US2265848A - Synchronizing-signal generator - Google Patents

Description

H. M. LEWBS SYNCHRQNIZING-SIGNAL GENERATOR 2 Sheets-Shee t 1 Filed July 27, 1940 FIG. I.

INVENTOR HAROLD m. LEWIS AORNEY Patented Dec. 9, 1941 UNITED 4 STATES PATENT OFFICE ;f

smcmaomm s rz sn air-Neuron I ware . Harold M. Lewis, 'Great'Neck, N.Y., assignor to I Baseltine Corporation, a corporation of Dela- Application July 2'1, 1940, Serial No. 347,817 13 Claims; (01. ire-7.2)

This invention relates to synchronizing-signal generators for television transmitters and, while the generator of the invention is of general utility, it is particularly useful in a portable television transmitter because of the relatively small amount of apparatus comprised in the generator.

It is conventional to develop at a television transmitter a composite synchronizing signal includingiine-synchronizing components and fieldsynchronizing components for transmission with the video-signal components on a common carrier wave. Such a composite signal has conveniently been developed by the artifice of generating each of the required synchronizing-signal components in vacuum-tube circuits and combining the generatedcomponents in other vacuumtube circuits to develop a composite synchronizing signal. Very, complicated circuit arrangements have been provided for the purpose. Thus, it has been customary to provide a "timer chain" which is synchronized from the alternating current source for the transmitter and which develops oscillations of suitable frequencies for developing and keying the required pulses into the composite synchronizing signal. Also, the composite synchronizing signals generally utilized are suitable for effecting multiple-interlaced scanning, and such systems require synchronizing-signal components during one field period which are dliferent from those during a succeeding field period. Thus, the feature of multiple interlace in a television system also adds materially to the complexity of the apparatus required for generating the required type of composite synchronizing signal. Furthermore, the composite synchronizing signals conventionally utilized for multiple-interlaced scanning systems comprise line-doubling components in thesignal.

preceding and succeeding the field-synchronizing components of the signal. These linedoubling pulses have been provided in the same manner described above, rendering the apparatus required still more complicated.'-

Furthermore, the signal components of a com-- posite synchronizing signal, developed'in the manner described above, may require consider one or more of the above-mentioned disadvantages of prior art generators.

In accordance with the invention, a nizing-signal generator for a television transmitter, adapted to generate a synchronizing signal for use in a multiple-interlaced scanning system in which synchronizing components thereof during one field periodare different from those during a succeeding field period. comprises a device .including a plurality of radially-displaced circumferential patterns having predetermined angular portions thereof corresponding to predeter-j mined portions of the signal to be generated.

Means are provided for continuously scanning I the patterns in successive substantially circumferential paths having predetermined angular portions radially displaced on the device and corresponding to the dissimilarity of the field periods oi the desired synchronizing Bisnal to develop an electrical effect corresponding to the pattern scanned.

In accordance with a preferred embodiment of the invention, the above-mentioned portions of the circumferential patterns correspond. rapestively; to the portions of the signal to be generated including the line-synchronizing components; which line-synchronizing components of one .field period are substantially differently spaced with reference to the field-synchronizing components than are the line-synchronizing 85 portion corresponding to the field-synchronizing components to be generated and the other comprises a portion corresponding tothe line-synchronizing components to be generated. Inaccordance with a preferred modification of this 4 last-mentioned preferred embodiment of the invention, the pattern corresponding to the fieldsynchronizing components comprises substantially all of one of theabove-ment'ioned circumable shaping in order to procure" satisfactory" operation. It is, therefore, also desirable to provide a synchronizing-signal generator in which the individual components are of a uniform and precisely determined wave form.

It is an object of the invention, therefore, to

provide improved television synchronizingsignal generator which is effective to eliminate the appended claim 7 ferential patterns and another of the circumferential patterns, corresponding to the linesynchronizing components to be generated, is I scanned a plurality of times for each s'cansion of the pattern corresponding to the field-scanning period.

