503,555

PATENT SPECIFICATION

Application Date: Oct. 14, 1937. No. 27929/37

Complete Specification Left: Sept. 15, 1938.

Complete Specification Accepted: April 11, 1939.

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PROVISION SPECIFICATION

Improvements in or relating to Television Transmitting and Receiving Systems

I, ALAN DOWER BLUMLEIN, of 37, The Ridings, Ealing, London, W.5, a British subject, do hereby declare the nature of this invention to be as follows:

This invention relates to television transmitting and receiving systems and has for its chief object to provide an improved transmitting and receiving system for use therewith in which the picture detail of a transmitted image is increased thereby permitting the detail in the reproduced image at the receiver to be correspondingly increased.

The present transmitting system employs a cathode ray transmitting tube in which an object of an image is projected on to a mosaic screen composed of a multiplicity of photo-electric mutually insulated elements which acquire an electrostatic charge according to the intensity of elementary areas of the incident image and a cathode ray is caused to scan the mosaic screen, scanning restoring the elements to a datum value and generating in an associated signal plate picture signals for transmission. It will be understood that with a system of this kind the detail of the picture transmitted depends upon the number of lines in to which the picture is resolved and the consequent diameter of the scanning spot of cathode rays. It is clear that detail can be improved providing that the number of lines is increased and the scanning spot size reduced accordingly, but this introduces difficulties not only on account of the fact that the frequency of the transmitted signals is thereby considerably increased but also on account of the fact that many receiving systems might be in operation which would necessitate reconstruction for the reception of signals from a transmitter in which the frequency of the scanning lines is increased as suggested above.

For these reasons therefore it is desirable to provide an improved transmitting system in which detail of the transmitted picture can be increased without increasing the line scanning frequency thereby enabling existing receiving systems to receive the improved transmission but without the increased detail whilst permitting receivers specially designed for the improved transmission to reproduce the received pictures with greater detail than receivers as constructed heretofore.

According to one feature of the invention a transmitting system is provided in which an image of an object is resolved into signals suitable for transmission by scanning a screen with a beam of cathode rays in which, in addition to the normal movements executed by the scanning beam a further component of motion is imparted thereto so that in scanning a line of the image the beam is caused to oscillate about the axis of said line, the diameter of the spot being made smaller than the width of the line effectively scanned.

With the existing transmitting system it will be appreciated that the diameter of the spot determines the width of the line scanned and consequently if this line embraces a horizontal black portion and a horizontal white portion the resultant picture signals generated on scanning the line instead of being resolved into black and white signals will be resolved into a composite grey signal.

With a system according to the invention, however, the diameter of the spot may be made to correspond to one-half the difference between the axes of adjacent lines and since the scanning spot oscillates about the axis of the line it will be appreciated that with a line containing horizontal black and white edges the scanning spot whilst resolving the picture into the same number of lines as an existing system will, nevertheless, resolve individually the black and white horizontal edges so that the picture signals generated will be truly representative of the image so increasing the detail in the transmitted signals. The oscillating motion imparted to the scanning beam is preferably of a sinusoidal form although other forms of oscillation motion may be imparted thereto such as motions of a sawtooth or similar form.

In a receiver constructed to receive the improved transmission and employing a cathode ray reproducing device the cathode ray beam will be modulated with the picture signals and the beam caused to traverse the fluorescent screen in synchronism with the scanning movement of the cathode ray beam at the transmitter. In other words, in traversing a line on the reproducing tube, oscillating motion of the same form as that applied to the scanning beam at the transmitter will be synchronously applied to the said beam; consequently detail in the reproduced picture will be improved.

The invention may be applied to interlaced or non-interlaced transmitting and receiving systems. It will of course be necessary in the transmitted signals to transmit suitable synchronising signals or other signals of suitable wave form in addition to those normally transmitted for the purpose of synchronising the oscillating motion imparted to the cathode ray beam at the receiver with that at the transmitter.

