US2471903A - Vertical blanking circuit for television transmitter systems - Google Patents

Description

May 31, 1949- 0. H. SCHADE 2,471,903

VERTICAL BLANKING CIRCUIT FOR TELEVISION TRANSMITTER SYSTEMS Original Filed Deo. 3l, 1941 ma. 75o Il m 2 wil/[1:7443

BY 'N75 TSM/vw.

ATTORN EY Patented May 31,1949

VERTICAL BLANKING CIRCUIT FOR TELE- VISION TRANSMITTER/SYSTEMS Otto `lll. Schade, West CaldwelhN. J., assignor` to` Radio Corporation of America, a corporation of Delaware Original application-December 31, 1941, Serial No.

425,088. Divided and this application December 29, 1944, Serial No. 570,369

3 Claims.

1, This invention is a division of U. S. Patent toi Otto H. Schade, No. 2,402,091, filed December 3l,` 1941, issued June 11, 1946,` and relates toan.y

improvement in-` television.` systems; More particularly, the present invention relates to an.I improvement in systems for generating synchronizing signals, blanking` impulses, andthe necessary deflection voltage variations for use in a television transmitting, apparatus.

ln` present-day television systems the receiving apparatus are maintained in, synchronous.l

operation with the transmitting apparatus by; means of: transmitted horizontal and vertical'` synchronizing signals. These signals are normally` transmitted `along with the picture signals, the picture signals and the synchronizing signals being used to modulate a single radio frequency carrier wave. In order that the synchronizing sign-als may be interspersed with` the picture signals, the picture signals vare entirely eliminated during periods of synchronization and in lieu of. theeliminated picture signalsthe desired vertical or. horizontalA synchronizing signals are transmitted. It is also conventional practice to. transmit the synchronizing signals in such a direction that they are in the direction of black` in' the picture and extend further in that `direction than `the blackest black (i. e., they are blackerthan-black) so that when the composite series istapplied to a television receiving tube the synchronizing signals will inherently cause blanking ofthe cathode ray beam in the receiving tube during return deflection intervals.

Various systems' have been used for producing the desired blanking, synchronizing and deflection voltage variations that are necessary at the transmitter but in most instances such systems are rather complicated and involve :a considerable number of tubes and .circuit components. `Furthermore, in some systems,` considerable additional circuit arrangements have been included in order to` transmit impulses of double horizontal deilection `frequency immediately preceding, during, and immediately following the transmis--y sion of the vertical synchronizing impulse. Such transmission is generally known as slotted vertical synchronizing and .although the use of such a synchronizing method has certain advantages it` has been found that by using the circuits of thev present invention, as herein described for instance, it is not necessary to include the socalled double line frequency preparatory impulses nor is it necessary to slot the vertical synchronizing impulse at double line frequency. In the absence of such slotting and `in the absence of the double line preparatory impulses the horizontal deection` generator may momentarily lose synchronism; however, synchronous operation of the horizontal oscillator will be resumed almost immediately following the verticalusynchronizing impulse period. Furthermore, it has been found, that adequate interlaced scanning at both the` transmitter and the receiver maybe accomplished,

even in the absence` of the use of the double` line frequency impulses.

It is thereforeone purpose of the present invention to provide a new, improved and simplified; synchronizing signal and wave form generatingy system which includes a relatively small` number` of tubes and circuitv elements and which` will produce a picture ,and synchronizingsignal series which is entirely effective to maintain synchronous operation of all-receivers tunedto the trans.-y mitting station.

Another purpose of the present invention resides inthe provision of `a simplified systemy for producing the necessary picture signal series blanking impulses and the necessary horizontaland vertical synchronizing impulses that are transmitted during the blanking period.

Still another purpose` of the present invention resides inthe provision of means for simultaneously generatingdefiection voltage Variations which may be used to directly cause deflectionv of the scanning cathode ray beam in the television transmitting tube or which may be used,v to drive a power tube for deflecting the scanning cathode ray beam.

