US2320699A - Method and system for television communication - Google Patents

Description

June 1943. J. H. 'HoM lsHous 2,320,699

METHOD AND SYSTEM FOR TELEVISION COMMUNICATION Filed may 15, 1940 {Sheets-Sheet 1' FIG I [3 J ,9 q

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Moron June 1, 1943.

J. H. HOMRIGHOUS METHOD AND SYSTEM FOR TELEVISION COMMUNICATION Filed May 13, 1940 FIG? Flsl FIGS FIELD T 2. 7 FIGII 4-FIGIO o- FIGIO FIGS FIGS J4 4 Sheets-Sheet 2 INVENTOR.

Jime l, 1943. I J. H. HOMRIGHOUS 2,3

METHOD AND SYSTEM FOR TELEVISION COMMUNICATION Fild May 13. 1940 4 Sheets-Sheet 's HALFWAVE REC.

FULL WAVE POWER HALFWAVE AMP. REC.

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' June 1, 1943. J; H. HOMRIGHOUS METHOD AND SYSTEM FOR TELE VISION COMMUNICATION Filed May 13, 1940 4 Sheets-Sheet 4 IN VENTOR.

Patented June 1, 1943 METHOD AND SYSTEM FOR TELEVISION COM1YIUNIGATION John H. Homrighous, Oak Park, 111.

Application May 13. 1940, Serial No. 334,864

(o1. 1vs 516.).

12 Claims.

My invention relates to improvements in method and systems for television'communication and particularly to systems for producing synchronizing signals for controlling and timing. the various impulses required for the production of a picture at both the transmitter and receiver.

One of the objects of my invention is to provide improved cathode ray deflecting systems for producing interlace scanning by applying a different electrical condition to the vertical deflecting means in alternate fields or by changing. the time interval of every other field.

Another object of my invention is to provide a synchronizing signal generating mechanism for producing the various impulses" necessary for the control of scanning in a cathode ray tube with provision for adjusting the speed of the mechanism to develop substantially wide frequency range of impulses.

Another object of my invention is the provision of synchronizing signal mechanism at the receiver which permits greater flexibility so that such mechanism may respond to signals repre-' senting different picture rates and also different number of lines per picture.

One of the main objects of my invention is an improved method of altering the number of picturechanges or frames in a given-time in order to televise motion-picture film at 24 frames per second, or, the standard for television practice of frames per second, or at any other desired number of frames per second.

Another object of my invention is the provision of a switching device for changing the number of horizontal lines per field or frame without] changing the frame frequency.

Another object of my invention is the provision of an element in the cathode-ray picture tube to initiate pulses of current to be used for blanking purposes or for reducing the intensity of the electron beam during the retracing period or backward movement.

Another object of my invention is the provision of elements in the cathode-ray reproducing tube to initiate pulses of-current to blank or re.-

duce the intensity of the electron beam during the retracing period.

Another object of my invention is the provision of means for automatically adjusting the lines horizontally in each image field.

Another object pf my invention is the provision of means sensitive to variations of light in the reproduced images for controlling the brightness of the images.

A feature of my invention is the generation of an alternating voltage wave and the actual transmission of this wave to the receiver whereby the same wave form and frequency may be regenerated and other frequencies may also be generated from the source of power at the receiver.

Several methods for producing interlace scanning have been devised. One system, known as the even line system, requires that the up and down movements of the cathode ray be of unequal lengtli, which has been very diflicult'to obtain. In my present invention, I have devised a more positive method for developing control impulses giving alternate short and long spaced periods of time. Another system, known .as the odd line method, has been devised which requires a whole number of lines plus a fraction of a line in each field so that the electron ray will start the second field at a fraction of a line distant from the start of the first line in the first field. This system depends upon equal field length and exactly alike vertical deflecting means for all fields. In the preferred embodiment'of my in vention, I apply a different electrical condition to the vertical deflecting means in alternate fields to shift the electron ray vertically the distance equal to the space of one horizontal line.

