US2295023A - Television system - Google Patents

Television system Download PDF

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Publication number
US2295023A
US2295023A US325954A US32595440A US2295023A US 2295023 A US2295023 A US 2295023A US 325954 A US325954 A US 325954A US 32595440 A US32595440 A US 32595440A US 2295023 A US2295023 A US 2295023A
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United States
Prior art keywords
pulses
synchronising
line
pulse
frame
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Expired - Lifetime
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US325954A
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English (en)
Inventor
Beatty William Arnold
Chatterjea Prafuila Kumar
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International Standard Electric Corp
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International Standard Electric Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/16—Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level
    • H04N5/165—Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level to maintain the black level constant
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N11/00—Colour television systems
    • H04N11/06—Transmission systems characterised by the manner in which the individual colour picture signal components are combined
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising
    • H04N5/06—Generation of synchronising signals
    • H04N5/067—Arrangements or circuits at the transmitter end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising
    • H04N5/06—Generation of synchronising signals
    • H04N5/067—Arrangements or circuits at the transmitter end
    • H04N5/0675—Arrangements or circuits at the transmitter end for mixing the synchronising signals with the picture signal or mutually
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/04—Systems for the transmission of one television signal, i.e. both picture and sound, by a single carrier
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/08—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division
    • H04N7/084—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the horizontal blanking interval only

