US2164297A

US2164297A - Television system

Info

Publication number: US2164297A
Application number: US56860A
Authority: US
Inventors: Alda V Bedford
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1935-12-31
Filing date: 1935-12-31
Publication date: 1939-06-27
Anticipated expiration: 1956-06-27
Also published as: GB488268A; GB490203A

Description

June 27, 1939. A. v. BEDFORD TELEVISION SYSTEM Filed Des. 31, 1935 4 Sheets-Sheet l Ffic;.1.

HMP.

1cono scopa Mill/V GCE/VE M Mrd 6 Nr 50 A. ww 1 ===..I8 w B m V m W% d m 1939- b A. v. BEDFORD 21642971 TELEVISION SYSTEM Filed Des. 31, 1935 4 Sheets-Sheet 2 E G. Z.

' ICONOSCOPE +B KEYING SIGNHLG fl fli2d to Hoc/fing iu.be

June 27, 1939.

A. v. BEDFORD 2,164297 TELEVISION SYSTEM Filed Des. 51, 1955 4 Sheets-Sheet 3 inne 27, 1939. v BEDFORD 2,164297 TELEVISION SYSTEM Filed Dec. 31, 1935 4 Sheets-Sheet 4 TUBE INVEN7'OR Witness: y fllda VBedford Patented June 27, 1939 PATENT OFFICE TELEVISION SYSTEM Alda V. Bedi'ord, Colllngswood, N. J. assirnor I;o Radio Corporation o! America, a corporation o! Delaware Application December 31, 1935, Serial N0. 56,860

20 Clalms.

My invention relates to picturg transmisslon and particuiarly to a method of and means for transmitting pictures in such manner that their composition may be varied a1; will.

For various reasons it may be desired to combine two 01' more scenes to produce a composite picture a.t the receiver. .For example, lt may be advantageous to announce the call letters cf the transmitting station while a program is in progress by making the call letters appear at the bottom er at one side of the picture program. Similarly, for commercial reasons, it is advantageous to be able 130 insert advertising material in program pictures, and especially to be able to insert such material without disturbing the actors in the studio.

It is, accordingly, an object of my invention to provide an improved method of and means for transmitting pictures.

A further object 015 my invention is 130 provide an improved method of and means for combining a plurality of scenes for television transmiss1on.

A further object o1 my invention is to provide an improved method f and means or changing the composition of a picture a.t will during transmission.

A still further object of my invention is to provide a. method of and means for inserting scenes, legends, or the like in any desired portion 01' a picture being te1evised.

In one embodiment of rny invention, one scene, such as the main pftzture, is picked up by one cathode-ray transmitter tube camei'a while another scene, such as an advertising legend, is picked up by a second cathode-ray transmitter tube camera. The signals from the two transmitter tubes are passed through two separate keying amplifiers of a type which may be made inoperative by impressing keying signals thereon.

The two scenes are combined by mixing the outputs of the two keying amplifiers and by impressing suitable keying impulses upon the keying amplifiers in such a way that while one of these amplifiers 1's operative, the other amplifier is inoperative. In this way, a portion 01' the main scene isblanked out and the advertising matter or the like inserted in the blanked out portion.

Other objects, features and advantages of my invention Will appear from the following description taken in connection with the accompanying drawings, in which Figure 1 is a, clrcuit and block dlagram 01' one embodiment 01 my invention;

Figs. 1a and 1b are views of films which may be employed in one embodlment of my Invention;

Fig. 2 1s a circuit diagram of the keying ampliflers shown in Fig. 1;

Fig. 3 is a diagram showing the tlme relation between saw-tooth deflecting waves and keying or blanking impulses which are lmpressed upon the keying ampliflers;

Flg. 4 isa view representlng a composite picture which may be transmitted by the system shown in Fig. 1;

Flg. 5 is a circuit and block diagram 01 another embodiment 01 my invention;

'Flg. 6 is a. diagram showing the time relation between saw-to0th defiecting Impulses and keying or blanking Impulses which may be supplied by the circuit shown in Fig. 5;

Fig. 7 is a group of curves which are referred to in explaining the operation of the system shown in Fig. 5; and

Fig. 8 is a group of views showing composite pictures which may be transmltted by the system shown in Fig. 5.

