will light up each time ri decreases sufliciently, that is to say at each top, while said tube remains unresponsive on the contrary to any increase of ri, that is to say to the television modulation.

Another object of the invention is to enable the two types of signals to be selected with complete security. Its principle is based on the combination of an impedance (in general a resistance) through which fiows the said plate current, with an auxiliary electromotive force and a system having a more or less perfectly unilateral conductability similar to a detector.. It will be understood a priori that with the connections suitably established and for a suitable value of the auxiliary electromotive force, the detector can choke all the television oscillations and only let through the synchronizing signal.

In the device illustrated in Fig. 3 for selecting the two types of signals mentioned above, the detector system is constituted by the filamentgrid space of a triode S.

The plate current i of the detector valve D flows through the resistance R and produces a difference of potential Ri which decreases by at least one quarter of its valve upon receptionof a synchronizing top. The grid of the valve S is subjected to said potential difference Ri through the medium of a grid biassing battery E.

The voltage of said battery is such that a negative potential is-impressed on the grid of the valve S (for the mean value of R2 corresponding to the modulating television signals) which annuls the plate current of said valve S. Under these circumstances, said signals have no effect on the transformer T. The incoming synchronizing signal causes R2 to fall appreciably in value during the duration of said synchronizing signal, which moreover is very short, and the grid potential of the valve S rises during this time to a higher value thereby giving rise to an anode current which flows through the primary of the transformer T. The making or breaking of this current generates an electromotive force in the secondary which is utilized to light up the pilot lamp disclosed in certain of my co-pending applications, and in particular in the aforementioned application Serial No. 415,537 filed December The condenser K shunted across the ends of the primary of the transformer T constitutes with the self-inductance of said primary the stopper circuit referred to above and still further promotes selection of the signals.

In this manner, by using a suitable bend of a characteristic curve of a valve and an auxiliary voltage, it is possible to select two types of signals modulating alternately and in different directions the same carrier wave.

The television signals are transmitted to the succeeding amplifying valves such as BF by means of any suitable coupling, as for example a condenser C.

The invention is likewise concerned with a modified circuit arrangement of the detector-selector at the receiving end.

The current variations detected by television are transmitted and amplified by an amplifier which must be designed to faithfully reproduce a large range of frequencies; in Fig. 4 the current oscillations detected-are applied through the medium of a condenser C and a resistance R on the controlling grid g of an amplifying valve. In Fig. 5 have been illustrated the voltage oscillations which take place in the resistance R. During the whole time of transmission of the television signals, the grid voltage drops by an amount of mean value a. The oscillations of maximum amplitude are for example (ua+u:), then upon passage of the synchronizing signal, the grid voltage increases by us which is substantially higher than the value m.

If, in conformance with the invention, the valve is used as a detector, the television signals will be eliminated and, the grid being suitably biassed, only the oscillations of the anode current i in the transformer T due to the synchronizing signals will be observed (Fig. 6). With sufilcient negative grid bias, the plate current will be annulled even in the case of the strong- Obviously the valve might include other electrodes and the grid be charged through the medium of another coupling without departing from the spirit of the invention.

The current pulsations obtained may then be readily used for synchronizing with extreme accuracy the rotation of the television scanning disc, by using the devices disclosed in others of my patents.

The above described method of separating synchronizing from television signals by using the bend of the characteristic curve of a receiving valve and negatively biassing its grid, requires that the bias shall be sufficient to prevent television signals from producing oscillations in the plate circuit of the valve, but it must not be so great that the synchronizing signal is also choked. The mean value of the biassing voltage must therefore be determined as a function of the current at the receiving end. Such adjustment is readily accomplished but if the current at the receiving end is variable, as is frequently the case, in wireless transmission, this operation becomes diflicult.

The invention is likewise concerned with an automatic adjustment for the biassing voltage obtained by producing said voltage by the received current itself, of course after suitable transformation.

This is achieved by producing in the amplifier of the receiver, generally in the low frequency stage, a voltage proportional to the mean amplitude of the detected oscillations, in converting said alternating voltage into a substantially direct voltage by means of a valve and filter, (which may be only a simple condenser) and in applying said voltage in a suitable direction to the grid circuit of the signal selecting valve.

