US2256530A

US2256530A - Synchronizing system

Info

Publication number: US2256530A
Application number: US233553A
Authority: US
Inventors: Stuart W Seeley
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1938-10-06
Filing date: 1938-10-06
Publication date: 1941-09-23
Anticipated expiration: 1958-09-23
Also published as: GB535578A

Description

Sept. 23, 1941. s. w. SEELEY 2,256,530

SYNCHRONIZING SYSTEM Filed Oct. 6, 1938 2 Sheets-Sheet l 43 J- FILTER (AUTOMATIC CPI/ASE FREQUENCY asrscron CONTROL UNIT 01/ T PU T 70 TRANSMITTER INVEN TOR. STUART WJ'EELEY ATTORNEY.

Sept. 23, 1941. s. w. SEELEY SYNCHRONIZING SYSTEM Filed Oct. 6, 1938 Z Sheets-Sheet 2 9523M a 55m I NV EN TOR. STUART m SEELEV A TTO RN E Y.

Patented Sept. 23, 1941 SYNCHRONIZIN G SYSTEM Stuart W. Sceley, Baysidc, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application October c, 1938, Serial No. 233,553

6 Claims.

The present invention relates to television systems and is particularly directed to a system for controlling the production of the so-called oddline type of interlaced television images. The invention also relates generally to circuits for controlling the repetition of such types of produced television images in receiver apparatus so that the received image is at all times properly and adequately synchronized and the spacing between the lines of each field of the interlaced images accurately maintained in constant relationship.

In its fundamental form the invention, as it is to be described herein, includes a suitable form of oscillator from which is developed or produced oscillatory electrical energy of a substantiallyv the supply circuits.

is produced from successive halves of like polarity of the developed sine wave energy a series of electrical impulses which are caused to become recurring at repetition frequency of each line of the picture. v invention means are also provided to derive from Further, as a part of the the developed sine wave energy further successions of uniform impulses which are caused to occur at twice the frequency and repetition rate of the line synchronizing impulses.

The invention further contemplates making suitable provision for combining all of these serval forms of different frequency in a proper sequency to form a complete chain of control impulses which serve to synchronize the line and field repetition rates of a received television image reproduction. I

In the July 1938 issue of Electronics there is described on pages 28, 29 and 55 a certain form According to the presently used methods of transmitting television-signals television pictures of 441 lines are produced. These television pictures are repeated at the rate of 30 picture frames per second. However, because of a desire to interlace the produced pictures, in order that the flicker may be substantially reduced, each picture frame is transmitted in the form .of two picture fields, of 220 lines each with a result that the transmitted field frequency is picture fields per second. This particular field frequency is quite desirable because it permits interlocking the field repetition frequency with the usual power supply frequency of 60 cycles per second. Proper synchronization and interlock of the field frequency and the power supply frequency reduces hum bands in the received picture which might result from ripple in the deflection and The interlacing of the various picture fields one withthe other occurs as a natural consequence of the non-integral relationship between the field repetition frequency, herein assumed as 60, and the line repetition frequency herein assumed as 13230. (this being formed from picture fields of 441 lines each repeated 30 times per second.

As was explained, however, in the Electronics publication, herein above referred to, during the time period when the field patterns are changing in the interlacing operation and during the vertical synchronizing interval a special form of signal is transmitted in order that the horizontal synchronism may not be lost and it is further an object of the present invention to provide ways and means for producing these signals and further to provide for controlling the time period when they become efiective in the transmission.

Other objects of the present invention are to provide a greatly simplified arrangement for transmitting synchronizing signals which shall cause television images to be repeated at the desired frame and field repetition rates for a given number of picture lines and also to provide for the production of synchronizing signals which shall follow in proper time relationship the complete train of image signals which result from scanning the subject of which the'electro-optical imageis to be produced on the viewing instrument.

It is a still further object of my invention to provide an improved form of pure electronic type of generator for generating the above described forms of impulses which shall be used at receiver points for synchronization of television images. I

A further object. of my invention is to provide frequency doubler.

an improved method of and means for controlling, delaying, shifting or otherwise determining the time at which such produced electrical impulses shall become effective in the transmitting circuits.

