US2230284A

US2230284A - Television synchronizing system

Info

Publication number: US2230284A
Application number: US177697A
Authority: US
Inventors: Cawein Madison
Original assignee: Hazeltine Corp
Current assignee: BAE Systems Aerospace Inc
Priority date: 1937-12-02
Filing date: 1937-12-02
Publication date: 1941-02-04
Anticipated expiration: 1958-02-04

Description

l Feb. 4, 1941'. m.v cAwElN y l TELEVISION SYNCHRONIZI-HG SYSTEM Filed Dec. 2, 1951 3 Shets-Sheet 1 ATTORN EY Feb. 4, 1941. M. cAwElN TELEVISION SYNGHRONIZI'HG SYSTEH 5 Shoots-Sheet 2..

y Fi;ed Dec. 2, 1937 ATTORN EY Patented Feb. 4, 1941 TELEVISION SYNCHRONIZING SYSTEM Madison Cawein. Mal'iliasect,v N. Y., assignor to Haxeltine Corporation, a corporation of Dela- `ware Application December 2, 1937. SerialfNo. 177,697 19 Claims. (Cl. P18-6.8)

This invention relates to television systems and, more particularly, to signal-generating and receiving apparatus for use in such systems. The invention is especiallyv concerned with the provision of an improved method of, and means for, effecting synchronization of television scanning apparatus.

In accordance with present television practice, there is developed and transmitted a signal which 19 comprises a carrier, modulated during successive intervals or trace periods by video-frequency components representative of the light and shade values of an image being transmitted. During retrace intervals between the trace periods, the l carrier is modulated by synchronizing impulses or components which correspond to the initiations of successive lines and elds in the scanning ofthe image. At the receiver, a beam is so deected as to scan and illuminate a target in a 20 series of parallel lines. The video-frequency components of the received signal are utilized to control the intensity oi the beam. The lineand field-scanning synchronizing components are separated from the video-frequency components and from each other and utilized to synchronize the operation of the receiver scanning apparatus with the similar scanning apparatus utilized at the transmitter in developing the signal. The transmitted image is thereby reproduced on the target of the receiver.

In scanning of the interlaced type, the line and ileld vfrequencies are so related that successive fields are staggered, the lines of one field falling between or interlacing those of a preced- 85 ing field, and, due to persistence of vision, the optical effect produced is as though each frame or group of ilelds comprised a multiple of the actual number of lines scanned per field and the frame-scanning frequency equalled the eldscanning frequency.

Various types of .carrier-signal modulation, scanning, and synchronizing methods and apparatus heretofore have been proposed. The type of synchronizing signal required ordinarily depends upon the type of Video signal employed and the type of scanning utilized. For example, in certain systems, negative modulation is employed, that is, a decrease in carrier amplitude corresponds to an increase in illumination, while in other systems positive modulation is utilized,

in which an increase in carrier amplitude corresponds to an increase in illumination. The synchronizing components of the signals used in these systems ordinarily have amplitude values ll outside oi.' the` range ofthe video-frequency comfield-synchronizing impulses must occur between line-synchronizing impulses. In order that the lineand frame-synchronizing impulses may be successfully separated from the video-frequency components and from each other for utilization, 10 various types of synchronizing signals and separating apparatus have been proposed, for example, signals in which the held-synchronizing impulses are of greater height or of longer duration than the line-synchronizing impulses and sepa- 15 rating apparatus comprising amplitude-discriminating or integrating circuits. Such arrangements, however, have been found to be subject to various objections, such as being unstable, requiring an undesirably large portion of the total 20 carrier amplitude, and involving relatively complicated 'separating apparatus.

It is an object of the present invention, therefore, to provide an improved method of, and means for, effecting scanning synchronization in 25 a television system which will overcome the above-mentioned disadvantages of the prior art.

In accordance with the present invention, there is provided a television synchronizing system which comprises means for developing and transmitting a composite synchronizing signal including line-synchronizing impulses each having an edge of a predetermined slope and eldsynchronizing impulses each having an edge of a predetermined slope steeper than that of the said edge oi' the line-synchronizing impulses.v Means are further provided for receiving and utilizing the composite signal which preferably comprises a single translating path for said composite synchronizing signal including a single 40 slope-responsive device for eiectively separating the line-synchronizing and eld synchronizing impulses. Line-synchronizing and eld-synchronizing circuits are coupled to the abovementioned single path for individual control by 45 the effectively separated line-synchronizing and field-synchronizing pulses, respectively.