For a better understanding of the present invention, 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 out in synchroi Fig. 1 of the drawings is a circuit diagram, partly schematic, of a complete television signalgenerating and -transmitting station including a synchronizing-signal generator in accordance with the present invention; Fig. 2 is a detail illustrationpf a portion of the synchronizing-signal generator of Fig. 1; Figs. 3a and 3b are graphs .of wave forms developed by a modification of the generator of Fig. 1 while Fig. 3c is a detail illus tration of a modification of the generator of Fig. 1 for generating the wave forms of Figs. 3a

and 3b; Fig. 54 is a schematic diagram of a synchronizing-signal generator in accordance with the present invention which comprises a scanning disc; Fig. 5 is a circuit diagram of a further modification of. the synchronizing-signal generator of Fig. 1; while Fig. 6 illustrates in detail a portion of the modified synchronizing-signal generator of Fig. 5.

Referring now more particularly to the drawings, in Fig. 1 there is shown a complete television signal transmitter in accordance with the invention. This transmitter comprises a conventional signal-generating and-transmitting circuit adapted to be synchronized by, and to transmit a composite synchronizing signal developed by. a synchronizing-signal generator constructed in accordance with the present invention; that is, a modulated-carrier signal is developed for radiation by an antenna circuit l2, l3 which comprises, as modulation components thereon, the video signals to be transmitted and the composite synchronizing signal generated b the synchroniz ng-signal generator |l.

The synchronizing-signal generator II, which is adapted to generate a synchronizing signal for use in a multiple-interlace scanning system in which synchronizing components thereof during one field period are different from those-during a successive field period, includes a cathode-ray tube |5 having therein an electron gun comprising a cathode l4, a control electrode I6, first and second accelerating anodes I1 and Hi, a target electrode l9, and a collector electrode 20, together with suitable horizontal and vertical defleeting electrodes 2|, 22 and 23, 24, respectively. Suitable unidirectional operating potentials are provided for cathode-ray tube |5 in a conventional manner. Target electrode |9 includes a surface having thereon a plurality of, or speferential pattern including portionsF, F; corresponding to the field-synchronizing components of the composite signal to be generated, a circumferential pattern including carbon deposits L corresponding to the line-synchronizing components of one field period of the synchronizing signal to be generated,and a radially displaced I circumferential pattern including carbon deposits L corresponding to the line-synchronizing combe considered to comprise field-synchronizing components and line-synchronizing components of one field period which are differently spaced with reference to the field-synchronizing components than the line-synchronizing components of the succeeding field period.

In order to develop a composite synchronizing signal by means of the cathode-ray tube synchronizing-signal generator ofFig. 1, the patterns of target electrode 9 are continuously scanned in successive substantially circumferential paths, having predetermined angular portions radially-displaced on the target electrode l9 and corresponding-to the dissimilarity between successive field'periods of the desired synchroniz-.

ing signal, to develop an'electrical signal corresponding to the pattern scanned. Scanning circuits are provided for the cathode-ray tube l5 so that the .cathode ray of the tube scans the patterns on target electrode I9 in substantially circular paths. In order to provide the required scanningpotentials for cathode-ray tube I5, the

primary winding of a transformer 28 is connected to a suitable sinusoidal alternating current source, for example, the 60-cycle supply circuit. Secondary windings 29 and 30 of transformer 28 are coupled to two suitable phase-splitting circuits in order to develop phase-displaced voltages. One of the phase-splitting circuits includes series-connected condenser 3| and resistor 32 coupled across windings 29 and 30 in series through resistors 33 and 34, while the other of the phase-splitting circuits includes a series-connected condenser 35 and resistor 36 connected across windings 29 and 30 in series through resistors 3'! and 38. The coupling resistors 33, 34 and 31, 38 are sufficiently large so that the current in each phase-splitting circuit is substantially in phase with the secondary voltage of transformer 28. Therefore, the voltage across condenser 3| is in quadrature with that across resistor 32 and the voltage across condenser 35 ponents of the succeeding field period of the composite signal to'be generated. That is, the composite synchronizing signal to be generated can 75 is in quadrature with that across resistor 35. The

voltages across condensers 3| and 35 are, however, of opposite polarity and are applied, respectively, to the control electrodes of tubes 39 and 40 to develop a balanced sinusoidal output voltage across load resistors 4| and 42 provided for tubes 39 and 40, respectively. This output voltage is applied to the horizontal deflecting plates 2| and 22 by way of coupling condensers 43 and 44. A resistor 45 is coupled between defleeting electrode 22 and a tap 46 of a potential divider 41 to provide horizontal centering of the cathode-ray beam of tube l5 prior to deflection.