In none of the present systems can the number of pictures in a given time be changed from 24 to 30 pictures to televise motion picture film at a much lower rate, 24 frames per second, than the proposed standard rate for television, 30 frames per second; as described further along.

None of the above systems show elements added to the cathode-ray tubes to initiate voltage pulses for blanking purposes.

In my prior application, Serial #306,537. filed Nov. 28, 1939, the picture signals are combined with control and sound or audio signals in sucha manner that all three are transmitted and reproduced as picture or video signals.

According to a preferred embodiment of my present invention, a voltage wave at the frame. frequency is generated at the transmitter, and combined with the audio signals on a separate intermediate'carrier frequency, which in turn is modulated on the video carrier frequency and transmitted by radio to the receiver.

' Another advantage of my invention the generation of blanking pulses by the pickup and viewing tubes, thereby eliminating the transmission of these-signals by radio and the necessary filtering equipment.

ing drawings, illustrating an embodiment thereof in which:

Figures .1 and 2 are simplified diagrammatic view of a television transmitting station and a television receiving station, respectively, illustrating the principles applied in this invention.

Figure 3 is a motor device for generating control frequencies.

Figures 4 and 5 are end views of the disks shown in Figure 3 for generating the control or frame frequency.

Figures 6 and '7 are simplified diagrams showing the circuit figure numbers used in generating the sweep frequencies.

Figures 8, 9, 10, and 11 show circuits used in my invention.

Figure 12 shows a circuit for identifying certain line scanning pulses.

Figure 13 shows a motor and control circuit.

Figure 14 shows an end view of disk used in Figure 13.

Figure 15 shows picture control character, reproduced at the receiver.

Figure 16 shows my improved cathode-ray pick up tube with circuit connections.

Figure 1'7 is a top view of the mosaic used in tube shown in Figure 12.

Figure 18 shows my improved cathode-ray viewing tube with circuit connections.

In Figure 1, the numeral I designates a cathode-ray pick up tube of the conventional type and is known as an Iconoscope. It is to be understood that other tubes such as the Orposite side, and an electron gun i r gen rating a ray ofelectrons directed at the screen, and two sets of deflecting plates for deflecting the electron ray at the line and field frequencies, so that it is caused to scan the screen. The picture and certain other control characters are thereby developed and fed from one of themetallic plates by an output connector 2 to a modulating am-,

plifier 3. The other connector 4 leads to a blanking pulse circuit Ito be further described in connection with Figur 12.

A carrier wave is provided by an oscillator. 6 in the power amplifier 1. This carrier now is power amplifier stage Il produced by the oscillator I8. The signals from the amplifier I I are fed to the mixer circuit 9 through the conductor l9.

The two carrier waves, one modulated by sweep frequency control signals and audio signals, the other modulated by video signals.are mixed in the mixer circuit 9 and fed to the common antenna 20 for transmission by radio.

The sweep control signals are transmitted in th form of sine waves, which are used to synchronize or control the scanning action with the transmitter. The antenna 2| receives the combined carrier signals from the transmitter antenna 20 to a. radio frequency amplifier 22, an oscillator 23 reacts with these signals in the first stage 24 on the superheterodyne principle, to produce two intermediate-frequency signals which are fed to the two stages 25 and 26.

to cause it to scan the screen. It is to be understood, that electromagnetic means may be used for deflecting the electron ray. 1 The video signals areapplied to a control electrode of the electron gun to change the intensity of the electron-ray in accordance with picture or video signals.

In this cathode-ray tub I also provide two narrow metallic plates separated by an insulator and placed on the right side of the tube facing the reproduced picture. are for producing blanking pulses at the receiver. which will be further explained in connection with Figure 18. I

'Referring to the intermediate frequency stage 26 which contains the sweep signals and the audio signals and through the action of the second detector 30 the output of which goes to two selective filter 3| and 32. The low frequency sweep control signals after leaving the filter 3|, still in modulated form on a carrier, are demodulated at 33 and fed to the frequency generator 34 where the signals may be amplified and operate a signal generator to redevelop control signals, or the signals may be used after suitable amplification to directly control the scanning acmodulated by the frequency band video or picture signals through the modulation amplifier 3. The signals from the amplifier I are supplied by a connection 8 to the mixing circuit 9.- Certain control signals are also transmitted as video signals.

