US2350536A - Synchronizing signal generator - Google Patents

Description

6 Sheets-Sheet 1 Filed July 30, 1942 Kvm. Re...

NQQI- Y msm Wmskkk b kNOmTV ATTORNEY June 6, 944- v K. scHLEslNGER 2,350,536

SYNCHRONIZING SIGNAL GENERATOR Filed July 50, 19442 A 6 Sheets-511881l 2 "'F (a) IIII all E y I/l 1 1 e 875// (9,) 6e) S e?) U A j lNvENToR T'TORNEY K. SCHLESINGER 2,350,536

SYNCHRONIZING SIGNAL GENERATOR `Fume 6, i944.

6 Shee'ts-Sheet 5 Filed July 30, 1942 INENo `A'TTORNEY June 6, 1944. v K SCHH-:SINGER 2,350,536

SYNCHRONIZING SIGNAL GENERATOR ATTRNEY June 6, 1944- K. scHLEslNGER SYNCHRONIZING SIGNAL GENERATOR Filed July so, 1942 mwa.

6 Sheets-Sheet 6 INVENOR my ATTORNEY Patented June 6, 1944 SYNCHRONIZING SIGNAL GENERATO Kurt Schlesinger, West Lafayette, Ind., assignor to Radio Corporation oi' America, a corporation of Delaware Application July 30, 1942, Serial No. 452,921

(Cl. Uil-69.5)

8 Claims.

This invention is directed to television systems, and particularly to a method and means for producing synchronizing signals (hereinafter termed sync signals because of usage in the art).

Further, the invention is directed to systems wherein the produced sync signals shall be in accordance with standards proposed by the Federal Communications Commission and reported ln its Docket 5806, dated May 3, 1941.

In the prior art, sync signal generators have been developed and used successfully. Such apparatus has been proposed in'various forms, and one ,form which has been used, to some extent, is that disclosed in brief form in Principles of Television Engineering by D. G. Fink, published by McGraw-Hill Book Company, Inc., New York, 1940, and particular reference is made to that portion of the publication referred to which commences on page 402, under the title Synchronizing Signal Generator, and which continues through page 414.

In the prior art arrangements for instance, the sync signal generator included, mainly, two units, of which one was generally designated as the timing unit and the other was designated as the shaping unit. The timing unit is usually interlocked with a power supply frequency and serves to control the second unit which, as before stated, is known'as the wave shaping unit. These various units are described in some detail in the publication hereinabove referred to, and, when in operation, serve to provide a synchronizing signal wave form of the general character hereinafter disclosed by Fig. l of the drawings which will be described in what is to follow;

The wave form for controlling television image reproduction generally comprises horizontal synchronizing pulses which, after a predetermined time, are followed by certain equalizing pulses. The equalizing pulses are six in number and occur at twice the line frequency, or, in other words, at twice the frequency of the horizontal synchronizing pulses. Following the six equalizlng pulses there are produced vertical synchronizing pulses over a period of time corresponding to the time required to produce three'lines of picture transmission. The vertical synchronizing pulses are each slotted, so there' result, in effect, six separate slotted pulses. These vertical impulses are then followed by six additional equalizing pulses occurring at double line frequency which,-

' are a certain predetermined nm Following the second groupoiequalizin pulses v y '.,imtitg the first of the equalizingfpulsesraboverefered to again occurs, which, asis'evidentgwilljbe'at the time of completing eachsucceedingjpicture field transmission. i

According to the proposedfst VHclardsl for mission, vertical blanking in rvthe'picture` :sfintended to take place during theperiod off transmission of all of thevrst' grou'pfv ofl ,equalizing pulses, the group of vertical synchronizingpulses,

' the second group of equalizing pulses, and acertain portion of the succeeding group of horizontal The .Yerial' blkig period may thus be assumed to"includeL a period of time (according to proposed standards) corresponding to.0.075 Vi0l005 V,','where-Vjrepref sents the time from the start of one picture' eld to the start of the next succeeding picture eld'.

According to the present invention, it.i spr`o posed to develop, with apparatus `of asubsta'n- Y tially simplied nature, synchronizing signals of the general form hereinabove describedjand known in the art, and to thifsend, provisionis made for accomplishing-y `the 'results' bym purely 4electronic means of simplified hating, y

1t is an object'of the` presentmvenuon1-tb pi; vide a system for producing television synchro,-

Anizing signal wave forms particularly adaptable for amplitude modulationoi' the video intelligence which conform completely to presently .existing standards. f 1

Another object of the invention/is to provide for developing signals of the aforesaid'character by means of purely electronicappafatus. v .g

Still another object of the 'invention toprovide a system for developing synchronizing sig,- nals where all of the signals arelderived 'from one and the same master` oscillator which is preferably a non-sinusoidal pulse generator ofA pre-l distorted waveform.

Another object is to provide for generating sig,- nals of the above character ,with apparatus which overcomes one or more known and existing l ,disjadvantages and defectsof the'prior ,artarrangements. For example, the relativephaseshift of signal is made invariable `withthe presentjapparatus, and all groups of signals havle'the same leading edgein common. g A further object of the invention is to provide and develop a system rwherein n the j number of 2. tubesrequiredtogeneratethedesiredfrmof munmbstanuauy reduced.

Still a further obiect is that of developing a system vfor generating sinals of the aforesaid signal generator which'occupies a relatively small space because ofthe reduced number of tubes and other component parts to provide a system for developingsignals of the aforesaid character which is easily serviced and maintained in satisfactory stable operation. and a system which is relatively simple in its arrangement and construction.

Other and further objects and advantages naturally will becomeapparent to those skilled in the art from a reading of the following specification in connection with the accompanying drawings, whei'ein-l Fig. 1 is a diagrammatic representation of the general form of synchronizing signal now considered as standard:

Fig. 2 is a schematic representation of certain wave forms serving to illustrate the general principles of operation of the herein to be described device;

Fig. 3 is a schematic block diagram of the circuit instrumentalities herein to be disclosed:

Fig. 4 is a diagrammatic representation of certain wave forms occurring in the apparatus diagrammatically represented by Fig. 3

Fig. 5 is a series of curves relating particularly to theoperation 'of the single pulse relay schematically disclosed as a part of Fig. 3 and more particularly set forth by Fig. 6; and,

Fig. 6 is a schematic diagram of one form of the complete circuit instrumentality diagrammatically represented in block form by Fig. 3.

Referring now to the drawings for a further understanding of the invention, the system in general is based upon an arrangement wherein the various groupsof sync signals, namely, the line pulses, the equalizing pulses and the frame pulses (commonly referred to as L. E. F.) as well as the blanking signals, are derived from one and the same master oscillator by relatively simple clipping devices to which variable biases are applied. 'Ihe master oscillator generates pulse energy of a predetermined non-sinusoidal wave form in which the duration is made equal to that desired for the equalizing pulses and the repetition rate is twice the line frequency. For leach oscillatory cycle the energy is first negative and then positive with cessation of operation after the negative and positive pulses for approximately '76% of the cycle. s

Such a system, as will herein be described in more detail, oers an important advantage in that the relative phase relation is' invariable at al1 times, and all signal groups have the same leading edge in common, sc that the phase relationship between all groups of signals is always fixed and correct.

the input and the output signals is subject to variance to some extent. Therefore, the present would be subject to shift in a somewhat erratic manner with reference to the line signals, but, by making provisions so that the output signal is taken as a sort of potential impulse, for in stance, a highly precise timing signal may be obtained by using the impulse from the master oscillator to control the final signal production.

It will be apparent from the showing of Fig. l that the television synchronizing wave form., as it has now been approved by the Commission, comprises recurring line synchronizing impulses I which occur with their leading edges spaced with a time separation H (one picture line period). At the bottom of each picture field transmitted, a series of six equalizlng pulses 3 are initiated. These equalizing impulses are each of the same amplitude as the line synchronizing impulses, so that in transmission they represent, as do the line synchronizing impulses, substantially 100% modulation of the carrier. However, the equalizing impulses are of less width and less duration than the line synchronizing impulses, and, according to the adopted standards, the area is permitted to vary between 0.45 and 0.5 of the area of each horizontal or line synchronizing impulse. After the series of six equalizing pulses are developed these are followed by the vertical synchronizing impulses 5, which are slotted as shown at 1.

The time period indicated between the beginning of one vertical synchronizing impulse and the beginning of the next succeeding vertical synchronizing impulse is 0.5 times the time between any two successive line synchronizing impulses. I-'he width of the slotted portion of the vertical synchronizing impulse is to be equal to approximately 0.07K, where H is the time from the start of one line synchronizing pulse to the start of According to some prior art systems, frequency y entirely, because the phase relationship between the next line synchronizing pulse, so that it be comes evident that the width of each vertical synchronizing pulse is approximately 0.43H.

After the succession of six vertical synchronizing pulses 5 has been produced within the time period represented by three times the time expiring between the beginning of one line synchronizing impulse and the beginning of the next succeeding line synchronizing impulse, a second series of equalizing pulses 3', also six in number, is developed, and these equalizing pulses then are followed by the normal line synchronizing impulses 0.