Definitions

  • I mm 3 1 may W.
  • This invention relates to methods of utilising synchronising pulses in television systems in such a manner that information or intelligence other than the normal frame and line synchronising information is conveyed in the various trains of line and/or frame synchronising pulses, the said additional information being inserted into the trains of pulses in such a manner that the normal frame and line synchronising information is still available.
  • additional information can, for instance, relate to the D. C. component of a television transmission; alternatively, discrimination between one frame and another can be achieved in colour or stereoscopic television, or the system can be adapted for conveying information relating to interlaced scanning, or to the expansion or compression of the volume range of a sound signal accompanying a vision signal.
  • the system can be applied to television transmissions in which vision intelligence is radiated either as a positive or as a negative signal from a definite carrier level representing black, synchronising signals for the said vision intelligence being radiated as amplitude modulations of the carrier in the blacker than black carrier levels.
  • vision intelligence is radiated either as a positive or as a negative signal from a definite carrier level representing black
  • synchronising signals for the said vision intelligence being radiated as amplitude modulations of the carrier in the blacker than black carrier levels.
  • Fig. 1 shows a curve illustrating portions of a vision signal and frame pulse train as at present radiated by the B. B. C.;
  • Figs. 2 and 5 show diagrams illustrating carrier levels under different conditions
  • Fig. 6 illustrates a type of target plate suitable for generating one type of time modulated pulse
  • Fig. 7 is a circuit arrangement of a D. C. component restoration embodiment of the proposal;
  • Fig. 9 shows a special pulse utilised for the purpose of controlling the insertion of time modulated pulses.
  • the desirability of retaining or restoring the D. C. component in television transmission and reception is well known.
  • the usual methods of restoring the D. C. component are either that a fixed and frequently repeated peak value of radiated signal, such as a definite maximum or a definite minimum is observed and utilised in stored, or that the average value of the vision or like signal is observed and utilised so that the D. C. component is restored.
  • Partial D. C. restoration can also be achieved by observing and utilising the average value of picture signals.
  • the energy control of a television picture transmission can be considered as being made up of two energy components one of which (i. e. all signals up to black out level) is fixed,
  • the characteristics of the transmission be varied in such a manner that some or all of the signals having a fixed peak value, as for instance line and frame synchronising signals, or lines rising to black carrier level in the frame pulse series, be time modulated in such a, manner that the energy content of this time modulated portion of the combined vision and synchronising signal is a function of average brightness, identical to or practically identical to the energy content function of average brightness of the combined vision and synchronising signal.
  • a frame of 202 lines comprises 188 lines as shown at A, 4 lines such a manner that the D. C. component is reas shown at B, and 10 lines as shown at C.
  • the line scanning periods shown at A can be considered as commencing at the points H, when the carrier falls from 30% to zero for-a duration of .1 of a line scanning period, rising at point i2 to 30% carrier, at which black level the carrier 5 is maintained for a further 5% of a line scanning period This 15% of the line scanning period is known as the synchronising and following black out period. Following this period vision signals are radiated for .845 of a line scanning period,
  • the 4 line scanning periods shown at B comprise 8 frame pulses of .4 of a line period, when the carrier falls from 30% level to zero, each pulse being followed by a period of .1 of a line period during which the carrier rises to 30% level.
  • the 10 line scanning periods shown at C comprise pulses of .1 of a line period during which the carrier falls from 30% to zero, followed by .9 of a line period during which the carrier is maintained at 30% level.
  • the 30 carrier can be variable above 30% of carrier level for a time equal to only 160 line periods, and 9 that the carrier rises toi30% for a time equal to 20 line periods, while zero level is maintained for a time equal to 22.5 line periods.
  • FIG. 2 there are shown three block diagram of which H indicates the carrier value when an all white picture is being transmitted, and J when an all black picture is being transmitted.
  • the diagrams are drawn approximately to scale, the various carrier levels being indicated along the ordinates and the line scanning periods" along the abscissa. If the carrier levels over the frame period as indicated by diagram H, Fig. 2, are integrated it will be seen that the average level is 83% of maximum carrier, indicatedby dotted line LiLi while integration of carrier levels shown in diagram J gives an average carrier level of 27% indicated by line InLs. by 3.1 to 1 from an all white picture to an all black picture.
  • Diagram K shows in a similar manner the carrier level LsLa for a grey picture.
  • the area F shall also be made variable, 5 and that this variation shall be such that when considering this area as a positive pulse, or a train of positive pulses, the D. C. level of such train of pulses will vary in the same manner as I the D. C. level of the whole signal.
  • One method of varying the area F is to time modulate the line synchronising pulses in such a manner that these pulses when integrated with the frame pulses shown at B, Fig. 1, give an area I F which is variable in the desired manner.
  • FIG. 3 there is shown a vision and synchronising signal similar to that shown in Fig. 1 except that the line synchronising pulses are .025 of a line scanning period followed by aninterval of .125 of a line scanning period,
  • the line synchronising pulses When an all white signal is being transmitted, the line synchronising pulses have been time modulated in such a manner that they now have a duration of .105 line scanning periods, being followed by an interval of .045 line scanning periods during which the carrier level is maintained at 30% level.
  • Fig. 4' which is similar to Fig. 3, except that the line pulses have been lengthened
