US2100279A - Television system - Google Patents

Description

Nw. 23, 3.937. R. H. GEORGE Er A1.

TELEVISION SYSTEM Filed Sept. 2. 1931 Patented Nov. 23, 1937 OFFICE andere 'retevision sustraer Application September 2, 193i, Serial No. 566398 :la Claims. (Cl. lit-7.5)

This invention relates to television systems, and particularly to aA system in which synchronism between the transmitting and receiving stations will be maintained during time intervals substantially less than that required for the scanning of a complete picture or frame.

This invention contemplates the transmission of synchronizing signals during the time interval occurring between the completion of` one pictorial element and the beginning of a succeeding pictorial element. Thus, in the case of the ordinary scanning system, where a linear pictorial element, usually along one dimension of the image, is taken, an idle time interval occurs o between the end oi one linear element and beginning o'i a new linear element. If the linear element is taken at the top of the picture from left to right, in a generally horizontal direction, the second linear element is taken below the rst, and substantiaily parallel therewith. These linear elements aretalsen until the bottom of the.

picture is reached, when a new frame or picture is started all over again. Hence, the complete scanning operation consists of a repeated series of discontinuous cycles, each cycle representing a continuous linear pictorial element. Eachseries of discontinuous cycles may be considered as making up a completeframe and by repeating the series, a number of frames make up a scene.

This invention contemplates the transmission of synchronizing impulses during the periods of discontinuity of image currents. Furthermore,

a special synchronizing impulse occurring dur-I ing the interval between the endof one frame and the beginning of a new frame is transmitted for framing the image. Since such synchronizing impulses occur during periods of non-transmission of picture impulses, the same transmission channel may be used without the necessity `for any special modulating or combining of the synchronizing and picture impulses. This results in simplicity at the transmitting system.

By making the synchronizing impulses of an amplitude substantially greater -than any normal o picture impulses, it is possible to effectivelysepa'- rate the two sets of impulses from each other at the receiving station without the use -o the customary filters or other series of resonant circuits.

This invention contemplates a receiving system in which a remarkable degree of freedom from mechanical devices is obtained. In the receiving system the scanning movements ofthe light spot are obtained by electric means, in contradistinction to the usual mechanical means of the pres-i ent-day receivers. The synchronizing adjustment of the receiving station merely consists of one or more resistances, whose value may be simply and easily changed. A property oi this receiving system is its ability to change either one of the dimensions of the image independently oi the other, thus making it possible to transform ordinary scenes into grotesque or comic scenes.

A television system of the above character is characterized by its utter simplicity, particularly at the receiving end, and it is adaptable to largescale production.

While in the system disclosed herein, scanning is effected as pointed out above, it is to be understood that any method of scanning may be used. In certain types of scanning, such as the spiral curve, it is clear that only one synchronizing impulse occurring between successive pictures would be practical.

in the receiving system herein disclosed, a feature of the invention lies in the fact that the actual scanning or movement of light spot along the image is eected by the receiving mechanism substantially independently of the transmitting mechanism, and that the assumption of a new initial position by the spot of light for repeating a previous cycle is governed by the transmitting station.

This action in the receiver is obtained by steady variation' of a potential ultimately applied to the scanning means, which potential is suddenly changed in an opposite sense in value by means of a synchronizing impulse. This synchronizing impulse, which is preferably built up to a certain 5 4ing potential is applied to the grid of a grid controlled gaseous discharge tube.