The time period between the start of the first equalizing impulse of the ilrst group and the commenment of the next succeeding transmission of video signals represented conventionally at il, is made equal substantially to 0.075 V, where V represents the time from the start of one picture ileid to the start of the next picture field, and, according to the illustrated wave form, it will be seen that eight horizontal synchronizing pulses follow the second group of six equalizing pulses prior to the commencement of the4 transmission of video signals, represented at ii, for the top of the next picture field.

As shown, each horizontal synchronizing Pulse, each equalizing pulse and each vertical pulse is maintained vat substantially 25% greater carrier voltage than any video signal Il, as is customary in any system wherein negative modulation" is Provided, by which is meant that white of resent substantially 100% modulation of the carrier, and consequently producesignalsfwhich can be describedv as being "blacker than the blackest z black.

With the foregoing thoughts in mind, reference may be made to Fig. 2 oi' the drawings, and first to curve a thereof. By this curve, as in all'others, the ordinates represent amplitude and the abscissae represent time. By referring to curve a of Fig. 2, it will be seen Ithat this curve represents generally the wave form I5 of the master oscillator which develops output pulse -energy at a frequency of 31,500 cycles per second (assuming a 525 line television picture as will be herein assumed for illustrative purposes). Thus, lthe elapsed time between any two peaks of the output energy is represented as I/mo second, and the width of the pulse in the negative direction (to form the slots in the vertical sync) is represented as 8% H, where again H, as in Fig. l, represents the time elapsed between the starting of one line andthe starting of the next succeeding line, while the width in the positive direction (to develop the equalizing pulses) is 4% H.

It can be seen from the showing of curve a.of Fig. 2 that the master wave thus developed is a sequence of pulses occurring in the desired width and at the desired frequency and starting with a peak in the negative direction. Each wave trace, comprising'the negative and the positive half, has a' combined period of 12% of the repetition period of each line, with the'duration of either the positive portion of the pulse amounting to 4% of the line frequency, which line frequency may be derived from the master frequency by a frequency reduction of the order of.1:2. The 4% width is intended to be the duration ofi the equalizing pulses to occur between the line synchronizing pulses and the vertical synchronizing pulses, as was' hereinabove explained, in accordance with the standards of the RMA and those recommended by the Federal Communications Commission, all as above stated.

In curve a of Fig. 2, one clipping level, above the zero reference line `O, inthe positive direction has been indicated by the legend E, from which the equalizing pulses will be derived, and` a second clipping level has been indicated as spaced from the zero reference line O by a distance represented by F from which the frame synchronizing signals are to be derived. There thus results from clipping the master wave at the level E, a series of pulses such as those shown, for instance, by curve b of Fig. 2, which appear as a series of pulses l1 each spaced in time, one from the other, by $51,500 second, and for a resultant signal resulting from clipping, at the level F, a signal such as that shown shematically by curve c of Fig. 2 is found to be developed. This series of signals will be those' resulting from clipping below the zero line of curve a, andconsethe start of each succeeding line of synchroniz-L1 ing impulses and the interruption periods designated by the recesses 2| provide signal interruptions existing ior 8% of the line period, as shown by curve a. and which thus correspond to the periods of interruption in the vertical sync pulse interval 1, as shown by Fig. l. l

It can be seen further, from what has-been above stated, that the leading edge of both the lequalizing pulses I1v and the .frame signals I9 are coincident in time. The line and the blanking signals are derivedfrom the ysame master wave by frequency halving after the master wave is inverted, as shown by curve d of Fig. 2.

Let -it now be assumed that the frequency halver responds to a positive peak and is given an exponential output wave shape by a capacity loading. The wave form may be considered to be as shown by curve e of Fig. 2. In this case, the blanking and super sync pulses may be derived from the output, again by two clipping procedures indicated by clipping at the levels S and B representing, respectively, the 'clipping levels for the high level super sync signals and low level blanking signals. The S level clipping may easily be placed at such a voltage that the leading edge of the resultant sync pulse becomes coincident with the leading edge of the equalizers and frame signals, as is shown, for instance, by

blanking signals conventionally Ashown at 21.

Reference may now be made to Fig. 3 of the drawings which is a schematic representation of the general arrangement of the various tube circuits, which, in co-operative relationship, produce the various clipping and wave shaping effects schematically represented in Fig. 2 above discussed. In connection with a consideration of the diagrammatic representation of Fig. 3, reference should also be-had to Fig. 4, wherein various wave shapes appearing in the different instrumentalities diagrammatically represented in Fig.

3, are indicated. By the various portions of Fig.

4, the letters indicate the wave shapes at the points where -the letter indications appear in Referring now to Fig. 3, the master oscillator 3| is provided for developing pulse energy of a wave form shown, for instance, by the waves of Fig. 2a or Fig. 4a. These pulses are generated as was indicated, to be repeated at a frequency of 31,500 cycles per second (assuming herein, as-

` above stated, that the system disclosed is operatvelapsed time being with a `525 line television picture, although it is perfectly evident that the same circuits are applicable to systems using a different number of picture lines and a different number of picture frames and fields than the assumed 30 and 60 respectively). It was above noted also that the wave should be inverted to produce some of the effects necessary. l

, It has accordingly been provided so that the master oscillator 3| is the source from which three separate signals are derived. To provide this effect, the output from the master oscillator Such' pulses are represented schematically by the,

issupplied (nrstlto acathode follower' or buffer stage Il: (second) to supplyfan inverted output wave such as that .shown by Fig. 2d orl'ig. 4b to the line oscillator Il and a frequency divider I'I, and (lastly) to control a super sync mixer ll witha wave form such as shown in Fig. 2a. The cathode follower or buifer stage 3l feeds its output, in turn. to a series of frequency dividers Il, 4I, and Il respectively, each of which is driven from the preceding oscillator, and the cathode follower or buifer stage acts to prevent any possible load variations in the frequency divider stages from being introduced upon the masteroscillator Il by the controlled frequency reducing system.

'111e line oscillator Il is adapted to generate output energy at a frequencywhich is half that of the master oscillator ll, and, accordingly, the

output pulses therefrom occurat a rate of 15,750 cycles per second. Along with the line frequency oscillator ll, the inverted energy from the master oscillator 3l is applied also to a frequency divider unit 31 which operates to develop an outmaticfrequencycontrolactionmustbecarried out. Accordingly. l portion of the output yenergy from the last frequency divider Il is appiiedtov, an automatic frequency control unit 4l. ."lfhe wave form output from the last frequency divider of the group has, as indicated. a generally quasi-linear shape as derived from the last stage quasi-linear form of 4d--and then fed back by oscillator, or.5,250 cycles, which is keyed for the duration of the frame pulses. Finally, the master oscillator also feeds its nonlnverted output wave, such as that shown by Fig. 2a or Fig. 4a, to the super sync mixer ll, wherein wave formations corresponding to waves e, f and g of Fig. 2' are developed by suitable clipping actions'. 1

As was above stated, the master oscillator generstes its wave output, such as that shown by Fig. 2a or 4a, so that it starts with a negative peak. From the cathode follower or buffer stage 33, a series of positive pulses, at double line frequency, as shown by the pulses of wave form Fig. 4, curve c, are developed, and these pulses are thensupplied to the first frequency divider 4I. Essentially, the frequency .dividers Il, 42, Il and Il are blocking oscillators, the circuits of which will be more particularly appreciated from the showing of Fig. 6. Each of the blocking oscillators or frequency dividers 4I, I2, I3 and Il is interlocked so as to give a resultant frequency division or reduction of 525 to l. Accordingly, the output from the first frequency divider Il appears at t/s the frequency of the master oscillator 3l, or at 10,500 cycles. The output from the second frequency divider I2 is V; thel frequency of the output of the iirst frequency divider 4i, or 1115 the frequency of the master oscillator Il, and consequently is developed at 2,100 cycles. Similarly, the frequency divider 43 reduces the output frequency `of the frequency divider 42 by y', and thus is 1/15 the frequency of the master oscillator 3|, or 420 cycles. Lastly, the frequency divider 44 reduces the output frequency of the frequency divider by 1/1. so that its output frequency is 1,625 of higher frequencies becauseot slightly greater stability and simplicity of reduction.

It is evident, from what has heretofore been known in the art relating to frequency dividers and sync signal generators, that the last stage 44 of the frequency divider group is supposed to develop output energy precisely at the ileld frequency oi 60 cycles per second. But, to obtain this frequency accurately, a certain autoway of aconductor such as Il to the master oscillator 3l, so as to control its frequency and maintain it at exactly 31,500 cycles per second, which is 525 x 60.

It will be apparent, from the showing of Fig.1, that the line synchronizing impulses are to be produced continually except for the duration of nine line periods which correspond to the period of time required to produce and transmit the first series oi' equalizing pulses, the vertical sync pulse interval and the second series of equalizing pulses. Accordingly. it is apparent that the inverted output of the master oscillator Il may be fed into two separate devices, namely, the line frequency oscillator Il which operates continuously at one-half the frequency of the master oscillator (that is a frequency of 15,750 cycles) and is synchronized by it through the energy supplied by way of conductor Il. Also, the lso-called frequency divider or start-stop system 31, which contains the frequency divider operating at V6 the frequency of the master oscillator 3|, is energized from and controlled by the master oscillator 3i by way of energy supplied by conductor 52. Tire output energy from the frequency divided 31 is in a step-down ratio 1:6 with a pulse outputof 5,250 cycles. corresponding to a duration period of three times the time interval between successive line synchronizing pulses. o'r. in other words, a time duration 3H.