The numeral l0 designates a generator for producing pulsating voltage waves or waves of sine form for controlling the sweep frequencies at the desired frame frequency. The low frequency sweep control voltage waves or signals through the medium of amplifier, I I, modulates another carrier produced by oscillator l2 in its amplifier stage l3.

The audio or sound signals from the ruler phone ll are passed through an amplifier l5.

The sweep control signals and the audio sigapplied through a mixer circuit ii to sents a 'motor which is operated from the local tion at the receiver which will be explained in more detail later.

The audio signal from the filter 32 is fed to the=loud speaker 35.

In Figure 2, the, numeral '36 represents what maybe called an automatic brightness control circuit andderives its energy from the changes in brightness of a spot or mark 31 televised from the transmitting tube and directed into a photo-cell circuit. The output from this circuit is used to adjust the bias on previous stages to aid in maintaining the brightness of the reproduced picture substantially constant;

Referring to Figure 3, the numeral 38 represupply current and formally runs at approximately 1800 R. P. M. Operated from the-motor" through the action of a cone shaped pulley 33 and the contacting pulley 40 are two disks of modulate a second main carrier were 1!; ill? 7i light polarizing material ll and 42, revolving normally at approximately 1800 R. P. M. and re- These metallic plates volving past stationary pieces of polarizing material 43, 44, and 45 and also separate sources of light 46, 41, and 48 respectively.

' The revolving and stationary members are better shown in Figures 4 and 5. In Figure l the disk 42 is made up of two halves of polarising material: each half may be rotated through a very small angle and as shown on the drawings the planes of polarization are not parallel. This angle depending upon the desired size of the dark portion 49 or the period of the gap between pairs of pulses as illustrated at 56.

From the above it will be seen that when the disk 42 is rotated past the stationary member 45 and between its source of light 48 and photoelectriccell l, that the intensity of the light reaching the photo-cell will vary from zero to maximum value and back to zero when rotated through approximately 180 degrees.

Referring to Figure 5 the numeral 4| represents a disk of light-polarizing material having a certain part painted or blacked out so that rotating it in a clockwise direction past its stationary polarized members 43 and 44 and between its sources of light 46 and 41 and their respective photo- cells 52 and 53 the intensity of light reaching each photo-cell will vary from zero value to maximum value and back to zero during one half of a revolution and during the'other half of the revolution there will be no light change.

A system for producing the proper sweep voltages and control signals ,is shown in Figures 8 to 12 inclusive. In Figure 6 I have shown a photocell 54 which may be the photo-cell 5| in Figure 3. This cell is responsive to the variations of light intensity caused by the rotation of disk 42 pre- .9, where the pulsating voltages from transformer winding 56 are induced into the transformer secondary winding to drive the grid of tube58 positive, discharging the condenser 59 through the tube 58-. Thus by alternately charging the condenser 59 through the resistance 60 and discharging it through the tube 58 a saw tooth voltage is circuits of Figures 8 and 9. I may also use disk 4| ,having associated with it .two sources of light 46 and 41 and their respective photo- cells 52 and 53. These cells are responsive to the variation of light intensity caused by the rotationof the disk 4| as previously explained.

Referring to Figure 11, I have shown a circuit for producing an alternating current from the variation of light occurring in the photo- cells 62 and 63 which may be'the photo- cells 52 and 58 shown in Figure 3. These photo-cells control the grid excitation of . grids 64 and 65, of amplifier tubes 66 and 61; the anodes 68 are connected in parallel through the primary winding of transformer 69 to the positive side of voltage divider 18. The cathodes 1| are connected in parallel to an intermediate point of the voltage divider 18. The cathode 13 of photo-cell 62 is connected to the grid 64 of amplifier 66 and through resistance 14 to negative potential at the voltage divider, thereby maintaining the grid 64 at a negative potential with respect to cathode 1| and plate 68'; the circuit is so arranged that an increase in the-intensity of light on the photo-cell 62 will increase the photo-current of tube 66. The photo-- cell 63 has its anode 15 connected to the grid of amplifier tube 61, and it is maintained at a positive potential with respect to its cathode 16.

winding. These control voltages from winding 69 may be induced into the transformer winding of Figure 9 to control the vertical deflection, and

' by'changing the speedof rotation of the disk 4| the duration of the time per field is changed so that any desired number of frames per second may be produced.