Preferably, the lineand frame-synchronizing impulses are of the same amplitude and prefer-l ably are impressed as modulation upon a trans- 5o mitted carrier which is positively modulated so that they appear as decreases in the carrier amplitude which preferably approaches zero during the synchronizing impulse peaks, While video- Irequency components representing increases in u illumination arerepresented by increases in carrier amplitude.

In the preferred embodiment of the invention, the line-synchronizing impulses are of spaced parabolic-impulse form, while the field-synchronizing impulses are of rectangularor peakedimpulse form such that their leading edges or wave fronts are substantially steeper than the leading edges or wave fronts of the line-synchronizing impulses, the lineand frame-synchronizing impulses being separately developed and combined to develop the composite signal. Diierentiating apparatus is provided at the receiver to derive from the composite synchronizing signal,'a synchronizing signal in which each of the synchronizing impulses appears as a double pulse, one pulse of each of the double frame-synchronizing impulses being of substantially greater amplitude than that of any of the other pulses' developed. The lineand frame-synchronizing impulses are thus effectively separated and may be utilized individually to control 'separate lineand frame-scanning apparatus.

For a better understanding of the Iinvention, together with other and' further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed outin the appended claims.

In the accompanying drawings, Fig. 1 is a circuit diagram, partially schematic, of a complete television transmitting apparatus embodying the invention; Fig. 2 is a circuit diagram, partially schematic, of a complete television receiving system embodying the invention and Figs. 3-9, inclusive, are curves illustrating the Wave forms of periodic voltage Waves developed at various points in the systems of Figs. 1 and 2 to aid in the understanding of the invention.

Referring now more 'particularly to Fig. 1 of the drawings, there is illustrated a television transmitting system comprising a signal generator I0, which may be of a conventional design including the usual cathode-ray signal-generating tube and scanning elements. For developing scanning voltages or currents for the generator I0, there are provided a line-frequency saw-tooth wave generator II and a frame-frequency sawtooth wave generator I2, the out-put circuits of these generators being connected to the scanning elements of the signal' generator Il! in the usual manner. In order to block out the cathode ray of the generator III during the retrace scanning periods, there is provided a block-out wave generator I3 having its output circuit suitably connected to the lsignal generator I0. For providing impulses to suppress undesirable signal impulses during retrace scanning periods and to ensure proper form of themodulation signal to be developed, there is provided a pedestal-impulse generator I4 and, in order to develop a, scanning synchronizing signal in accordance with the present invention, there is provided synchronizing signal-generating apparatus indicated vgenerally at I5 and hereinafter more fully described.

For the purpose of synchronizing the generators II-III, inclusive, and the apparatus I5, there l is provided a timing-impulse generator I6 having of periodic voltage, for example, to the powerl supply.circuit or to the synchronizing voltage source of a-motlon picture mechanism, where l chronizing signal-generating apparatus I5 is coupled to the video-frequency amplifier 20.

Neglecting for the moment the details of the synchronizing signal-generating apparatus I5, the system just described comprises the elements of a television transmitting system of conventional design and, the various parts thereof which are illustrated schematically being of any wellknown construction, a detailed description of the general system and its operation is unnecessary. Briefly, however, the image of a scene to be transmitted is focused on the target of the signal generator I0 in which tube a cathode ray is developed, focused, and accelerated toward the target in the usual manner. Scanning or deecting currents or voltages developed by the generators Il and I2 are applied to the scanning elements of the generator I0 to provide electric elds which serve to deiect the cathode ray horizontally and vertically, thereby to scan successive series of parallel lines, or elds, upon the target. The deflecting currentsor voltages and, hence, the scanning iields, are of well-known saw-tooth wave form, providing a relatively slow linear trace and rapid retrace. The number of lines per eld is determined by the relative values of linescanning and held-scanning frequencies. The linescanning frequency is preferably a fractional multiple of the field-scanning frequency so that the successive elds of parallel lines traced on the target are interlaced .in the well-known manner. The line-scanning and frame-scanning frequencies may, for example, be 13,230 and 60 cycles, respectively.