  • the leading edges 44 of the pulses shown in Fig. 4 coinciding with the leading edges ii of the pulses in Fig. 3.
  • FIG. 5 diagrams L, M, P show average carrier levels with the time modulated line synchronising pulse, for all white, all black, and grey pic-' tures respectively. These diagrams follow the same general arrangement as the diagrams H,
  • the side QR of the target is used to determine the leading e es of the synchronising pulses, such edges occurring at equal time intervals.
  • the variable trailing edges of the pulses are determined by the side S. T. Pulses of minimum duration with a D. C. level of 28.75% are obtained by scanning along the line QS, while pulses of maximum duration with a D. C. level of 82.5% are obtained by scanning along the line RT.
  • the side RT is 4.2 times the length of QS.
  • the shape of the plate is determined by assuming small increases in brightness with corresponding increases in the area F. Fig. 5, and integrating the averagecarrier level for each brightness condition. Graphically plotting the variations of F minus a fixed amount representing the 8 frame synchronising pulses during the period 3132, against average carrier level, gives a diagram corresponding to the plate shape shown.
  • the combined vision and synchronising signal is applied via condenser I9 to the control grid 20 of the cathode ray tube 2
  • the valve 22, and associated network serve to restore the D. C. component the manner of operation being as follows.
  • the new type of synchronising, pulse is not obtained at the expense of other information or desirable conditions.
  • the leading edges of the pulses occur at equal time intervals, the said leading edges being utilised for the synchronising of line scanning generators in'receivers, while the duration of the pulse plus following black out period, remains constant thus providing an adequate fly-back interval for the back stroke of the signals generated by line scanning generators.
  • a television signal incorporating the new type of pulse be fed to an output valve in a video amplifier, the valve having a bias resistor of such a value that, when the vision signals appear as positive signals at the anode, the synchronising sig als in known manner appear as positive signals at the cathode; the average level of the synchronising pulses integrated over 9. frame period is identical with the average level of the combined signal taken from the anode.
  • the average level of the synchronising pulses depends upon their duration, this average level is not affected by any amplitude distortion which may occur in video aniplifiers either at the transmitter or the receiver, and it can be seen that once the pulse duration has been determined by the average level of an early transmitter stage, the synchronising pulses can be readily utilised either at the transmitter or receiver to control or reinsert D. C. levels, when these have been partially lost due to amplitude distortion of the amplifying stages, or wholly lost by employing resistance-capacitycoupled amplifying stages in a video amplifier;
  • an output valve 15 receives a combined vision and synchronising signal, the latter being time modulated and being applied to the control grid IS.
  • the D. C. compo- The reversed phase signals appearing at the cathode it are fed to any known type of amplitude filter shown as a block diagram A. F. such as are at present used for the purpose of separating synchronising pulses from a combined vision and synchronising signal, and giving synchronising pulses of constant amplitude under all conditions of average carrier level.
  • the amplitude filter AF can be utilised to supply time modulated pulses of constant amplitude to the valve 22, via the condenser 24 for the purpose of restoring the D. C. component, which has been lost by the manner of utilising the output of the time constant which is longer than a line scannlng period and shorter than the lowest cut of! frequency of any previous amplifier stage which may be for exampl 200 cycles per second.
  • the battery 26 supplies current to the potentiometer 21, which is so adjusted in conjunction with the resistors 28 and 29 having common connectors with the anode 30 of the valve 25 and the oathode 3l of the cathode ray tube 2
  • the screen is illuminated in a known manner, but at the same time the synchronising'pulses appearing on the control grid 32 of the valve 22 have a longer duration and owing to the time constant of the circuit 23, 24 there is arise in voltage across the resistor 25 making the control grid 32 of the valve 22 more positive.
  • the D. C. component can be restored without effective change of grid input load to the cathode ray tube, thus ofiering an advantage over previously proposed systems of D. C. restoration.
  • FIG. 8 there is shown a portion of a vision signal and frame pulse period identical to that shown in Fig. 1, except that the pulses 34 have been time modulated in accordance with average carrier level in a manner similar to that previously described.
  • the time modulation is carried out in such a manner that the trailing edge 35 of the pulses 34 occur at equal time intervals, thus maintaining line synchronising,
  • the integrated duration of the eight fixed duration pulses 36 and the ten variable duration pulses 34 is a linear function of the average carrier level of the combined vision and synchronising signal.
  • the method of determining and producing such pulses should now be obvious from the previous example.
  • a method of producing variabl duration pulses having their trailing edges occurring at equal time intervals is described in the above-mentioned application No. 313,041, and similar means can be employed in this instance.
  • a long pulse covering a period of ten line-scanning periods as shown in Fig. 9, can be utilised to make operative or disable circuits controlling the generation or insertion of the different types of puls in such a manner that variable duration pulses 34 are.
  • auxiliary receiver which functions only during the frame pulse period.
  • Such receivers are already known, having been used for observing the am plitude of framepulse signals for the purpose of achieving automatic gain control of video amplifiers; If a similar type of receiver is utilised for the observation of the energy content of a train of frame pulses having the characteristics specified, then the output from this receiver can be utilised for the purpose of restoring the D. C.
  • a mean value of vision signal pulse duration can be made to correspond with a definite degree of amplification control at the sound transmitter input, compression of signals above a required volume being accompanied by a corresponding lengthening of the duration of the pulses, while expansion of the signals is accompanied by a shortening of the pulse duration.