One method or system for producing interlace scanning uses the disk 4|, Figure 5, with Figure 11, to develop impulses to trigger the sweep generator, Figure 9, to thereby control the vertical reciprocating movement of the electron ray at generated. The vertical sweep pulses generated by the disk 42 in the wave forming circuits Figure 9 is fed to conductor 6| at the transmitting tube Figure l and as diagrammatically shown in Figure 6. The circuit of Fig. 9 is also used to produce the line sweep voltages.

From the above description it will be seen that each revolution of the disk 42 will produce two similar impulses in the transformer winding 56 to trigger the discharge tube 58. The tube 58 may be biased so that only the positive pulses applied to the grid will operate the tube. Since there is a gap 49 in the disk 42 successive impulses will occur at differently spaced intervals.- Changing the speed of the disk by the adjustment of the cone pulley 39 will change the picture rate without changing the number of lines per picture.

The control voltages produced in Figure 8 may be transmitted to the receiving station to govern the scanning thereat.

The pulses generated by the disk 42 can be different time, intervals whereby one field period will be of a greater duration than the next succeeding field since the-dark portion on disk 4| extends through more than an 180 degree arc. Therefore, the return trace time in alternate fields will be greater than in the intervening fields, causing a fractional part of a line to be included in each field, which will have the effect of placing the lines of alternate fields between those of intervening fields.

From the above it will be seen that I have devised a novel method of producing unequal field periods of time to effect interlace scanning.

used to produce the line scanning control pulses In the preferred embodiment of my invention I use the disk I00, Figure 14, instead of the disk 4|, with Figure 11, to develop trigger impulses at equal sp'aced periods of time. This circuit is to be used as diagrammaticallyillustrated in Figure '1 to develop line and field trigger or control signals and a-sine form wave to modulate a carrier as previously explained. The circuit figure members shownin Figure-7, plus Figure 3, constitute the frequency generator shown at IU, Figure 1.

It is proposed to use frequency multiplying cirand from these frequencies the higher line frequencies are produced.

Referring to Figure 10, two stages of frequency multiplication are shown. The secondary'winding 18 is connected to the transformer winding 88 in Figure 11 which supplies alternating pulses to the tapped secondary and in turn to the full number of pulses or cycles to the tuned filter comprising the condenser 80 and the next transformer primary winding 8|. This .double cycle signal is supplied by the taped secondary 82 to the full wave rectifier 83 where it'is again doubled and fed to the next succeeding transformer primary 8. The tapped secondary 85 delivers wave rectifier tube '19 which delivers twice thealternating current to the next stage and so on until the desired high frequency for line scanning is obtained. While I have shown a circuit to double or to multiply the frequencies, other frequency multiplying circuits may be used.

,In my invention I prefer to use the doublers and obtain 128 or 256 lines per field, where each field will have exactly the same number of pulses, therefore, the same number of lines for eachfield and to avoid interference with local power, all that is necessary to do is to slightly change the field rate,-which will of course change the line frequency butwill not change the number of lines per field.