Block-out impulses developed by the generator I3 are applied to the control electrode of thecathode-ray tube to suppress or block out the beam during retrace portions of the scanning cycles, while pedestal impulses developed by the generator I4 are applied to the amplifier I9 to modify the shape of the resultant video-frequency wave developed to aid in separating the linescanning and frame-scanning synchronizing impulses at the receiver. The synchronizing-imi pulse signal developed by the apparatus I5 is applied to the modulation amplier 20, while the timing impulses developed by the generator I6 are applied to the generators II-I4, inclusive, and the apparatus I5vto lock these generators and apparatus in synchronism.

The photosensitive elements of the targetin the cathode-ray tube of the generator I4 being electricallyaffected tol an extentv dependent upon the varying values of light and shade at the corresponding incremental areas of the image fo.

cused thereon, as the cathode rayv scans the target, a video-frequency voltage of correspondingly varying amplitude is developed in the output circuit of the generator I0 and applied to the videofrequency amplifier I8, wherein this voltage is amplified and from which it is translated to'the amplifier I 9. Here the video-frequency voltage is further amplified and mixed with pedestal impulses supplied from the generator I 4. The amso v.

' plified mixed voltages in the output circuit of the amplifier Il are thereupon applied to the ampli- `ner 20, whereinv they are further amplied and mixed with the synchronizing-impulse signal supplied from the apparatus Il. .The modulation voltages are thereupon supplied to the modulator 2|-, wherein they are so impressed upon the carrier wave generated by the oscillator 22 as to develop a positively modulated carrier, such as described above. The resultant modulated-carrier signal is delivered to the power amplifier 23 for amplification and is thereafter impressed upon the antenna system 2,4, 2l to be broadcast.

Referring now more particularly to the apparatus i5 embodying the presentinvention, for the purpose of developing line-synchronizing signal impulses of the desired Wave form, there is connected in cascade a saw-tooth wave generator 23, an integrating circuit or parabolic wave generator 21, and a limiter andampliiler 23. The generator 23 may comprise any suitable signal-generating apparatus of conventional type adapted to develop a periodic wave of the desired line-scanning frequency, for example, 13,230 cycles per second for interlaced scanning, and of saw-tooth wave form, as indicated immediately below the generator 26. The input circuit of this generator is coupled to the timing generator I6 for synchronization.

The integrating circuit or parabolic-impulse wave generator 21 may comprise a pentode vacuum tube 29 having its input circuit connected to the generator 2B by way of a coupling condenser 30 and leak resistor 3| and ircluding in its anode circuit a condenser 32 and a feed resistor 33. Operating potentials are applied to the grid by way of resistor 3| directly to the screen, and to the anode by way of' the resistor 33 from suitable sources, indicated at C, +Sc, and +B, respectively. With suitable operating potentials applied to the electrodes of such a tube, it has a \high internal impedance so that the current in its output circuit is of substantially the same wave form as the voltage applied to its input circuit, the wave form preferably being of sawtooth type. 'I'he current flowing through condenser 32 is integrated thereby to develop thereacross a voltage wave of a second predetermined wave form which is the integral of the wave form of `the voltage applied to the input of tube 29, this wave form beingyin the preferred case, of parabolic type. More particularly, with a voltage wave of saw-tooth wave form applied to the input circuit of tube 29, a voltage wave of parabolic wave form is developed across its output circuit, as indicated inmediately below the generator 21. The input of the limiter and amplifier 28 is connected across the condenser 32 and may comprise any suitable conventional circuit arrangement including, for example, a two-stage resistance coupled amplifier so biased as to cut ofi a predetermined portion of the wave applied thereto, thereby to limit the translated wave to obtain pulses of parabolic-impulse wave form and to develop in its output circuit a periodic line synchronizing wave comprising such spaced parabolic impulses, as indicated below the limiter and amplifier 28. f

For the purpose of developing held-synchronizing impulses, there is provided a periodic wave generator 34 which may be of any suitable conventional construction adapted to develop a periodic-impulse wave of the desired eld-scanning frequency, for example, 60 cycles, the impulses of which are of rectangular .peaked-impulse wave form, as indicated immediately below this generator and having leading edges of steeper slope than the leading edges of the linesynchronizing impulses. The vinput circuit of the generator 34 is coupled to the timing generator i3 -for synchronization, while its output circuit is coupled to a limiter and amplifier 3l. Dre!- erably a single-stage unit which may otherwise be similar in construction and 'operation to the Hunter and amplifier 23 and effective to cut of! all but a desired portion of fthe impulses generated by the unit 34.; vThe output circuits of the limiters and

amplifiers

23 and 35 are coupled toa mixing amplifier 3 3 to combine the linesynchronizing and field-synchronizing impulses, while the output circuit of the amplier 33 is, in turn, coupled to the video-frequency amplier 2li, as explained above.