The frequency divider or start-stop system 31. however, does not operate continuously, but is brought into action only during the picture retrace moment, and for this purpose the frequency divider unit 31 is keyed by the output of the frequency divider unit 44 which is developing the 60 cycle output, as shown by wave d of Fig. 4, and this 60 cycle energy is f ed to the frequency divider 31 by way of conductor 53. The energy fed to the frequency divider unit 31 by way of conductor 53 is of the general wave form corresponding to, curve f, Fig. 4, and it will be noted, fol-instance. that this keying signal is slightly longer than that actually required and consequently it only serves to actuate the frequency divider at 5,250 cycles, but cannot be used for correct timing or switching action from the line to the frame signals and back again.

In the output of' the frequency divider 31 the wave form, as shown by curve o of Fig. 4, appears in the conductor l5 which feeds the energy voutput'from the unit l1 into the square wave these four pulses which are used vto trigger the square wave generator 51, whose output is shown by the curve h of Fig. 4 and appears to be a square wave voltage which is symmetrically arranged above and below the axis and starts with negative polarity. Special precaution is taken that this polarity is always the same, that is to say, the square wave generator 51 must be designed so that it is of a type which might be called non-communicative. This voltage then is used to serve as a bias for the master oscillations (as per curve a of Fig. 4) which are supplied by way of conductor 58, and consequently the two voltages represented by curves a and h. of Fig. 4 are summed up and applied to the super sync mixer 39.

From what is to follow in the description of Fig. 6, it will be seen that these two superimposed voltages are fed into one of the two pentodes which are in co-opgration in the super sync mixer 39 and are used to feed the line signals and the equalizing and the frame signals into the same output line.

To obtain this mixing action, a special relay unit 59 is provided. This relay unit 59 is supplied with energy by way of conductor 6| from the square wave generator 51, and its purpose is that of generating a one-signal pulse of either positive or negative polarity which 'will be of' a duration corresponding exactly to a period of 9H, that is, a period of nine line sync pulses. The single pulse relay 59 is shown in more detail in Fig. 5, and further reference will be made to it, but at this time it should be borne in mind that the single pulse relay 59 is, as above mentioned, of the class termed non-communicative, that is to say, its pulses are required to have a definite polarity.

The output 'energy from the single pulse relay 59 is shown in wave form k of Fig. 4, and the relay itself is triggered by wave energy which is represented by the curve f, also of Fig. 4. 'Ihis .wave form energy is derived from the square Wave generator 51 by diierentiation and, accordingly, the curve :i consists of a sequence of four separate pulses alternating in polarity and each of very short duration, which are separated from each other by a time period represented by 3H. Accordingly, the pulses have an altering polarity sequence of plus and minus.

In order to provide the desired type of signal, the single pulse relay 59 has an inherent quality, as will be appreciated from a further consideration of Fig. later to be discussed in detail, of standing by in an attending or waiting position or state until the rst positive pulse of Wave i arrives. The relay then respondsy to this one pulse but does not cease operation or fall back until the second negative pulse arrives, and, for the purpose of maintaining 'a state of operation of this character, electrical inertia ls introi duced into the circuit of the relay in a manner which will be described particularly in connection with the specic description of Fig. 5.

By the co-operative relationship of the square wave generator and the single pulse relay 59, the super sync mixer 39 produces, at its output, the desired succession of super sync signals which may be impressed upon a predetermined type of transmission line 60, for example, a 10,000 ohm line, but the wave fronts of these resulting signals are generally not suiciently steep to provide the exact desired signal form. To improve the wave form, a wave shaping amplifier 5l is provided between the transmission line 60 and the output terminals 62 and 63.

Essentially. as will be seen from the description of Fig. 6, this shaping amplier includes. primarily, tubes of the pentode class which are particularly capable of re-shaping the wave' as desired. Fundamentally, the purpose of the shaping amplii'ler 6| is to increase the steepness of the leading and trailing edges to a predetermined precision of timing which will correspond to somewhat less than three picture elements.

(according to RMA standards). At the same time, the amplifier 6I acts as an amplitude clipper, as well as a power amplier. As a result, approximately a 50 volt pulse amplitude is obtainable in either the positive or the negative direction across a load connected to the terminals 62 and 63 which may be of 1,000 ohms or less. wherein all output signals have substantially equal height and equal slope. This general result its pictorially represented by the curve m in Fig.

For the purpose of obtaining the blanking pulses according to the standards pictorially represented by Fig. 1, certain additional tubes and elements are provided. To this end, there is required an additional wave shaping amplier 85 which is of substantially like nature to the wave shaping amplier 6l' for the purpose of shaping the super sync signals and giving the same output power and voltage. A mixing of the line and frame blanking signals is obtained in a blanking mixer 61, which preferably comprises but a single pentode connected in co-operative relationship with the suppressor grid of one of the'amplier tubes of the shaping amplier 85.

The blanking mixer 61 acts generally as an amplitude clipper and it receives an input signal a time period equal to the duration of one equalizer pulse or a time period of, say 0.08H.

To provide the proper length of the frame blanking signal and to operate the mixer unit 61. another single pulse relay 69 is provided. This relay 69 is adjusted to give an output pulse of exactly 12H, see curve n of Fig. 4, to provide for the picture retrace blanking, and the leading edge of this pulse is (intended to be coincident with the leading edge of the rst of the equalizers in the super sync. For this purpose, the relay 69 is triggered by the same series of pulses that control the relay 59, which are represented by curve i of Fig. 4, and, as Wasl hereinabove stated, this wave is derived from the square wave generator 51 by electrical differentiation. Means next are provided to superimpose a 10% fraction of the super sync signals upon the blanking signals, and thus the transmitters may be modulated over a single channel. The output from the wave shaping unit 65, as shown for instance by -curve p of Fig. 4, appears at the terminal points 1l and 12.

Reference now may be made to Fig. 6 of the drawings which is a schematic circuit diagram of a complete sync signal generator. As was outlined in reference to Fig. 3, the various tube elements shown in the circuit arrangement ot Fig. 6, have their counterparts in the schematic representations. For the purpose lof enabling the tube units readily to be identified in Fig. 6 and compared with the schematic representations of Fig. 3, it will be seen that the combination' of the master oscillator 3| and the buffer stage 33 is provided by the tube A and its associated circuit elements.

The frequency dividers 4|, 42 and 43 are provided by the blocking oscillator tubes and circuits, generally designated B, C and D. Tube E and its circuit elements co-operate to provide thev 60 cycle stage and the frame key signal generator. The automatic frequency control, schematically designated by the unit 45 on Fig. 3, is provided by the tube F and its circuit elements. The line frequency oscillator 35, which is maintained in a state of continuous oscillation, is provided by the tube G and its associated circuit elements. The frequency divider 31, which pro-- vides output energy of one-sixth the frequency of the master oscillator, is shown by the tube H and its circuit elements, with the keying action thereon being provided by the tube and circuit E. Tubes I and J and their circuits together represent the square wave generator, generally designated in Fig. 3 as the element 51.

The single pulse relay for developing energy pulses of the duration 9H is schematically represented in Fig. 3 where the element 59 is shown as comprising the tube K and its associated circuit elements. The tube P and its associated circuit elements provides the single pulse relay corresponding to the element 69 of Fig. 3, and is for the purpose of developing the pulses such as shown by curve n of Fig. 4 and which are of a duration |2H. 'I'he tubes L and M co-operate with their circuit' elements to provide the mixer stages for the super sync, such as shown by the conventional representation 39 in Fig. 3.

From the description to follow, it will be seen that the tube L and its circuit elements develops the equalizer and frame pulses, while the tube M develops the line pulses, and both of these tubes are keyed, in turn, by the single pulse relay K. The tube N with its circuit elements forms the slope shaping amplier, such as the amplifier 6| of Fig. 3, while the tube O and its circuit elements provides the super sync output stage.

The blanking mixer 61 of Fig. 3 is represented f by the tube Q and its circuit elements in Fig. 6, and the tube R, together with the co-operating circuit elements, finds its counterpart in the shaping amplifier 65 of Fig. 3. The tube S functions as the output blanking stage. 'I 'he tube T functions merely as a rectifier in the power supply line, and the other two illustrated tubes X and Y, in Fig. 6, comprise merely two voltage regulating lamps in the power supply chain.

Now making reference more particularly to the specific circuit of which that disclosed by Fig. 6 represents one form which has been found suitable in its function for the described purpose, it will be seen that the master oscillator A comprises a twin triode tube 15, which, for illustrative purposes, may be a tube of the general type known as the 6F8. The first portion of this tube, comprising the cathode 11, thecontrol electrode 18 and the anode 19, is connected as a blocking oscillator with the tuned plate circuit. The interruption period is provided by a tuned circuit comprising the condenser 8| in series with resistance elements 83 and 85, of which the resistor 83 is (where desired) made variable and thus is capable of providing the necessary tuning. A coupling between the plate circuit and. the grid circuit of the rst section of the tube is provided by way of the primary and secondary windings of the transformer 81, as indicated.