Still a` further purpose ofI the present inven-` tion resides in the provision, of Ia circuit for generating voltage variations which may be used to deflect a cathode ray beam in a monitoring oscilloscope.

Another purpose of the present invention resides in the provision of a circuit for generating voltage variations of saw-tooth wave form that may be, used to `control devices for producing shading control signals.

A still further purpose of the present invention resides in the provision of a circuit arrangementJ which will produce the above `referred to voltage variations in response to` the application` of properly timed horizontal and Vertical synchronizing impulses.

Alstill further purpose of the present invention resides inthe provisionl of a circuit arrangement for producing a desired composite picture and synchronizing signal series which may be used` directly` to modulate a radio frequency oscillator in order that the composite signal may be transmitted to` a remote receiving station.

Still other purposes and advantages of the present invention will become more lapparent to thoseskilled in the art from the following speciiication and drawings wherein the single figure represents a preferred form of the present invention. Furthermore, the ligure also shows various curves of` voltage variations appearing at various parts of the circuit.`

For controlling the apparatus and circuit arrangement shown in the single figure and` described in the following specification, a source of horizontal and vertical synchronizing impulses must be provided. Such a source is not shown in the drawing and it is to be understood that the horizontal and vertical synchronizing impulses may be derived from any appropriate generator. It is only necessary that the horizontal and vertical synchronizing impulses be of the desired frequency and be spaced with respect to each other by the desired amount. By way of example, a generator for supplying such impulses is shown and described in Schade Patent No. 2,254,626, issued on September 2, 1941.

Referring now to the drawing, the picture signals which are derived from a television transmitting tube are applied to terminals I6 and II, the latter of which is connected to ground. These signals may be derived from any desired television transmitting tube. The horizontal synchronizing impulses from any appropriate source may be applied to the terminal I2 while the vertical synchronizing impulses are applied to the terminal I4.

The system includes discharge tube I6, which in turn includes cathodes I8, two control electrodes 20 and 22, and two anodes 24 and 26.

These elements may be enclosed in a single tube envelope (as shown) or they may constitute the elements yof two separate triode or multi-electrode tubes. The elements are connected as a multi-vibrator and the operation of the multivibrator is synchronized by means of horizontal impulses which are applied to the terminal I2 from any desired appropriate source. The impulses which are impressed upon the input terminal I2 are applied to the control electrode 26 through coupling condenser 28.. The control electrode 2|) is connected to ground by way of the usual grid resistor 30 and in order that the control electrode may be operated at a proper potential with respect to cathode I8 a resistance 32 is also included between the control electrode and terminal 34 to which a positive potential is applied. The positive supply potential that is applied to terminal 34 is de-coupled from the elements of tube I6 by de-coupling resistance 36 and condenser 38. The anodes 24 and 26 are also connected to the positive terminal 34 by way of anode load resistance 40 and 42, respectively. The anode 24 is coupled to the control electrode 22 by means of coupling condenser 44 while the control electrode 22 is connected to the cathodes I8 by means of resistance 46 and potentiometer 48. One end of the resistance element of the potentiometer 48 is connected to the resistance 46 whereas the other end of the resistance element of the potentiometer, as well as the movable contact thereof, are connected to the cathodes I8. The anode 26 is connected to output terminal 50 and to ground through condenser 52 while the control electrode 22 is connected to output terminal 54 by way of resistance 56. The resistance 56 has connected in parallel therewith a condenser 58. The cathodes I8 are connected to ground by way of variable resistance 6I and inductance 62 while the inductance 62 has connected in parallel therewith a resistance 63. The purpose of providing the inductance in the cathode circuit of tube I6 is to provide an inductive feedback impedance in order that short impulses of high amplitude may be produced. The widths of the produced imipulses may be readily controlled by varying the amount of the resistance 6I which vcontrols. the cathode impedance. The speed of 4 operation of the multi-vibrator which includes the elements of tube I6 may be controlled by adjusting the potentiometer 48.