This tube, when properly connected in the circuit, has the property of having a gaseous discharge initiated therein upon a suitable change of grid bias. Such change may be of an exceedingly minute character, so that the system is trigger-like in its action. Such a tube is shown in British Pat- ?.Ill N9, .280,870. f

l 40. of the lsynchronizing;photo cell is substantially Iliferrinc to theerawmg; l

' Figurevlvis av diagrammatic showing of a telef vision transmitting system; f

I .FigurelZv shows the relation of the synchroniz vingilnpulsesto the pictureimpulses; and e Figure 3 shows a receiving system.

y The transmitting system may be of any type v whatsoever and, as shown here, comprises'a motor driving the usual Scanning disc with a series iol ' vthe scanning disc is rotated, each aperturev travels v of apertures arrangdiin thel form of a spiral. yAs' along a substantially linear element, horizontalture impulses *correspondingin intensity tothe vkall variations of llight inthe pictureare transmit-` y ted byv a photocell to a suitable ampliflenfrom there toa; modulatonandth'en'ce tosome transcuit and only picture impulses arev effective in' thefpicture portion'oi' the circuit, f

, The leadvgoin'g tothe synchronizingportion of l mitting system. i y

s Arrangedto rotate with the scanning disc is 'a synchronizing disc having avseries Iof apertures corresponding to the scanning disc apertures'.

The vsynchronizing` aizlertures are so related to v ing the source of lighten the photo-electric cell u at a sufflcientlyclose distance to thesynchronizingv disc sothat as one of the synchronizing aper# imres,:indicated by LS, ashes by, a linear syn- 1 chronizing signal of exceedingly short duration y lis emitted by the photo-electric cell. rThe rela-I v v tive amplitudes of the impulses fronibctl'i photolelectric cells are'so adjusted that the amplitude greater than any ordinary picture impulse. By having an exceedingly powerful source of illumination or by suitably amplifying the synchronizing impulses relatively to the scanning impulses, synchronizing impulses of greater amplitude than any normal picture impulses may be obtained. By having a one stage or any odd numbered stage amplifier between the synchronizing and picture photo cells, a phase reversal between the two types of impulses is obtained. Hence the amplitude of the synchronizing impulses represents a decrease in light intensity.

The type of wave sent out by the transmission system of Figure 1 is shown in full lines in Figure 2. The substantially square top, indicated by LI, indicates the linear synchronizing impulses, while the remaining portions of the curve are examples of picture impulses. As is clear from the curves, a certain base line is taken for absolute darkness and current impulses of greater amplitude represent synchronizing impulses and have no effect on the picture portion of the system.

In order to synchronize the complete frame at both ends-in other words, to synchronize the end of the spiral of the scanning disc with the corresponding mechanism at the receiving end-, I preferably dispose a slot FS in the synchronizing disc adjacent one of the linear synchronizing apertures. Slot FS is large enough so that a light impulse of a duration substantially longer than the linear synchronizing impulses is flashed to the photo cell. Obviously, the framing slot may be located at any portion of the framing tainv predetermined point.

frame.v f f L The combined vpicture synchronizing vimpulses arereceived'infthe kusual manner, 'and if trans mittecl on a carrier' wave are amplified by aksuit-y 'ableamplifien The amplified vimpulses are then led along twofclrcuitaone'of themlgoing to av synchronizing portion ofr the system and the other going to the picture generating'portion vof thel circuit.I 'While,'electrically, both types of impulsesareconducted to bothy circuits indiscriminately, practically they arecompletely sep# i y n arated so'that only synchronizingimpulses are2r effective! in the synchronizing portion of the cirthe system vconducts the impulses to the grid 3 'of a synchronizingv detector SD.y This detectoris preferably so biased that only impulses having synchronizing amplitudes are l detected.v Thev 7 i cathode IIl yof this detectory *completes the vcirciiit thereto the negative terminals oftwo sources 'ot transformers. Transformer 8 is preferably of the 'iron core.

kof the detector and kwith theipositive terminal f of a Isuitable,sourceof current. Primary lI of transformer has a by-pass condenser I2 of just enough capacity so that the relatively high frequency linear element synchronizing impulses pass therethrough rather than through the primary I I. The secondaries I4 and I5 of the transformers are connected, respectively, to grids I8 and I9 of two grid controlled gaseous discharge tubes. The other ends of the Vsecondaries are connected to a suitable biasing battery 23. The cathodes of these grid controlled gaseous discharge tubes may be energized by a battery 2| and are connected to the bias battery 23 and grounded at 22. Anodes 28 and 29 of the two grid controlled gaseous discharge tubes are connected to junction points 30 and 3I, respectively. Junction 3D has a circuit 32 and 33 connected thereto, including a battery 34, rheostat and cathode 36 of a rectifier 37. Junction point 30 is also connected to a condenser 38, the other plate of which is grounded. Junction point 3I is similarly connected through a cathode circuit 40, 4I, battery 42, rheostat 43 and cathode 44 of the rectier 45. This junction is also connected to a grounded condenser 4S. Anodes 50 and 5I of the two rectiflers are connected to the positive terminal of a suitable source of potential.