In order to provide for changing the pulse width, for reasons hereinafter to be more fully explained, an additional capacitor 38 is provided and connects to ground at 9|. Also connected between the cathode 11 and ground |41 is a cathode resistor 80, preferably of the variable type, which is, in turn, shunted by a condenser 84.V The cathode resistor 80, it will be seen, may furnish a convenient means to obtain a rather delicate adjustment of the frequency control in contrast to the more or less coarse adjustment which would be experienced by a variation of the grid leak resistor 83, but which is, of course, entirely practical.

Considering the general arrangement of the oscillator comprising the rst half of the tube 15 or the tube A, the coupling transformer 81 has a relatively low stray capacity, so that its natural frequency is generally high, which means a distributed winding should be used; and, on the other hand, the grid leak condenser 8| is of relatively high value. Under these conditions, it can be seen that as the circuit starts to oscillate, it acts somewhat as if the grid coil were tuned by the grid condenser 8|, and the grid cathode resistance then becomes substantially negligible for the positive half of the cycle. For the negative half cycle, however, the loading effect of the grid condenser 8| through the tube section comprising the cathode 11, the grid 18 and the anode 89, substantially disappears and the period is greatly reduced substantially to the i natural period of the coils, which may be adjusted, furthermore, by the small capacitor 88. It is thus apparent that the output of the blocking oscillator section of the tube 15 is a wave of the general character shown by curves a of each of Figs. 2 and 4, and this may be of the order of approximately 200 volts peak, as indicated.

For the purpose of lengthening the slot width in the vertical signal (that is to provide the 0.08K slot width) it can be appreciated that by eliminating the tuning of the plate coil of the transformer 81 of the master oscillator and increasing the blocking condenser 8|, while decreasing or shunting grid and cathode limiters 83 and 80, the width of the pulse can be made wider, for example, without in en y way departing from the disclosure of the present invention, but by eliminating the tuning provided by the condenser 89 and the resistor 90, which was made small enough to give the plate circuit of the iirst half of the tube 15 a generally oscillatory character, the outputl characteristic may be modied. Of course, in this connection also it is desirable to eliminate the tuning of the grid coil.

If, now, it be assumed that the distributed capacity across the plate and grid coils of the transformer 81 is represented by a value Cz, and this value is substantially negligible, then it becomes immediately apparent that the output pulse energy from the blocking oscillator 15 is of the general wave form shown by the curve a of Fig. 2, except that the first negative portion of the cycle is wider than the positive portion of the cycle. The grid and the plate voltage are equal in amplitude and opposite in polarity and, accordingly, the flrsthalf period is made longer than the second half period so that the width of the lower portion of the pulse from the blockfactories y and 89, functioning respectively as the line freing oscillator then becomes of a value such that the slots 1 (Fig. 1) are obtained by clipping at level F. At the same time, the narrower pulse shown by the designation 0.04H of Fig. 2. curve a, for instance, which represents the equalizing pulse, is attained by the leading and trailing edges of both pulses in combination with`the condition of coincidence, hereinabove explained, when clipping at level E.

This condition of operation is explainable by considering that the grid coil of the transformer i81 is connected in parallel with the blocking condenser 8| through the grid to cathode path 18 and 11. during the first or positive cycle of the grid swing. As the cycle reverses, however, this path in the tube becomes non-conducting and the coil is left alone with its distributed capacity hereinabove assumed as Cz which is divided equally between the plate coil and the grid coil as the load. Obviously, the natural period of ,the circuit in the rst condition is bound to be longer than the period of the succeeding cycle, and consequently the length of the slot pulse, as shown by curve c of Fig. 2 can readily be changed within predetermined limiting values with regard to the desired width 0.08H by changing the value of the capacity while the repetition frequency of all the pulses can readily. be adjusted to the desired frequency by means of adjustment of the leakage resistor 03 or 80.

It is also quite apparent that the back-kick, as shown by the curves of Fig. 2. is substantially exponential of the time constant equal to where L is the inductance of the coil and R1 is the internal resistance of the tube, and, accordingly, it becomes apparent that for very high oscillation frequencies the ratio of the pulse width in the negative direction to the pulse width in the positive direction can be considered as ii' it were proportional to the square root of the distributed capacity across the primary and the secondary coils divided by the value of the effective capacity 8| which actually may be only a fraction of the grid capacity, due to the interaction of the grid to cathode resistance in series with it. In this instance, the capacity 8| is of relatively large value, for instance, of the order of 10,000 mmf. and, on the other hand, the stray capacity is of the order of about 100 mmf.; this is found to produce the positive pulse equal to about half the width of the negative pulse, with the result that the increased width of the slots in the vertical sync signal, as shown by Fig. 1, is readily obtained from the circuit here shown by providing the master oscillator` tube 15 with distributed winding and omitting plate tuning circuit connections.

The blocking transformer 81 comprises two further windings 92 and 93, each of which has an output of approximately one-tenth that of the blocking oscillator, or about 20 volts (assuming a 200 volt output from the oscillator), with the winding 92 being in phase with the plate voltage at plate 19 of the tube 15, and the winding 93 providing an output of opposite phase, as shown by the curve b of Fig. 4 for instance. The output from the winding 92 is caused to appear in the circuits of the tubes J and L, and thus appears directly in the output after suitable clipping and switching. The winding 03, however, is used directly to synchronize the various line and keying oscillators, such asv represented by the tubes 95 quency oscillator G and the frequency divider H.

The second portion of the master oscillator A, represented by the tube 15. comprises the section including the cathode Ill, the control electrode or grid |02 and the plate or anode |03. This section of the tube Vis connected as a cathode follower stage. The anode or plate |03 is connected to the terminal of the winding of the transformer 81, through which positive voltage is supplied, to energize the plate or anode elements 19 and |03 of the tube. The cathode element |0| is connected to ground potential through the cathode resistors |04 and |05. 'I'he control electrode |02 connects back to receive energy, such as that supplied by the blocking oscillator tube control electrode 18. The second half of the tube 75 thus becomes effective in the operation to prevent undesired grouping of the lines in the received picture, and if this buer section were not present, and if the frequencydivider chain formed from tubes B, C, D and E were energized directly from the oscillating system comprising the rst half of the tube 15, it will be seen that grouping might occur which amounted to several picture elements so as to disrupt, to some extent at least, the transmission of the vertical lines of the picture.

Referring next to the frequency division provided by the various frequency dividers, such as those represented schematically in Fig. 3 and shown more particularly in Fig. 6 by the tubes B, C, D and E, it will be seen that al1 thetubes B, C and D are of the general triode type, such as tubes of the 6J5 type. So considered, the rst frequency divider thus comprises the tube |05; the second frequency divider the tube |01, and the third frequency divider the tube |09.

The output energy of the second half of tube 15 is cathode coupled to the input of the ilrst tube |05 so that tube |05 is energizedby way of the conductor I in accordance with the voltage drop across resistor |08.` The tube |05 comprises the usual cathode ||3, control electrode H5 and thel anode or plate H1, which latter element is connected to one winding of the transformer ||9 and also to a source of positive voltage as applied to the bonductor |2| through appropriate resistors |22 and |23, and high frequencies are by-passed to ground |24 by way of the by-pass condenser |25. The arrangement thus is similar to that by which the tube 15 receives its plate .or anode voltage from the conductor |2|, and similar to that in which high frequency energy is by-passed to ground from the tube 15 through a similar condenser |25. A

In order to tune the period of the blocking oscillator tube |05, provision is made for the use of a grid condenser |21 and suitable grid leak elements |28 and |29, of which the latter is preferably variable in order to provide the necessary tuning. From what was above stated, it appears that the output energy from the tube |05, corresponding to the first frequency divider B, is energizedat a period of 10,500 cycles, which will be assumed to correspond to one-third the frequency of the master oscillator tube A or 15. This output energy is fed by way of the coupling provided with the cathode resistor |3I, the coupling resistor |32 and the coupling resistor |33, which together form a coupling network of the general type identified as a 1r network and consist purely of ohmic resistances of low impedance, for instance of the order of about ohms each. The

energy output from the first frequency divider' tube B or is thus fed to the second frequency divider tube C or |01 in essentially the same manner as the output from the buffer stage of the tube is applied to the tube |05.

The secondfrequency divider tube |01 comprises the usual cathode element |35, the control electrode |36 and the plate or anode |31. The plate or anode |31 connects to one winding of the transformerV |39, and also connectsto the high voltage line |2| by way of resistors |22 and |23, as referred to with regard to the tube |05.

As was explained in connection with the first frequency divider tube |05, this second frequency divider tube 01, which also may be of the general type known in the art as the 6.15, is tuned by means of the condenser |4| operating in conjunction with the resistors |42 and |43, of which the latter is preferably made variable.

The indicated connections to ground |41 are common for a great many tubes in the frequency divider and other portion of the unit.

Output energy from the second frequency di vider stage |01 is fed by way of the resistor |49 in accordance with the voltage drop occurring across the cathode coupling resistor ISI. The resistors |49 and |5l, together with the resistor |53, again form a 1r section lter, as did the resistors |3|, |32 and |33 serving to couple the output of the first frequency divider tube |05 to the input of the second frequency divider tube |01.

