US2240507A - Television synchronizing and control system - Google Patents

Television synchronizing and control system Download PDF

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Publication number
US2240507A
US2240507A US233371A US23337138A US2240507A US 2240507 A US2240507 A US 2240507A US 233371 A US233371 A US 233371A US 23337138 A US23337138 A US 23337138A US 2240507 A US2240507 A US 2240507A
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United States
Prior art keywords
components
signal
synchronizing
peaks
control
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US233371A
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English (en)
Inventor
Harold M Lewis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BAE Systems Aerospace Inc
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Hazeltine Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hazeltine Corp filed Critical Hazeltine Corp
Priority to US233371A priority Critical patent/US2240507A/en
Priority to GB25996/39A priority patent/GB541005A/en
Priority to DEH5432D priority patent/DE966059C/de
Priority to BE436528D priority patent/BE436528A/xx
Priority to FR863095D priority patent/FR863095A/fr
Application granted granted Critical
Publication of US2240507A publication Critical patent/US2240507A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
    • H04N5/52—Automatic gain control
    • H04N5/53—Keyed automatic gain control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising
    • H04N5/08—Separation of synchronising signals from picture signals

Definitions

  • This invention relates to television receiving apparatus and more particularly to synchronizing and control systems for such apparatus.
  • the invention is especially directed to the provision of a combined synchronizing-signal-separating and automatic amplification control system for television receivers.
  • a transmitted signal comprises a carrier wave modulated by light-modulation components representative of varying light values in successiveincremental areas of an image being transmitted and of its average background illumination, ⁇ and synchronizing-modulation components which correspond to initiations of successive lines and fields in the scanning of the image.
  • the latter components ordinarily have amplitude values outside of the amplitude range of the lightmodulation components and extending in the direction of black.
  • a beam is so deflected as to scan and illuminate a, target in a series of fields of parallel lines.
  • the synchronizing-modulation components of the received signal are utilized to control the scanning apparatus so as to synchro- ⁇ nize its operation with that of similar apparatus utilized at the transmitter in developing the sig-
  • the intensity of the cathode ray is controlled by the video-frequency components of the received signal, as well as by the unidirectional background illumination voltage developed in the receiver, thereby to reconstruct the transmitted image.
  • Essential functions which must be performed ina television receiving system of the type described include deriving from the signal separate line-frequency and field frequency synchronizing pulses as Well as developing a, unidirectional-bias voltage representative of the average intensity of the carrier and independent of its light modulation and the utilization of this voltage automatically to control one or more operating characteristics of the receiver, for example, to effect automatic amplification control.
  • Various methods have heretofore been devised for performing these functions but, in general, they have involved relatively complicated and/or unstable apparatus, or have otherwise left something to be desired.
  • a television receiver adapted for reproducing a signal carrier having combined lightmodulation components and synchronizingmodulation components, the latter having amplitude values outside the amplitude range of the light-modulation components.
  • the ⁇ receiver includes a rectifying device, means for deriving from a signal translated by said receiver a signal having components representingy the peaks of said synchronizing modulation components at a level corresponding to the unmodulated peaks of said carrier wave, and means for applying the derived signal to the rectifying device which includes means for maintaining the peaks of the synchronizing signals at the above-mentioned level to derive the synchronizing components separate from the other modulation components and a control effect, such as a unidirectional bias voltage, proportional to the average intensity of the received signal can'ier and independent of its light-modulation components.
  • Means are further provided for utilizing the derived synchronizing components for synchronizing the operation of the receiver and for utilizing the control effect for controlling an operating characteristic of the receiver, for example, for automatic ampliilcation control.
  • Apreferred embodiment of the invention includes a dioderectiiier for developing the bias voltage and impedance means connected in circuit with the same diode rectifier for deriving the synchronizing components.
  • Fig. 1 is a circuit diagram, partially schematic, of a cathoderay tube television reproducing system including circuits embodying the present invention
  • Fig. 2 is a group of curves representing certainoperating characteristics of the system of Fig. 1 to aid in the understanding of the invention
  • Fig. 3 is ⁇ a circuit diagram illustrating a modified form of the invention.
  • television signals intercepted by the antenna circuit I-I I' are selected and amplified in the radio-frequency ampliiier I2 and supplied to the oscillatormodulator I3, where they are converted to intermediate-frequency signals which, in turn, are selectively amplified in the intermediate-frequency amplier I4 and delivered to the detector I5.
  • the modulation components of the signal are derived by the detector I and are supplied to the video-frequency amplier I6 wherein they are amplified and from which they are supplied in the usual manner toa brilliancy-control element of the image-reproducing device I1.
  • a resistor 29 may be included in series with the condenser 28 and the diode 2
  • the resistor 29 is nf suchvalue as to have a relatively low impedance compared to that of the condenser 28 at the synchronizing frequencies.
  • the input circuitsY of the line-frequency and held-frequency generators I8 and I9 are connected across the resistor 29 by way ofa suitable lead 30. Conventional circuits may be included in the generators I8 and I 9 for separating the line-synchronizing and field-synchronizing pulses from each other.
  • the negative terminal of resistor 21 is connected, by way of a suitable Vfilter including series resistors 3l and shunt condensers 32 and conductors 33, to the control electrodes of one or more of the vacuum tubes included in the amplifier I2, oscillatormodulator I3, and amplifier I4, as shown.