Referring to the embodizflent of my invention 'shown in Fig. 1, it comprisestwo separate picture channels, one channel including a cathode ray transmltter tube, which may be the weil known iconoscope, and associated camera or lens system indicated at I and a keying amplifler A. The apparatus represented by the block I includes, in addition to the cathode ray transmitter tube and the camera, suitable deflecting circuits and pre-ampllfiers.

The mein scene or program plcture which is picked up by the iconoscope I is represented by the arrow 2. The picture signal appearing in the output circuit of the Isst pre-amplifler stage is supplied 110 the input circuit of the keying amplifler A. After passing through the keying amplifier A, the Signal is further amplified in an amplifler 3 and supplied to a suitable radio transmitter indicated a.t 4.

In the other picture channel, the camera and other apparatus represented by the rectangle 6 may be the same as the apparatus represented by the rectangle l in the first picture channel. The scene which is picked up by this camera and which is to be combined with the main scene is represented by the arrow I. The picture signal appearing in the output clrcuit of the iconoscope 6 is supplied to a keying amplifier B, which may be the same as the keying amplifier A, and it is then supplied to the amplifier 3 where it ls combined with the plcture signal representing the main scene.

The deflecting circuits for the two transmitter tubes at: I and 6 are driven by synchronizing impulses which are supplied from a suitable synchronizlng impulse generator 8. This generator may be cf any suitable type such as the one described in my copendlng application Serial N0. 729,730, filed June 9, 1934, and assigned I;o the Radio Corporation of America.

In order to make the keying amplifier A operative only at the proper time and in order to malte the other keying amplifier B imperative durlng thls time, keying or blanking impulses are generated by means of a system which may inclu de a. scannlng disc 9 and a film II, and these Impulses are then supplled -directly to the keying amplifier B and to the other keying ampllfier A through an amplifier stage I2 which reverses their phase.

In addition to the scanning disc 9 and film II, the keying impulse generator comprises a suitable source of light I3, a lens system I4, a photoelectric cell I8 and an amplifier I1. The

scanning disc 9 is driven by a synchronous motor I8 which is supplied with power from a cycle line,. the synchronous motor I8 and the synchronizing impulse generator 8 being maintained in synchronism by means of a control clr-' cuit included in the apparatus indicated at: 8, which circuit also is supplied with current from the 60 cycle line through a conductor I9. One circuit by means of which the synchronous motor I8 and the impulse generator 8 may be maintalned in synchronism is described and clalmed in my above mentioned copending application.

By making certain portions of a pioture frame dark, as indicated by the shading on the film II, keying impulses may be generated which will blank out any desired portion of the main scene. With the film II in the position indicated in the drawings, the scanning disc 9 causes the beam of light to scan the picture frame 2I having a dark rectangle 22 in its lower left-hand corner. The adjustment: of the photoelectric cell amplifier I'I is such that an impulse is produced during the time the scanning light beam traverses the darkened area of the picture frame. Therefore, the impulses which appear in the output circuit of the amplifier I'I have the characteristic represented by the curve 23 shown in Fig. 3. Curve 23 also represents the signals applied to the blocking tube in amplifier B. The Impulses which are applied to the blocking tube in amplifier A are indicated at 24.

In Fig. 3 there are also shown the vertical deflecting saw-tooth waves 26 and the horizontal defiecting saw-tooth waves 21 which causes the cathode ray deflection in the above mentioned transmitter tubes. In the transmitter tubes, the

cathode ray scans the picture from top to bottom and from left to right, this also being the way the picture frame 2I is scanned by the scanning disc 9. II: will be evident that the keying impulses which appear in the output circuit 0f the amplifier I'I should occur in the time relatlon shown in Fig. 3 since they must: occur as the lower part 0f the picture frame is being scanned and sirlce they also must occur only during the first part of a horizontal scanning line.

Instead of making the rectangle 22 dark with respect to the remainder of the picture frame, obviously it may be made light With respect thereto and an additional resistance coupled amplifier stage added to reverse the phase of the impulses. y

At the receiver, the resulting composite picture has the general character shown in Fig. 4. If the scene ptcked up by the auxiliary camera 6 is a legend or group cf letters, it: will appear in the lower leih band corner of the picture as indicated. The rast of the picture will be the main scene which ls belng picked up by the main camera I. It will be apparent that the scene which is picked up by the auxlliary camera 6 may be inserted aI: any time and at any point in the main scene, and that this can be done without the knowledge of the actors in the studio. Of course, the image of the scene picked up by the auxiliary camera is projected onto only a corner o1 other desired area of the mosalc 'of the iconoscope.