At this point it might be well to point out that the 1r section filter used for coupling offers some advantages in that, by omitting the coupling impedance it is easily possible to pre-set each stage independently, because the subsequent connection affects the natural frequency but very slightly. Further, it is possible to adjust the degree of coupling readily by changing the coupling resistor, and also there is no lag with this type of coupling, and, as another point, the degree of frequency division may be counted readily since both the driving pulses and the reduced frequency pulses appear across the output end of the 1r'network.

The third frequency divider tube |09, which is also preferably of the general type known in the art as the 6J5, serves to reduce the frequency still further, and while the input frequency corresponding to the output of tube |01 is assumed to be 2100 cycles, the output from the frequency from the tube |09 will preferably be 420 cycles.

The tube |09 comprises the usual cathode I, the control electrode |55 and the plate or anode |56 which connects to one winding of the transformer |51. This transformer winding serves to connect high voltage from the conductor |2| to the plate or anode |56 by way of the resistor elements |59 and |60 at the junction of which --a condenser |6| is connected toV by-pass any possible high frequencies to ground |24. The other winding of the transformerv |51 is connected receive the energy output fromthe tube |01, and by means of the condenser element |63 and the resistors |64 and |66, of which the latter is preferably variable. the period of the oscillator is adjusted.

In connectionwith the frequency reduction to the lower frequencies, as provided by the tube |09, it is, however, desirable to tune the circuit including the grid or control electrode |55 by means of the condenser |65 which is connected in parallel to the grid coil of the transformer |51. For the higher frequency stages, such as provided |05 and |01, it has been found that the natural capacity of the windings is generally satisfactory to provide satisfactory perfomance. at least with the ordinary way of non-distributed wind-ing, so that in other circuits the tuning condenser |65 may, as a general rule, be eliminated, although it is apparent from what is here stated that ytiming of this character may be resorted to in any frequency' divider stage.

The output energy from the tube |09 which appears at 420 cycles, isthen fed through still another 1r section filter comprising the de-coupling cathode resistor |61 of the tube |09. the coupling resistor |69 and the grid resistor |69 of the last frequency divider tube E or |1I. Thus tube |1| is preferably of the 6F8 type, as is the tube 15, and it uses the first portion thereof as a blocking oscillator section which is of a slightly unusual form in that the storage circuit is connected between the cathode |12 and ground |41 and there is no storage provided in the grid (control electrode) or plate (anode) circuits.

In this connection the energy output of the tube |09 is fed to the grid coil of the transformer |14 and the tuning to control the duration of plate pulse is brought about by means of the condenser |15 in a manner somewhat similar to that explained in connection with the condenser |65 of the tube |09. This condenser |15 connects, as shown, to the control electrode |16 of the first section of the tube |1| whose plate or anode element |11 connects by way of the plate coil of the transformer |14 and a pair of resistors |18 and |19 to the conductory |23, at which the high positive potential appears by way of the connection at the terminal |80.

As was explained in connection with all of the other frequency reducing tubes, a condenser |8| connects between the resistors |18 and |19 and ground |24 to by-pass any high frequencies. Output energy from the first section of the tube between the cathode |12 and ground |41 is of quasi saw-tooth character with a positive peak such as shown by curve d of Fig. 4. This energy is caused to appear across the cathode resistors |83 and |84, of which the latter is preferably variable and used to determine the repetition i frequency of the system, and is fed by way of a conductor |86 to a phase control tube |90 which, for example, may be of the general type known in the art as a 6J1. The condenser |9| serves to by-pass any high frequencies to'ground.

The quasivsaw-tooth wave, as it appears in the conductor |86 corresponding to the output of the first half of the tube |1|, is to serve the purpose of automatic frequency control which is provided by beating this output with the 60 cycles per second of the power supply frequency which is connected at the terminals |92 and |92', and this is possible because there is a particular linear relationship between phase displacement and the D. C. output in such a wave. Further, in con! nection with the tube |1|, the output from the 'plate or anode element |11 ,is preferably of a pulse nature and ls adjusted to be of a duration of approximately IIH, as was indicated by curve f of Fig. 4, and this adjustment of the length of the pulse is, as above stated, brought about by tuning in the grid circuit by means of the condenser |15 in series with a resistor |92 and the grid coil of the transformer |14.

It was already explained that it ls desirable that this signal output for the plate |11 of the tube |1| shall have a duration lof slightly more than 9H but less than |2H asthis is the character of signal required to operate the square wave generator `for just three cycles of 3H duration, but no longer. The second portion of the tube 1|, comprising the cathode |93, the control electrode or grid |94 and the plate or anode |95 is, generally speaking, connected as a cathode follower. It draws current which is cut off for the duration of the pulses, and thereby an inherently at top level of the key signal is secured for a time duration ofi-'approximately HH. This keying signal is developed across the cathode resistor |96 and serves to operate the second half of the frequency divider tube 99, which is for the purpose of reducing the frequency to one-sixth that of the master oscillator 15.

Simultaneously, the plate current of the second half of this tube |1| is applied to the relay tube 200 tomake it of a non-commutative character. This effect is obtained by feeding this output energy through the conductor 20|, so that it iiows through an appreciable portion (the part 219) of the plate resistor 202 and 219 for the tube 200, and this results in a definite unbalance of this'relay during certain predetermined periods and it is not vuntil the emission in the tube |1| is out o that the balance in the relay tube 200 is re-established, as will become apparent from a further discussion of this tube in what is to follow. The effect is, however, that the relay tube 200 shall be in a predetermined and definite state with regard to operation when the rst directional pulse from the square wave generator and triggering tube 204 reaches it, as will later be explained and as is set forth in companion application Serial No. 445,253, filed May 30th, 1942, which is entitled Electronic relays.

Now, referring more particularly to the automatic frequency control tube |90 which receives energy of quasi saw-tooth character on its #l grid 206 from the conductor |86 by way of the time constant circuit 201 comprising the parallel capacity 208 and resistance 209, it will readily be appreciated that the impressed energy is a sawtooth voltage of substantially cycles. Consequently, the amount of direct current which the tube |90 can pass will depend upon the instant at which the tube is made conductive by a pulse derived from the 60 cycle power supply line assumed to be connected to the terminals |92 and |93 being supplied to the #2 grid 2|0 by Way of the transformer 2|| and the resistance' capacity circuit 2 I2.

Normally, the #2 grid (screen grid) of the tube |90 is negative and no plate current flows through the tube. However, during the positive swing of the power supply frequency connected to be supplied through the transformer 2| it is apparent that the tube |90 may be made conductive for a short instant. The necessary negative bias s uperimposed between the 60 cycle per second voltage and the screen or #2 electrode 2 I0 is provided by the resistance-capacity circuit comprising the resistance 2|3 and the capacity 2 i4 which provides a self-biasing effect. It is evident that the nearer the conductor period comes to the positive peak of the #l cr control grid swing the more current will flow, as determined by the quasi saw-tooth applied thereto. Any A. C. components in the output of the tube |90 may readily be filtered in the filter chain comprising the condensers 2|S and 2|1, each connecting to ground |41 and having the smoothing resistance 2 I 0 connected therebetween so that the resulting direct current output may be measured by means of the meter 2|9 (conventionally represented) and fed back by way of the conductor 220 through the resistor 22| to be applied to the control electrode 18 of the master oscillator 15 where it is caused to vary the bias on the control electrode and thereby control the operational cycle.

It is apparent that in operation the polarity of the variations should be rendered such that the automatic stabilization of the frequency is obtained within a very small range of direct current, for example, one milliampere, and this permits the control of a wider frequency variation than ever is to be expected in practice, -even under adverse conditions.

By means ofthe variable resistors 83 (coarse) `or (fine) connected to the control electrode 18` of the master oscillator tube 15, the direct current output from the tube is adjusted so as to appear at approximately the center of the scale 4of' the meter 2 |9, so that positive and negative variations of the power line frequency are equally well compensated. Any high frequencies induced into the secondary winding of the transformer 2| are readily by-passed to ground by means of the bypass condenser 222.

The tubes 99, 204 and 200 respectively serve to provide the necessary square wave bias so as to obtain equalizing and frame signal clipping within a mixer tube 225 (also preferably of the general type known as a 6.17) which will be later explained in further detail. Ihe tube 99 is arranged to function as a frequency divider tube and is essentially for the purpose of providing a frequency output corresponding to one-sixth the frequency of the master oscillator 15. o In its broadest aspect, the tube 99 is connected in the same manner as was disclosed for the frequency divider unit set forth and claimed in my co-pending application Serial No. 433,289, filed March 4, 1942, entitled Frequency divider (RCA Docket 21,107). Energy to drive the frequency divider unit 99 is derived from the coil 93 associated with the transformer winding 81, and the wave energy (as shown by curve Fig. 4b for example) induced into this coil is then fed by way of a time constant circuit comprising the parallel combination of resistor 221 and condenser 228 to the control electrode 229 of tube 99.

The time constant of the resistance capacity circuit 221-228 is essentially such that operation takes place at approximately one-sixth the frequency of the master oscillator 15 and, as was above explained, when the energy from the tube 15 is fed to the control electrode 229 of the tube 99 it is supplied in inverted polarity, as was indicathed for instance by curve b of Fig. 4. It is apparent that the inversion of polarity, in effect, gains time so that the switching mechanism is ready to supply the required bias on the mixer tube 225 prior to the time the rst equalizer pulse is applied by way of the condenser 23 I'.