'I'he operation of the synchronizing portion of the system is substantially .as follows:

'I'he output of the RF amplifier is suitably detected and fed to the two transformer primaries in series. Frequencies of the order of linear signaling impulses will induce impulses of suitable potential in the secondary I4 and impress these potentials on grid I8. The corresponding irn- Ithrough ground' andi preferably has rconnected ys.; y aircore type, while transformer Qmay vhave an ,Ihetwo primaries mand II of'each of thesetransformers are in series kwiththe anode' pulses through primary I0 .will be by-passed 75 lso when the grid controlled gaseous discharge tubes through condenser i 2 and have no'eiiect on transformer 9. On`the other hand, framing impulses of a substantially lower frequency will pass through transformer primary l andl ii, condenser i2 being too small topermit such impulses to pass through. Through the action of transformer 9 impulses of suitable potential will be impressed upon grid i9 of the grid controlled gaseous discharge tube.

As previously pointed out, grid controlled gaseous discharge tubes have the peculiar property of permitting a gaseous discharge to start upon the slightest change of potential of the grid above a certain critical value. This property of the grid controlled gaseous discharge tubes is availed of by biasing grids i8 and i9 so that any impulses having an amplitude less than synchronizing impulses will fail to exceed the critical potential. Hence, no discharge will be initiated in the grid controlled gaseous discharge tube. In order to obtain a desirable form oi the impulse on grids I3 and i9 of the two grid controlled gaseous discharge tubes, secondaries itl and i5 may be shunted by damping resistances 24 and 25 of a proper value. These resistances may serve to atten out the synchronizing impulses and insure the operation of the grid controlled gaseous discharge tubes. v

Assuming that a synchronizing impulse is im'- pressed upon one of the grids of the grid controlled gaseous discharge tube, this impulse having been amplied tothe proper potential, va gaseous discharge between anode and cathode of the grid controlled gaseous discharge tube in question is initiated. Upon this condition, a relatively low impedance path from junction point 39, ii?l the linear synchronizing impulses are considered, to ground, through the grid controlled gaseous dischargev tube, is effected. The tendency of any rush of currentfrom anode 5i! of rectifier 31 through the grid controlled gaseous discharge tube and to ground will be checked by the rapidly rising drop across rectifier 31. The result will be that the potential of junction point 30 and of anode 28 of the controlled gaseous discharge tube will quickly drop to a value too low to support the gaseous discharge through thetube. The gaseous discharge, therefore, will be extlnguished.

During the period of inactivity of the grid controlled gaseous discharge tube, condenser 38 is charged up through rectifier 31 and the current supply. During the discharge of the grid con-. trolled gaseous discharge tube, condenser 33 is discharged so that charging up of the condenser occurs during the interval between discharges in the grid controlled gaseous discharge tube. By varying the value of resistance 35, the emission from cathode 35 will be varied, with the result that the spacecurrent through rectier 31 will be controlled. Hence, the rate ci charge of con-r, denser 38 may be adjusted within certain limits.