  • variable duration pulses can be separated from the combined vision and synchronising pulse signal, and in this case the output of the pulse discriminating receiver can be utilised for the purpose of controlling the gain of the sound receiver accompanying the vision receiver, compression at the transmitter being counteracted by automatic expansion at the receiver, while expansion at the transmitter is automatically counteracted by compression at the receiver.
  • gain control circuits can be adapted for the purpose of carrying out this proposal.
  • variable duration synchronising signals are characterised in that the edge of such signals used for synchronising purposes occur at equal time intervals, while the other edge not used for synchronising occurs at varying time intervals, such variations occurring in steps in a definite cyclical order.
  • every third frame alternate frames can be obtained in certain proposed methods of stereoscopic television, such methods and the necessity for the discrimination being discussed in the above mentioned pat-' ent specification.
  • the A variable duration pulse system as described can also be utilised in such a manner that a television sequential scanning system can be changed into an interlaced scanning system at the receiver, or an existing interlaced scanning system can have the interlacing factor multiplied at the receiver.
  • the existing A definite manner of in- 405 line television system transmitted by the B. B. C. can have the frame synchronising pulses modified in such a manner that existing synchronising methods are not interfered with and at the same time specially adapted time bases would be capable of giving in receivers line spacing equivalent to 1215 lines, i. e. three times as fine a line spacing as is possible, with a correctly interlaced 405 line picture.
  • Fig. a there is shown a train of 6 pulses similar to those shown at A, Fig. 1. As is known, these pulses are used for synchronising the frame scanning time base generator. There has also been proposed a method of obtaining very definit-e synchronising of frame-scanning time-base generators. Briefly, this method depends upon the deriving of very short pulses from the leading or trailing edges of the frame and line pulses, and during the frame pulse period utilising one of these derived pulses to synchronise the framescanning time-base generator.
  • synchronising by a derived pulse occurring at definite intervals is achieved by additively combining the derived pulses with the frame pulses from which said derived pulses have been derived, one group of signals being passed over a transmission channel with a time delay, while the other group of signals is passed over a transmission channel having a smaller or no delay.
  • a modification of the method outlined above can now be used for the purpose of increasing the interlacing factor of a received picture. If matters are so arranged that the synchronising blocking circuit is operative up to the commencement of the sixth pulse and if synchronising is obtained by utilising the next short pulse derived from the trailing edge of the sixth pulse, then synchronising is dependent upon the duration of the sixth pulse. It is now proposed that the final pulse in a train of frame pulses be made of variable duration, as shown in Figs. 10b and 100. In 10b, the pulse is shortened by /6 of a line scanning period, and in 100 by V of a line scanning period, the leading edges of the pulses occurring at equal time intervals while the trailing edges are variable.
  • variable pulse can be used in the same transmission, for instance, time-modulated line-synchronising pulses giving D. C. light control can be used at the same time as time-modulated black-out line periods in a frame pulse period, give colour synchronisation in a colour television system.
  • time-modulated line-synchronising pulses giving D. C. light control can be used at the same time as time-modulated black-out line periods in a frame pulse period, give colour synchronisation in a colour television system.
  • a dual variable-pulse system it is necessary to compensate the variations of one pulse in accordance with the change in the variations in the other pulse. This can be readily achieved by utilising the average value of one pulse series to modify in a suitable manner the deflection of the beam across the target used for generating the other variable, duration pulses.
  • means for setting up picture signal voltages means for generating and superimposing on said signal voltages a train of substantially rectangular pulses of time durations concurrent with and greater than said picture signals, said rectangular pulses being of the same polarity as said picture signals, said rectangular pulses each having an edge equally spaced in time from a corresponding edge of a succeeding pulse for synchronization purposes, means for deriving a control voltage to produce varying spacing of the other, each of said pulses in accordance with said variation, relating to intelligence to be transmitted, means for varying the duration of transmission of said synchronising impulses in accordance with said control voltage means including an amplitude filter for separating out said pulses, and means for deriving a regulating voltage from said separated pulses.
  • Receivers which are not specially adapted to utilise the sixth frame pulse of variable duration would have their frame time bases synchronised in any well known manner, thus achieving the normal 405 line picture. It will be seen that normal line synchronising is maintained through the various frame pulse sequences.
  • control voltage being a function of the average signal level of the picture signal voltages.
  • control voltage being a function of the average signal level of the picture signal voltages
  • the system including a, receiver and brightness regulating means in said receiver controlled by said regulating voltage.
  • System including means for setting up in successive periods signal voltages corresponding to alternate eye views for stereoscopic transmission, wherein said control voltage and hence the pulse duration defines alternate eye viewing periods.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Television Systems (AREA)
  • Color Television Systems (AREA)
US325954A 1939-04-03 1940-03-26 Television system Expired - Lifetime US2295023A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB10344/39A GB527310A (en) 1939-04-03 1939-04-03 Improvements in or relating to television systems