The frequency divider tube 99 is operated in a start-stop manner, and the bias on the control electrode 232 of the second half of the tube is made highly positive as long as the plate current in the second half of the tube |1| is not interrupted. 'I'he cathode output of the tube 1| as it appears across the resistor 96, is supplied to the control electrode 232 by way of the conductor 233, but the cathode element 234 of tube 99, acting as a cathode follower stage, is biased highly positive,

and the plate current iiowing in the rst half of 'of picture scanning -corresponding to the time tion HH, as shown by curve f of Fig. 4, the grid.

bias applied to the control grid 232 of the second haii' of the tube 99 is reduced and the cathode 234 follows. Consequently, the rst half of the tube 99 comprising the cathode 234, the control electrode 229 and the anode or plate 235 comes into action as a frequency divider and provides an output at a frequency of one-sixth the frequency of the master oscillator, or at 5250 cycles, at the conductor 236 and across the resistor 231. Consequently, it is apparent that a series of four positive pulses with intermissions of a period 3H will appear across the resistor 238 connected to the anode or plate 239 of the second half of the tube 99, and it is further apparent that no more than four such pulses can be produced because, in the period between 9H and 2H (see Fig. 4. curve f) the plate current in the second half of the tube |1| is restored and the action of the tube 99 thereby ended.

In companion application Serial No. 445,253, led May 30, 1942, entitled Electronic relays, it has been explained how square waves may be produced by two triodes in vspecial connection, as shown by the tubes 204 and 200 under the inhuence of positive triggering pulses.

The arrangement of Fig. 4 of the last mentioned specication, showed generally an arrangement closely related to that embodied in the useof the tube 204 as the driver tube or the square wave generator trigger tube, and the tube 200 as the relay tube and ampliiler tube. It is, however, to be noted that in contrast to the arrangement shown by the last mentioned co-pending application, a tube of the general type known in the art as the 6F8 (with separate cathodes) is substituted for the form of relay tube previously shown, so that adequate power output may be de-` livered for the action of the mixer channel including the tubes 225 and 226 by cathode-follower coupling. i

Output energy from the frequency divider unit or tube 99 is fed to the control electrodes 24| and 242 of the driver tube 204 by way of the coupling condensers 243 and 244 respectively. This tube has its cathode element 246 appropriately biased relative to ground 241 by meansl of a bias resistor 248 in accordance with potential supplied by the resistor 249 from the positive potential conductor 250 which also supplies plate voltage for the plate or anode elements 235 and 239 of the tube 99 through the resistor 25| The control electrodes 24| and 242 of the driver tube are connected with the control electrodes 253 and 254 of the relay tube 258, so that the condenser 243 and the resistor 255 form one time constant cirouit and the condenser 244 and the resistor 256 form the second time constant cir.- cuit, both time constants being the same.

The cathode elements 251 and 258 of thevtube 20|) obtain bias relative to ground 241 by way of resistors 259 and 260 connecting through a common resistor 26| to ground, with a condenser 262 by-passing high frequencies to ground around the resistor 26|. Output energy from the rst half of the relay tube 200 flows from the plate or anode 263 thereof by way of the conductors 265 and 261 and the coupling condensers 268 and 269 to the relay tubes 21| and 212 (or P and K) respectively. Also from the cathode 258 of the second half of the relay tube 280 output energy is derived :ln accordance with the Voltage drop across the cathode resistor 260, and this output, as before stated in the discussion of Fig. 3, flows through the coil 92 and the coupling condenser 23| to the control electrode 213 of the mixer tube 225, so that at the control electrode 213'voltage .waves corresponding to the curve a of Fig. 2 (the frequency output of the master oscillator starting with negative polarity) and curve h of Fig. 4 are combined. A leak resistor 214 connects the control electrode 213 to the cathode 215 of Athe mixer tube 225, and the cathode 215 is biased relative to ground 241 by the biasing resistor 211.

, level Will be as indicated by the line E in Fig. 2a.

In connection with the square wave generator units 204 and 200, it was above pointed out that under normal circumstances it might be possible for the tube 200 to become conducting, so that one or the other of the two halves of the tube would draw current when the first trigger pulse arrives. However, for the purpose of developing a synchronizing signal generator arrangement, it is essential that it be determined which of the two halves of the relay tube 200 vshall conduct, and, to this end, an unbalanced condition is provided by causing the output current from the second half of the tube |1| to flow through a portion 219 of the plate resistors 202 and 219 of the second half of the tube 200, Once the current flowing through the second half of the tube |1| is cut off, the relay tube 200 is balanced, in that the plate resistor 280 for the rst half of the tube is made equal to the series resistance provided by' the series combination of the resistors 202 and 219.

It thus becomes apparent that the relay tube 200 will always start in operation with the second half, comprising the cathode 258, the control electrode 253 and the plate or anode 28| conducting, and in this way the curve h of Fig. 4 is obtained in such a way that there is provided an output pulse which is symmetrically positioned about the axis with no D. C. component, in' contrast to the normally expected D. C. component which would ordinarily appear with D. C. coupling.

Reference now may be made to the mixer tubes 226 and 283 which each have their #l grid or control electrodes 285 and 281 respectively connected to the output electrode 289 and the plate resistor 290 of the second half of the line frequency oscillator tube 95. Thus, connections are made to the mixer tube 226 via the conductors 29| and 292 and the coupling condenser 293, anf' to the blanking tube mixer 283 by way of the conductor 29|, the resistor 294 (used to drop the voltage) and the coupling condenser 295.

The grid leak resistor 296 is connected between the control electrode 285 and the cathode 291 of the mixer tube 226, and likewise the leak resistor 298 is connected between the grid or control electrode 281 and the cathode 299 of the mixer tube 283, and each of these resistors is of relatively high value. In. each case, automatic grid bias of such a magnitude is built up in the tubes that only the positive peaks of the line frequency impulses, forming the output from the tube 95, are ampliiied in the super sync mixer tube 226.

ammassol i The blanking tube mixer 233, however, hasincluded between the conductor 29| and the coupling condenser 295, through which the output of the tube 95 is supplied, the series resistor 294 hereinabove mentioned which serves to limit the grid current and consequently results in a clipping action taking place within the tube 263 at a lower level. This, of course, results then in the production of a longer duration pulse from the i tube 283 than is obtained from the tube 226 as would be expected from the showings of curves e, f and y respectively of Fig. 2. which diagrammatically illustrate the production of the line blanking and the synchronizing pulses from the common pre-shaped input signal.

Suitable positive voltage for the mixer tubes 225 and 226 is supplied to the plate or anode elements 300 and 30| thereof by way of the high voltage conductor 250 and the resistors 303 and 304 with the condenser 305 serving to by-pass any high frequencies to ground 241. Similarly, the line frequency oscillator tube 95 and the relay tube 212 each derive positive plate potential by way of the conductor 301 connecting with the conductor 250 and the plate resistors, as indicated, so that plate potential is supplied to the first half of the tube 95 by way of the resistors 308 and 309 with the by-pass of high frequencies to ground 241 being provided by the condenser 3|0, and plate potential to the second half of the tube 95 is then provided by the plate resistors 308 and 290 hereinabove mentioned. Likewise, plate potential for the anode or plate element of the relay tube 212 is provided from the .conductor 301 by way of the resistor 3|| and the resistor 3|2 for the rst half of the tube, and the resistor 3|3 for "the second half of the tube.

`The general circuit arrangement of the single pulse relays 59 and 69 of Fig. 3 are shown more particularly by the tubes 212 and 21| and associated circuits respectively, used to control the operation of the mixing tubes 225 and 226 as well as the shaping amplifier 3|1 later to be described.

' Further, the single pulse relay arrangement shown particularly by the tubes 212 and 21| respectively, and their associated circuit elements form the subject matter of a separate co-pending application identified as Single pulse relay, filed July 30, 1942, Serial No. 452,922.

In some senses the relay arranement 212 (and consequently also the relay 21|) tends to func* tion as a multi-vibrator, but is of a somewhat diierent form than the well known multi-vibrator in that it is of the type which may be stated to be A. C.D. C. coupled.

'I'he second half of the single pulse relay tube 212, which includes the cathode 3|9, the control electrode 32| and the plate or anode element 323 is A. C. coupled through the condenser 325 and the bleeder resistor combination comprising the resistors 326 and 321, so that the 'energy from the second half of the tube is fed back to the control electrode 329 of the first half of the tube which includes also the plate or anode element with a connection being made from the controlelectrode 32| and the junction of the resistor 334 to ground byway of the resistor element 335.