The invention will be described more in detail with reference to a transmitting system in which a picture is resolved into picture signals by scanning with 400 lines non-interlaced and employing a cathode ray transmitting tube having a mosaic screen of the kind referred to above. With such a system employing 25 frames per second, the line frequency is 10,000 cycles per second and the so-called dot frequency is two megacycles per second. The cathode ray beam is caused to scan the mosaic screen by applying to the beam the usual line and frame frequency oscillations. In accordance with the invention the diameter of the scanning spot is made smaller than that normally employed as, for example, by making the sport diameter equal to half the distance between the axes of the lines normally scanned, and instead of the scanning spot scanning a line substantially rectilinearly as is usual, the scanning spot is caused to oscillate about the axis of the line during its progression from one edge of the mosaic screen to the other. The frequency of the additional oscillation motion imparted to the scanning spot may be about three to four megacycles per second and may be of sinusoidal form the amplitude of oscillation being approximately one-half the distance between the axes of the lines normally scanned.

Although the diameter of the spot is only one-half of that normally used, since additional oscillation motion is imparted thereto, it effectively scans substantially the whole of the area scanned by a spot with a diameter of the normal size and consequently it is capable of resolving a line of the image with greater detail than that of a normal system. Theoretically, in order to obtain optimum detail the diameter of the scanning spot should be made equal to the diameter of the mosaic elements of the screen so that each element of the screen is individually scanned. With mosaic screens as at present in use it is not practicable to reduce the size of the scanning spot to the diameter of the mosaic elements owing to the resultant increase in the line scanning frequency although it will be appreciated that with the present invention the smaller the diameter of the spot, together with the use of an oscillation motion of suitable frequency, so the detail in the picture transmitted can be improved, whilst still maintaining a practical number of lines for each frame scanned. The picture signals generated in the transmitting tube are transmitted in the normal manner although, in view of the increased definition, it is necessary for the band width of the transmitted signals to be wider than that corresponding to a normal 400 line scanning system, a suitable band width being five or more megacycles of modulation frequency.

The oscillating motion of the scanning beam at the transmitter may be effected by super-imposing upon the frame frequency oscillations sinusoidal oscillations of the frequency of the order above mentioned.

A receiver designed to receive the improved transmission is arranged so that the beam of cathode rays is focussed to a diameter about one-half its normal size and oscillations of the same form as the oscillations applied to the scanning beam at the transmitter are applied in synchronism thereto so that the movement of the cathode ray beam at the receiver is substantially the same as that of the scanning beam at the transmitter. The transmitted signals are caused to modulate the cathode ray beam at the receiver, the frequency range than heretofore in view of the increased band width of the picture signals. Providing synchronism is preserved between the oscillation motion of the cathode ray beam at the receiver with that of the scanning beam at the transmitter, the reproduced picture will be integrated with the increased detail resulting from the improved scanning at the transmitter.

As stated above, with a normal system, assuming that a line scanned embraces a horizontal white edge and a horizontal black edge, the scanning spot instead of resolving such a line into its component shades will resolve the line into a shade corresponding to a combination of the shades of the image which in the present example, will be grey.

With the improved transmission system since the scanning spot oscillates about the axes of the line, upward and downward excursions of the scanning spot will resolve the black and white edges individually and these black and white edges will consequently be reproduced in a receiving tube with the component shades instead of, in the normal case, into a single shade of grey.

For the purpose of ensuring synchronism between the scanning spot at the receiver with that of the scanning spot at the transmitter, it is necessary to transmit suitable synchronising or other signals from the transmitter. This may be effected in a variety of manners. For example, a separate sub-carrier frequency on the main transmitter carrier frequency may be used or, alternatively the synchronising signals or signals of the required wave-form may be radiated directly as a medium wave signal. The preferred method, however, is to transmit the necessary oscillation frequency which imparts the desire motion to the beam as a phase or frequency modulation of the transmitted vision signals. Such phase modulation may be effected in known manner as, for example, by deriving an amplitude modulated signal and injecting sufficient carrier frequency oscillations of suitable phase in order to turn the effective carrier oscillations through 90 degrees so that the resultant signals are phase-modulated. For example, in a transmitting system employing a final push-pull modulated amplifier the vision signals for modulating the carrier are applied as a bias to the control grids of the valves in the push-pull amplifier. With the present invention the oscillations which are to be modulated with the picture signals are previously phase-modulated with the additional frequency which is effected in earlier stages of the amplifier in known manner. In a system in which the line and frame synchronising signals are represented by zero carrier frequency, i.e. the synchronising signals are in the blacker-than-black sense the modulation frequencies which are applied to the last stage of the amplifier will suppress the carrier wave, and likewise the phase-modulation entirely during the synchronising signals. With such a system the picture signals have a minimum value higher than zero carrier frequency and consequently the picture signals will have the necessary phase-modulation from which the signals for oscillating the scanning beam at the receiver can be derived. The necessary phase-modulation may amount to some 10%.