Further objects, features and advantages of my invention, of course, will become apparent and.

at once familiar to those skilled in the .art to which the invention is directed by reading the following specification and claims in connection with the accompanying drawings, wherein:

minal 52.

Fig. 1 diagrammatically illustrates one form pulses of the type hereinabove described; and wherein Fig. 2 illustrates schematically the wave form of the several impulses which result from the operation of the circuit of Fig. 1.

- of arrangement and circuit for producing the im- Referring now to the drawings there is provided an electronic oscillating tube II which may be of the general type known in the art as the 6A8 which is adapted to generate electric oscillations of sine wave formation at a frequency assumed to be 13230 cycles for a 441 line television picture to be repeated thirty times per second. The tube includesa cathode |3,a No. 1 grid I5, and a No. 2 grid H which electrodes cooperatively function as a first part or section of the tube which is termed the oscillator section. In addition, there is provided within the tube II a No. 4 grid l9 and a No. 5 grid 2|, as well as the usual output electrode or anode 23. The'oscillating portion of the tube includes the cathode l3 and the No. 1 and 2 grids l5 and II,

respectively, of which the latter serves as an anode or output element. These grid elements are connected to the terminals of a tuned circuit 25 comprising the inductance element 21 and the two

capacity elements

29 and 30 of which one or both may be variable. The

capacity elements

29 and 30 are serially connected and the junction point is connected to ground (or fixed potential) at 3| as indicated. The series connected ca pacity elements 29 and 3| are shunted by the inductance element 21 so that with the N052 grid connected by way of the

conductors

32 and 33 to one end of the resonant circuit 25 and the N0. 1 grid connected by way of the

conductors

34 and 35 through the capacity element 36 to the other end 31 of this tuned circuit 25 oscillations will be developed when suitable energy is supplied to the tube Such operating energy is supplied by way of the choke coil 38 connected to a source of positive potential at the terminal 39 and bias voltage is supplied. to the No. 1 grid l5 by way of the bias resistor 4| connected to ground.

The connection of the oscillatory circuit immediately above described is essentially a form of the well known Colpitts oscillator so that with suitable operating potentials applied there will be generated or developed in the tuned circuit 25 electrical energy of a frequency determined by the circuit constant and of a sine wave characteristic. Electrica energy of a frequency double that appearing in the circuit 25 can be developed 'in the output section of the tube II by connecting the tube (as indicated) so thatit operates as a In the form in which the tube is connectedthe tuned tank circuit 43, comprising the inductance'44 and the capacity 45 (variable, if desired), is tuned totwice the frequency of the tuned circuit 25. This tuned circuit 43 is c'onnectedby way of the coupling condenser I4 1 at one end to the anode element 23 of interlacing with the line frequency (that frethe tube II and at the other end to ground at 3| by way of the conductor 48 and then also by way of the conductor 49 and the coupling condenser 50 back to the electrode 2| of the tube ll.

Suitable anode voltage for the tube II is supplied by way of the resistor 5| connected to ter- Operating voltage forthe electrode 2| is supplied by way of the terminal connection 53 and the electrode I9 is operated at cathode potential by way of the connection to ground at 54'. In view of the well recognized desire to develop the synchronizing impulses to initiate the frequency division which is finally to equal the field frequency from the same source that develops the line synchronizing controls, it is desirable that energy of double the frequency of the initially developed oscillations shall result in order that ultimate frequency division shall be equal to the field frequency desired. This is substantially due to a condition imposed by the odd-line quency developed in the tuned circuit 25) shall constitute no harmonic of the field frequency and further that the second harmonic of the, line frequency which appears in the tuned circuit 43 shall constitute no even harmonic of the field frequency.