The general arrangement of the system thus disclosed is one which operates in such a manner that lt can develop but one output pulse at a time, and the duration of the operational cycle may -be readily controlled by the pre-arranged time constant determined by the capacity 325 and the sum of the resistor values of the resistors 326 and 321, as well as the general tube constants. If there are no triggering impulses applied to the system by way of the conductor 261 connecting to the output of the relay tube- 200 and supplying energy by way of the condenser 269 (which is quite small), the relay arrangement is maintained in a state where the left hand half of the relay tube 212 is conduct'- ing and the second half of the tube is blocked 01T because the grid or control electrode 329 is connected to the cathode 3|9 across the resistor 321. Consequently, the output pulse will be noncommutative. l

If reference is now made, however.l to the curves of Fig. 5, and first to curve a thereof, it will -be seen that the relay device may be triggered by the arrival of a pulse of negative polarity, such as that shown by the rst pulse, reading from leit to right, in curve a of Fig. 5. Normally, the relay tube 212 would trigger in the opposite direction by the arrival of the second pulse shown b'y second curve a of Fig. 5, Wluch second pulse is of positive polarity, under conditions where the time constant of the operation was of a time order comparable to the inn is no energy feedback terruption period -between pulses. However, provision can be made whereby the relay tube 212 will not follow the first positive pulse received subsequent to the receipt of the operation initiating negative pulse, but rather the relay will be triggered in the opposite sense by the arrival of the second positive pulse following the controlling negative pulse and this delay can readily be established by lengthening the time constant provided by the system to a value approximately twice as long as the rst and second the time vbetween the rst negative and the rst positive pulse.

If these conditions are followed, then the relay will switch back to its normal state (that is, the second half non-conducting and the rst half conducting) upon the arrival of the second positive pulse (as in curve a of Fig. 5), following the operation initiating negative pulses, and for this purpose the time constant of the relay tube arrangement 212 is made to coincide with a time period of operation of the order of 9H (see Fig.

The relay tube 21| is of the same general nature as the relay 212 and, in its normal state, the second half of the tube, comprising the cathode 339, the control electrode or grid 340 and the plate or anode 34|, does not pass current, so that there -by way of the condenser 343 and the resistor elements 344 and 345, at the junction of which resistorelements the control electrode 346 of the rst half of the tube is connected, as indicated.

The plate or anode 341 of the iirst half of the tube connects back to the control electrode or grid 340 of the second half of the tube by way of the D. C. coupling resistor 349 and tofground 241 by way of the resistor element 350, as was shown for tube 212. Also, as was the case with the relay tube 212, a common cathode bias, relative to ground 241, for both halves of the tube is provided by the cathode resistor 35| which, if desired, may be by-passed for high frequencies by the capacitor 352.

The relay tube 21| essentially is intended tol act as a frame blanking commutator and, accordingly, the time constant is so chosen that its' period of operation, as determined by the capacity 343 and the sum of the resistors 344 and 345, should be longer than for the relay 212 and preferably of a time period of the order of about |2H, so that the condenser 343 is usually somewhat larger than the condenser 325 of the relay tube 212.

In order that the relay tube 21| shall not operate to render the rst half non-conducting upon the arrival of the second positive pulse (such as that shown by curve a of Fig. 5) but at a subsequent pulse, it is understood, of course, that the relay tube 21| is controlled from the same source provided by the tube 200 as is the relay tube 212.

Wave forms of the cathode and plate ouputs of the single puise relays 212 and 21| are generally shown by curves b, c and d respectively of Fig. 5, and from these pulse indications it will be seen that the sync pulses are not flat topped but nevertheless show a linear increase and decrease respectively in amplitude plotted against time. This is due to the interaction of the two plate currents owing in the tubes 212 or 21| through the common cathode resistors 332 and 35| and acting in opposite senses thereupon.

In order to obtain a pulse output of desired wave form and height, the plate and cathode pulses may be mixed in a common resistive net- Work which is provided by means of the resistors 353 and 354 for the first half of the relay tube 212, and the resistors 355 and 356 for the second plate circuit of the same tube, so that the output from the first half of the tube, as it appears in the conductor 351, shall coincide approximately with the wave form e1 of. Fig. 5, and the output energy as appearing in the conductor 358 shall be approximately of the wave form as shown in e2 of Fig. 5, by selecting the appropriate and critical tapping point across the respective bleeder resistors last named. In this way, the pulse output from the first half of the relay tube 212, as it appears in the conductor 351, is always positive in sign, and the pulse output from the second half of the tube 212, as it appears in the conductor 359, is always negative in sign.

By appropriate selection of voltage for the plate supply of the tubes 21| and 212 at a value of the order of about 200 volts, both of these outputs may be made of approximately 50 volts by an appropriate choice of circuit constants.

The arrangement of the relay tube 21| is approximately the same as that disclosed for the tube 212, except that the output energy from the second half of the tube, as it appears in the coinductor 36|, is of negative sign, and, like the arrangement of the relay 212, the tube functions to produce relay action of a. predetermined time duration in response to input voltages which exceed a predetermined value, or to the receipt of input pulses.

Reference now may` be made to the line frequency oscillator tube 95 which is connected to receive energy at a frequency of the master oscillator tube as such energy is picked up in the coil 93 associated as an independent winding upon the main oscillator transformer 81. The pulse of energy as it appears in the winding 93, and as it is fed by way of the conductor'363 to control the control electrode 365 by way of the assenso coupling condenser 363 is initially of positive polarity, as shown for instance by curve b of rig. 4.

The general arrangement of the line frequencyA oscillator tube is substantially like that disclosed and claimed in my co-pending application Serial No. 433,289, led March 4, 1942., where reference may be made particularly to Fig. 2 thereof, for instance. In the arrangement herein disclosed, the ilrst half Yof the tube 95 comprising the cathode 351, the control electrode 365 and the plate or anode 359 feeds its energy by way of the potential divider provided by the resistors 359 and 319 so as to supply energy to the control electrode 31| of the second half of the tube 95.

-The cathode 361 is appropriately biased to ground 241 by way of the cathode resistor 313 and the second half of the tube 95, as was explained in the last referred to co-pending application, acts as a cathode follower stage so that through the appropriate choice of the time constant and the tube operation as weil as the circuit elements provided by the condenser 366 and the leak resistor 315, the tube 95 may be caused to produce a pulse output from the plate or anode 239 of the second half thereof which will appear in the output conductor 29| in positive sign, so as to be applied by way of the coupling condenser 293 to energize the control electrode 285 of the mixer tube 226.A This same mixer tube 226 has energy pulses of negative polarity (like pulses of curve e2 of Fig. 5) supplied to the #3 grid 316 through the coupling condenser 311.

The output pulsesA from the relay tube' 212, which are of positive sign as shown by curve e of Fig. 5, and which appear in the conductor 351. are applied directly to the #3 grid 319 of the mixer tube 225. Thus, it can be seen that with the mixer tubes 225 and 226 connected together with a common plate supply and a common plate output circuit, output energy can be fed to the shaping amplifier tube 390 across the resistor 39|, so that this energy is then applied between the #l grid 392 and ground 241. The cathode 394 of thetube 399 is appropriately biased relative to ground 241 bythe bias resistor 395 and any high frequencies may be by-passed, as desired, by the by-pass condenser 396.

It is, of course, apparent that the circuit parameters of the tubes 225 and 226 may be adjusted in such a way that the energy wave form applied tov the grid or control electrode 392 of the shaping amplifier tube390 is'of the general wave form corresponding to that diagrammatically represented, for instance, by curve m oi Fig. 4 (only with "round" edges), and this is determined, in turn, by the relative polarity of the energy impressed upon the #l and #3 grids of the mixer tubes 225 and 226 which is caused to appear in the wave form fed through the resistor 39|.4

The operation of the wave shaping amplifier tube 390 which, for instance, may be of the general type known in the art as the GAC?, is such as to increase the steepness of the leading and trailing edges of the pulses applied thereto, anc' will be further explained in connection with a discussion of the wave shaping tube 3|1, which is also preferably of the same general type as the tube 390.

The output energy from the second half of thi relay tube 21| is supplied, as above stated, by way of the conductorv 36| and the coupling condenser 398 to the #3 grid 399 of the shaping amplier 311, so that this energy appears across the resistor 40| and is applied between the #3 grid 399 and the tube cathode 402, which latter element is biased relative to ground 241 by the cathode bias resistor 403. Similarly, the output from the blanking tube mixer 283, as it appears in the plate circuit of this tube and in the conductor 405, is supplied to the #l grid 401 by way of the time constant circuit comprising the resistor 403 and the capacity 09 and caused toappear across the leak resistor 410 connected between the #l grid 301 and ground 261. Thus, output energy pulses from the relay tube 211, which are ot a duration approximately 12H, as shown by curve n of Fig. 4, are applied in the negative sense to the #3 grid 399 of the shaping amplifier tube 311 and the output energy pulses from the blanking mixer 283 are applied simultaneously to the #l grid 301 of the shaping amplifier tube 311.

Referring back now to the relay tubes 212 and 21 1, it will be appreciated that With the first half of each tube normally conducting prior to the receipt of the triggering pulses as shown, for instance, by curve a of Fig. 5, the potential appearing in conductor 351 and applied to the y:r3 grid of the tube 225 is negative with respect to the potential which this grid will assume when. the first half of the tube 212 ceases to draw current as of the time when the iirst negative pulse is impressed upon the control electrode 329 by way of the coupling condenser 269.

Likewise, the #3 grid 31E of the tube 226 is normally held at the potential of its cathode 291 by virtue of the connection thereto through the grid leak resistor 313, and then when the relay 212 is triggered so that current ows through the second half of the tube including the plate or anode 323, the control electrode 32| and the cathode 319, a negative impulse such as shown by curve ez is fed by way of conductor 358.

The signals appearing in the output of the second half of the tube 21| are, as above stated, of the same general character as the output signals of the second half of the tube 212, and, accordingly, the tube 21| is arranged to control and operate the shaping amplifier 311 by virtue of the impulse applied through the condenser 398 to the control electrode 399.