In the operation of the synchronizing signalgenerating apparatus I3, the generator 23, synchronized by the timing generator i6, develops a `periodic saw-tooth wave of line-scanning frequency and delivers this wave to the generator 21, wherein a parabolic wave of the same frequency vis developed, as explained above. The latter wave is impressed upon the limiter and amplifier 28, whereby, by virtue of its limiting or cutof and amplifying action, a periodic linesynchronizing wave comprising spaced parabolic impulses is developed. I'he generator 34, synchronized by the timing generator i6, develops a periodic wave of rectangularor peakedimpulse wave form and of the desired fieldscanning frequency and this wave is applied to the limiter and amplifier 35, which operates to cut lofi' and -amplify the impulses, thereby to develop a field-synchronizing wave of rectangularor peaked-impulse wave form, the impulses of which have leading edges which are substantially steeper than the corresponding edges of the line-synchronizing impulses. The line-synchronizlng and field-synchronizing impulses are applied to the mixing amplifier 33 and combined therein to produce a composite lineand framesynchronizing wave, which is', inl turn, applied to the amplifier 20, as mentioned above. The significance of the particular shapes of the synchronizing impulses just described will be better understood in connection with the following description of receiving apparatus embodying the present invention and the general explanation of the system in connection with the curves of Figs. 39, inclusive. l

Referring more particularly to Fig. 2, the system there illustrated comprises a television receiver of the superheterodyne type including an antenna system 31, 33 connected to a radiofrequency amplifier 39 to which there is connected in cascade, in the order named, an oscillater-modulator 40, an intermediate-frequency .amplifier 4|, a detector 42, a video-frequency amplifier 43, and a cathode-ray signal-reproducrator 46 being so biased as to -be responsive only to impulses of relatively great amplitude, that is, greater than the amplitude of the impulses by which the synchronizing circuit ofthe generator 45 is operated. The stages or units 89--45, in-

elusive; mayV all be of conventional well-known construction, so that'detailed illustrations and descriptions thereof are deemed unnecessary herein.

vReferring briefly, however, to the operation of the receiving system,A television signals transmitted, ior example, from a system such as shown in Fig. 1 and intercepted by the antenna circuit 31. 38 are selected and amplied in the radiofrequency ampliiier 39 and supplied to the 'oscillater-modulator 48, wherein they are converted to intermediate-frequency signals which, in turn,

are selectively ampliiled in the intermediate-l frequency amplifier 4l and delivered'to the detector 42. 'I'he modulation components of the signal are derived by the detector 42 and are supplied to the video-frequency ampliiler V43, wherein they are ampliied and from which they are supplied in the usual manner to a brilliancycontrol electrode of the cathode-ray tube 44. The intensity of the electron lbeam of the tube 44 is thus modulated or controlled in accordance with the video-frequency voltages impressed upon the control electrode of the tube in the usual manner.

The modulation components from detector 42/ are also supplied to the apparatus 41, wherein .the synchronizing components 'are separated from the video-frequency components and the lineand frame-synchronizing components are effectively separated from each other and apn plied to the control circuits of the generators 45 and 4B, as will hereinafter be further explained. Saw-tooth current or voltage, scanning waves are generated in the lineand frame-frequencygenerators 45 and 45, which are controlled by synchronizing voltage impulses supplied from the apparatus 41. 'Ihe scanning waves are applied to the scanning elements of the cathode-ray tube 44 to produce electric scanning fields, thereby to deflect the intensitymodulated ray vertically and horizontally so as to trace successive interlaced flelds of parallel lines on the screen of the tube. to reproduce the transmitted picture. y