With further reference to Figure 7, I have provided two switches 86 and 81 for shorting out one or more stages of doublers; for instance, certain stations could be operating on 256 lines per field and other stations on 128 lines per field. I

In order to produce or develop interlaced scan ning from a sine form voltage: wave it is necessary to identify every other field pulse and in some manner cause the horizontal lines of one field to fall in between the lines produced in the other field or the lines of one field are even numbered and in the second field they are odd numbered. I accomplish there features by the circuit shown in Figure 12. In this circuit, voltage waves of sine form are supplied from the circuit of Figure 11 to a full wave rectifier 86 of conventional design, which may be one stage of Fig. 10. The output wave form is shown at 81; these pulses are fed through the transformer winding 88 which may be the winding 8| in Fig. 10 to wave forming circuit Figure 9 to drive the grid of tube 58 positive discharging the condenser 59, thereby producing sawtooth form waves "for vertical scanning as previously described. Inductively connected with the transfomer winding 68 of Fig. 11 is a'half wave rectifier 88, the output on the plate of amplifier 9| is adjustable, depending upon the space between lines.

The rectifier 89 and amplifier 8| will operate during eachpositive pulse to increase or decrease the potential on one of the deflecting plates without changingj'the potential on the opposite plate which will have the effect of raising or lowering the horizontal lines. 4

From the above description it will be seen that I have provided a novel,and very simple means for interlacescanning or for shifting the position of the horizontal lines scanned in a cathode-ray tube, during alternate field pulses and which are controlled by the generator at the transmitting station. Thus eliminating the necessity of transmitting by radio synchronizing pulses other than the one sine form wave,

At the receiver I employ the same means for identifying the positive pulses and at the same time causing the shift in the position of horizontal lines on the viewing tube screen.

The circuit figure numbers shown in Figure '7, omitting Figure 11, may constitute in one receiving station the frequency generator shown at 34, Figure 2.

From the above description it will be seen that the line pulses are definitely locked with the field pulses, or in other words, the same pulse that triggers the vertical deflection also supplies through multiplying circuits the trigger pulses for line scanning.

Furthermore, from the above description, the control of the field and line deflecting circuits at the receiver from the sine form voltage wave transmitted by radio from the transmitting station will cause the cathode-ray or electron ray at the viewing tube to be in exact synchronization with the cathode-ray in the pick up tube,

' in the pick up tube is focused on midpoint of line wave form is shown at 88. The current in the half wave rectifier lead can be adjusted to impress voltage pulses on the grid of tube 9! out of .phase with the voltage pulses developed in the fullwave rectifier 86. The anode of amplifier 9| isconnected through the primary transformer for-the duration of each pulse and in phase with the vertical sawtooth voltage waves. The con- .ductor 83 supplies potential through 'a centering resistance to one verticaldeflec'ting plate. The

other vertical deflecting plate is supplied with potential from the same source through another centering resistance not shown. The potential 75 number 40, then since a single frequency or control voltage wave generated at the transmitter station times the deflection of both the field and the horizontal lines at both the transmitting station and receiving station, the cathode-ray at the viewing tube would automatically be focused at the midpoint of line 40 on the screen of the viewing tube, and furthermore since I have provided through the medium of a half wave rectifier, Figure 12, means for associating the positive pulse in each cycle of thecontrol voltage wave with a certain field, the focused electron ray in' each tube would als'o'fall in the proper field.

The picture produced from this system will be approximately ashigh as they are wide, since there is no necessity of reserving space at the bottom of picture for synchronizing pulses.

Another system for controlling the scanning operations at the receiving station may comprise the motor 84, Figure 13, having control circuits for keeping the position of the rotor-11in step with the altematingcurrent signals. The motor 94 drives disks or mechanisms similar to those explained in connection with Figure 3 to in turn develop line and field trigger potentials,

utilizing the circuits shown in Figure '7. The

motor and mechanism shown in Figure 13, to-

gether with the circuits shown in Figure 7 may constitute the frequency generator 34, Figure 2,

in another receiving station.

The power amplifier 95 may be supplied with signal current from the detector 33, Figure 2. These signals after proper amplification at 95 are fed to the motor 94 through contact 96 and 91. The half wave rectifier 98 will supply the positive pulses to one winding of relay 99. The motor 94 is small and carries a very light load; therefore very little power is required to operate it. Se-

cured to its shaft are three disks of polarizing" material, two of which are exactlylike those shown in Figures 4 and with their associated stationary polarized members and photo-cells.