  • a suitable Vfilter including series resistors 3l and shunt condensers 32 and conductors 33, to the control electrodes of one or more of the vacuum tubes included in the amplifier I2, oscillatormodulator I3, and amplifier I4, as shown.
  • curve A illustrates the load characteristics of the peak rectifier 2
  • a control signal-translating channel for the purpose of developing a control-bias voltage, there is provided a control signal-translating channel, .separate from the main signal-translating channel previously described, and comprising a vacuum-tube amplifier 20 and a rectifier device 2I connected in the order mentioned.
  • the tube 20 may be of any suitable type having an input circuit comprising a coupling condenser 22 and leak resistor 23 connected to the output circuit of the ampliii'er I4.
  • the output circuit of the tube 20 includles the primary winding 24 of a transformer 25, the
  • the resistor 21 may be of the order of 500,000 ohms and the condenser 28 of the orderof 500 microby curve C, which shows the wave form of the envelope of the negatively modulated-carrier signal as developed inthe output circuit of the intermediate-frequency amplifier I4 and applied by way of the tube 20 and transformer 25 to the diode 2I.
  • is also effective to maintain the peaks of the synchronizing modulation components at the above-mentioned level.
  • the light-modulation components and synchronizing-modulation components are indicated at L and S, respectively, the latter, it will be noted, extending beyond the amplitude range of the former.
  • Signal levels corresponding to white and black are indicated inthe iigure at W and B, respectively.
  • passes current only during the occurrence of synchronizing pulses, which represent the peak values of the modulated-carrier wave on one side of its axis, this being determined by the largetime constant circuit provided by the resistor 21 and condenser 28. There is thus built up across the load l circuit 21, 28 a unidirectional voltage, illustrated tion components.
  • the filter comprising the resistors 3
  • the single 4rectifying circuit described above thus serves to derive from the signal both a unidirectional biasvoltage proportional to the intensityof the modulated-signal'carrier and independent of its light-modulation components and the synchronizing-modulation componentsl separate from the othermodulation components.
  • Fig. 3 shows a ⁇ diode Vrectiiier arrangement which may be substituted for that shown in Fig. l...
  • thearrangement is the same as in Fig. l except that resistor ⁇ 29 is connected betweenl the diode cathode and its load circuit rather than in its load circuit.
  • Theoperation of this arrangement is substantially ⁇ the -same as, that of Fig. 1.
  • theA control system of the present invention may be energized v'vith ⁇ the detected signal as well as the modulated-carrier signal.
  • theinput circuit of rectifierilZI may be directly connected, that is; conthe light-modulation components comprising, a
  • main ⁇ signal-translating channel a separate control signal-translating channel, means for applying a signal translated by said receiver and having components -representing the peaks of said synchronizing-modulation components at a level corresponding to the unmodulated peaks of said carrier wave to both of said channels, a recnected by a direct current connection, to the output circuit of the detector instead oi.' the amplier I4 and the detected modulation-signal envelope, that is; the envelope of half the wave. s C shown inFig, 2, is impressed on the diode rectier 2i. The operation is otherwise the same as that described above.
  • an essential feature oi the arrangement of the invention is ⁇ that the signal rectifying means be energized by a sign-al translated by the receiver and having components representing the peaks of the corresponding to the unmodulated peaks of ⁇ the received signal-carrier wave.
  • a television receiver ladapted'to reproduce a signal-carrier wave having combined lightmodulation components and synchronizing-modulation components "having amplitude values outside the amplitude range of a light-modulation components comprising, a rectifying device.
  • means for applying said signal applied to said Hcontrol channel to said device including means for maintaining said peaks at said level to derive said synchronizing components separate from said other modulation components and a control eiTect proportional tothe peak intensity of said carrier wavek and independent of llight-modulation components, means for utilizing said control eiect for controlling an operating characteristic of said main channel, and means for 'utilizing said separated ⁇ synchronizing compolated by said receiver and having components representing the peaks of said synchronizingmodulation-components at a level corresponding to the unmodulated peaks of said carrier wave to'.
  • both of said channels a rectifying device ineluded in said control channel, means for apply-j ing said signal applied to said control channel -to said device including means for maintaining said peaks at said level to derive a control-bias voltage proportional to said peak value Vof said carrier wave and to develop from said signal said synchronizing components separate from the other modulation components, means ⁇ ior utilizing said control-biasl voltage for controlling an operating characteristic of said main channel, and means for utilizing said separated synchronizing components for synchronizing the operation of the receiver.
  • a television receiveraclapted for the reception of a television signal-carrier wave modulated negatively by light components and modulated by synchronizing components having amplitude values outside the amplitude range of the light components ⁇ a rectifying device, means for deriving from a signal translated by said receiver a signal having ⁇ components representing the' peaks of said synchronizing-modulation components at a level corresponding to the unmodulated peaks of said carrier Wave, means for applying said derived signal to said device including means for maintaining said peaks at said regeiver adapted to reproduce a ⁇ ,modulation components and level to derive a control-bias voltageA proportional to the peak value of said carrier on one side of its axis and to derive said synchronizing components separate from said yother modulation components, means for utilizing said control-bias voltage for controlling an operating characteristic of the receiver, and means for utilizing said separated synchronizing components for synchronizing the operation of the receiver.