A section of the main scene of any desired shape may be blanked out. For example, a circular portion may be blanked out of the middle of the scene by providing a circular darkened area in the center of a picture frame indieated at: 28 which may be moved into position for scanning. The entire lower portion of the picture may be blanlged out by providing a darkened strip across the bottom of the picture frame as indicated at 29. Other portions may be blanked out as indicated by the darkened areas in the frames 3I and 32.

The keying ampllfiers A and B in Fig. 1 may be of any type which may be rendered inoperatlve without producing a transient sigma] in the output; circuit of the amplifier at the same time. One such amplifier is shown in Fig. 2. The main amplifier channel includes two

screen grid tubes

33 and 34 connected in cascade. This amplifier channel is to be rendered inoperative by driving the tube 34, which is called a blocking tube, to cut-ofi. The tube 34 is driven to cut-off by means of the above mentioned keying or blanking Signals which are supplied through an amplifier taube 36 to the grld circuit of the blocking tube. Since driving this tube to cut-off produces an undesired signal in the output ci1cuit oi' the taube, a balancing circuit is provided.

The balanclng circuit includes a screen grid taube 31 which is a linear amplifier and which has the same gain characteristics as the amplifier tube 36. It is connected in cascade wit'n another screen grid tube 38 which is so adjusted that: lt is driven to cut-olf at the same time as the taube 34. The two

tubes

34 and 38 which are swung to cut-off have the same characteristics whereby their outputs are the same. Thus, if the outputs of the two tubes are fed into a circuit 180 degrees out 0f phase, they will be balanced out: and no undesired transient signal Will appear in the amplifier output circuit as a result of the amplifier being blocked.

In order to balance out the undesired signal, the output of the screen grid taube 38 is supplied to another screen grid tube 39 which reverses the phase of the signal, and the signal with reversed phase is then supplied to the output circuit of the blocking tube 34 of the main amplifier channel. This phase reversing tube 39, like the first amplifier taube 33 is a linear amplifier. In order to keep the amplitude of the balancing signal at the same amplitude as that of the signal to be balanced out, the gain of the screen grid tube 38 is made very low by employing a plate resistor having a very low resistance. This resistance may be of the order of 500 ohms.

The

tubes

34 and 38 are preferably provided with an adjustable bias to permit blocking 0f the tubes by keylng impulses o1 diflerent wave shapes.

It ls deslrable to have the biss Ior each tube adjustable by operation of a single cont'rol device as indioated at 4l whereby the two

tubes

34 and 38 am always adjusted to have the same characteristlc.

Perhaps lt should be pointecl out that one key- Ing arhplifler in Fig. 1 will be adjusted to block ab a lower voltage than the other keying amplifier. The reason for thls will be apparent by referring to the curve 23 in Flg. 3. The A. C. axis for this Signal is represented by the dotted line. It; will be noted that the amplitude a: of the signal on the lower o1 negative sicle of the axis is much less than the amplitude 1 on the upper side, the keying amplifler B being adjusted to be blocked by the negative signal. The amplifier A, on the other band, is adjusted to be blocked by the negatlve part of the signal 24 which has the amplitude u.

Instead 015 operating the transmltter as descrlbed above, the flrst signal channel only may be employed, and the slgnals appearing in the output circult of the photoelectric cell amplifier I! applied to the keying amplifler A for the purpose of varying lts gain. When the apparatus is operated in thls way. the

switches

42 and 43 are opened whlle the third switch ls closed 44.

If lt is desired to obtain the efiect of a spotlight projected upon the middle of the Scene, the picture frame 23 is scanned and the amplifier l'l so adjusted that the signals which are produced as the scanning light beam traverses the dark ciroular area are of the correct polarlty und amplitude to increase the gain of the keylng amplifier A. This polarity is the reverse of the polarltygiven to the signals.

for the method 012 operation first described. Also, it will be understood that when operated in thls way the signals from the amplifier I1 never block amplifier A but merely vary it's gain in accordance with some predetermined pattern, in this instance, a clrcular area. For this use of the apparatus the

tubes

34 and 38 would be of the "variable-mu type.