Accordingly, as is well known in the art and as has already been explained in the patent of John Paul Smith, No. 2,132,654, issued Oct. 16, 1938, frequency division of the double frequency appearing in the tuned circuit 43, which is at twice the frequency which appears in the tuned circuit 25, may be divided by a chain of stabilized multi-vibrators. Such a chain of multi-vibrators may, where it is, assumed that the system is operating to produce a 441-line picture repeated at picture fields per second, comprise three separate

multi-vibrator stages

51, 58 and 59 where the output from the multi-vibrator stage 51 will be equal .to

where F is the frequency of the fundamental or the frequency developed and appearing in the tuned circuit 25. This output is then fed to the second multi-vibrator stage 58 whose output is 'equal to Y and likewise the output from this multi-vibrator stage is fed to a third multi-vibrator 59.whoscmulti-vibrator 59 through a suitable form of detector, such as a phase detector to which is also supplied energy of the power supply frequency. wherein the phase "of the developed energy is compared with the phase of the 60 cycle power supply frequency. The output .of such a phase detector may be through a suitable form of filter network and thence to an automatic frequency control unit of known character to control or stabilize the frequency of the oscillator l I. How.

ever, such a control feature is not specifically a part of the present invention, and, therefore, it is desirable to consider a second portion of the output of the multi-vibrator 59 which is to control the timing and wave shaping units which shall produce the synchronizing signals of the form indicated by Fig; 2 of the drawings.

For this purpose, there is coupled to the inductance element 21 of the tuned circuit 25- a coupling coil 6| having one terminal thereof grounded by conductor 82 at ground'3l and the other terminal thereof is connected by way of conductor 83 to be supplied to a suitable form of rectifier element such as the push-pull rectifier 85. The other portion of the output multi-vibrator 59 is -then supplied by way of conductor 55 to control, in a manner later to be described, the keying of the horizontal synchronizing impulses in the'output of the wave shaping unit connected with the output of the rectifier 65.

It was above explained that the oscillatory energy for developing the synchronizing impulses was in the form of sine wave energy since it was relatively easy accurately to control and stabilize an oscillator to develop sine wave energy as contrasted with units, such as uncontrolled multivibrators and the like, to develop energy of an impulse form.

According to the form of transmission now most commonly used experimentally, it has been found that the duration ofv the synchronizing interval occurring at the end of each picture field shall be of the order of 7% of a of a second. Accordingly, the synchronizing control which shall control the vertical motion of the cathode ray beam used to reproduce the teleyision picture must become effective during this time period and, in ,some sense, of course, provision must be made so that the horizontal synchronizing control does' not cease operating during such time period. Uniess a very definite interlock is to be obtained, asa practical matter, due to the return time during the reproduction of each picture field being a relatively large percentage of the time required to reproduce each picture field,

there might result .a substantial drift in horizontal line production of the initial portion, at 7 least, of each produced picture. Hence, by the arrangement described herein the sine wave energy developed at line frequency and derived by way of the coupling coil 8| from the tuned circuit 25 iscaused to pass through the wave shaping unit connected to the output 'of the rectifier 65 and therein be so modified by the so-called clipping, integrating, differentiating and keying processes, which will be later described herein, in order to produce the desired form of control signal.

In this form of apparatus the line frequency sine wave energy supplied from the tuned circuit 25 through conductor 63 is applied to each half of the tube 65 (which tube may beone of the type known in the ,art as type 6H8) in phase opposition through the transformer 6'! having its primary'winding 88 shunted, for tuning purposes if'desired, for purposes of symmetry in each half of the ware, by a condenser 89 connected to ground at 18 and having its secondary winding H center-tapped to ground in the usual manner by way of the conductor 12. The anode elements 13 and 14 of the double diode 65 are connected respectively to the control electrodes 15 and 18 of wave shaping tubes 11 and 18. It is quite desirable in such a connection, however, that the half of the secondary winding 1| of the transformer which is connected between the

cathode elements

19 and 88 of the two halves of the tube be accurately balanced with respect to ground 18 and for this purpose the winding 'II should preferably be bifilar and the core of the transformer 61 should be such that it does not show excessive loss at the assumed line frequency supplied through the conductor 83.

Connected between the control electrodes I5 and 16 of the tubes TI and I8 and the cathode elements thereof are the usual diode resistors 8| and 82. The voltages which appear across these diode resistors 8| and 82 are negative in sign so that when rectified half wave portions of the energy in conductor 63 are impressed upon the tubes l1 and 18 (which tubes are preferably, although not necessarily, tubes of the type known in the art as the type 1851) the control electrodes l5 and 16 will be driven well beyond a cut-off potential so as to clip in this way the two alternate half waves.