In Figure 2 the dotted line curves indicated by LC show the rise of potential across the terminals of condenser 38 or junction point 3B and ground. The lower portion of the synchronizing system operating on the framing impulses works in a similar manner, with the exception that the various constants of the circuit, such as condenser 46 and resistance 43, will have to be changed to operate at the proper frequency. The dotted line across FC indicates the buildingl up of the framing charge in condenser 45. The vertical dotted lines indicate the sudden drop in potential of junction points V3o and 3| occurring have a discharge therethrough. It is preferable to so arrange transformer 8 that framing impulses will-also trip the associated grid controlled gaseous discharge tube and start a new linear scanning element. This, however, is not essential, since by making the two transformers responsive to ythe two frequencies, the timing of the two impulses may be independently adjusted. Y It is desirable to have the tuning range of the two transformers 8 and 9 Wide enough to include the variations in frequency due to variation in number of lines per frame and frames per second customarily encountered. 'This may be accomplished by close coupling of the windings of each trans.- iormer. Hence; only synchronizing impulses either of the linear or framing type result in the rapid drop in potential of junction points 30 and- -t and permit these junction points to steadily -rise in potential during intervals between such impulses. It is these changes in potential of the junction points which are utilized in imparting scanning movements at the receiving end.

The output of the RF amplier lis fed to the light generative portion of the system, and, as shown, such impulses go through the primary 55 of a transformer 6| to ground. Shunted across secondary 62 is a. tuning condenser 63 and anode Sd of a full wave rectier 55. Cathode 66 of this rectifier may be energized by any suitable source of current, such as transformer' winding 61, and the center thereofI is connected through a load resistance 12, back to center 1i of secondary 62.' 'I'he output of the RF amplifier is, therefore, rectied andl results in differences of potential across load resistance 12.

These impulses, which contain both the synchronizlng and picture impulses, are translated into light impulses of corresponding intensity. This translating means may take on any form whatsoever and, as shown here, is a variation of the well-known Braun cathode ray-tube. Such tube. has an electron emitting cathode, one or more anodes which function to attract electrons from the cathode, the geometry of the tube structure being such that the electrons, by virtue of their speed, by-pass the anodes and bombard a suitable screen. This screen, as is well-known in the art, emits a phosphorescent glow, the intensity of which depends on the electron speed as well as the electron density.

The cathode ray tube here shown and indicated by numeral 16, has a cathode and a plurality of electrodes 85 and 86. Electrode 80 may consist of a. cup-shaped member having an aperture 8l, through which the Aelectron stream from cathode 15 is adapted to pass. Electrode 8D functions as a control electrode and is connected by lead 82 back to point 1l von secondary 62". Cathode 15, which may be energized by transformer winding 11, is connected by. lead 13 to cathode 66 of the full-wave rectifier 65. The result is that variations of potential across load resistance 12, representing rectified picture ard synchronizing impulses, are impressed von electrode 80 and cathode 15. This change in bias of electrode 80 functions in a manner similar to a grid in a vacuum tube to control the intensity of the electron beam.

Electrode 85, which is shown here as a cupshaped member whose open end is away from the cathode, is connected to a suitable source of potential, here shown as a point on a resistance |26, across the terminals of which a suitable direct potential is maintained. Electrode 86, which may be a fiat member, has impressed thereon a still higher positive potential. Electrodes 85 and 86 are both provided with suitable apertures, which register with the aperture 8| of electrode 80. All these electrodes are disposed in longitudinal alignment with the axis of the tube.

The electron stream, after having passed through the apertures 80, 85 and 86, has been accelerated so that the electrons are traveling at a sufficiently high speed for creating light flashes on screen 95. In order to impart scanning movements to the light flashes, the direction of the electron stream is varied. This is done in a wellknown manner, by having two sets of scanning i condensers 92 and 93, the planes of which are at right angles to each other, disposed along the axis of the tube so that the electron stream tends to pass between the plates of the condensers. It will be noted that one of the plates of each of condensers 92 and 93 is connected so that both are at the same potential as electrode 86, which, vas previously pointed out, is maintained at a constant positive potential. Junction points 30 and 3| are respectively connected to the other plate of scanning condenser 93 and 92 by leads |30 and |3|. Inasmuch as the potentials of these two junction points with respect to ground vary, as pointed out before, it is clear that the effective potential across the scanning condensers 92 and S3 varies in accordance with the synchronizing impulses. 4

synchronizing impulses at the control electrode f tube 'I6 will not be translated into light impulses since they represent darkness.