The system may be operated in still a different way, still employlng only the Single picture channel. By closing the switch 43 and opening the first and

third switches

42 and 44 the signal supplled from the photoelectric cell amplifier I'l may be added to or mixed with the picture signal for the purpose 015 varylng the shading of the picture. F01 example, lf only one corner of the picture is too dark lt may be made lighter by" adding a suitable signal component produced by the proper shading of one 01 the plcture frames, such as the 1'rame 34.

It will be understood that an iconoscope, such as the ones employed in the'rest of the system, may be substltuted for the scanning disc 9 and film II. Such an iconoscope is indicated at 46. The desired keying blanking r shading signals may be produced by focusing the iconoscope camera on a screen 41 having the deslred pattern thereon. A simple way of obtaining the desired pattern is to project one or more Spots o1 patterns 01 light upon the screen. -In the drawings, a, beam of light is shown projected upon one corner of the screen whereby the correspond ing corner of the main picture is blanked out to permit the Insertion of a legend, o1 the like. Either the disc system or the lconoscope system may be utllized by throwing the switch 48 to either the contae't point 49 or the contact point 5l.

Referring to the second embodimentof my inventlon shown in Fig. 5, the circuit is substantially the same as shown in Flg. 1, except that electric discharge tubegenerators are employed in place f4she scanning disc for producing the keying impulses. In the two figures like parts are indicatecl by the same reference numerals.

In this modification of the inventlon, the 60 cycle impulses and the 10290 cycle impulses supplied by the impulse generator 8 are utilized as keying impulses to besupplied to the two keying amplifiers A and B. The 60 cycle impulses are passed through a suitable phase shifter 53 to a multlvibxator 54 or the like adjusted to supply 60 cycle impulses. These impulses are supplied throuzzh a conductor 55 and switch 55 to a switch contact point M.

The phase shifter 53 may be of axiysuitable type, the particular one illustrated comprlsing a delay network consisting of series inductance coils 51 and shunt conclensers 58 suitably terminated by a resistor 59. By means of a switch GI, the primary of a transformer 62 may be comnected across any desired seetion of the delay network in orcler to obtaln approximately the desired delay or phase shift. The fine phase shift adjustment is made by means of another phase shifting circuit which includes the secondary of the transformer 62 which has its mid-point comnected to ground and a condenser 63 and a variable resistor 64 connected in series across the secondary. The junction point of the condenser 63 ai1d resistor 64 is connected through a couplin'g condenser 66 to the multivibrator 54. The final phase shift adjustment is made by varying the value of the resistor 64.

The reason for supplying the 60 cycle impulses which appear in the output circuit of the phase shifter 53 to the multivibrator 54 is that the shifter distorts the 60 cycle impulses from their original rectangular shape. These distorted impulses, however, are perfectly satisfactory for. driving the multivibrat'or 54 which produces impulses of substantially rectangular wave form. It will be understood that if the impulses appearing' in the output circuit of the multivibrator 54 do not have just the desired wave shape or width, they may be passed through clipping tubes and wave shaping tubes to produce the desired impulses as described in application Serial N0. 8,659 filed February 28, 1935 in the name of John P. Smith, and assigned to Radio Corporation of America. Also a blocking oscillator, or the like, may be employed in place of a multlvibrator.

The 10,290 cycle imp1flses are also passed through a phase shifter 61 which may be the same as the phase shifter 53. Because of the distortion of these impulses produced by the phase shifter, they are impressed upon a multivibrator 68 adjusted to produce impulses occurring at the rate of 10,290 per second. This multivibrator as well as the multivibrator above mentioned may be of the type described in the above mentioned Smith application. The output of the multivibrator is supplied through a conductor 69 to a contact point N of the switch 55.

By moving the switch arm 55 to either the contact point M or the contact point N, either the 60 cycle impulse or the 10,290 cycle impulse may be supplied over a conductor H to the two keying amplifiers A and B where they cause a. portion of the main scene to be blanked out and an additional scene inserted just as described in connection with the circuit shown in Fig. 1.