  • a television receiver adapted for the reception of a television signal-carrier Wave modulated negatively by light components and modulated by synchronizing components having amplitude values outside the amplitude range of the light components, a main signal-translating channel, ay separate control signal-translating channel, means for applying a signal translated by said reeciver and having components representing the peaks of said synchronizing-modulation components at a level corresponding to the unmodulated peaks of said carrier wave to both said channels, ⁇ a rectifying device included in said control channel, means for applying said signal applied to said control channel to said device including means for maintaining said peaks at said level to derive a control-bias voltage proportional to the peak value of said carrier on one side of its axis and to derive said synchronizing components separate from said other modulation components, means for utilizing 'said control-bias voltage for controlling an operating characteristic of said main channel, and means for utilizing said separated synchronizing components for synchronizing the operation of the receiver.
  • a television receiver adapted to reproduce a signal-carrier wave having combined lightmodulation components having amplitude values outside the amplitude range of the light components, said wave having a wide range of sigsynchronizingcarrier wave, means for applying said derived signal to said device including means for maintaining said peaks at said level to derive a control bias voltage proportional to the intensity of said carrier independent of light modulations and to derive said synchronizing components separate from the other modulation components, means for utilizing said control-bias voltage for maintaining the intensity of the signal output of said main channel within a relatively narrow range for a Wide range of received signal input intensities, and means for utilizing said synchronizing components to synchronize the operation of the receiver.
  • a television receiver adapted to reproduce a signal-carrier wave having combined lightmodulation and synchronizing-modulation comnal-input intensities, comprising, a. rectiiying device means for deriving from a signal translated by said receiver a signal having components representing the peaks of said synchronizingmodulation components at a level corresponding to the unmodulated peaks of said carrier wave, means for applying said derived signal to said device including means for maintaining said peaks at said level to derive a control-bias voltage proportional to the intensity of said carrier Wave and independent of light-modulation components and to derive said synchronizing components separate from the other modulation components, means for utilizing said control-bias voltage for maintaining the intensity of the signal output of said receiver within a relatively narrow range for a wide range of received signal input intensities, and means for utilizing said synchronizing components to synchronize the operation of the receiver.
  • a television receiver adapted to reproduce a signal-carrier wave having combined lightmodulation components and synchronizing-modulation components having amplitude values outside the amplitude range of the light components
  • said Wave having a wide range of signal-input intensities comprising a main signal-translating channel, a separate control signal translating channel, a rectifying device, means included in said control channel for deriving from a Signal translated by said receiver a signal having components representing the peaks cf said synchronizing-modulation components at a level corresponding to the unmodulated peaks of said ponents having amplitude values outside the amplitude range of the light-modulation components, comprising, a diode rectifier, means for deriving from a signal translated by said receiver a signal having components representing the peaks of said synchronizing-modulation components at a level corresponding to the unmodu lated peaks of said carrier wave, means for applying said derived signal to said device including means for maintaining said peaks at said level to derive a control-bias voltage proportional to the intensity of the carrier wave and independent of its light-modulation components, impedance means in circuit with said rectiier for deriving from said signal synchronizing components separate from the other modul
  • a television receiver adapted to reproduce a signal-carrier Wave having combined lightmodulation and synchronizing-modulation cornponents having amplitude values outside the amplitude range of the light-modulation comnents, comprising a diode rectier having a load circuit including a resistor and condenser connected in parallel and providing a time constant circuit, means for deriving from a signal translated by said receiver a signal having components representing the peaks of said synchronizing-modulation components at a level corresponding to the unmodulated peaks of said carrier Wave, means for applying said derived signal to said device including means for maintaining said peaks at said level to derive a controlbias voltage proportional to the intensity of the carrier wave and independent of its light-modulation components, a" resistor connected in series with said diode and said condenser for deriving from said signal synchronizing components separate from the other modulation components, means for utilizing said control-bias voltage for controlling an operating characteristic of said receiver, and means for utilizing said separated synchronizing components for
  • a television receiver adapted to reproduce a signal-carrier wave having' combined lightmodulation and synchronizing-modulation components having amplitude values outside the amplitude range 'of the light-modulation components, comprising a main signal-translating channel, a separate control signal-translating lation components at a level corresponding to the' unmodulated peaks of said carrier wave to said channels, a diode rectifier included in said control channel, means for applying said signal applied to said control channel to said device including means for maintaining said peaks atsaid level to derive a control-bias voltage proportiona1 ⁇ to the peak value of said signal-carrier wave on one side of its axis, impedance means in circuit with said rectier' for deriving from said signal synchronizing components separate from thje other modulation components.
  • means for utilizing said control-bias voltage for controlling an operating characteristic yo1 the receiver, andFV means for utilizing said separated synchronizing components for synchronizing the operation of the receiver.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Details Of Television Scanning (AREA)
  • Optical Communication System (AREA)
US233371A 1938-10-05 1938-10-05 Television synchronizing and control system Expired - Lifetime US2240507A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US233371A US2240507A (en) 1938-10-05 1938-10-05 Television synchronizing and control system
GB25996/39A GB541005A (en) 1938-10-05 1939-09-16 Television synchronizing and control system
DEH5432D DE966059C (de) 1938-10-05 1939-09-27 Schaltung zur Abtrennung der Synchronisierimpulse eines Fernsehsignals
BE436528D BE436528A (en)) 1938-10-05 1939-09-29
FR863095D FR863095A (fr) 1938-10-05 1940-01-27 Système de commande et de synchronisation en télévision