When horizontal synchronizing impulses are applied to the'terminal I2 with the impulses extending in a negative direction, electronic current from cathode I8 to anode 24 is reduced during application of the individual impulses. This reduction in anodic current causes positive impulses to appear at the anode of tube 24 and these impulses are applied to the control electrode 22 of tube I6 through condenser 44. The heavy cathode current that is caused to flow drives the cathodes in a positive direction causing the current to anode 24 to be completely cutoif and since the anode 24 is connected to terminal 60, the strong impulses produced at anode 24 are then available at terminal 6I) and may have a wave form such as that represented by the curve 65. Naturally the impulses extend in a positive direction and occur at a frequency corresponding to the synchronizing impulses applied to the control electrode 20 but of a time duration (or width) determined by the resistance 6I.

The circuit also provides a source of deflection voltage variations which may be derived from terminal 54 and which may have a wave form similar to that shown by curve 64. These impulses are derived from the control grid 22 and the parallel resistance and condenser combinationy 56-58 are included between the control electrode 22 and the terminal 54 in order to produce wave shaping (and biasing of the following tube) to provide the desired voltage variation or wave form. It will be noticed that this wave form is substantially that necessary for driving a power tube for supplying horizontal deflection voltages for deflecting the scanning cathode ray beam in an Iconoscope or similar television transmitting tube where electromagnetic deflection is used.

When condenser 52 is connected between the anode 26 and ground, the triode section including anode 26 of tube I6 operates as a discharge tube as well as a part of the multi-vibrator with the result that voltage Variations of substantially sawtooth wave form may be obtained from the anode 26. As stated above, these voltage variations are available at terminal 50 and may have a wave form corresponding to the curve shown at 66. In so far as this part of the operation is concerned, the condenser 52 charges through load resistance 42 and de-coupling resistance 36 and is discharged by current ilow between cathode I and anode 26.

From the above it may be seen, therefore, that` the single tube I6, together with its associated circuit elements, operates both as a multi-vibrator and as a discharge tube for producing several sources of voltage Variation. From the terminal 6I] may be derived horizontal blanking impulses of a width determined by the resistance 6I while from the terminal 54 may be derived voltage variations of a wave form such as are suitable for driving a horizontal deflection power tube. Furthermore, the saw-tooth wave form Voltage variations which are derived from terminal 50 may be conveniently used for horizontally deilecting the cathode ray beam in an oscilloscope tube, particularly where the cathode ray beam of the oscilloscope is electrostatically deflected. This voltage, as stated above, may also be used to control a shading signal generating device.

A somewhat similar circuit arrangement .is alsoprovided for producing similar voltage variaatentos 'tions at vertical deiiection frequency. This cirfcitarrangement includes tube 68 which inturn indludes cathodes control electrodes `'|2 and "Tllaswell 'asanodes 'T6 andf'l. The elements "fofftlie tube68are connected asa multi-vibrator ""the "operationof the multi-vibrator is synhronized by vertical synchronizing signals ap- Yplied to the 'terminal M. Resistances 30, 82 and f`i6`4"`ar`e connected inseries and the series arrangeent "is connected from input terminal |4 to round. The control electrode '|2 is connected to 1the "junction fof 'resistance 82 Aand 34 by `means of series connectedresistance 86 and condenser v"88; Furthermoraa condenser 96 is connected betWeen the control relectrode 'l2 and ground. -"Ihe inclusion of the resistance 86 and the condenser 9[|"provides a time delay circuit in order that the vertical synchronizing impulses which "are applied to the terminal I4 will be delayed by fa predetermined amount before being applied to 'the control electrode "|2. The anode 16 is "connected toiterminal 35, to Which is applied a "positivepotential, by means of load resistance 92, potentiometer 94 and de-coupling resistance 96. ,infile-coupling condenserQB is connected between thejunctionofpotentiometer 94 and de-coupling resistance-S6 while the `movable contact of the fpotentiometer'Bfl is also connected to the junc- "tionofthe potentiometer and the de-coupling resistance"`96`. Theanode 18 is also connected to @the de-coupling resistance by means of po- `ftentio-Jn'ieter-Iiltl The cathodes 'lll are connected to 'groun'dby way of cathode resistance |02, the resistance being bypassed by condenser |04 in 1order to round off the front edge of the feediback'impulse. This action, in so far as the feedback is concerned, is effective to prevent unstable triggering of the circuit and greatly infcreases the stability of interlace. Voltage varia- Ltions which are present at the anode '|6 are "ap'pliedtothe control electrode 'M by way of coulpiling condenser |64 while the control electrode |"4"'is connecteditoground by Way of resistance l`|`|f|ia`nd potentiometer |08. The potentiometer ""IUS `is connected as a variable resistance and is effective to control the free operating speed of the multi-vibrator.