The disks are designated by the same numbers 4| and 42 and operate the circuits shown in Figure '1, as previously explained, in connection with the transmitting station. In the preferred embodiment of my invention I propose to substitute the disk I00, Figure 14, for the disk M to thereby develop a series of trigger impulses having equally spaced periods of time.

The third disk in Figure 13, designated I00,

and like the view shown in Figure 14 is secured to the motor shaft in such a manner that when it is rotated one-half of a revolution to alter the light in the photo-cell IOI (which may be substituted for the photo-cell 54, Figure 8) to produce a pulse of current in the transformer winding 56 of Figure 8, which is then fed to a circuit containing the lower winding of relay 99, in the interval between the pulses produced by rectifier 93, the rotor may be considered in stepwith the positive pulses of the sine form voltage wave supplied to the power amplifier 95.

The relay 99 will not operate by separate pulse 'from either the rectifier 98 or photo-cell IOI.

But since the motor is two pole, the rotor may be out of step several degrees; in which case the relay would receive aiding pulses from both the rectifier 98 andthe photo-cell I0I and would operate to open its contacts at 91 which would include the resistance I02 in the motor circuit momentarilyin order to slow its speed sufiiciently after a few revolutions to slip the rotor back in step with the supply current.

, From the above description it is shown that the disk secured to the motor shaft -will automatically keep in step with the current supply and that the other disk connected to the motor shaft will also generate voltage waves and pulses of current in exact phase relation and in synchronism with the supply. 1

This motor generator circuit or frequency generating device,,Figure 13, may be used to supply the line and frame control frequencies at the receiver in a similar manner to that shown in Fig. 3, at the transmitter.

When using this circuit the picture signals developed in one horizontal line may be slightly out of adjustment with the signals developed in the next following line and to overcome this automatically I have provided a horizontal line I03, Figure 15, which is reproduced from the permanent mark 31 at the transmitting tube, Figure 1, and will occur in all picture changes and frames. From a point, just at the left of this horizontal line I03, a ray of light is directed by mirror I04 and suitable lenses to a photo-cell I05. This photo-cell may be used in the circuit of Figure 8 which has been previouslydescribed. The transspeed lag the picture speed which will render relay I01 inoperative and give a slightly longer interval for thehorizontal' lines. However, should the motor speed lead the picture time, the mark would move to the right causing light to enter the photo-cell I05 which would operate relay I01 momentarily to include resistance I08 in the motor circuit, thereby reducing the speed of motor. This feature has been disclosed in my prior application, referred to before.

The mark I03, Figure 15, also serves another purpose, that is, it automatically controls the brightness of the picture reproduced by the refiections of the. changes in the intensity of the line or mark I03 into the photo-cell I09 from the mirror. The photo-cell I09 may be substituted for the one shown in Figure '8, whereby this circuit will function to adjust the bias on previous stages as shown in Figure-2 to assist in maintaining practically constant brightness in the reproduced picture.

With reference to Figure 16, I have shown my improved pick up tube I, which improvement consists in dividing the metallic plate on the back of the mosaic H0 into two parts III and 2, better shown in top view, Figure 17, with conductors extending from each metallic plate former winding 56 would be inductively connected to the winding I06, Figure 13, which winding is connected through the control relay I01. The mark will move to the left, should the motor through the tube, the mosaic may be in two parts also, otherwise this pickup tube is of conventional design. The conductor I I3 extending from the smaller of the two plates I II which is located on the left side of the tube facing the front, controls the grid excitation of grid II4 of amplifier tube H5. The anode of tube H5 is connected through primary winding II6 of a transformer to positive battery.