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US233371A US2240507A (en) 1938-10-05 1938-10-05 Television synchronizing and control system

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US2240507A true US2240507A (en) 1941-05-06

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US233371A Expired - Lifetime US2240507A (en) 1938-10-05 1938-10-05 Television synchronizing and control system

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US (1) US2240507A (en))
BE (1) BE436528A (en))
DE (1) DE966059C (en))
FR (1) FR863095A (en))
GB (1) GB541005A (en))

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2498839A (en) * 1947-10-25 1950-02-28 Philco Corp Double time constant automatic volume control circuit
US2566763A (en) * 1946-09-28 1951-09-04 Motorola Inc Synchronizing signal separator and keyed automatic gain control
DE959113C (de) * 1951-06-16 1957-02-28 Interessengemeinschaft Fuer Ru Schaltung zur Abtrennung von Synchronisierimpulsen aus einem Signalgemisch mit Hilfe einer vorgespannten Diode

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL48119C (en)) * 1930-05-21
BE407481A (en)) * 1934-01-25
AT143054B (de) * 1934-10-08 1935-10-10 Karl Dipl Pulvari-Pulvermacher Schaltanordnung zum störungsfreien Empfang elektrischer Schwingungen.
AT150571B (de) * 1935-09-21 1937-09-10 Telefunken Gmbh Schaltungsanordnung für Fernsehzwecke.
DE693115C (de) * 1936-04-10 1940-07-02 Telefunken Gmbh er von atmosphaerischen oder aehnlichen Stoerungen herruehrenden Knackgeraeusche

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2566763A (en) * 1946-09-28 1951-09-04 Motorola Inc Synchronizing signal separator and keyed automatic gain control
US2498839A (en) * 1947-10-25 1950-02-28 Philco Corp Double time constant automatic volume control circuit
DE959113C (de) * 1951-06-16 1957-02-28 Interessengemeinschaft Fuer Ru Schaltung zur Abtrennung von Synchronisierimpulsen aus einem Signalgemisch mit Hilfe einer vorgespannten Diode

Also Published As

Publication number Publication date
GB541005A (en) 1941-11-10
FR863095A (fr) 1941-03-22
DE966059C (de) 1957-07-04
BE436528A (en)) 1940-01-31

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