At a receiver for receiving the improved transmission with signals transmitted as above described the transmitted signals are arranged to be received with both side bands and are demodulated in the normal manner for deriving signals for modulating the cathode ray beam. A portion of the unmodulated signals may be passed through a suitable circuit employing an amplitude limiter for affording a constant amplitude output at a level slightly lower than that corresponding to black in the transmitted signals. The signals so obtained may be passed through a sharply tuned resonant circuit tuned off the carrier frequency in such a manner that the phase-modulation is partially converted into a single side band amplitude modulated oscillation. The signals so obtained are then demodulated and added to the frame scanning oscillations so that the required additional oscillations are applied to the scanning spot. In order that the phase of the additional oscillations at the receiver may be made the same as the additional oscillations at the transmitter a suitable phase-changing device may be provided at the receiver.

The invention may also be applied to an interlaced scanning system the additional oscillations of the cathode ray beam at the transmitter being applied as above described. With such an arrangement the effective lines in a single frame, i.e. 800 lines, are scanned in pairs and consequently if the reproduced picture is observed closely, flicker may be observed. To obviate this the amplitude of the additional oscillations at the transmitter and at the receiver may be increased to that corresponding to between two thirds and one-and-a-half times the distance between the axes of the lines in a picture normally scanned in as interlaced system. With such an arrangement the scanning produced in one line will overlap the scanning produced by the next line so that flicker will not be produced and without loss of detail in the reproduced picture providing that the beam at the receiver traverses the fluorescent screen with a similar amplitude of movement.

With receivers designed for the reception of normal transmission, such receivers may be operated with the improved transmission without structural alteration since the line and frame scanning frequencies are the same and since the transmitted signals representing the additional oscillation of the scanning beam and the modulation frequencies produced as a result of this additional oscillation will be outside the band width of the existing receivers.

Dated this 13th day of October 1937

F.W. Cackett

Chartered Patent Agent

COMPLETE SPECIFICATION

Improvements in or relating to Television Transmitting and Receiving Systems

I, ALAN DOWER BLUMLEIN, of 37, The Ridings, Ealing, London, W.5, a British subject, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:

This invention relates to television transmitting and receiving systems and has for its chief object to provide an improved transmitting and receiving system for use therewith in which the picture detail of a transmitted image is increased thereby permitting the detail in the reproduced image at the receiver to be correspondingly increased.

The present transmitting system employs a cathode ray transmitting tube in which an object of an image is projected on to a mosaic screen composed of a multiplicity of photo-electric mutually insulated elements which acquire an electrostatic charge according to the intensity of elementary areas of the incident image and a cathode ray is caused to scan the mosaic screen, scanning restoring the elements to a datum value and generating in an associated signal plate picture signals for transmission. It will be understood that with a system of this kind the detail of the picture transmitted depends upon the number of lines in to which the picture is resolved and the consequent diameter of the scanning spot of cathode rays. It is clear that detail can be improved providing that the number of lines is increased and the scanning spot size reduced accordingly, but this introduces difficulties not only on account of the fact that the frequency of the transmitted signals is thereby considerably increased but also on account of the fact that many receiving systems might be in operation which would necessitate reconstruction for the reception of signals from a transmitter in which the frequency of the scanning lines is increased as suggested above.

For these reasons therefore it is desirable to provide an improved transmitting system in which detail of the transmitted picture can be increased without increasing the line scanning frequency thereby enabling existing receiving systems to receive the improved transmission but without the increased detail whilst permitting receivers specially designed for the improved transmission to reproduce the received pictures with greater detail than receivers as constructed heretofore.

According to one feature of the present invention, there is provided a television transmitting system in which an image for transmission is resolved into picture signals by scanning in a plurality of lines by a suitable scanning spot the effective diameter of which is smaller than the width of each line, and wherein, in addition to normal movements executed by the scanning spot, a further component of motion is imparted thereto so that in scanning a line of the image the spot is caused to oscillate about the axis of the line, the arrangement serving to increase the picture detail of the transmitted image.

According to another feature of this invention, means are provided for transmitting synchronising signals capable of synchronising the reproducing spot of a receiver with the oscillations about the scanning line imparted to the scanning spot at the transmitter.