The operation of this circuit is as follows: As the electron beam moves from right to left across the mosaic IIO when scanning the image it will at the end of each scanning line he focused on a vertical image of full height of the picture caused by a narrow permanent fiat bar I I1, shown outside the lens system in Figure 1. This mark will appear in all the fields, so that each time the scanning beam reaches this vertical image a small potential change will be produced in the grid II4 of the amplifier 5, which may be further amplified in other stages, to in turn produce a pulse of current in the primary transformer winding H6 which is induced into the secondary transformer winding IIB to change the potential on the control grid H9 to reduce the intensity oi. the electron ray during the retrace period which is commonly known as blanking. These pulses, before being applied to the control grid, may be slightly delayed by well known pulse delaying methods so that the inten-' sity of the electron beam will be reduced Just at the right instant. I

With reference to Figure 18, I have shown a very similar arrangement to that shown in Figure 16 for blanking the electron ray in the viewing tube at the receiver.

The element I20 on the inside of the viewing fication and as explained for the pick up tube. Thus at the-end of each horizontal line the intensity of the electron ray in the viewing tube is reduced for the retrace interval.

From the above description it will be seen that I have provided a very simple and novel arrangement for blanking the electron ray in pick up and viewing tubes during the vertical and horizontal line retrace.

It will be understood that numerous modifications are possible without departing from the spirit of my invention or the scope of the claims.

Having thus described my invention, I claim: 1. In a television system, a cathode ray camera tube having an image ,plate and an electron ray' directed toward the image plate, a motor, means f or movingthe said electron ray to scan the said I image'plate, including mechanism driven at adjustable speeds'by the said motor, said mechanism provided with apparatus and suitable circuits to control the movement of said electron ray in vertical directions during spaced periods of time, and provided with other apparatus and suitable circuits to control the movement of said electron rayin horizontal reciprocating directions, said mechanism also provided with a. half wave rectifier, and suitable-circuits for adjusting the said electron rayvertically, during alternate which there is provided means including a part ofsaid image plate to control the intensity of i the said electron ray during its backward move ment.

4. The system,.in accordance with claim 1, in

which there is provided switching means to vary the number of line locations that may be scanned on the 'said image plate in any of the said periods.'

5. In a television system, a cathode ray camera tube having an image plate and an electron ray directed toward the imageplate, a motor, means for moving the said electron ray to scan the said imageplate, including mechanism, driven at adjustable speeds by the saidmotor, said mechanism having vertical deflecting means to control the movement of said electron ray in vertical directions during spaced periods of time, and horizontaldeflecting-means to control the movement of said electron ray in horizontal reciprocating directions, said mechanism also having means for applying 'a diflerentcondition to the said vertical deflecting means for alternate periods, relative to the saidvertical'deflecting means for the intervening periods, whereby even line locations on said image plate are scanned during alternate periods and odd line locations on said image plate are scanned during the intervening periods.

6. The system, in accordance with claim 5, in which there is provided means for adjusting the speed of said mechanism to scan all line locations on the said image plate twenty-four to thirty times per second.

7. The system, in accordance with claim 5, in which there is provided means including a part of said image plate to control the intensity of the said electron ray during its backward movement.

8. The system, in accordance'with claim 5, in which there is provided switching means 'tovary the number of line locations that may be scanned on the said image plate in any of the said periods.

9. In a television system, a cathode ray viewing tube, provided with an image screen, and an electron ray directed toward the image screen,

- a motor arranged to be driven by received synchronizin'g signals, means, including mechanism, driven by the said motor, for moving the said electron ray over the said image screen to produce successive images from received picture signals, said mechanism having vertical deflecting means to control the movement of said electron ray in vertical directions during spaced periods of time, and horizontal deflecting means to control the movement of said electron ray in horizontal reciprocating directions, said mecha-.

locations on said image screen are scanned during intervening periods. 7

10. The system, in accordance with claim 9, in which there is provided an electron ray contacting member at one edge 'of the said image screen, and means including said contacting member for controlling the intensity of the said electron ray during its backward movement. a

11. The system, in accordance with claim 9, in which there is provided switching means to vary the number ofline locations that may be scanned on said image screen in any of the said periods. 12. The system, in accordance with claim 9, in which there is included a mark in the said image. and means controlled by said mark reproduced in all images for momentarily changing the motorspeed to adjust the lines horizontally on said-image screen.

JOHN H. HOMRIGHOUS.

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