Theivertical synchronizing impulses which are "applied to terminal i4 are also applied to the control electrode of tube I0. riorthis tube is connected tothe junction of re- "isistance 80 andfl by means of series connected "resistance vl |2 and condenser H4. The voltage Variations Which are applied to the control electrode of tube l) are therefore not delayed and "precede the'voltage variations which are applied "tothe control electrode l2 by` a predetermined ""amount. The controlelectrode of tube H0 is also connected to groundby a usual grid resist- "ance H6. The cathode of tube ||6 is connected "jto ground by cathode resistance H8 While the "fanode of the tube is connected to the positive ftiezrminal 34 by means of anode load resistance 0.

`When vertical synchronizing impulse signals fareapplied to the control electrode l2 of the multi-vibrator tube 68 after a predetermined time delay, the operation of the multi-vibrator is controlled and synchronized with the vertical "synchronizing impulsesand the circuit operates Atoproduce at the anode '|6 delayed voltage variahltions Whichextend in a positive direction. These voltage variations are presenten conductor |22 fand-are appliedto a further delay circuit including resistances |24 and |26 as Well as condensers The control `electrode 6 :|28 and L| 30. Thecombination of resistance |254 and `condenser^|28 as well as'the combination of resistance |26 and `condenser |30 lprovide a further 'time delay lfor the voltage variations present at anode T6 and these delayed voltage variations are then available at conductor |32. The wave form ofthedelayedvoltage variations may have a Wave formsimilar to that shown at curve |34. Theianode of tube |||l is connected to conductor |32 b y `means of resistance and since the voltage variations appearing at the anode of tube `||`l) are not delayed, these voltage variations when combined with the delayed voltage `variations from the anode of tube i6 produce a vertical blanking impulse such as shown at curve |38 the duration of which is sulicient toprovide `the necessary vertical blanking.

Furthermore, the multi-vibrator including tube 68 and its associated circuit elements also produces voltage Variations which are available at the control electrode 'I4 and which are applied to terminal |40, these voltage variations being similar to those shown by curve |42 and suitable for energizing a vertical deflection power tube. These voltage variations are therefore similar^ to'the voltage variations which areavailable at terminal 54`and may-be ultimately used in deflectingthe cathode ray beam in the television'transmitting tube, particularly where thefbeam isdeected'by electromagnetic means as is vanode L78. Actually,"these voltage variations are available from the movable contact'of potentiometer |66 and are applied to terminal lM6.

They may have a Wave form such as that shown lby curve |48. Asexplainedabove, these voltage 45.v

variations of sawtooth Wave form may be conveniently 'used for 'deecting the cathode ray beam in an oscilloscope particularly Where electrostatic 'deflectionis used.` The voltage variations rnay be useddirectly or after appropriate amplification. Theymay also be used to control vertical shading tubes.

From the circuitas so far described, it may be seen that very simple and convenient circuit arrangementhas been provided for generating `horizontal and vertical blanking impulses and for simultaneously generating horizontal and vertical deflection driving voltage variations. These deflection driving voltagevariations, after appropriate amplification, may be used to deneet the cathode rayv beam in the television transymitting tube.