According to a furthe rfeature of this invention, the television receiver designed to receive signals from the said television transmitting system has means for synchronously applying to the reproducing spot the effective diameter of which is made smaller than the width of each line scanned, an additional oscillating motion of substantially the same form so that imparted to the spot at the transmitter for the purpose of causing the reproducting spot to oscillate about the axis of the lines traced by the spot in synchronism with the scanning spot at the transmitter, the arrangement serving to increase the detail in the reproduced image.

With the existing transmitting system it will be appreciated that the diameter of the spot determines the width of the line scanned and consequently if this line embraces a horizontal black portion and a horizontal white portion the resultant picture signals generated on scanning the line instead of being resolved into black and white signals will be resolved into a composite grey signal.

With a system according to the invention, however, the diameter of the spot may be made to correspond to one-half the difference between the axes of adjacent lines and since the scanning spot oscillates about the axis of the line it will be appreciated that with a line containing horizontal black and white edges the scanning spot whilst resolving the picture into the same number of lines as an existing system will, nevertheless, resolve individually the black and white horizontal edges so that the picture signals generated will be truly representative of the image so increasing the detail in the transmitted signals. The oscillating motion imparted to the scanning beam is preferably of a sinusoidal form although other forms of oscillation motion may be imparted thereto such as motions of a sawtooth or similar form.

The invention may be applied to interlaced transmitting and receiving systems. It will, of course, be necessary in the transmitted signals to transmit suitable synchronising signals or other signals of suitable wave form, in addition to those normally transmitted, for the purpose of synchronising the oscillating motion imparted to the reproducing spot at the receiver with that at the transmitter.

This invention is especially applicable to television transmitting and receiving systems which employ a beam of cathode rays for scanning purposes.

In order that the invention may be clearly understood and readily carried into effect, it will now be more fully described with reference to the Figures of the accompanying drawing in which:

Figure 1 is a diagram which is used for explanation purposes and

Figure 2 shows a portion of a raster traced out by the scanning or reproducing spot.

The invention will now be described with reference to a transmitting system in which a picture is resolved into picture signals by scanning with 400 lines non-interlaced and employing a cathode ray transmitting tube having a mosaic screen of the kind referred to above. With such a system employing 25 frames per second, the line frequency is 10,000 cycles per second and the so-called dot frequency is two megacycles per second. The cathode ray beam is caused to scan the mosaic screen by applying to the beam the usual line and frame frequency oscillations. In accordance with the invention, the diameter of the scanning spot is made smaller than that normally employed as, for example, by making the spot diameter equal to half the distance between the axes of the lines normally scanned, and instead of the scanning spot scanning a line substantially rectilinearly as is usual, the scanning spot is caused to osicllate about the axis of the line during its progression from one edge of the mosaic screen to the other. The frequency of the additional oscillation motion imparted to the scanning spot may be about three to four megacycles per second, and may be of sinusoidal form, the amplitude of oscillation being approximately one-half the distance between the axes of the lines normally scanned.

Figure 1 of the accompanying drawing diagrammatically shows a portion of the raster traced out by the scanning or reproducing spot. 1, 2 and 3 represent portions of consecutive lines of the picture when scanned in a normal fashion, the axes of these lines being reproduced by the lines 4, 5 and 6 respectively. When the diameter of the spot is reduced to a diameter equal to half the distance between the axes of the lines normally scanned and an additional sinusoidal oscillation imparted to the spot of an amplitude of one half the distance between the axes of the line normally scanned, the spot then traces out a raster, a portion of which is represented by 7, 8 and 9.

Since, however, with the additional sinusoidal oscillation having a frequency to afford the configuration shown in Figure 1, comparatively large portions of the picture are left unscanned, it is desirable to choose such a frequency for the additional oscillation that the spot covers practically the whole of the area of the line. If the frequency of the additional sinusoidal oscillation shown in Figure 1 is increased three times the resulting area covered by the spot will be as shown shaded in Figure 2.