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US2295023A true US2295023A (en) 1942-09-08

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US325954A Expired - Lifetime US2295023A (en) 1939-04-03 1940-03-26 Television system

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US (1) US2295023A (ja)
BE (1) BE475931A (ja)
DE (1) DE943000C (ja)
ES (1) ES177868A1 (ja)
FR (1) FR864645A (ja)
GB (1) GB527310A (ja)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2465371A (en) * 1945-01-13 1949-03-29 Standard Telephones Cables Ltd Color television
US2527967A (en) * 1947-11-12 1950-10-31 Rca Corp Multiplex transmission of television signals
US2539440A (en) * 1945-09-27 1951-01-30 Standard Telephones Cables Ltd Single carrier, sound and color vision pulse system
US2543015A (en) * 1945-09-27 1951-02-27 Standard Telephones Cables Ltd Receiver circuit
US2589100A (en) * 1946-01-08 1952-03-11 Pye Ltd Television receiver with sound recurring as pulses during blanking periods
US2628274A (en) * 1944-06-27 1953-02-10 John H Homrighous Multiplex television system
US2707210A (en) * 1951-03-30 1955-04-26 Rca Corp Pulse amplitude multiplex cross talk reduction systems
US4150397A (en) * 1977-09-13 1979-04-17 Eli S. Jacobs Repetition reduced digital data record and playback system
US5140420A (en) * 1990-10-05 1992-08-18 General Electric Company Information in vertical blanking interval of video sync signal
US5298913A (en) * 1987-05-29 1994-03-29 Sharp Kabushiki Kaisha Ferroelectric liquid crystal display device and driving system thereof for driving the display by an integrated scanning method
US5327238A (en) * 1992-11-10 1994-07-05 Chou Wayne W Method and apparatus for modulating a separated television horizontal sync pulse as a subcarrier of audio information

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1194895B (de) * 1954-10-22 1965-06-16 Telefunken Patent Fernsehuebertragungssystem

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2083245A (en) * 1937-06-08 Picture reproducing apparatus
US1887237A (en) * 1929-05-31 1932-11-08 Rca Corp Signaling system
US2089639A (en) * 1933-04-08 1937-08-10 Rca Corp Intelligence transmission
US2061734A (en) * 1934-09-29 1936-11-24 Rca Corp Signaling system
US2086918A (en) * 1935-08-22 1937-07-13 Rca Corp Method of frequency or phase modulation
GB483372A (en) * 1936-03-26 1938-04-19 Marconi Wireless Telegraph Co Improvements in or relating to television and other signal transmission systems

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2628274A (en) * 1944-06-27 1953-02-10 John H Homrighous Multiplex television system
US2465371A (en) * 1945-01-13 1949-03-29 Standard Telephones Cables Ltd Color television
US2539440A (en) * 1945-09-27 1951-01-30 Standard Telephones Cables Ltd Single carrier, sound and color vision pulse system
US2543015A (en) * 1945-09-27 1951-02-27 Standard Telephones Cables Ltd Receiver circuit
US2589100A (en) * 1946-01-08 1952-03-11 Pye Ltd Television receiver with sound recurring as pulses during blanking periods
US2527967A (en) * 1947-11-12 1950-10-31 Rca Corp Multiplex transmission of television signals
US2707210A (en) * 1951-03-30 1955-04-26 Rca Corp Pulse amplitude multiplex cross talk reduction systems
US4150397A (en) * 1977-09-13 1979-04-17 Eli S. Jacobs Repetition reduced digital data record and playback system
US5298913A (en) * 1987-05-29 1994-03-29 Sharp Kabushiki Kaisha Ferroelectric liquid crystal display device and driving system thereof for driving the display by an integrated scanning method
US5140420A (en) * 1990-10-05 1992-08-18 General Electric Company Information in vertical blanking interval of video sync signal
US5327238A (en) * 1992-11-10 1994-07-05 Chou Wayne W Method and apparatus for modulating a separated television horizontal sync pulse as a subcarrier of audio information

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Publication number Publication date
FR864645A (fr) 1941-05-01
GB527310A (en) 1940-10-07
ES177868A1 (es) 1947-06-16
DE943000C (de) 1956-05-09
BE475931A (ja)

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