The voltages across resistors '32 and 36 are also of opposite polarity andare applied, respectively,

to the input electrodes of tubes 48 and 49 to develop a balanced sinusoidal output voltage for vertical deflection across load resistors 50 and 5| provided for tubes 48 and 43, respectively. This v output voltage is applied to the vertical deflecting plates 23, 24 through coupling condensers 52, 53. A resistor 54 is coupled between vertical deflecting plate 23 and a tap on potentiometer 41 to provide vertical centering of the cathode-ra beam of tube l5 prior to deflection. In order to provide for.scanning of the patterns of target electrode IS in a path, as represented by the dottedline path A, B, C, D of Fig. 2, that is, in substantially circumferential paths having angular portions radially displaced on target electrode l9 and corresponding to the dissimilarity of the successive field periods of the desired synchronizing signal, there is provided I ic intervals during the frame-scanning cycle of the system. This means comprises means for periodically varying the amplitudes of the scanning fields of the cathode ray tube l5. For this purpose, a keying signal is developed by a unit 55 which is utilized alternately to increase and decrease the amplification of tubes 39, Q and 45, 49. The unit 55 comprises tubes 56 and 51, to the input electrodes of which are applied, respectively, the voltage across condenser 3| and the voltage across resistor 32. These voltages are in quadrature and, therefore, a 60-cycle voltage having a phase determined by the relative amplification of tubes 55 and 51 is developed across a load resistor 58 whichis common to tubes 56 and 51. Variable degenerative cathode resistors 59 and 50 are provided, respectively, for tubes 56 and 51 in order that the relative amplification of will be seen that the amplitude of the quadrature space-displaced and phase-displaced scanning fields of cathode-ray tube I5 is periodically varied at aBO-cycle'rate, thus causing the cathode-ray beam to travel in circular paths of different diameters on the surface of target electrode l9. Furthermore, it will be seen that resistors 59 and 50 provide a suitable means for manually ad'- justing the phase of the 30-cycle keyingsignal and that the system may be adjusted so that the radial change in the scanning of the patterns on target electrode I9 takes place during the scanning of the field-synchronizing patterns F, F.

Therefore, the system described is effective to develop a suitable composite synchronizing signal across load resistor 25 for a double interlaced scanning cycle of 18% lines per field and 3'? lines per frame, 4 bread field-synchronizing pulses being developed during each field-retrace interval the tubes can be adjusted, thereby to develop an output voltage across load resistor 58 of any desired phase relationship with respect to the supply voltage to transformer 28.

The signal output of tubes 55 and 51 is utilized to synchronize a conventional multivibrator relaxation oscillator, having a frequency equal to half that of the supply voltage of the system. that is, 30 cycles per second, and comprising vacuum tubes BI and 62 and a load resistor 53. The circuit constants of the relaxation oscillator are so proportioned that the signal output derived from resistor 63, comprising synchronous keying pulses, is of rectangular wave form with positive and negative pulses of equal duration, as indicated by the curve W shown adjacent theretof The keying signal so derived is applied with a suitable amplitude,- which is adjustable by means of a tap on resistor 63, to the screen grids of tubes 39, 40 and 48, 49 to alter the ain of these tubes.

In considering the operation of the system just described, it will be seen that as the cathode ray beam of tube I5 is incident on various portions of the pattern of the target electrode l9, synchronizing-signal components are developed across a of the system. It will be understood that a suitable output voltage could also be taken from a load circuit coupled to collector electrode 20 rather than from target electrode I9, as described.