It is frequently desirable, however, to vary the cut-off voltage on the tubes IT and I8 and hence the so-called

screen electrodes

83 and 84 are provided with an adjustable screen potential through their connection by way of the conductor 85 to the resistor element 86 as indicated. This form of arrangement permits a variation of the width of the clipped half waves.

Anode or plate potential for the tubes 11 and I8 is provided by way of the plate resistors 81, 81' from suitable voltage sources (not shown) connected to the free end of each of the anode resistors. The output energy from the tube 11 is supplied in parallel to a pair of

tubes

88 and 89 respectively through suitable conductors 90 and 9| and the coupling condensers so as to be impressed in parallel upon the control electrodes 92, 93 of these. tubes. The output energy from the tube 88 is fed by Way of the resistance coupling to a further wave shaping tube 95. Output from this tube is then fed to a keying tube,9l, later to be described.

Similarly, the output of the tube 89 is fed to tube 18 is supplied upon the control electrode l8l of a wave shaping tube I82 of a generally similar characteristic to the tube 88 connected to receive the output of the first wave shaping tube 17. The tube I82, it will be seen, has, together with the tube 89, a mutual plate or anode resistor I83 through which operating potentials are supplied. With the connection shown the output energy from the tube I82 is also supplied to the control electrode I88 of the tube 98 by way of the coupling condenser 99 and the conductor I84. In addition, the output energies from the tubes 89 and I82 are also combined by way of the conductor I'M and a coupling condenser I86 to be impressed upon the control electrode I81 of a wave shaping tube I88.

It will thus be seen from what has been above 8 described that there is impressed upon the

tubes

88 and 95 impulses of rectified current occurring at the line frequency corresponding to the frequency of the sine wave energy generated in the oscillator portion of tube II and appearing in the tuned. circuit 25. Upon the tubes '98 and I88 there is produced the combined output of tubes l1 and 18 so that in the output of the tubes 98 and I88 there results relatively square bottom pulses of a frequency double that which is impressed upon the rectifier tube 55 through the transformer 61. :Theoutput energy from the tubes 90 and I is supplied to additional keying tubes I I0 and H2, later to be described in more detail.

In general, the wave shaping channel including and capacity in these two channels are chosen of somewhatdifferent value from that, in which included tube I08 so that the re'sultantfimpulses which are. supplied to the control electrodes of thekeying tubes I I0 and H2 shall, in the one instance, be of relatively long duration V the frequency divider or multi-vibrator '59, which is supplied by way' of the conductor 55, it will. be noted that this output energy is impressed .in parallel upon the..tubes H3 and H4 by way of the suitable coupling condensers. Through a suitable choice of resistance and capacity elements H5, H6 and II1ythe impulse which is upplied tothe control electrode IIB of the tube H3 is delayed for a short time period which is equal to the equalizing pulse interval (see Fig. 2) immediately following the last line of picture or video signals and occurring prior to the time when the vertical synchronizing pulses appear. The output energy from-the tube 3 is then fed by way of the resistance coupling connection,

- the tube 98 is similar to that channel including the tube I00, except that the values 0f resistancequency are impressed upon the control electrode I of the tube II4 substantially without delay, as contrasted to the delay introduced in the application of these impulses upon the .tube H3. The output energy from the tube H4 is fed by way of the coupling condenser I 21 to the con-- trol electrode I28 of an inverting tube I29 whose output is, in turn, coupled to the input of a tube I30 by way of a coupling condenser I3l so as to" be impressed upon the control electrode I32 of the tube I30; The output energy from the tube I30 is. supplied in parallel upon the control elec- I, trodes m and I35 of a pair of tubes I31 and I38 of which the'latt'er functions, as will be hereinafter explained, as a tube for'keying one of the series of impulses resulting from the rectification of the sine wave energy developed by the tube II at line frequency and supplied to the rectifier 55. Those impulses which are fed from the output of the tube I 30 to the tube I38 are passed by way of the condenser I40 to the con-.