This will be more clearly understood by referring to Fig. 6, in which figuxe the vertical deflectingsaw-tooth waves and the horizontal deflecting saw-tooth waves for the cathode ray transmitter tubes are indicated by the

curves

26 and 21, respectively. The 60 cycle keying impulses are indlcated at 12M. As shown in this figure, the keying impulses I2M are supplied to the keying ampllfiers A and B in such time relation that; they block the keying amplifier A in the main picture channel during the period the bottom of the picture normally would be transmitted. In other words, the keying amplifier A is blocked during the occurrence of the last few horizontal scanning lines. The resulting composite picture is represented by the view 13 in Fig. 8. By adjusting the phase shifter 53, the 60 cycle impulses may be caused to occur at a different time during the vertical defiection of the cathode ray to blank out a different portion of the main picture. For example, if the keying impulses are caused to occur at the beginning of the vertical defiecting saw-tooth wave, the inserted advertising material or the like will appear at the top of the plcture, as indicated in the view 14 in Fig. 8.

The use of the 10,290 cycle impulses from the contact point N is the same as the use of the keying impulses shown in Fig. 3. In this particular case, however, the impulses are occurring continuously as shown in Flg. 7 by curve I6N so that a complete strip of the main picture is blanked out from the top to the bottom of the picture. This blanked strip may be either on the right band side of the picture, as shown by the view 11 in Fig. 8, or at some other position depending upon the adjustrnent of the phase shifter 61.

If it is deslred to insert an auxiliary scene or legend in a rectangular area of the main picture, as in the corner of the picture, for example, the necessary keying impulses may be obtained by mixing the 60 cycle impulses and the 10,290 cycle impulses. In Fig. 5 the two groups of impulses are shown supplied to a common plate resistor .18 through the

amplifier tubes

19 and 81 whereby the signals add to produce a signal wave of the character represented by the curve 82 in Fig. '7. This curve 82 ls obtained by adding the curves 83 and I6N of Fig. '7, these curves representing the 60 cycle and 10,290 cycle impulses, respectlvely. The two added signals are then supplied to an amplifier taube 84 which is biased substantially to cut-off, as indicated by the characteristic curve 86 in Fig. '7.

By supplying the signal represented by the curve 82 to the ampllfier tube 84, in the polarity relation indicated in Fig. 7, only the impulses which have been made more positive by the addition of the 60 cycle impulses pass through the amplifier tube, the remaining impulses being cut ofl. As a result, the impulses appearlng in the output circuit of the tube 84 and supplied to the contact point P have the characteristic indicated by the curve 8'IP. It will be apparent that these impulses are of the same kind as the keying impulses shown in Fig. 3, and that by applying thern to the keylng amplifiers in the proper phase, they may be utilized to blank out a rectangular portion of the main picture to permit the insertion of the desired auxiliary scene as shown by the view 88 in Fig. 8.

Various uses for my invention, other than those described above, will be found. For example{ my transmitting system may be empl0yed for transferring or fadlng fr om one scene to another. When the system ls operatied in this way, the scene being transmlttedis picked up by one iconoscope, such as the iconoscope l (Fig. 1), while the scene which ls to be transmitted next or faded in ls picked up by the other iconoscope 6.

When it is desired to transfer from one scene to the next, the film which may be shaded as shown in Fig. 1a, ls moved past the diso 9 in the direction indicated by the arrow, whereby one scene begins 1:0 appear at one corner 013 the picture and gradually increases in size whereas the other scene gradually diminishes in size and. finally disappears at the diagonally opposite corner. It will be understood that with the film shaded, as shown in Fig. 1a, to be moved opposite the scanning disc, the scanning holes should not be placed on a spiral but should all be 10- cated the same distance from the centerof the disc since the movemeni; of the film provides a soanning component in the vertical direotion. Obviously, the same result may be obtained by employing the disc with the scanning holes placed on a spiral and with the film moved inl:o position successively by means of an intermittent in the usual manner. In that case successive picture frames may be shaded, as shown in Fig. 1b, the darkened area of the picture frames becoming greater with each successive frame.

There are many other uses for my invention: for example, a story-teller and the drama of the story could be presented with the pioture of the story-teller appearing as a small insert. Also the thoughts of an actor could be shown as an insert in the picture of an actor. Also various tricks of photography such as showing difierent objects simultaneously in diiferent slzed scales, and weird and ghost effects could be duplicated.