In Figs-3a and 3b of thedrawings, there are illustrated in detail portions of a composite synchronizing signal for successive fields conforming to the present standards of the Radio Manufacturers Association." This signal comprises linedoubling or equalizing pulses D and field synchronizing pulses F for each field period, line-synchronizing pulses L for one field period, and line pulses L for the succeeding field period which are displaced one-half of the line period fromthe line varies as the scanning beam is, or is not,incident on one of the target patterns of target electrode l9. Furthermore, it will be seen that, if the scanning of target electrode I9 is in a path such as is indicated by A, B, C, D in Fig. 2, a composite synchronizing signal is developed for the transmitting circuit III of 18 line-synchronizing pulses per field period, 37 line-synchronizing pulses per frame period, and 4 broad pulses during each field-retrace period, the generated synchronizing signal thus being suitable for double interlace scanning systems. Furthermore, it will be seen that neglecting the efi'ect of unit 55, the

- quadrature space-displaced and time-displaced scanning fields developed by the deflecting plates of cathode-ray tube l5 due to the voltages applied thereto from tubes 35, 40 and .48, 49 would cause the cathode-ray beam of tube l5 to be driven in a circle at the frequency of the power supply source utilized to energize the primary winding of transformer 28. In considering theoperation 'of the complete'system just described.

in view of the partial descriptions given above, it

pulses L of the first field period. A portion of a target electrode l9 corresponding .to target electrode I9 of Fig. 1 is shown in Fig. 30 having patterns thereon suitable for developing a composite synchronizing signal conforming to the above-mentioned standards; portions of the pattern of element I9 which correspond to pattern portions of element l9 have similar reference numerals.

It is believed that the operation of the modification of the invention illustrated inFigsalia, 3b

and 30 will be readily understood from the de-- scription given with reference to the operation of Fig. 1, and it will be understood that the patterns of element 19' are scanned in a path A, B, C, D, corresponding to path A, B, C, D of Fig. 2.

In Fig. 4 there is illustrated schematically a television synchronizing-signal generator-in accordance with the invention utilizing a scanning disc in place of the synchronously-operated cathode-ray tube 15 of Fig. 1. The generator of Fig. 4 thus comprises a scanning disc I0 operated by a motor H through suitable supply leads 12, 13. The motor H is of the synchronous type and scanning disc 10 comprises thereon a series Jiil - the inner circumferential pattern path. A suit I of slots arranged in a pattern corresponding to either of the target patterns described above. In order to develop a suitable synchronizing signal from the arrangement, a light source is provided including lamps H and 15. lamp 14 being dis-v posed to transmit light through the apertures in the outer circumferential pattern path and' lamp 15 being disposed to transmit light through able synchronous switch I5 is'provided for energizing lights 14 and I5 alternately while a photo-sensitive device 1|, responsive to light transmitted through the apertures in disc Ill,

is utilized to develop a composite synchronizing signal which is thereafter supplied to an ampli fler 18, from the output terminals I9 and of which is derived the desired composite syn-. chronizing signal. The synchronous switch 18 may be similar to the synchronous keying unit 55 of Fig. 1 and is so arranged that one of the lights 14, is always energized and the switching is That is, it is immaterial above-mentioned standards, a pattern including 441 radial bars is required, the bars corresponding to the line-synchronizing pulses during a complete frame-scanning cycle.

These bars must be resolved in thescanning process, which requires a cathode-ray beam having an extremely fine .spot size at the target or a target electrode in the cathode-ray tube of a very large diameter. The modification of the invention illustrated in Fig. 5 is one in which these severe requisites are not present. In the arrangement of Fig. 5, the cathode-ray beam is caused to traverse the same circular path a plurality of times during each field period in order to generate line-synchronizing components and is then radially-displaced to scan another pattern to generate field-synchronizing components and line-doubling components so that a composite synchronizing signal in accordance with the R. M. A. standards is developed. In order to effect rotation of the cathode-ray beam at the relatively high frequency required, an oscillator 95 is providedfor generating sinusoidal oscillations at a frequency of 630 cycles per second,