Although the diameter of the spot is only one half of that normally used, since additional oscillation motion is imparted thereto, it effectively scans substantially the whole of the area scanned by a spot with a diameter of the normal size and consequently it is capable of resolving a line of the image with greater detail than that of a normal system. If desired the scanning spot may be made smaller than half the line spacing thus tending to enhance the picture detail. In television systems which employ cathode ray scanning means at the transmitter and receiver, the scanning spot has not definite boundaries but consists of a distribution having a centre portion of relatively high intensity, the intensity falling away rapidly to a comparatively low value outside the centre potion. It is the usual practice to make the width of the major portion i.e. the effective diameter of the spot smaller than line spacing, or for the purpose of this invention less than half the line spacing. With the usual method of using mosaic screens it is not practicable to reduce the size of a scanning spot to a very small value owing to the resultant increase in the line scanning frequency which would be necessary to cause the spot to scan the whole area of the screen although it will be appreciated that with the present invention the diameter of the spot is made smaller and by the use of an oscillation motion of suitable frequency, the detail in the picture transmitted can be improved, whilst still maintaining a practical number of lines for each frame scanned. The picture signals generated in the transmitting tube are transmitted in the normal manner although, in view of the increased definition, it is necessary for the band width of the transmitted signals to be wider than that corresponding to a normal 400 line scanning system, a suitable band width being five or more megacycles of modulation frequency

The oscillating motion of the scanning beam at the transmitter may be effected by super-imposed upon the frame frequency oscillations sinusoidal oscillations of the frequency of the order above mentioned.

A receiver designed to receive the improved transmission is arranged so that the beam of cathode rays is focussed to a diameter about one-half its normal size and oscillations of the same form as the oscillations applied to the scanning beam at the transmitter are applied in synchronism thereto so that the movement of the cathode ray beam at the receiver is substantially the same as that of the scanning beam at the transmitter. The transmitted signals are caused to modulate the cathode ray beam at the receiver, the receiver being designed to handle a wider frequency range than heretofore in view of the increased and width of the picture signals. Providing synchronism is preserved between the oscillation motion of the cathode ray beam at the receiver with that of the scanning beam at the transmitter, the reproduced picture will be integrated with the increased detail resulting from the improved scanning at the transmitter.

As stated above, with a normal system, assuming that a line scanned embraces a horizontal white edge and a horizontal black edge, the scanning spot instead of resolving such a line into its component shades will resolve the line into a shade corresponding to a combination of the shades of the image which in the present example, will be grey.

With the improved transmission system since the scanning spot oscillates about the axis of the line, upward and downward excursions of the scanning spot will resolve the black and white edges individually and these black and white edges will consequently be reproduced in a receiving tube with the component shades instead of, in the normal case, into a single shade of grey.

For the purpose of ensuring synchronism between the scanning spot at the receiver with that of the scanning spot at the transmitter it is necessary to transmit suitable synchronising or other signals from the transmitter. This may be effected in a variety of manners. For example, a separate sub—carrier frequency on the main transmitter carrier frequency may be used or, alternatively, the synchronising signals or signals of the required wave-form may be radiated directly as a medium wave signal. The preferred method, however, is to transmit the necessary oscillation frequency which imparts the desired motion to the beam as a phase of frequency modulation of the transmitted vision signals. Such phase modulation may be effected in known manner as, for example, by deriving as amplitude modulated signal and injecting sufficient carrier frequency oscillations of suitable phase in order to turn the effective carrier oscillations through 90 degs. so that the resultant signals are phase-modulated. For example, in a transmitting system employing a final push-pull modulated amplifier the vision signals for modulating the carrier are applied as a bias to the control grids of the valves in the push-pull amplifier. With the present invention the oscillations which are to be modulated with the picture signals are previously phase-modulated with the additional frequency which is affected in earlier stages of the amplifier in known manner. In a system in which the line and frame synchronising signals are represented by zero carrier frequency, i.e. the synchronising signals are in the blacker-than-black sense the modulation frequencies which are applied to the last stage of the amplifier will suppress the modulation, entirely during the synchronising signals. With such a system the picture signals have a minimum value higher than zero carrier frequency and consequently the picture signals will have the necessary phase-modulation from which the signals for oscillating the scanning beam at the receiver can be derived. The necessary phase-modulation may amount to some 10%.

At a receiver for receiving the improved transmission with signals transmitted as above described the transmitted signals are arranged to be received with both side bands and are demodulated in the normal manner for deriving signals for modulating the cathode ray beam. A portion of the unmodulated signals may be passed through a suitable circuit employing an amplitude limiter for affording a constant amplitude output at a level slightly lower than that corresponding to black in the transmitted signals. The signals so obtained may be passed through a sharply tuned resonant circuit tuned off the carrier frequency in such a manner that the phase-modulation is partially converted into a single side band amplitude modulated oscillation. The signals so obtained are the demodulated and added to the frame scanning oscillations so that the required additional oscillations are applied to the scanning spot. In order that the phase of the additional oscillations at the receiver may be made the same as the additional oscillations at the transmitter a suitable phase-changing device may be provided at the receiver.