While any source of unvarying potential may be used to bias tube 16, I preferably use the one disclosed here, since it results in the generation of high voltages at the tube without the necessity for handling such high voltages at more than a` few places. Such a power supply consists of a transformer having a primary |00, energized in any suitable manner, and a. secondary |0| connected between two leads |02 and |03. Lead |03 is connected to anode |04 of ahalf-wave rectifier |09 and cathode |06 of another half-wave rectifier |01. Cathode |06 may be energized in any suitable manner, as by a transformer |08. Cathode of rectifier |09 may be energized by transformer winding and is connected t'o a lead ||2,-grounded at H3. Anode ||8 of rectiiier |01 is connected to a lead ||9, which is connected to a cathode |20 of a current limiting tube. Cathode |20 may besuitably energized by a source |2|. Lead |02 is connected through condensersi I1 and |24, respectively, to leads ||2 and H9. Anode |22 of the current limiting tube is connected to a lead |23 to cathode 15 of the cathode ray tube 16. From lead |23 across to lead ||2 a resistance |26 is disposed, which functions to smooth out the rectified output, as well provide a convenient voltage divider to a point of which electrode 85, as previously pointed out, is connected. Electrode 86 and one of the plates of each of scanning condensers 92 and 93 are all connected to a lead ||4,wh1ch is connected to lead ||2.

' In the normal operation of the rectifying system, each cycle from secondary |0| of the transformer'will serve to charge one of the two condensers ||1 and |24, and at-the same time go through one of the rectiflers |01 or |09. The discharge of one of condensers ||1 or |24 added to the current going through one of the two rectiers, functions to practically double the voltage ,across the secondary of the transformer. Inasmuch as the current required to operate the twov is quite minute, the resistance suffices, in ordinary practice, to lter out the output.

In order to operate the receiving system, the only adjustments necessary, under normal conditions, are at rheostats 35 and 43. These adjustments serve to vary the charging rates to condensers 38 and 46, respectively. This is equivalent to changing `the slope of the dotted lines in Figure2 indicated by letters LC and FC and serves to vary the dimension of the image. In

order to obtain synchronization with the transmitting station, it is only necessary to adjust both rheostats until the image is of normal p-roportions. In order to obtain comic effects as the result of the distortion of the image in one direction relative to another direction, it is possible to adjust one of rheostats 35 or 43 away from its normal position. This results in increasing or decreasing the charging rate of one condenser and results in the beam within tube 16 scanning in one direction at a faster or slower `rate compared to the other direction. It may be desirable to vary the potential of electrode 85 to control beam focus.

We claim: y

1. In a television receiver adapted to have im- Dressed thereon two series of synchronizing impulses, scanning means comprising two .transformers, the primaries thereof being in series with each other, means for rendering one of said transformers responsive to both series of synchronizing impulses, means for rendering the other transformer responsive to only one series of vsynchronizing impulses, damping means associated with each of said transformer secondaries and means including a grid controlled gaseous discharge device associated with each of said transformer secondaries for utilizing said synchronizing impulses for scanning purposes.

2. A television receiver adapted to operate with two series of synchronizing impulses having different times of duration, light generating means for transforming electrical image impulses into light, and scanning means therefor comprising two separate circuits, means for rendering one of said circuits responsive to both series of syn- Vchronizing impulses, means for rendering the other circuit responsive to only one series of synchronizing impulses, local means associated with each of said circuits whereby the potential in each said circuits rises at a predetermined rate only during the interval between successive synchronizing impulses of the same series, and means conductively isolated from said aforementioned local means and including a gaseous discharge device for effecting a sudden drop in said potential.`

3. In a television receiving system the combination of a circuit having electrical picture impulses on a carrier frequency therein, means for amplifying the carrier frequency impulses 'to the full degree of amplification, a full wave rectier connected with the output of the amplifying means and supplied with energy therefrom, a load circuit connected with the output of said rectifier and light generating means directly connected across said load for transforming said electrical picture impulses into light impulses.