Referring now more particularly to the p0rtion of the system of Fig. 2 embodying the present invention, for the purpose of effectively separating the lineand frame-synchronizing impulses so that they may be applied to the generators 45 and 46 free vfrom mutual interference, the apparatus 41 `comprises a pentode tube 48 having its control grid coupled to the output of the detector 42 by way of a suitable coupling condenser 49 and leak resistor 50. A substantially ideal inductance element 5I is included in the anode circuit of the tube 48, and operating grid of the tube 48 in such polarity and with the control grid so biased that the video-frequency component of the signal is out ofi vor suppressed :ammassi and only the synchronizing impulses appear in its output circuit. The tube 48 operates as a conventional pentode ampliiler having highinternal impedance., so that -a periodic current wave flows in its anode circuit. comprising the lineand trame-synchronizing impulses of the same wave forms as those or the voltage wave impressed on its input circuit, that is, corresponding to the synchronizing wave developed at the transmitter. This currentr is dierentiated or translated as an infinitesimal calculus function of itself bythe inductance element 5l so that a periodic voltage wave is developed there'across comprising impulses., the form of which is dependent upon the shapes or wave forms of the Vapplied impulse, particularly the slopes of coi-,

responding edges such as the leading edges thereof. The diierential of both the parabolic line-synchronizing impulse and the peaked eldsynchronizing impulse developed across inductance 5l is a double impulse. By virtue of the fact that the leading edges of the .held-synchronizing impulses are or steeper slope than the leading edges of the line-synchronizing impulses, the rst pulse or half of each double eld-synchronizingrimpulse is relativelyy narrow and of substantially greater amplitude than any of the' Aple amplitude separation, since their pulses of one polarity are characterized by substantial difl ferences in amplitude.' v

As explained above, the synchronizing circuits of the generators 45 and 45 ar'e adapted to be controlled by negative impulses and the synchronizing circuit of the generator 46 is so biased as to be relatively insensitive, or responsive only to the impulses of relatively large amplitude,

such as the field-synchronizing impulses. The synchronizing impulses developed across the inductance element 5|, therefore, may be applied directly'to the generators 45 and 46.` The synchronizing circuit of the generator 45 is controlled solely by the held-synchronizing impulses and entirely without interruption from the impulses of the other type. While the negative pulses derived from the ileld-synchronizing impulses may -be of a character to control the line.

scanning generator 45, these pulses occur either substantially simultaneously with the negative pulses derived from the line-synchronizing impulse or substantially midway adjacent ones of said pulses.. in either of which cases -they do not ailect the operation of the line-scanning generator 45 for more than one line cycle.

'I'he general operation of both the transmit- 'tingand receiving systems, described above, mayv be readily explained by reference to the curves o! Figs. 3-9, inclusive, which illustrate the wave forms of waves developedat various points in the systems of Figs. 1 and 2, time being represented by the abscissae and relative amplitude by the ordinates in each instance. 'l The curve of Fig. 3 represents the preferred wave form of the frame-l synchronizing impulse wave developed in the output circuit of the limiter 35 in the system of Fig. 1. It will be noted that the impulse of this curve is characterized by a leading edge or relatively steep slope and a trailing edge of relatively gradual slope. The curves of Figs. 4 and 5 represent thefpreierred wave forms of the periodic line-synchronizing impulses developed in the output circuit of the limiter and ampliiler 28 as they appear during alternate held-scanning cycles; by virtue of the staggering of their impulses, resulting from the relative lineand iieldscanning frequencies, interlaced scanning is obtained.A In a preferred arrangement, for example, these frequencies may, as stated above, be 13,230 and 60 cycles, respectively.

'Ihe line-synchronizing impulses being of parabolie wave form their leading edges have relatively gradual slopes. After these lineand frame-synchronizing impulseshave been combined in the mixing amplifier 38 and the composite synchronizing signal thus derived has been further combined in the amplifier with the video-frequency signal, the combined signal, appearing in the output circuit of the amplifier 2B, is of a form such as shown by the curves of Figs. 6 and 7, where, as in Figs. 4 and 5, the two curves represent the signal as it appears during alternate field-scanning cycles, the lineand iieldsynchronizing impulses being readily distinguishable from each other by their different shapes;

' more particularly by the diflerences in slope oi their leading edges.