. the oscillator being synchronized from the power source 88, representing the alternating current source supplying the transmitter for which the synchronizing signal is to be generated. Phasedisplaced voltages are supplied from oscillator 85 to the cathode-ray tube of the system, through a phase adjuster 81 and suitable phase-splitting circuits and amplifiers similar to those of Fig. L Circuit elements in Fig. 5 which are similar to those of Fig. 1 have identical reference numerals with the addition of a prime. Thus, the circuit '01 Fig. 5 comprises a phase-splitting circuit including a series-connected resistor 88 and condenser 89 coupled across a winding 98 which,

in turn, is coupled to the output circuit of phase adjuster 81, for supplying a voltage of suitable tube 98. In order to develop a balanced output voltage, there is provided a-phase-inverting tube III, the control grid of which is connected by means of tap 95 to load resistor II of tube Hill. A common cathode resistor 96 is provided for tubes I88 and III. In order to scan angular portions or the target electrode in circumferential paths which are radially-displaced. there is provided a pulse generator 91, the function of tube I 00 in quadrature with that applied to a which is analogous to that of generator 55 of Fig. 1 and which may be of a similar type. The pulse generator 91 is synchronized by the alternating current source and is adapted to provide a rectangular-pulse wave form, the period I of the pulses being 60 cycles per second. The output of pulse generator 91 is of rectangular;

wave 'form with the duration of the positive pulses that of the negative pulses, as illustrated by curve W adjacent thereto. This pulse output of generator 91 is applied to the screen electrodes of tubes 98, 99, I00, and I iii in order to increase the amplification of these tubes during the positive pulses and decrease such amplification during the negative pulses.

In utilizing the modification of the invention illustrated by the circuit of Fig. 5, the cathoderay tube is provided with a target electrode in accordance with that represented by target electrode IQ" of Fig. 6. This target electrode comprises a pattern in which substantially all of the outer circumferential path corresponds to field 1 synchronizing components and line-doubling components of the signal which is to be generated, that is, to the field-retrace interval, while substantially all of the inner circumferential paththereof corresponds to line-synchronizing components to be generated. The signal to be generated can thus be considered to consist of line-synchronizing components, line-doubling components, and field-synchronizing components corresponding to one field period, and line-doubling and field-synchronizing components for a succeeding field period which are differently spaced with reference to the line-synchronizing components than those of the first-mentioned field period.

In considering the operation of the system of Fig. 5, it will be seen that quadrature phasedisplaced sinusoidal voltages of 630 cycles are applied to the deflecting plates of the cathoderay tube and that, in the absence of any further control, the cathode ray of the tube would be rotated in a circular path at a frequency of 630 cycles. However, as explained in connection with the circuit of Fig. 1, the amplitudes of the deflecting voltages supplied to the cathode-ray tube i5 are alternately increased and decreased by means of the applied pulse voltage.

The deflection potentials of the cathode-ray tube 15 of the modification of the invention illustrated in Fig. 5 are adjusted so that the cathoderay beam of the tube scans a circular pattern corresponding to the inner'path illustrated on the target electrode IQ" of Fig. 6 during the negative pul'sesfrom generator '91, and, during a positive pulse from generator 91, the cathoderay beam scans the outer circumferential path. The relative phase of the scanning potentials supplied to the deflecting plates and the pulses from generator 91 is adjusted by means of phase adjuster 81 so that the amplitude of the scanning potentials is caused to increase just before components corresponding to line-doubling and field-synchronizing components are to be generated and to decrease just after such components have been generated, Therefore, it will be seen that the cathode-ray beam of tube 15 is caused to scan the pattern illustrated by the dotted lines of Fig. 6. That is, beginning at point A", a pattern is scanned corresponding to one set of field-synchronizing and line-doubling components while, at point B", the scanning beam is switched back to the inner circle to scan portions oi the pattern corresponding to imam time the inner pattern is again scanned a plurality of times in order to generate line-synchronizing components for the succeeding field period,

after which the cycle repeats.

It will be noted that there are 21 line bars on the inner circle of target electrode l9" which also extend to the outer circle so that in 10 revolutions of the scanning beam on the inner circle and one-half revolution on the outer circle, a field of 220.5 lines is scanned, corresponding to. a total of 441 lines for the complete frame cycle of 21 revolutions.