4. The system of claim 3 in which said light generating means comprises a. cathode ray tube.

5. In a television receiving system, a receiving channel, a pair of channels branching off therefrom, one of said channels being adapted to excercise a scanning control, the other of said channels i andere vbeing adapted to exercise alight intensity control,

said scanning channel including the following, a pair oi hot cathode grid-controlled gas discharge. devices, means for impressing synchronizing impulses on each oi said grid controls to permit a discharge to take place, a condenser associated with each of said gas discharge devices, means for charging said condensers at a predetermined rate during the periods when said discharge devices are non-conducting, said discharge devices and condensers being so connected that said condensers can discharge through said gas devices when saiddevices are conducting, a cathode ray tube having a pair of electrostatic scanning controls, connections from each of said condensers to each of said scanning controls whereby the potential .of said condensers is communicated to said scanning control, said light control channel having impressed thereon both image and synchronizing impulses and comprising means for rectiiying said combined impulses, and said rectifying means being conductively isolated from said receiving channel, but conductiveiy connected to the cathode and control electrode of said cathode ra'y tube for transforming said signal impulses. into correspondingly varying electron streams.

6. .n a television receiver, a receiving channel. said receiving channel branching o into two channels, one of said channels comprising a scanning controlchannel and including means for selecting synchronizing impulses from combined image and synchronizing impulses, a grid-com. trolled gaseous discharge device, means for transmitting said selected synchronizing impulses to vthe control electrode of said gaseous discharge device, said control electrode circuit being damped, a condenser connected across the cathode and anode of said gas discharge device, means including a source of potential and a vacuum tube for charging said condenser ata predetermined rate, said gas discharge device being adapted to have a discharge initiated therein upon the existence of a synchronizing impulse on said control electrode and to discharge said condenser during this period, a cathode ray tube having an electrostatic control condenser, a connection between one plate of said control condenser and a plate of said first-mentioned condenser, whereby the potential of said control condenser varies with said inst-mentioned condenser, said other channel comprising a two-element rectlfying device and connections to said cathode ray tube whereby the output of said rectliler controls the electron stream of said cathode ray tube, and a high tension power supply for said cathode ray tube for biasing said scanning control condenser coml prising a pair of half-wave rectiers connected in series with each other and with a pair of seriesconnected condensers, a source of alternating potential bridged between said two rectiers and said two condensers, and connections from said power supply to said cathode ray tube for biasing said control condenser.

7. In a television system, the method of signalling which comprises scanning a picture subject along a series of lines to develop for each line of scanning picture signalling impulses varying in amplitude between a minimum. and a maximum value determinable by the intensity of light and shadow on the subject, producing synchronizing signalling impulses following in time relationship each series of picture signalling impulses for each line of scanning, reversing the polarity of the synchronizing impulses to produce a signal in the' direction of the minimum picture signal and of a .greater amplitude inl the direction of minimum picture signal than anyproduced picture signal,

and adding together the two produced series of signals to produce a composite series` of signals representing both the picture subject and the .synchronizing impulses.

8. In a television system, the method of signalling which comprises scanning a picture subject along a series of lines to develop for each line of .scanning picture signalling impulses varying in amplitude between a minimum and a maximum value determinable by the intensity of light and shadow on the subject, separately producing syn'- chronizing signalling impulses following in time Arelationship each seriesof picture, signalling impulses cr each line of scanning, reversing the polarity of tne synchronizing impulses to produce a signal in the direction of the minimum picture signal and of a greater amplitude in the direction of minimum picture signal than any produced picture signal, and adding together the two produced series of signals to produce a composite series of signals representing both the picture subject and the synchronizing impulses.

9. In a television system, the method of signalling which comprises scanning a picture subject along a series of lines to develop for each line.

of scanning picture signalling impulses varying in amplitude between a minimum and a maximum value determinable by the intensity of light and shadow on the subject, producing synchronizing signalling impulses following in time rela.-

tionship each series of picture signalling impulses for each line of scanning, electrically reversing the polarity of the synchronizing impulses to produce s. signal in the direction of the minimum picture signal and of a greater amplitude in the direction of minimum picture signal than any produced picture signal, and adding together the two produced series of signals to produce a composite series of signals representing both the picture subject and the synchronizing impulses.