=mustibe suppressed at'various regularly spaced intervals in order that the suppressed picture signalsfmaybe replaced by the desired horizontal Aand vertical synchronizing signals. The circuit (arrangement for producing the desired blanking and for interposing the desired synchronizing signals includes tubes |50, |52 and |54. Of these sertion tube.

. with condenser |02.

. trol impulses.

vat'arrpos rtubestube |50 is the picturesignal blanking tube whereas tube |52 is the synchronizing signal in- Both tubes when supplied with proper voltage variations operate to produce the final composite picture and synchronizing signal series.

Tube |54 includes cathodes |56, control electrodes |58 and |60 as well as anodes |62 and |64. The cathodes |56 are connected to ground while the control electrodes |58 and |60 are connected to ground by Way of grid resistors |66 and |68, respectively. The anodes |62 and |64 are connected to the positive terminal 34 by load resistances |l and |72, respectively.

The horizontal blanking impulses which are available at terminal 60 and which are derived from the anode 24 :of tube I6 are applied to the control electrode |50 by way of coupling condenser iit. Likewise, thevertical blanking impulses Which are available on conductor |312 are applied to the control electrode |60 by coupling condenser H6. Both the horizontal and the vertical blanking impulses have their voltage variations extending in a positive direction to cause modulation of anodic current in tube |54. Since .the blanking impulses extend in a positive direction, the voltage variations at the anodes |62 and |64 will extend in a negative direction upon ,the application of the blanking impulses to the control electrodes |58 and |60. The anode |62 is connected to the anode |64 by means of a tune circuit including inductance |18 and capacitance |86, this combination being connected in series The purpose of the inductance |70 and the condenser |80 is to improve the wave form of the horizontal blanking con- If desired, these elements may actually be omitted, in which case the anodes |62 and |64 are directly -connected together and a single common load resistance |12 is used. The voltage variations from the anodes |62 and |64 are combined and are applied to the suppressor grid or electrode of tube |50 by way of coupling condenser |05. The wave form of the combined blanking control impulses may be similar to that shown at |86. The screen grid of tube |150 is connected to positive terminal 34 by way of resistance |80 and potentiometer |90. The resistance element of the potentiometer |90 is connected between positive terminal and ground whereas the movable contact of the potentiometer is connected to the screen grid resistor |88. The screen grid is de-coupled for relatively rapid vvoltage variations by means of condenser |92.

The cathode -of tube |50 is connected to ground by an unbypassed cathode resistance |94, particularly if good white signals are available and .if the television transmitting (camera) tube is operated at normal gamma. conditions, and where a transmitting tube similar Under low light to an Iconoscope is used, a bypass condenser may be used to prevent degeneration and to increase the intensity of picture signals representative of white. The control electrode is also connected to ground by an appropriate grid resistance |96. The anode of tube |50 is connected to positive terminal 3ft by means of an appropriate load cirl resistance |08 and 200 is connected to the sup- Issor electrode by means of a further resistance Whenpicture signals are applied to the control electrode of tube |56 by Way of condenser 204 they operate to modulate the electron stream in that tube. The picture signals as applied toterminal i0 are polarized such that black in the picture is represented by a change in the negative direction whereas white in the picture is represented by a voltage change in the positive direction. Accordingly, when signals representing black are applied to the control electrode of tube |50, the voltage variations at the anode of that tube will extend in a positive direction. In order to afford the desired blanliing at horizontal and vertical deflection frequency, the voltage variations which are applied to the suppressor electrode by way of condenser |84 from anodes |62 and |54 of tube G54 are effective to cut-off the current flow through tube E50. As stated before, the voltage variations from the anodes |62 and |64 extend in a negative direction and are sufficiently intense to reduce the anode current in tube |50 to zero. Accordingly, during such blanking intervals, applied picture signals are ineifective to produce any potential change at the anode of tube i556 which is driven to its most positive potential. The height of the blanking pedestal or, in other words, the potential change of the anode of tube i5@ during blanking intervals may vbe controlled and determined by the position of the movable contacts on potentiometer Which .controls the energizing potential in the screen grid electrode of tube F50. The signal at the output of tube |50 therefore represents the picture signals applied to terminal I0 with certain intermittent portions of the picture signals being .suppressed or driven to a value representative of black in the picture.