It will also be understood that the principle the invention illustrated in Fig. is not limited to the particular scanning frequencies and the particular pattern shown but that the modification of the invention illustrated in Fig. 5 may be utilized with other scanning patterns and different numbers of bars on the target pattern. Furthermore, it will be understood that the principle of the invention illustrated in Fig. 5 is equally applicable to a system using other types of interlaced scanning. For example, in a systern utilizing triple'interlace'd scanning, the target electrode can be provided. with three groups of patterns on the outer circle representing the field-synchronizing pulses together with their associated line-doubling pulses for each of the three successive field-retrace intervals, and each of these patterns would then cover an angular portion of 120 degrees of the outer circumferential path.

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, 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: a

1. A synchronizing-signal generator for a television transmitter adapted togenerate a syn-' chronizing signal for use in a multiple-interlace scanning system-in which synchronizingcomponents thereof during one field period are different from those during a succeeding field period comprising, a device having a plurality of radiallydisplaced circumferential patterns having Predetermined'angular portions thereof corresponding to predetermined portions of the signal to be generated, and means for continuously scanning said patterns in successive substantially circumferential paths having predetermined angular portions radially displaced on said device and corresponding to the disslmflarity of said field periods of the desired synchronizing signal to develop an electrical signal corresponding to the patterns scanned.

2. A synchronizing-signal generator for a television transmitter adapted to generate a synchronizing signal for use in a multiple-interlace scanning system in which synchronizing components thereof during one field period are different components and field-synchronizing components paths having predetermined angular portions radially displaced on said device and corresponding to the vdissimilarity of said field Periods of the desired synchronizing signal to develop an electrical signal corresponding to the patterns scanned.

3..A synchronizing-signal generator for a television transmittei' adapted to generate a synchronizing signal including line-synchronizing for use in. a multiple-intei'lace scanning system in which synchronizing signals during one field period are different from those during a succeedmg field period comprising, a device having a plurality of radially-displaced circumferential patterns having predetermined angular portions thereof corresponding, respectively, to the porhum of me signal to be generated including the line-synchroniz ng components, said patterns corresponding to the line-syncnronlzlng components or one neld period being dliierently spaced Wit-1'1 reierence to tnose corresponding to the field-sylicni'onlzing components than those corresponding to mellne-syncnrunlznig components or a succeeding nerd period, and means ior contmuously scanning said patterns in successive substantially circumierentlal paths having predetermined angular portions radially dis laced components and field-synchronizing components r for use in a gnultlple-interlace scanning system in which synchronizing components during one Iield period are dinerent iro'm those during a succeeding nerd period comprising, a device having a plurality or radially-displaced clrcnnlierentlal patterns navmg dlnerent predetermined portions thereof corresponding to toe field-syncnronlzlng components to be generated and to the line-synchronizing components to be gen-- erased, and means ior contmuously scanmng said patterns in successive 'suoscantially cllcumlerenmal paths having predetermined angular portions radially displaced on said device and corresponding to the dissimilarity or said field periods of trie desired sync ronizing signal to develop an electrical signal corresponding to the patterns scanned.

5. A synchronizing-signal generator for atelevision transmitter adapted to generate a synchronizing signal including line-synchronizmg components, equalizing components, and fieldsynchronizing components for use in a multipleinterlace scanning system in which synchronizing component during one field period are different from those during a succeeding field period com-- prising, a device having a plurality of radiallydisplaced circumferential patterns having predetermined portions thereof, respectively, corre-' spon'ding to the field-synchronizing components and equalizing components to be generated and to the line-synchronizing components to be generated, and means for continuously scanning said patterns in successive substantially circumferential paths having predetermined angular portions radially displaced on said device and corresponding to the dissimilarity of said field periods of the desired synchronizing signal to develop an electrical signal corresponding to the patterns scanned.

6. A synchronizing-signal generator for a television transmitter adapted to generate a synchronizing signal including line-synchronizing components and field-synchronizing components for use in a multiple-interlace scanning system in which synchronizing components during one field period are different from those during a succeeding field period comprising, a device having a plurality of radially-displaced circumferential pattern including substantially an entire circumferential path corresponding to the fieldsynchronizingcomponents to be generated and the remaining patterns corresponding to the line-synchronizing components to be generated,

and means for continuously scanning said patterns in successive substantially circumferential paths having predetermined angular portions radially displaced on said device and corresponding to the dissimilarity of said field periods including means for scanning said pattern portions corresponding to the line-synchronizing components a plurality of times for each scansion of said pattern portion corresponding to the fieldsynchronizingcomponents to develop an electrical signal corresponding to the pattern scanned.