In Fig. 7 a television receiver having for example 3 stages of amplification includes a detector valve 1 and two amplifying valves 2 and 3, the latter acting on the luminescent tube N. Another valve 4 having suitable grid bias is provided for selecting the synchronizing signal, the amplitude of which is considerably greater than that of the television signals, and the brief pulsations of the synchronizing "top are converted in the anode circuit of said valve into oscillations of longer duration, by means of the condenser K and the transformer T in the manner indicated above; these long oscillations can then be utilized in the synchronizing device.

Automatic biassing of the grid of said valve 4, proportional to the current received, is secured according to the invention by applying a voltage u derived from the resistance R. There flows through said resistance a direct current caused by the oscillations which have been impressed on the valve N and which have been applied, through the medium of the transformer T, to a valve V which may be of any type of current rectifier. A condenser C of large capacity enables a practically direct voltage to be obtained which follows only the slow fluctuations at reception and which,

contains no high frequency terms produced by the modulation. The bias u is therefore proportional to the mean current received taken over a very long time interval.

Another arrangement based on the same principle, consists in using the rectifying properties of the triode 4 itself to obtain a valve effect and in using the voltage taken from the filament plate circuit in a suitable filter, the whole or part of the purified voltage derived therefrom being used to bias the grid in the manner desired.

Fig. 8 shows the detail of this device, which in addition to the advantage of simplicity only uses the energy proportional to the synchronizing signal, to the exclusion of the television signals, and feeds to the synchronizing circuit power which within wide limits is independent of the power received. This quality is of great value for the stability of the images in television.

The television amplifier receiver supplies at S a composite voltage one component of which is the television and synchronizing signals alternately, the amplitude of the latter being considerably greater than that of the television signals. This voltage is applied to the resistance 9 connecting the grid to the usual common point. An auxiliary biassing battery P which is not involtage R2, decreases.

dispensable, is so designed that in the absence of the signals, the anode current i supplied by the source U is practically nil. Under the effect of the incoming signals, the current 1 assumes a mean value which is not nil and the flow of said current in the resistance R produces a voltage drop which biases the grid negatively with respect to the cathode.

As said current i is formed by successive pulsations, if a condenser K of sufilcient capacity be mounted at the ends of the resistance R, there is created a biassing voltage proportional to the mean value i reckoned over a fairly long interval of time.

The value of R is so chosen moreover that the bias obtained shall be sufficient so that television signals proper shall take no part in producing the anode current and that only' the synchronizing signals of suificient amplitude shall produce the anode current and, consequently, automatically maintain the biassing voltage. Under these conditions, only the pulsations due to synchronization are transmitted to the motor M or to an additional amplifier through the medium of the transformer T combined with the condenser C. It is thus seen that the influence of the television modulation is completely eliminated.

Moreover the intensity of the synchronizing oscillations transmitted to the motor M is substantially constant, which is explained by the fact that if the incoming signals increase in strength, for example, the biassing voltage increases and, simultaneously, the real anode voltage, which is equal to the voltage U minus the These two efiects are cumulative, if the valve characteristics be considered, and limit the increase of power in the anode circuit which would be introduced by the increase in the strength of the signals and which would exist were the plate and grid potentials constant.

The circuit may be modified in several ways without departing from the scope of the invention. Thus instead of the simple resistance-capacity filter disclosed, a filter having several cells with a large time constant (not shown) may be usei in Fig. 8 has been disclosed an independent filament heating battery A but instead of said independent heating source the device of Fig. 9 may be used in which the cathode C of the valve 4 is indirectly heated by a filament F connected to the supply mains G. The advantage of this modification is that the potential of the cathode C can be adjusted at will.

I claim:

1. In a device for transmitting synchronizing signals using a carrier wave which is likewise modulated by a difierent type of signals such as television signals, the combination of an oscilla ticn generating triode having an input and an output circuit, means for impressing the carrier wave frequency on the input circuit of said valve, means for impressing television signals on the input circuit of said valve to modulate said carrier wave, and periodically operative means for impressing the synchronizing signals on the output circuit of said valve, the transmission of the television signals being discontinued during the transmission of the synchronizing signals.