'Ihe curves of Figs. 6 and '1 also represent the wave form of the signal developed in the output circuit of the detector 42 o! the receiver of Fig. 2.' 'Ihe video-frequency components of this signal are removed, as explainedabove, from the output circuit of tube 48 -by virtue of the bias on its control grid. The synchronizing signal current Aappearing in the output circuit of this tube is,

therefore, of the form shown by the portions of these curves below the dotted line. Since this current is differentiated by the inductance element 5I, the resultant `voltage developed across this element is `of the form shown by the curves ot Fig. 8 and 9 where, as explained above, the first half or pulse of each of the double iieldsynchronizing impulses is of relatively greater amplitude than that of any of the other pulses developed.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modications may be made therein without departing from the invention, and itis. therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A television synchronizing system comprising means for developing and transmitting a composite synchronizing signal including line-synchronizing impulses each having an edge of aY synchronizing and field-synchronizing circuits coupled to said single path for individual control by said effectively separated line-synchropredetermined slope and field-synchronizing im-` pulses each having an edge of a predetermined slope steeper than that of said edge oi said linesynchronizing impulses. means for receiving and utilizing sai'd composite signal comprising a single translating path for said composite synchronizing n signal including a single device for differentiating said synchronizing impulses for effectively separating said line-synchronizing and field-synchronizing impulses, and line-synchronizing and fieldsynchronizing circuits coupled .to said single .path

for individual control by said eiiectively separated line-synchronizing and held-synchronizing impulses. respectively.

3. Atelevision synchronizing system compris-v ing means for developing and transmitting a composite synchronizing signal including line-synchronizing impulses and ileld-synchronizing impulses having corresponding edges with diierent pled to said single path for individual control by said eil'ectively separated line-synchronizing and field-synchronizing impulses, respectively.

4. A television synchronizing system comprising means ior developing and transmitting a composite synchronizing signal including line-synchronizing impulses and eld-synchronizing impulses having corresponding edges with different slopes, the slopes oi' said edges of said field-synchronizing impulses being steeper than the slopes of said edges o! said line-synchronizing impulses and means-for receiving and utilizing said comf,

posite signal comprising a single transl-ating path 'for lsaid composite synchronizing signal including a single device for differentiating said synchronizing impulses for eiectively separating said line-4 synchronizing and eld-synchronizing impulses and line-synchronizing and eld-synchronizing circuits coupled to said differentiating means.

5. A television synchronizing system comprising means for developing and transmitting a composite synchronizing signal including line-synchronizing impulses having leading edges of a predetermined slope and ield-synchronizing impulses having leading edges of a steeper predetermined slope, means for receiving and u-tilizing said composite signal comprising a single translating path for said composite synchronizing signal including a single device responsive to the slopes of the leading edges of said synchronizing impulses for effectively separating said line-synchronizing and held-synchronizing impulses, and line-synchronizing and `held-synchronizing circuits coupled to said single path for individual control by said effectively separated line-synchronizing and field-synchronizing impulses, respectively.

6. A television synchronizing system comprising means for developing line-synchronizing impulses of a ypredetermined wave form, means for @developing heid-synchronizing impulses of a diflferent predetermined wave form such that predetermined edges of said held-synchronizing iinpulses have steeper slopes than corresponding `edges of said line-synchronizing impulses, and

means for combining said line-synchronizing and field-synchronizing i impulses vrto develop .a y coniposite synchronizingfsignal.

"7. A television synchronizing system compris ing means for developing line-synchronizing impulses, each havingan edge of'a predetermined syiichronizing impulses to develop a Acomposite synchronizing signal.

8. A television synchronizing system comprising means for developing line-synchronizing impulses having leading edges of a predetermined slope, means for developing field-synchronizing impulses, each having a leading edge correspondl ing to said leading edges of sard une-synchroniz- `in-g impulses and of a predetermined slope steeper than that of the leading edges of said line-synchronizing impulses, and means for combining said synchronizing impulses of both of said frequencies -to develop a composite scanning synchronizing signal.

9. A television synchronizing system comprising means for developing line-synchronizing impulses of .parabolic wave form, means for developing field-synchronizing impulses of peaked wave form having the leading edges correspon-ding to leading edges of said line-synchronizing impulses and of steeper slope than that of the leading edges of said line-synchronizing impulses, and means for combining said line-synchronizing and field-synchronizing impulses to develop a composite synchronizing signal.