'7. A synchronizing-signal generator for a television transmitter adapted to generate a synchronizing signal including line-synchronizing components and field-synchronizing components for use in a multiple-interlace scanning system in which synchronizing components during one field period are different from those during a succeeding field period comprising, a device having a plurality of radially-displaced circumferential patterns having predetermined portions thereof, respectively, corresponding to the fieldsynchronizing components to be generated and to the line-synchronizing components to be generated, and means for continuously scanning said patterns in successive substantially circumferential paths having predetermined angular portions radially displaced on said device and correspond ing to the dissimilarity of said field periods including means for scanning said pattern portions corresponding to the line-synchronizing components a plurality of times for each scansion of said pattern portion corresponding to the fieldsynchronizing components to develop an electrical signal corresponding to the pattern scanned.

8. A synchronizing-signal generator for a television transmitter adapted to generate a synchronizing signal including line-synchronizing "periods of the desired synchronizing signaland including means for scanning said other portion a plurality of times for each scansion of said one portion to develop an electrical signal correspending to the pattern scanned.

9. A synchronizing-signal generator for a television transmitter adapted to generate a synchronizing signal for use in a multiple-interlace scanning system in which synchronizing components during one field period are difierent from those during a succeeding field period comprising, a cathode-ray tube including a target having thereon a plurality of radially-displaced circumferential patterns having predetermined angular portions thereof corresponding to predetermined portions of the signal to be generated, means for continuously scanning said target in successive substantially circumferential paths having pre-' determined angular portions radially displaced on said device and corresponding to the dissimilarity of said field periods of the desiredsynchronizing signal to develop an electrical signal corresponding to the patterns scanned.

10. A synchronizing-signal generator for a television transmitter adapted to generate a synchronizing signal for use in a multiple-interlace scanning system in which synchronizing components during one field period are different from for periodicallyvvarying the amplitude of said fields for continuously scanning said target in successive substantially circumferential paths having predetermined portions radially displaced on said target and corresponding to the dissimilarity of said field periods to develop an electrical signal corresponding to the patterns scanned.

11. A sychronizing-signal generator for a television transmitter adapted to generate a synchronizing signal for use in' a multiple-interlace scanning system in which synchronizing components during one field period are different from those during a succeeding field period comprising, a cathode-ray tub'e including a target having thereon a plurality of radially-displaced circumferential patterns having predetermined angular portions thereof corresponding to predetermined portions of the signal to be generated, means for generating quadrature space-displaced and time-displaced sinusoidal scanning fields to scan said target in a circular path, means for generating synchronous keying pulses, and means for utilizing said keying pulses periodically to vary the amplitude of said scanning fields continuously to scan said target in successive sub stantially circumferential portions having predetermined paths radially displaced on said target and corresponding to the dissimilarity of said field periods to develop an electrical signal corresponding to the pattern scanned.

12. A synchronizing-signal generator for a mined angular portions thereof corresponding to predetermined portions or the signal to be generated, means including a photosensitive device and a light-source means for continuously scanning said apertures in successive substantially circumferential paths having predetermined angular portions radially displaced on said device and corresponding to the dissimilarity of said field periods of the desired synchronizing signal to develop an electrical signal corresponding to the apertures scanned.

13. A sychroni'zing-signal generator for a television transmitter adapted .to generate a synchronizing signal for use in a multiple-interlace scanning system in which synchronizing components thereof during one field period are different from those during a'succeeding field period comprising, a scanning disc having therein apertures forming a plurality of radially-dis- 4 placed circumferential patterns having predetermined angular portions thereof corresponding topredetermined portions. of the signal to be generated, means including a photosensitive device and a light-source means for continuously scanning said apertures in successive substantially circumferential paths, means for generating synchronous keying pulses, and means for utilizing said keying pulses to shift the scanningpath so-that said apertures are scanned in substantially circumferential paths having predetering to the apertures scanned.

mined angular portions radially displaced on said- HAROLD M. LEWIS.

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