2. In a device for transmitting and receiving synchronizing signals using a carrier wave which is likewise modulated by a different type of signals, such as television signals, the combination of an oscillation generating valve, means for impressing the carrier wave frequency on the grid circuit of said valve, means for impressing said television signals on the grid circuit of said valve, periodically operative means for impressing the synchronizing signals on the plate circuit of said valve, the transmission of the television signals being discontinued during the transmission of the synchronizing signals, receiving apparatus including a triode and means for impressing said modulated signals on the input side thereof, and means associated with said triode for deriving from the output side thereof diiferent potentials corresponding to the television signal and synchronizing signal modulations respectively.

3. In a device for transmitting and receiving synchronizing signals using a carrier wave which is likewise modulated by a different type of signals such as television signals, the combination of an oscillation generating triode, means for impressing the carrier wave frequency and modulating television signals on the input circuit of said triode, periodically operative means for impressing the modulating synchronizing signals on the output side of said triode, the transmission of said television signals being discontinued during the transmission of said synchronizing signals, a receiving triode on the input side, of which said modulated carrier wave is impressed, and an impedance mounted in the plate circuit of said receiving triode and across which a potential may be derived which is greater in the case of television signal modulations than in the case of synchronizing signal modulations.

4. In a device for transmitting and receiving synchronizing signals using a carrier wave which is likewise modulated by a different type of signals such as television signals, the combination of means for transmitting a carrier wave, means, alternating in operation, for producing modulations of said carrier wave by television signals and synchronizing signals respectively, said two kinds of modulations being of opposite signs with respect to the virtual value of said carrier wave, a receiving rectifying triode on the input side of which said modulated carrier waves are impressed, an impedance mounted in the plate circuit of said rectifying triode, and across which a higher potential is created on reception of said television signal modulations than on reception of said synchronizing signal modulations, an additional triode, a biassing battery mounted in the grid circuit of said additional triode and adapted in conjunction with said impedance to bias said grid negatively, said biassing battery being adapted when assisted by the potential across said impedance due to reception of said television modulations to bias the grid of said rectiher so strongly that substantially no current flows in the plate circuit of said rectifier whereas current flows therethrough when the potential across said impedance drops upon reception of the synchronizing modulations.

5. A device according to claim 4, in combination with a stopper circuit mounted in the plate circuit of said rectifier and tuned to the synchronizing signal frequency.

6. In a device for transmitting and receiving synchronizing signals using a carrier wave which is likewise modulated by a different type of signals such as television signals, the combination of means for transmitting a carrier wave, means, alternating in operation, for producing modulations of said carrier wave by television signals and synchronizing signals respectively, said two kinds of modulations being of opposite signs with respect to the virtual value of said carrier wave, a receiving triode including a grid circuit on which said modulated carrier waves are impressed, an impedance, and a biasing battery mounted in series with said impedance in said grid circuit, said battery being adapted to bias said grid negatively to such an extent that only the synchronizing signal modulations, but not the television signal modulations, are of sufficient amplitude to permit a plate current to flow.

7. In a device for transmitting and receiving synchronizing signals using a carrier wave which is likewise modulated by a different type of signals such as television signals, the combination of means for transmitting a carrier wave, means, alternating in operation, for producing modulations of said carrier wave by television signals and synchronizing signals respectively, said two kinds of modulations being of opposite signs with respect to the virtual value of said carrier wave, receiving apparatus including a triode, an impedance mounted in thegrid circuit of said triode, means for impressing the television and synchronizing modulations on the grid circuit of said triode, means for converting incoming television and synchronizing modulations into direct voltage, and means for applying said direct voltage across said impedance to bias said grid whereby only the synchronizing signal modulations are of suflicient amplitude to produce a current on the plate circuit of said triode.

8. In a device for transmitting and receiving synchronizing signals using a carrier wave which is likewise modulated by a different type of signals such as television signals, the combination of means for transmitting a carrier Wave, means alternating in operation, for producing modulations of said carrier wave by television signals and synchronizing signals respectively, said two kinds of modulations being of opposite signs with respect to the virtual value of said carrier wave, receiving apparatus including a rectifying triode, a plurality of amplifying triodes and a synchronizing signal selecting triode on the grid circuit of which the television and synchronizing signal modulations are impressed after rectification and amplification, an impedance mounted in the grid circuit of said synchronizing signal selecting triode, means for converting the rectified and amplified signal modulations into direct voltage, and means for applying said direct voltage across said impedance to bias the associated grid whereby only the synchronizing signal modulations are of sufficient amplitude to produce a current in the pate circuit of said synchronizing signal selecting triode.