".trol electrode I35 thereof.

comprising the usual output and leak resistors It will be seen that the tube I38 serves substantially as an isolating and buffer amplifier in whose output circuit there is fed by way of the conductor I4I a pulse of negativepolarity during time intervals when one of the several channels energized from the rectifier 65 isto be keyed. Contrasted with this polarity of output signal, the output from the tube I24'which is connected by way of the conductor I42 to key another of the series of impulses formedfrom the output of the rectifier 65 is of the opposite polarity, for

a purpose which will be hereinafter made more apparent.

As was above explained the output from the tube I30 while fed to thecontrol electrode I 35 Therefore, the pulse, as it appears in the output a tube I22 in theinput circuit of which the capacity element I23 and the leak resistor I24 are suitably chosen in value to shape and delay the impulse as necessary. The widthof the pulse applied upon the control electrode I2I of the tube I22 is controlled and the pulse is narrowed by this wave shaping and narrowing circuit. The output energy from tube I22 is then so connected as to energize a plurality of cascade connected of the tube I31 and as it is fed or supplied to the control electrode I45 of the tube I46 is of like polarity to that impulse which appears in the conductor I4I. However, the tube I46 functions again to .invert the polarity of this impulse and in the output circuit of the tube I46 there aptubes I 23 and I24 serving to amplify and isolate the output energy from the tube I 22. The output energy from.-the tube I24, wherein appears impulses which occur at the fleldfrequency, hereinabove assumed for the purpose of convenience, present practice and illustration only as occurring cycles per second, may then ,be' used to .03 andtransformer 61 upo'n the rectifying tube- During the time-period when impulses occur ring at the field frequency of 60 cycles are supplied to the tube 3' by way of the conductor 55 and the suitable coupling means, these same imD s are being supplied by way of the coupling condenser I25 upon the control electrode "I26 of the tube III of a second keying channel;

It will be seen from the arrangement indicated that the impulses occurring at the field frepears in the conductor I41 an impulse of a polarity opposite that in theconductor MI and of a polarity like thatin the conductor I42.

It can be seen from the connections shown that the output energy from the tube I30 is supplied by way of the conductor I4I to the screen electrode I49 of the tube 91. Similarly, the output energy from the tube 124 s supplied by wayof the conductor I 42 to the screen electrode I50 of the tube IIO while theoutput from the tube I46 is fed by way of the conductor I41 to the screen electrode I5I of the tube I I2. The polarity of the signal appearing in the conductors I42 and I 41 o the cathode at these time periods so that the normal bias (that is, as shown in the present case, at ground or cathode reference potential) which is supplied to these tubes to maintain them in an inoperative or non-conducting state is removed and the pulses of double frequency which appear in the-output circuits of the tubes 98 and 2,2se,sso

I08 respectively will be caused to energize the common output conductor I55 for all of the tubes 91, H and H2. Each of these tubes 9?, H0 and H2 has its anode or plate voltage supplied from a common source by way of suitable resistor I51.

In view of the fact that the field frequency impulses supplied to the tube H3, by way of the conductor 55, are delayed, as above described, for a predetermined time interval by delay networks comprising the resistors H5, H6 and condenser I'I'I, it will be seen that thekeying action applied to the tube H2 is such that the tube H2 is carried to a conductive state just slightly prior to the time'when the tube IIIlis rendered conductive by reason of its connection through conductor I42 to the output of the tube I24. However, at the instant when the tube H2 becomes conducting by reason of the positive potential applied to its screen electrode I5i by way of the conductor I4'I, there is applied to the screen electrode I49 of the tube 91' by way of the conductor I M a potential which is negative in sign or, in other words, opposite sign to that applied to the tube II2. Consequently, the tubes 91 and H2 are keyed in such a manner that'during the time periods when the tube 91 is operative to pass current the tube H2 is inoperative to draw plate current, so that during time periods when the tube H2 is operative, the tube 91 becomes inoperative. I These periods of operation have been indicated in a relative time relationcondenser I25 and the resistor reason of the parameters chosen for the coupling I25. This is evident from Fig. 2 of the drawing, wherein it ship by the numerical desig'nations applied to the synchronizing pulses shown in Fig. 2.