Obviously, the border between two different picture subjects may be made either sharp or it may be a gradual faded border.

Varlous other modifications may be made in my invention without departing from the spirit and. scope thereof and I desire, therefore, that only such limitations shall be imposed thereon as are necessitatecl by the prior art and are set forth in the appended claims.

I claim as my invention:

1. A picture transmitting system comprising means for producing electrical signals r8presentative of a scene or view, said means including means for scanning said view horizontally at a. comparatively high frequency and vertically ab a comparatively low frequency, a second means for producing electrical signals representative of a second scene or view, means for supplying said Signals representative of both views t0 a common signal channel, and. means for making efi'ective the transfer of the signals representative of one of said views 130 said common channel and for simultaneously making inefiective the transfer to said channel of the signals representative of the other view, said means including a source of additional signals which occur at the rate of said horizontal scanning and which make said transfers efiective and ineifective at said rate.

2. A picture transmitting system comprising means for producing electrical signals representative of a view, said means including means for scanning said view horizontally at a comparatively high frequency and vertically at a comparatively low frequency, a second means for producing electrical signals representative ot a second view, a slgna1 channel common to sa.1d flrst and second means, an ampllfler 'coupllng seid flrst means to said common channel, a second amplifler coupling said second means to sald common channel, and means for alternately rendering said ampliflers inoperativz at said high frequency to nass Signals.

3. A picture transmitting system comprising meana for producing electrical signals representative of a view, said means including means for scanning said view horizontally at a. comparatively high frequency and vertically at a. comparatively low frequency, a second means for producing electrical signals representative of a second view, a. signal channel common to said first and second means, an amplifier coupling said first means to said common channel, a second amplifier coupling said second means to sai d common channe1, means for producing keying signals occurring at said high frequency, means for blocking one 01 said amplifiers by means cf sa.id keying signals, means for reversing the polarity of said keying signals, and means for blocking the other 01 said amplifiers by means 011 said reversed polarity keying signals.

4. A. picture transmitting system comprising means for producing electridal signals representative of a view, said means cdmprising means for scanning sa.id view horizontally at a comparatively high frequency and vertically at a compant;ively low frequency, a second means for producing electrica1- signals representative of a second view, a signal channel common to said first and second means, an amplifier coupling said flrst means to said common channel, a second ampllfier coupling said second means to said common channel, means for producing rectangular impulses occurring at said high frequency, means for blocking one of sa.id amplifiers at said high.freqency by means of said impulses, means for reversing the polarity of said impulses, and means for blocking the other of said amplifiers at said high frequency by means f said reversed polarlty impulses.

5. A picture transmitting system comprising means for pr oducing electrical signals representative of a view, a second means for produclng electrical signals representative o! a second view, means for supplying said signals representative of both views to a common Signal channel, means for generating controlling Signals in accordance with a predetermined controlling view, and means for utilizing said controlling signals for preventing the transfer of the signals representative of one of said views to said common channel while the signals representative of the other view a.re being transferred to said channel.

6. A picture trahsmitting system comprising means for producing electrical signals representative of a view, said means comprising means for scanning said view horizontally at a comparatively high frequency and vertically at a. comparatively low frequency, a second means for producing electrical signals representative of a second view, means for supplying said signals representative of both views to a common signal channel, and means for alternately blocking at said high frequency the transfer of said signals from said first means to said channe1 and from said second means 1:0 said channel, said last means comprising a vacuum tube oscillator which produces control impulses periodically.

7. The invention according to claim 6, characterized in that said last means also includes a phase shifting device for shitt.ing the phase o1 said Impulses.

8. The invention according to cla1m 6, characterized in that said oscillator 1s a multlvibrator.

9. A picture trnsmitting system comprislng means includlng a cathode ray tube for producing electrical' signals representative of a view, a. second means including a cathode ray tube for producing electrical signals representative of a. sec-. ond view, means for supplying said signals representative of both views to a common sigma] channel, and means for alternately blocking the transfer of said signals from said first means to said channel and from said second means to said channel, said first and second means including deflecting means for deflecting said cathode rays both vertically and horizontally, said horizontal deflection being at a comparatively high frequency, and said last rr'1eans including an electric d1scharge tube oscillator which produces control impulses in synchronism with and ab the rate o1 sa.id deflection.