The invention may also be applied to an interlaced scanning system the additional oscillations of the cathode ray beam at the transmitter being applied as above described. With such an arrangement the effective lines in a single frame, i.e. 800 lines, are scanned in pairs and consequently if the reproduced picture is observed closely, flicker may be observed. To obviate this the amplitude of the additional oscillations at the transmitter and at the receiver may be increased to that corresponding to between two thirds and one-and-a-half times the distance between the axes of the lines in a picture normally scanned in an interlaced system. With such an arrangement the scanning produced in one line will overlap the scanning produced by the next line so that flicker will not be produced and without loss of detail in the reproduced picture providing that the beam at the receiver traverses the fluorescent screen with a similar amplitude of movement.

With receivers designed for the reception of normal transmission, such receivers may be operated with the improved transmission without structural alteration since the line and frame scanning frequencies are the same and since the transmitted signals representing the additional oscillation of the scanning beam and the modulation frequencies produced as a result of this additional oscillation will be outside the band width of the existing receivers.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

  1. A television transmitting system in which an image for transmission is resolved into picture signals by scanning in a plurality of lines by a suitable scanning spot the effective diameter of which is smaller than the width of each line, and wherein in addition to normal movements executed by the scanning spot, a further component of motion is imparted thereto so that in scanning a line of the image the spot is caused to oscillate about the axis of the line, the arrangement serving to increase the picture detail of the transmitted image.
  2. A television transmitting system according to claim 1, wherein means are provided for transmitting synchronising signals capable of synchronising the reproducing spot of receiver with the oscillations about the scanning line imparted to the scanning spot at the transmitter.
  3. A television receiver designed to receive signals from the television transmitting system claimed in claim 1 or 2, wherein means are provided for synchronously applying to the reproducing spot, the effective diameter of which is made smaller than the width of each line scanned, an additional oscillating motion of substantially the same form as that imparted to the spot at the transmitter for the purpose of causing the reproducing spot to oscillate about the axis of the lines traced by the spot in synchronism with the scanning spot at the transmitter, the arrangement serving to increase the detail in the reproduced image.
  4. A television transmitting system according to Claim 1 or 2, or a receiver according to Claim 3, wherein the amplitude of the oscillations about the axes of the lines is approximately one half the distance between the axes of the lines
  5. A television transmitting system according to Claim 1, 2 or 4, or a receiver according to Claim 3 or 4, wherein frame frequency oscillations are employed and the oscillating motion of the spot is effected by superimposing upon the said frame frequency oscillations sinusoidal or other suitable oscillations.
  6. A television transmitting system according to Claim 1, 2, 4 or 5 or a receiver according to Claim 3, 4 or 5, wherein the picture is scanned or reproduced in an interlaced manner, and wherein the amplitude of the addition oscillations is made between the axes of the lines
  7. A television transmitting system according to Claim 1, 2, 4, 5 or 6, wherein for the purpose of synchronising the reproducing spot of a receiver with the oscillations about the scanning line imparted to the scanning spot at the transmitter, suitable synchronising signals are transmitted on a sub-carrier.
  8. A television transmitting system according to Claim 1, 2, 4, 5 or 6, wherein for the purpose of synchronising the reproducing spot of a receiver with the oscillations about the scanning line imparted to the scanning spot at the transmitter synchronising signals are transmitted as phase or frequency modulations of the transmitted vision signals.
  9. A television receiver according to Claim 3, 4 or 5, and designed to receive signals from a television transmitting system claimed in Claim 8, wherein means are provided for deriving from said phase or frequency modulations oscillations which are caused to impart to the reproducing spot an additional oscillating motion which is of substantially the same form as that imparted to and which causes the spot at the transmitter to oscillate about the axis of a line.
  10. A television transmitting system substantially as described herein with reference to Figure 1 or 2 of the accompanying drawing.
  11. A television receiver substantially as described herein with reference to Figure 1 or 2 of the accompanying drawing.

Dated this 14th day of September 1938

F.W. Cackett

Chartered Patent Agent