t is the function of the synchronizing signal vinsertion tube i52 to superimpose upon the blanking signal the actual synchronizing signals which extend in the direction of black and which correspond to blacker than black in so far as their intensity is concerned. The synchronizing signals are not delayed with respect to the front edge of the blanking impulse as is the practice in some synchronizing systems since it has been found that the front edge of the synchronizing impulse and the front edge of the blanking impulse may coincide without producing any undesired results.

Tube |52 includes a cathode, a control electrode,

a screen grid electrode, a suppressor electrode and an anode. The cathode oi the tube is connected directly to ground whereas the control electrode is connected to ground by resistance 206 in parallel with which is connected a condenser 208.

The suppressor electrode is also connected to ground by resistance 2id and is coupled to a suppressor electrode of tube |50 by way of coupling condenser M2. The horizontal synchronizing signals are then applied to the suppressor electrode of tube |52 from the blanking tube |54 but in this connection is included condenser 2|2 and resistance 2&0. These elements perform a differentiating action to diierentiate the horizontal blanliing impulse to thereby produce a shorter horizontal synchronizing impulse. There therefore appears on the suppressor electrode of tube |52 the horizontal synchronizing impulse which is in fact the differentiated horizontal blanking impulse. The vertical synchronizing impulse is applied to the rst control electrode or control grid of tube |52 by means of resistor 2|4 and condenser 2|6 which are connected between the control electrode of tube |52 and terminal |4 einem,

to which. is applied the controlling vertical svnchronizing impulse. vlIwhle same signals that are used to control theVf-ltical multivibrator tube 611 are, therefore 'usedto supply vertical. synchronizing impulses tothe control electrode of tube |52.

Since the horizontal synchronizing impulses that are appliedA to the screen grid electrode |52 and the vertical synchronizing impulses that are applied to the control electrode of tube |52 extend in a negative direction, these impulses operate to reduce the current ovv through` tube |52 with the result that the anode is driven in a positive direction during suchintervals.

The` screen gridv of tube |52 is connected to the movable contact of a potentiometer 2 i8. One end of the resistance element of the potentiometer ZIB is connected to ground whereas the other end of the resistance element isconnected to the, positive terminal 34y by Way of. resistance 22B. This permits the application `of a predetermined relatively small positive potential to the screen grid electrode, thev electrode being by-passedl to ground in so far as `alternating current potentials are concerned by condenser 222. An adjustment of the value of the potential applied tol the screen grid electrode which is made possible by an adjustment of potentiometer 2 3 determines the height or intensity of the synchronizing signal impulses appearing at the anode of tube 52.

The anodes of the blanking tube i553 and the synchronizing signal insertion tube |52 yare connected together and are in turn rconnected to positive terminal 34dl through series connected inductance 224, a further inductance `226, a resistance 228 and 23!4 in order to stabilize the voltage applied to the anode vload circuit oitubes L50 and |52.. An` output circuit is provided between ground and the junction of inductances 224 and 226 through condenser 234 so that the output energy is available from terminals 236i The inductance 224 is paralleled by a resistance 23B in order to slightly modify the Wave form at the output terminals.