It will be seen further that during the period of time of the marked vertical synchronizing pulse interval, certain synchronizing impulses of longer duration are occurring. These are the impulses due to the keying provided by way of the channel including the tubes II3, I20, I22, I23, I24 and conductor I42 serving to supply positive voltage upon the screen electrode I50 of the tube IIO. It was pointed out above that the time delay constant for controlling the delay in which the energy in the conductor 55 was supplied to the control electrode I II! to the tube I I3 was such as to delay the pulse at the field frequency which is supplied by way of the conductor 55 is of a time indicated by the period vertical blanking in Fig. 2. However, with the relay of the time when this pulse should become effective of the control electrode N8 of the tube H3 being of a time period equal to the first equalizing pulse interval reading left to right in Fig. 2 the effects of this pulse for kteyiiig purposes will not be realized in this ins an It was pointed out hereinabove, however, that the tube I22 functioned as a pulse narrowing tube and that one of the principal reasons for this narrowing effect is because of the'parameters chosen of the resistor I24 and'condenser I 23'. This narrowing effect is such that an actually effective time period of the pulse. applied by way of conductor I42 to key the tube I Ill is narrowed from the time period normally expected so that it commences at a time period indicated by the legend marking the beginning of the vertical synchronizing pulse interval. These pulses are then continuing until the next time when picture signals are transmitted and until such time the actual modulation of the transmitter is only that given and indicated by the vertical synchronizing pulse interval on Fig. 2.

Further than this, there is some slight narrow-.

ing eflect which takes place in the keying channel includin's the tube II4 which becomes efiected by will be seen that the horizontal synchronizing pulses start prior to the time period when the vertical blanking pulses would normally terminate and at which time the video picture reproduction again takes place. This then permits the tube 9] to transmit to the common output circuit 555 line frequency impulses which result from the sine wave energy applied through conductor 5 53 to the transformer 61 and the narrowing effect of the vertical blanking is according to the schematic illustration of the wave form shown,

equal to the duration of seven picture lines, although there can be a reasonable degree of tolerance in this value and the blanking signal may be of slightly longer duration, in which event the narrowing eifect produced in'the channel including the tube H3 will have to be still greater than above explained for the same number of equalizing impulses indicated in Fig. 2 of the drawings. It is, of course, apparent that the number of equalizing pulses, as well as the vertical pulses is not of a particularly critical nature but for practical considerations the number of such values indicated in the present disclosure represents that number which has been found to be most satisfactory for general usage.

Under such conditions and with the tubes 91,

III], HZ all feeding their output into a common energy is then transferred by way of a coupling condenser III! to be impressed upon the input or control electrode ill of a tube "2 which functions by reason of-the bias applied by way of the resistor I73 as a clipping tube. As indicated by Fig. 2 of the drawings during the entire period represented by the production of the vertical synchronizing pulses, the tube H2 will have rendered operative by reason of the positive bias applied to the screen electrode I5I by way of the conductor I41 so that there is superimposed upon the edge of each of the vertical synchronizing pulses a pulse substantially like the equalizing pulses indicated immediately to the left of the vertical synchronizing pulses in Fig. 2. The tube HZ, therefore, functions to clip this pulse from the vertical impulse since it is of no material use in thesynchronizing control exercized upon the receiver. The output from the tube I12 may then be fed to a tube of substantially similar characteristics except that it is arranged to clip the impulse in the opposite direction. The output energy from the tube H2 is then supplied by way of the conductor I14 and the coupling condenser Il5 to the output terminal H6, from which it is introduced into a selected television transmitter where the picture synchronizing and blanking signals are mixed. There practically has been suggested diifererlt points in the transmitter in which this signal may be introduced but for practical purposes the combined signal may be introduced in one'of the amplifier stages preceding the modulation or in many instances should be introduced promptly into the modulator.

From what has been above described it is apparent that many modifications and changes may be made in the arrangement and circuit disclosed and it is, therefore, contemplated that any and all such modifications and changes which fall fairly within the spirit and scope of the invention as hereinafter claimedqnay readily be made 6 1 assisted I of line traces and repeated at a predetermined without departing from that subject matter herein described.