A 10. In a television system, the method of slg. nalllng which comprises scanning a picture subtionship each series of picture signalling impulses for each line of scanning, reversing the polarity of the synchronizing impulses to produce a signal in the direction of the minimum picture signal and of a greater amplitude in the direction of minimum picture signal than any produced plcture signal, and adding together the two produced series of signals to produce a composite series of signals representing both the picture subject and the synchronizing impulses.

l1. In a television system, the method of signailing which comprises scanning a picture subject along a series of lines to develop for .each line of scanning picture signalling impulses varying in amplitude between a minimum and a. maximum value determinable by the intensity of light and shadow on the subject, producing synchronizing signalling impulses of different duration for line and frame synchronizing following in time relationship each series of picture signalling lmpulses for each line of scanning, electrically reversing the polarity of the synchronizing impulses to produce a signal in the direction of the minimum picture signal and of a greater amplitude any producedpicture signal, and adding together the two produced series of signals to produce a compositefseries of signals representing both the picture subject and the synchronizing impulses.

12. In a television system, the method of signalling which comprises scanning a picture subject along a series of lines to develop for each line of scanning picture signalling impulses varying in amplitude between a minimum and maximum value determinable by the intensity of light and shade of the subject, independently producing signalling impulses following in time rela-- tionship each series of picture signalling impulses for each line of scanning, amplifying said independently developed impulses tothe exclusion of the picture signal impulses, addingV the picture signal impulses to said latter produced signalling impulses in such a manner that the polarity of said latter produced signalling impulses is such as to produce a signal in the direction of the minimumpicture signal and of a greater amplitude in -the vdirection of minimum signal than any produced picture signal, and producing from said added signals a composite series of signals representing both the picture subject and synchronizing impulses.

13. In a television system, the method of signailing which comprises scanning a picture subject along a serie-s of lines to develop for each line of scanning picture signalling impulses vary- -ing in amplitude between a minimum andinaximum value determinable by the intensity of light and shade ofthe subject, independently producing signalling impulses of a-predetermined dura- .tion following in time relationship each series of v picture signalling impulses for each line of scanning and of a diierent predetermined duration -following the complete series of picture lines,

amplifying said independently produced impulses to the exclusionof the picture signals, adding the picture signal impulses to said independently produced signalling impulses in such a manner l 2,100,279 in the direction of minimum picture signal' than..

that the polarity of said independently produced signalling impulses is such as to produce a signal in the direction of the minimum picture signal and of a greater amplitude in the direction oi minimum signal than any produced picture signal, and producing from said added signals a composite series of signals representing both the picture Asubject and synchronizing impulses for both line and frame synchronizing control.

14. In a television receiving system, a receiving channel, a pair of channels branching off therefrom, one of said channels being adapted to exercise a scanning control, the other of said channels being adapted to exercise a light intensity control, said scanning channel including the following, a. pair of hot cathode grid-controlled gas discharge devices, means for impressing synchronizing impulses on each of said grid controls to permit a discharge to'v take place,

.a condenser associated with each ofsaicl gas discharge devices, .means for charging said condensers at a predetermined rate during the period when said discharge devices are non-conducting, said discharge devices and condensers being so connected that said condensers can discharge through said gas devices when said devices are conducting, a cathode ray tube having a pair of cathode ray deflecting means, connections from ROSCOE H. GEORGE. HOWARD J. HEIM.

2,10O,279.R0sc'0e H. George and Howard J. Heim, La Fayette, Ind.'

Patent dated November 23, 1937.

Radio Corporation of America.

the subject matter of claims 7, 8, 9, 10, and 11 of TEM.

assignee,

Hereby enters this disclaimer to said patent.` f [Oficial Gazzette J wie 331941.]

TELEv-IsIoN SYS- Disclaimer filed May 6, 1941, by the

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