It may be seen therefore that picture signals when applied to the control electrode of tube |50 cause a corresponding voltage drop load resistance 22.8 to produce amplified voltage variations at the output terminal 23S. The horizontal and vertical` blanking impulses which are applied to the screen grid electrode of tube |53 reduce the current flow through. that tube to zero, withy the result that the potential at the output terminal 236 is altered in a positive direction. The plate current of the parallel synchronizing insertion tube |52 also causes a voltage drop in the common load circuit resistanceo228. The plate current ratio of `tube |52 to-tube 151| determines the ratio of the synchronizing signals (supersync) to blanking. rIlhis ratio can be controlled, as stated above,` by varying the screen potential applied. to tube |52 by means of potentiometer 2ML The vertical. synchronizing impulses, as stated above, are applied directly to the control electrode of tube L52 accordingly. cause tube |52 to be driven to cut-ofi during vertical synchronizing intervals. During this time no horizontal synchronizing impulses are present and accordingly no horizontal synchronizing signals are transmitted during the transmission of the uertical synchronizing signals. The inclusion of the inductances 224 and 22B prevents a loss of the high frequency components of the signal series.

Preferably tubes |50 and |52 should be of the high gain type such as, for example, tubes 6AC'7 mitted.

The circuit shown in the drawing and described above is particularly adapted for portable television equipment and provides the necessary voltage Variations for operating such equipment. The principal elements necessary in addition to the circuit described are naturally a source of picture signal, a source of horizontal and vertical synchronizing impulses and a source of radio frequency energy particularly Where radio transmission is desired. `With these additional elements it is possible ton transmit television images andto, in addition, monitorsuch `transmission by means of the usual, cathode ray oscilloscope.

The horizontal and vertical synchronizing mpulses which are applied to terminals |'2 and` i4; may be derived from` any desired source or, in

fact, these signals may be supplied from the main television transmitter so that they are properly related to the 60 cycle power supply line. The horizontal and vertical synchronizing impulses may be transmitted to the portable equipment from the main transmitter by theuse of a separate carrier for thatpurpose or such signalsmay be separated from the television signal transmitted from the principal transmitting station. The picture .signals may be derived from any television transmitting tube such as, for example,` an Iconoscopej an Orthicon or a Monoscope. i

Since the monitoring oscilloscope is generally. relatively small and it `has a screen of about 3` inches in diameter, the electron beamy in such a tube is normally electrostatically deflected and,V accordingly, the voltage Variations of saWtooth Wave form which are `available at terminals 5U. and |46' may -be conveniently used for horizon` tally and vertically deflecting the cathode ray beam in the monitortube, If it is desired to observe only the signal trace in the monitor tube then the horizontal deflection of a cathode ray beam therein may be produced by eitherthehorizontal or vertical deflection voltage while the vertical deflection of the `cathode ray beam may be produced as a function` of 4energy derived from the output terminals v236.

From the above it may be seen that a relatively compact andsimplii'ledr synchronizing signal generator has been provided which operates to produce not only the desired blanking and synchronizing impulses but also produces voltage variations which maybe used to deflect the cathode ray beam in the `television transmitting tube. Furthermore, the same system provides means for generating voltage Variations of sawtooth Wave .form in order that a monitoring cathode ray tube maybe used at 4the portable transmitter-` The system described also `operates to blank the picture signal series `at predetermined intervals and to supelmpose upon the blanking signals the desired synchronizing signals in order that a complete composite series of picture and syncbronizinc.r signals may be produced.

The vertical synchronizing impulses may be of any desired length but it is preferable if their length is chosen to equal approximately one line deflection duration as shown by the curve applied to the output terminals 236 in order to reduce the possibility of the horizontal deflection generator in the receiver from momentarily dropping out of synchronism. Vertical synchronizing signals persisting for only one-halt a line may even be used Without resulting in any difficulty in segregating the horizontal and vertical synchronizing signals.

Although the system is described in more or less detailed form it is to be understood that various alterations and modications may 'be made therein and any and all such modifications are to be considered Within the purview of the present invention except as limited by the hereinafter appended claims.