10. The invention according to claim 9 characterized in that said last means includes an electric discharge taube which produces control impulses in synchronism with said vertical deflection and an electric discharge tube which produces control impulses in synchronism w1th said horizontal defle ction, and further characterized in that means is provided for utilizingor said blopking action only the higher frequency control impulses which occur during the occurrence of the lower frequency control impulses.

11. A control system for television comprislng means 130 scan synchronously and simultaneously two object areas and a contro1 area to produce from each scanning an i ndependent series of signals representative of the light values upon successive elemental areas of each of said scanned areas, means for suppressing the signals from the one or the other of said object areas in accordance with the signals. from the concrol area, and mean's to assemble the unsuppressed impulses from the object areas into a single composite series of sigma] impulses whereby changes in the light value 0f said control area. will change the composite series cf signal impulses.

12. A control syscem for television comprising means 130 scan synchronously and simultaneously a pair of object areas and a control area to produce from each scanning an independent; series of signals representative of the lighc values upon successive elemental areas of each cf said scanned areas, means for alternately accentuating the signals from the object areas in accordance With the signals from the control area whereby changes in the light value of said control area will vary the alternate accentuation of the signals from the object areas.

13. A wipe-out system for television comprising separate means to synchronously and simultaneously scan two object areas and a control area whereby signal impulses may be produced from all of the areas, said control area being cornp0sed of high and low light value portions which may be 'difi'erentially varied in size and means whereby the variations of signals from said scanned coutrol area control the signals from said object areas.

14. A wipe-out system for television comprising means for producing difierent series o1 signal impulses by simultaneously and independently scanning an outgoing object area, an incoming object area and a control area, said last named area being composed of high and low light value portions which may be differentially varied in size, and means whereby the transmission of the signals from the first two named scanned area.s is permibted or prevented in accordance with the signals from said control area.

15. A wipe-out control system for television comprising separate means to simultaneously and synchronously scan two object areas and a control area to produce independent series of signals, said control area comprising high and low light value portions which may be difierentially varied in size, means for suppressing the signals from one of the object areas when the high light va1ue portion of the control area is being scanned, means for suppressing i:he signals from the other object area when the low light value portion of the cout-ro1 area is being scanned and means for combining the unsuppressed signals.

16. A wipe-out control system for television comprising separate means to synchronously and simultaneously scan an outgoing object; area, an incoming object area and a control area to produce independent series of signals, said control area comprising high and low light value portions which may be concurrently varied in size, means for suppressing the signals from the out-going object area when the high light value portion of the control area is being scanned, means for suppressing the signals from the incoming object area when the low light value portion 015 the cont1ol area is being scanned and means for combining the unsuppressed signals from the object areas.

1'7. The method 'of producing wipe-out eficcts in television image signals which comprises independently, synchronously and separately scanning an outgoing object area, an incoming object area, and a. control area to produce from each scanning a series of signals, utilizing the signals produced from the scanning of the control area 130 control and obscure the produced series cf signals from the object areas selectively combining the remaining signals from the object areas to produce a composite series 013 signals, and vary- Ing the light values of the contro1 area to alter the composite series of signals.

18. The method cf producing wipe-out eflects in television siguals which comprises independently, synchronously, and separately scanning an outgoing object; area, an incoming object area, and a control area to produce from each scanning a series of signals, obscuring and manifesting the produced series of signals from the object areas, selectively, in accordance with signals produced from the scanning of the control area, combining the remaining signals from the object areas to produce a composite series cf signals, and.vary- Ing the light va1ues of the contro] area 130 alter the composite series of signals.

19.- The method of producing wipe-out effects in television image signals which 'consists in independently and sepa1ately scanning an outgoing object area an incoming object area, and a coutrol area in synchronism to produce from each scanning a, series of signals, utilizing the signals f1om the control area to suppress selectively and alternately the signals from the object areas, combining the unsuppressed signals fron 1 the object areas to produce a composite series of signals and varying the light values of the control area 1:0 alter the composite series of signals.

20. The method of producing wipe-out effects in television image signals which comprises simultaneously, separately and synchronously scanning two object areas, to produce separate series of signals, simultaneously, separately and synchronously scanning a control area having high and low light value portions, combining the separate series 0f signals to form a single series