.10. A television synchronizing system comprising line-synchronizing impulse generating meansl including means for developing a periodic sawtooth wave'of a predetermined line-scanning frequency, means for integrating' said wave to develop a. parabolic-impulse wave of said predetermined frequency, means for limiting said parabolic wave to derive a spaced parabolic-impulse wave of said predetermined frequency, held-synchronizing impulse generating means including means vfor developing a periodic-impulse wave of a predetermined field-scanning frequency the impulses of which have relatively steep leading edges, and means for combining said parabolicimpulse wave and said held-synchronizing impulse waves to develop a composite synchronizing signal.v

11. A television synchronizing system comprising means for developing line-synchronizing i-mpulses of spaced parabolic-impulse wave form, means for developing held-synchronizing impulses including generating means :for developing a periodic wave of rectangular :peaked-impulse wave form and means forlimiting said last-mentioned Wave .to derive field-synchronizing waves having impulses with relatively steep leading edges, and means for combining said last-mentioned wave and said spaced parabolic-impulse* 2,'|2so,2e4

cuits coupled to said path for individual control by said effectively separated line-synchronizing and field-synchronizing impulses, respectively.

13. A television synchronizing system adapted for the reception of a composite scanning synchronizing signal including line-synchronizing and field-synchronizing impulses of substantially equal ampli-tudes but of diiferent -predetermined wave forms', comprising a single translating ,path for said composite synchronizing signal including a single device for deriving as an infinitesimal calculus function of said composite signal a synchronizing signal including line-synchronizing and field-,synchronizing impulses of different amplitudes, and separate line-scanning and neidscanning synchronizing circuits coupled .to said path for individual control by said line-synchro- .nizing and field-synchronizing impulses of different amplitude, respectively.

14. A television synchronizing system adapted for the reception of a synchronizing signal including line-synchronizing and field-synchronizing impulses having different predetermined wave forms, comprising a single, translating path for said composite synchronizing signal including a single device for diierentiating said signal eiIectively to separate saidV line-synchronizing .and field-synchronizing impulses, and separate linescanning and field-scanning synchronizing circuits coupled to said path for individual control by said eiectively separated line-synchronizing and field-synchronizing impulses, respectively.

15. A television synchronizing system adapted for the reception of a composite scanning synchronizingy signal including` line-synchronizing impulses and field-synchronizing impulses having corresponding edges with different slopes comprising a single translating path for said composite synchronizing signal including a single device responsive to the slopes of 4the corresponding edges of said synchronizing impulses for effectdvely separating said line-synchronizing and field-synchronizing impulses, and separate linescanning'and held-scanning synchronizing circuits coupled to said path for individual control by said effectively separated line-synchronizing and field-synchronizing impulses, respectively.

16. Ay television synchronizing system adapted for the reception of a compositescanning synchronizing signal including line-synchronizing impulses and field-synchronizingimpulses having leading edges of dlierent predetermined slope, comprising a single translating path for' said composite synchronizing signal including a. single device responsive to the slopes of the leading edges of said synchronizing impulses for effectively separating said line-synchronizing and nem-synchronizing impulses, and separate linescanning and field-scanning synchronizing circuits .coupled to said path for individual control by said effectively separated line-synchronizing and eld-synchronizing impulses, respectively.

' Y 17. A television synchronizing system adapted forthe reception of a .composite scanning synchronizing signal including line-synchronizing impulses and field-synchronizing impulses having leading edges of diierent predetermined slopes,"

comprising a single translating path for said comfield-synchronizing impulses, andseparate linescanning and e'ld-scanning synchronizing circuits coupled .to said path for individual control masones composite synchronizing signal including linesynchronizing impulses of a predetermined shape and field-synchronizing impulses of a predetermined shape difierent from the shape of said line- Y synchronizing impulses. and means i'or receiving and utilizing said composite signal comprising a single translating path for said composite synchronizing signal including a single slope-responsive device Ior reffectively separating said linesynchronizing and eld-synchronizing impulses, and line-synchronizing and field-synchronizing circuits adapted to be excited by impulses of the same polarity directly coupled to said single path.

19. A television synchronizing system adapted for the reception of a composite scanning synchronizing signal including line-synchronizing and eld-synchronizing impulses of different predetermined wave forms, comprising -a single translating path for said composite synchronizing signal including a single slope-responsive device for etectively separating said line-synchronizing and held-synchronizing impulses, and separate line-scanning and held-scanning synchronizing circuits adapted to be excited by impulses ort .the same polarity coupled to said path for individual control by said effectively separated line-synchronizing and field-synchronizing impulses, respectively.

MADISON CAWEIN.