I claim:

1. A television transmitting system including a source of vertical synchronizing impulses, a multi-vibrator including means for generating a first electron discharge stream, means for generating a second electron discharge stream, each means including a cathode, a control electrode and an anode, means including separate load impedances for maintaining said anodes positive with respect to their associated cathodes, a condenser for coupling the anode of the rst electron discharge stream to the control electrode of the second electron discharge stream, means including a time delaycircuit for applying the vertical synchronizing impulses to the control electrode of the rst electron discharge stream to produce delayed voltage variations of a predetermined adjustable amplitude and duration at the associated anode, an electron discharge tube including a cathode, a control electrode and an anode, a load impedance for maintaining the anode of said electron discharge tube positive with respect to its cathode, means for applying the undelayed vertical synchronizing impulses to the control electrode of said electron discharge tube to produce voltage variations of a predetermined adjustable amplitude and duration, means to further delay the produced delayed voltage variations, means for combining the further delayed voltage variations produced at the ano-de of the iirstelectron discharge stream with the voltage variations produced at the anode of said electron discharge tube to produce vertical hlanking impulses having a predetermined amplitude and time duration, and a condenser connected between the anode of said second electron discharge tube and a point of fixed potential whereby voltage variations of substantially sawtooth Wave form may be derived from the anode of said second electron discharge tube.

2. A television transmitting system including a source of vertical synchronizing impulses, a multi-vibrator including means for generating a rst electron discharge stream, means for generating a second electron discharge stream, each 'means including a cathode, a control electrode and an anode, means including separate load impedances for maintaining said anodes positive with respect to their associated cathodes, a condenser for coupling the anode of the rst electron discharge stream to the control electrode in the second electron discharge stream, means including a time delay circuit for applying the vertical synchronizing impulses to the control c 12 electrode in the first electron discharge stream to produce delayed voltage variations of a predetermined amplitude and duration at the anode of said electron stream, circuit means to further delay the produced delayed voltage variations, an electron discharge tube including a cathode, a control electrode and an anode, a load impedance for maintaining the anode of said third electron discharge tube positive with respect to its cathode, means for applying the undelayed vertical synchronizing impulses to the control electrode of said electron discharge tube to produce voltage variations of a predetermined amplitude and duration, and means for combining the further delayed voltage variations produced at the anode of the first electron discharge stream with the voltage variations produced at the anode of said electron discharge tube to produce vertical blanking impulses having a predetermined amplitude and time duration.

3. A television transmitting system including a source of vertical synchronizing impulses, a multi-vibrator including a first and a second electron discharge tube, each including a cathode, a control electrode and an anode, means includlng separate load impedances for maintaining the anodes of the electron discharge tubes positive with respect to their associated cathodes, a condenser coupling the anode of the first electron discharge tube to the control electrode of the second electron discharge tube, means including a time delay Vcircuit forapplying the vertical synchronizing impulses to the control electrode of the first electron discharge tube to generate delayed voltage variations of a predetermined amplitude and duration at the anode of said tube, circuit means to further delay the produced delayed voltage variations, a third electron discharge tube including a cathode, a control electrode and an anode, a load impedance for maintaining the anode of said third electron discharge tube positive with respect to its cathode,`

means for applying the undelayed vertical synchronizing impulses to the control electrode oi the third electron discharge tube to generate voltage variations of a predetermined amplitude and duration at the anode of said tube, means for combining the further delayed voltage variations generated at the anodes of the lirst and the third electron discharge tube to produce vertical blanking control impulses having a prodetcrmined amplitude and time duration, and an electron storage device connected between the anode of said second electron discharge tube and a point of fixed potential whereby voltage variations of substantially sawtooth Wave form may be derived from the anode of said second electron discharge tube.

OTTO H. SCHADE.

REFERENCES CITED The following references are of record in the :Eile of this patent:

.UNITED STATES PATENTS Number Name Date 1,587,520 Hartley June 8, 1926 2,153,217 Van der Mark Apr. 4, 1939 2,241,619 Sherman May 13, 1941 2,366,307 Anderson Jan. 2, 1945 2,368,448 Cook Jan. 30, 1945

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