9. A device according to claim 8, in which said means for converting the rectified and amplified modulations into a direct voltage comprise a rectifying tube and a filter circuit in circuit therewith.

10. In combination with a device according to claim 4, a filter circuit mounted in the plate cir cuit of said additional triode and adapted to choke any television modulations that may get through to the plate circuit of said additional triode.

11. In combination with a device according to claim '7, independent heating means for the-cathode of said triode.

RENE BARTHELEMY.

US531794A 1930-05-21 1931-04-21 Synchronizing system Expired - Lifetime US1940161A (en)

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FR579664X 1930-05-21

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US531794A Expired - Lifetime US1940161A (en) 1930-05-21 1931-04-21 Synchronizing system

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US (1) US1940161A (en)
DE (1) DE579664C (en)
FR (5) FR711446A (en)
GB (1) GB363605A (en)
NL (1) NL48119C (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2577355A (en) * 1944-12-09 1951-12-04 Bell Telephone Labor Inc Pulse forming and shaping circuits

Families Citing this family (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE967256C (en) * 1933-02-10 1957-10-31 Emi Ltd Circuitry for extracting a certain minimum value of the carriage of amplitudes of a synchronizing pulse
BE401738A (en) * 1933-03-01
BE402568A (en) * 1933-04-13
DE756008C (en) * 1933-05-20 1954-11-22 Opta Radio A G An arrangement for screening-out of the synchronizing pulses and the control Verstaerkungsgrades
US2178234A (en) * 1934-02-28 1939-10-31 Rca Corp Television system
DE748742C (en) * 1934-07-31 1944-11-09 Television broadcasting method, wherein the image modulation of the one side and the drop frame sync pulses from the other side of a fixed value (black value or value Largest brightness) are given from
NL46321C (en) * 1934-09-18
GB450675A (en) * 1934-11-19 1936-07-20 Cecil Oswald Browne Improvements in or relating to television and the like transmitting systems
DE972011C (en) * 1935-06-12 1959-05-06 Fernseh Gmbh Double-sided sync separator
BE422316A (en) * 1936-07-05
DE766547C (en) * 1936-11-12 1954-08-09 Fernseh Gmbh Circuit with variable Verstaerkungsgrad for reinforcing symbols
DE959375C (en) * 1937-07-22 1957-03-07 Telefunken Gmbh Circuit arrangement for the synchronization of an operation by means of pulses, in particular for television purposes
US2240507A (en) * 1938-10-05 1941-05-06 Hazeltine Corp Television synchronizing and control system
DE751692C (en) * 1941-02-27 1953-12-21 Lorenz C Ag Measurement methods, especially for broadband cable
DE975765C (en) * 1941-12-13 1962-08-23 Philips Nv Means for receiving by means of pulses of constant amplitude signals transmitted
NL74381C (en) * 1944-07-13
DE977647C (en) * 1950-07-21 1967-11-30 Aga Ab Apparatus for separating the sync pulses in a Fernsehempfangsgeraet
US2698358A (en) * 1950-11-30 1954-12-28 Rca Corp Video amplifier control by combined a. g. c. and d. c. voltages
DE959113C (en) * 1951-06-16 1957-02-28 Rundfunkschutzrechte Ev Circuit for separating synchronizing pulses from a composite signal with the aid of a biased diode
DE1168950B (en) * 1956-04-13 1964-04-30 Loewe Opta Ag Circuit arrangement for interference suppression in the separation of the synchronizing pulses in the constructed as Mehrgitterroehre amplitude screen tube of a television receiver
GB933262A (en) * 1959-03-26 1963-08-08 Int Computers & Tabulators Ltd Improvements in or relating to amplitude selection circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2577355A (en) * 1944-12-09 1951-12-04 Bell Telephone Labor Inc Pulse forming and shaping circuits

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GB363605A (en) 1931-12-24
FR40750E (en) 1932-08-22
FR40289E (en) 1932-06-08
FR49468E (en) 1939-05-01
FR711446A (en) 1931-09-09
FR39944E (en) 1932-03-19
DE579664C (en) 1933-07-01
NL48119C (en)

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