I claim:

1. A'system for producingline and frame synchronizing impulses for use in a television system comprising means for producing a substantially sine wave of .electrical energy at linev repetition frequency, means for deriving-impulses of line synchronizing frequency from successive halves of like polarity of said produced sine wave, means for deriving from each half of said produced sine wave without regard to polarity a succession of uniform impulses at twice repetition rate of the first'named produced impulses, means to produce a first series of impulses of frame synchronizing frequency, means to'produce a second series of I .impulses of frame synchronizing frequency delayed with respect to said first series of impulses of frame synchronizing frequency, and means to control the transmission of the impulses of line synchronizing frequency and the impulses of twice line synchronizing frequency by the first and second series of impulses of frame synchro nizing frequency. 1 2. A system for producing line and frame synchronizing impulses for use in a television system comprising an electronic oscillator producing substantially sine waves of electrical energy at a predetermined line repetition frequency, electronic wave shaping means for deriving impulses of line synchronizing frequency from successive halves of like polarity of said produced sine waves, means for deriving from each half of said produced sine wave withoutregard to polarity a plurality of successions of uniform impulses at twice the repetition rate of the first named produced impulses, means to produce two series of impulses of frame synchronizing frequency, said two series of impulses being displaced in phase relationship by a predetermined amount,

and means to control the transmission of the impulses of line synchronizing frequency and the impulses of twice line synchronizing frequency by the two series of impulses of frame synchronizing frequency.

3. A system for producing line and frame synchronizing impulses for use in a television system comprising oscillator means for producinga substantially sine wave of electrical energy at line repetition frequency, wave shaping means for deriving impulses of line synchronizing frequency pattern repetition rate from alternating fields in a television system comprising, means for producing substantially sine wave oscillations at a frequency corresponding to the line repetition rate, means for producing line synchronizing impulses from successive halves of like polarity of the developed sine waves, means for producing impulses at twice the line frequency from each of the produced sine waves by inverting alternate halves of the sine waves to produce impulses of substantially uniform configuration and polarity, means to produce under the control of the sine wave oscillation impulses of a frequency 'corresponding to the field repetition rate, a keying circuit, means for energizing the keying circuit by said field frequency energy, means controlled by the keying circuit for combining the impulses produced at line frequency and at twice the line frequency alternately and successively, and an output circuit for all of said impulses.

. 5. A synchronizing system for producing interlaced electro-optical patterns each of a predeterfromsuccessive halves of like polarity of said producedsine wave, a full .wave rectifier means,

vmeans for deriving from the rectified alternating halves of said produced sine wave a succession of uniform impulses at twice the line synchronizing frequency, means for producing two series of impulses of frame synchronizing frequency,

said two series of impulses being phase displaced by a predetermined amount, and means to control the transmissionhof. the impulsesof line synchronizlng frequency and the impulses of twice line synchronizing frequency by the two series of impulses of, frame synchronizing frequency.

4.1 system for producing synchronizing impulses for controlling the production of electrooptical patterns each of a predetermined number mined number of line traces and repeated at a predetermined pattern repetition rate from alternating fields in a television system comprising means for producing substantially sine wave oscillations at a frequency corresponding to the line repetition rate, means for producing line synchronizing impulses from successive halves of like polarity of the developed sinewaves, means for producing impulses at twice the line frequency from each of the produced sine waves by inverting alternate halves of the sine waves to produce impulsesof substantially uniform configuration and polarity, means to produce under the control of the sine wave oscillations impulses of a frequency corresponding to the fieldrepetition rate, and means for alternately 40 and sequentially combining the impulses produced at line frequency and at twice the line frequency under the control of the impulses produced at field frequency.

6. The method of developing synchronizing signals for producing interlaced electro-optical patterns each of a predetermined number of line traces repeated at a predetermined pattern repetition rate from alternating fields in a television system comprising the steps of producing substantially sine wave oscillations at a frequency corresponding to the line repetition rate, producing synchronizing impulses at the line repetition frequency from successive halves of like polarity of the developed sine waves, inverting alternate halves of the sine Waves to produce impulses of substantially uniform configuration and polarity to produce impulses at twice the line frequency from each of the produced sine waves, generating from the sine wave oscillations impulses of a frequency corresponding to the field repetition rate, and alternately and sequentially combining the impulses produced at line frequency and at twice the line frequency under the controlof the impulses produced at the field repetition rate.

' STUART W. SEELEY.