In order that the mixer tubes L and M and Q and their associated shaping ampliers N and R may be properly operated to derive the desired form of signal pulse, the time constant of the relay tube 212 is made of the order of 9H while for the relay tube 21| this time constant is lengthened to the order of 12H,` although therelay tube 21| is controlled from the same source as the relay 212, but by lengthening the time constant the relay 21| will not operate as does the relay 212 upon receipt of the second positive pulse, as shown by curve a of Fig. 5, but will change its state of operation in accordance with the adjustment and size of the condenser 343. After the sync signals and the blanking signals have been mixed in their respective channels, and as they appear individually across the load resistors 304 of the tubes 225y and 223 and the load resistor of the type known in the art as the 1852 or the as desired. It thus becomes apparent that across 415 of the tube 283, the signals are then red into high gain tubes, such as the shaping ampliers 390 and 311 respectively for the sync and the blanking signals.

As was above pointed out, the amplifiers 390 and 311 areprimarily for increasing the steepness of the leading and trailing edges of the signal pulses applied thereto, and this is readily done by using a high gain tube, for instance, one

the plate resistor -415 of the tube 283 only the line blanking. signals appear, as the complete' blank- -ing sequence has not been provided up to this point of the circuit. The addition of the frame blanking impulses is provided by the use of the rst blanking-shaping amplifier tube 311 which is used in a sense as a modulator by applying the blanking impulses upon the #3 grid 399.

Referring now more particularly to the sync signal channel, the output signals from the mixer tubes 225 and 226 are applied through the circuit comprising the parallel combination of the resistor 915 and condenser M1 so as to be impressed upon the control electrode 392. The parallel combination of the' resistor. 415 and the condenser 311 acts, in generates a low frequency compensator and corrects the iniiuence of the plate lter combination comprising the resistor 3113 and the condenser 305 which becomes slightly charged during the frame impulses. Generally speaking, the eiiect of this low frequency emphasis is cancelled when the circuit comprising the resistance 415 and the condenser 411 is so designed that it has a time constant substantially equal to that of the plate filter combination of the tube. ,1n addition, the arrangement provides means by which positive bias may be applied to the grid or control electrode 352 of the tube 39d, and this has some advantageous eect in reducing ripple and hum underlying the basis of the pulse sequence introduced by the plate supply to the tubes 225 and 216. Output energy from the tube 39u is then fed by way or' the conductor 419 and coupling condenser 42| so as to be impressed upon tne ampliiier tube 425 which is provided with the usual leak resistor 421. 'lhe shaping ampiiiier tube 3911 is adapted to emphasize the high Irequencies by reason oi' the capacity 39u' being arranged to shunt the degenerative cathode resistor 395. 'lhe tube 42e is coupled to receive the output from the shaping tube 39u. For this purpose, the signal output from the tube 39u is red from the plate -429 through the conductor 419 of the coupling condenser 1121 to be 'impressed upon the control electrode 431 of the tune 425, and then appears in the output circuit of this tube across the output-resistor 433. 'lhe tube 325 is primarily for the purpose of providing power and polarity inversion. The tube 425 delivers positive super sync by cathode follower action across its cathode resistor 453, and simultaneously delivers negative super sync of equal amplitude across its plate or output resistor 433. Each, however, represents a slightly higher impedance and makes a separate matching tube orten desirable, if it is desired to connect this output upon a low impedance line.

With` regard to the blanking signals as amplied in the shaping amplier 311, it will be noted that the degenerative en'ect of the cathode resistor 433 is substantially overcome through the inciusion of a by-pass condenser 635 similar to the condenser 316 used with the tube 391) to by-pass its cathode resistor. c

For the purpose of improving the high frequency response in the shaping amplifier 311, a peaking coil 431 is included in the plate circuit, and the output from the tube 311 is then fed across the load resistor 439 through the conductor 441 and coupling condenser 442 to be impressed upon the control electrode 443 of the output blanking amplifier tube 445. The output blanking amplifier 445, like the output sync amplifier 425, is also preferably of a reasonably high gain typetube and functions in a manner quite related to the tube 425 just diSCuSSed and might be described as a power matching tube.

Signal energy. output from the tube 445 is derived from the plate or anode element 441 across the load resistor 448 and also across the cathode resistor 449 which serves to bias the cathode 450 relative to ground. A similar bias is applied to the cathode 45| of the tube 425 by way of the cathode resistor 453.

In order that either positive or negative synchronizing and blanking pulses may be derived from the blanking output amplifier 445 and the sync amplifier 425, suitable terminal points 460 and 462 are provided for the tubes 445 respectively to obtain negative polarity blanking and sync signals, and terminal points 464 and 466 are provided respectively for obtaining the positive polarity signals which, as is apparent, are obtained across the cathode output resistors 449 and 453 respectively.

Under these circumstances, the ends of the conductors 461 and 468 respectively may be connected on the one hand to terminals 469 and 462 for cases where the negative blanking and sync signals` are desired, or, as indicated by the dotted line, the connection between the ends of the cong ductors 461 and 468 to the terminal points 464 and 466 respectively. Where it is desired that the blanking and sync pulses be of a positive polarity, connections may be made by the terminal points 464 and 466, so that the'outputs supplied to these conductors are taken respectively across the cathode output resistors 449 and 453 of the output blanling and output sync amplier tubes 445 and 425 respectively. These signals are then fed through the loading resistors. 41| and 413 to be supplied from the terminal point 415, at which point it is apparent that there is a superposition of both the blanking and the sync pulses so that there is obtainable at the terminal pointA 415 a pedestal signal with adjustable super sync pulse combined.

Power for operating the complete system is derived by way of the transformer 41.1, for instance, whose primary winding 418 is connected to terminal points 419 and 489 which are, in turn, con` nected to a suitable source of power supply energy not shown. The secondary winding 46| of the transformer 411 is connected in known manner to the plate elements 482 and 482' of the full wave rectifier tube 483. The midpoint of the transformer secondary 46| isconnected to ground 241 in known manner.

Suitable smoothing is provided by way of the shunt condensers 485, 485 and 481' and the series resistors 488 and 439 which QOnnect to the positive or cathode terminal 490 of the rectier tube. For the purpose of providin`g`,\further stabilization of the output voltage from*k the system, a pair of series connected voltage regulator lamps 492 and 493 is provided in well known manner.

It can be appreciated, from the connections shown, that the positive voltage for the various tubes of the system is derived from the positive voltage conductors 495 and 496 respectively which are arranged to connect with the various conductors indicated as supplying voltage to the various tubes of the arrangement and also to the terminal points such as |80, which connection is not shown in detail for the sake of simplicity ofl showing. In this connection, it may be pointed out that a regulated power supply is generally required for the timing and correcting circuits only, but, as a general rule, not for shaping and power amplifiers.

What I claim is:

1. A television synchronizing signal generator comprising a master oscillator for generating steep front asymmetric impulse energy waves of a predetermined frequency and impulse duration, clipping means for deriving each of a plurality of separate energy waves from the master oscillator by clipping at predetermined separate amplitude levels of the impulse energy waves, frequency reducing means to derive energy from the master oscillator at a sub-harmonic thereof, clipping means for deriving from the reduced frequency waves energy at each of a plurality of predetermined energy levels, and means to combine the Several produced energy Waves.

2. A synchronizing signalfgenerator for interlaced television comprising a master oscillator for generating steep front asymmetric impulse energy Waves of a predetermined frequency and impulse duration, clipping means for deriving equalizing and frame synchronizing energy waves from the master by clipping the asymmetric energy output waves at predetermined separate amplitude levels, means to develop a phase-advanced energy wave from the master oscillator output, frequency reducing means to develop line frequency synchronizing signals, means to control said frequency reducing means by said phase-advanced energy wave to derive energy under the control of the master oscillator at a sub-harmonic frequency thereofl clipping means for deriving from the reduced frequency waves energy at each of a plurality of predetermined energy levels of the said wave, and a combining circuit to combine the several developed signals.

3. A synchronizing signal generator for interlaced television comprising a master oscillator for generating steep front asymmetric impulse energy waves of a predetermined frequency and impulse duration, clipping means for deriving each of a plurality of separate enrgy waves from the master oscillator output by clipping said output energy Waves at predetermined separate amplitude levels, means for deriving a phase-advanced energy wave from the master oscillator output, frequency reducing means, means to energize the frequency reducing means under the control of the phase-advanced energy wave to derive energy at a sub-harmonic frequency of the master oscillator, clipping means for deriving from the reduced frequency Waves energy at each of a plurality of predetermined energy levels of the said waves, and means to combine the several produced energy Waves.

4. A television synchronizing signal generator comprising a master oscillator for generating steep front asymmetric impulse energy Waves of a predetermined frequency and impulse durationA with predetermined width in positive and negative portions of the cycle, clipping means for deriving each of a plurality of separate energy waves from the master by clipping at predetermined separate amplitude levels of the impulse energy waves, frequency reducing means to derive energy from the master oscillator at a subliarmonic thereof, clipping means forderiviug from the reduced frequency waves energy at each of a plurality of predetermined energy levels, and mixer means operating under the control of the master oscillator to combine the several energy waves developed.

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