US2329339A

US2329339A - Electrical circuit

Info

Publication number: US2329339A
Application number: US433757A
Authority: US
Inventors: Baun James Russell De
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1942-03-07
Filing date: 1942-03-07
Publication date: 1943-09-14
Anticipated expiration: 1960-09-14

Description

Sept. 14, 1943.

J. R. DE BAUN ELECTRICAL CIRCUIT Filed March 7, 1942 4 Sheets-Sheet 1 BY M1/w] ATTORNEY Sept 14, l943- J. R. DE BAUN ELECTRICAL CIRCUIT Filed'March 7, 1942 4 Sheets-Sheet 2 Sept. 14, 1943. J. R. DE BAUN ELECTRICAL CIRCUIT Filed March 7, 1942 Sept- 14, 1943- J. R. DE BAUN 2,329,339

ELECTRICAL CIRCUIT Filed March '7, 1942 4 Sheets-Sheet 4 INVENTOR c/Z/y/Es a ELL .055/1044 Patented Sept. 14, 1943.

ELECTRICMJ CIRCUIT James Russell De Baun, Flushing, N. Y., assigner to Radio Corporation of America, a corporation of Delaware Application March '7, 1942, Serial No. 433,757

(Cl. P18-7.2)

16 Claims.

lized by the transmitted signals. In order to avoid f irregularities in the scanning raster, it is customary at the transmitting station to synchronize the generator of synchronizing' signals, normally called the synchronizing generator, with the 60-cycle per second supply which furnishes power to the system. Conventionally, this is done by utilizing a master oscillator whose frequency is a' multiple to that of the line frequency of the Ascanning pattern and to produce electrical wave energy Whose frequency is 60 cycles by a system .of electrical dividers from the master oscillator.

The produced 60 cycles per second is thereafter compared with the (iO-cycles per second energy of the supply mains and the difference between the two is utilized to control the frequency yof the master oscillator in such a direction as to either increase or decrease the master oscillator frequency until the frequency supplied at the output of the dividers is identical with that of the 60-cycle supply main. 'I'his insures that the transmitted synchronizing signals are always in synchronism with the 60-cycle supply main. Such apparatus is well known in the art and one form widely used is described in detail in a paper by Smith and Bedford which appeared in the RCA Review for July, 1940, vol. 5, #1, pages 51- 68, A Precision Television synchronizing Signal Generator."

Such a system is perfectly satisfactory where only a single transmitting chain is used or where programs originate only at a single point. When, however, programs originate from a remote point and are sent to the main studios for retransmission, then it becomes desirable to supply some means for locking in the synchronizing generator at the remote point with that at' local or main station. This feature is desired because the remote pick-up equipment may be operating on a different Gli-cycle supply from that of the main studios. Switching, therefore, from the remote program to that of the main studio, or vice versa, results in an abrupt change in phase and frequency of the synchronizing signal with the result that at the receiver the picture drops out momentarily, since the receiver can not accommodate an abrupt change in phase and frequency of scanning of the received signals.

Moreover, in the transmission of special eects, such as lap dissolves or composite pictures by superimposing of two or more cameras, it is nec'- essary to insure synchronism and proper phasing of each individual camera chain'with each other. This is necessary to prevent any blurring arising from the drifting of one picture past the other in the case of superimposed pictures and to insure that no displacement between the pictures occurs in the lap dissolve.

My invention provides both a method and apparatus for insuring synchronism between master oscillators or master synchronizing generators so that no tearing out of the picture at the receiver is produced and to insure proper operation for lap dissolves and composite picture transmissions. Briefly, my invention utilizes the synchronizing signal from one of the generators to produce a source of synchronizing wave energy which may be shifted in-phase and which is supplied to the other of the synchronizing generators to control its frequency, in lieu of exercising control of. the second synchronizing generator by the -cycle supply main. It should be appreciated that not onlyis it necessary to control the second oscillator with respect to frequency but that it is also necessary that the second oscillator be maintained in phase with the rst oscillator. i

In this respect it is not only necessary that the line synchronizing signals be maintained in phase but that the vertical synchronizing signals likewise be in phase. In addition, since double interlace scanning is generally provided, it is necessary that the vertical synchronizing signals be in phase for the proper field. It will be understood that a vertical synchronizing signal from one of the generators could be superimposed upon the vertical synchronizing signal of a second generator which would indicate proper phase and yet result in an improper transmission,4 since the rst vertical synchronizing signal may be that which follows the scanning of the odd field While the vertical synchronizing impulse of the second generator may be that which follows the scanning of the even field. It will thus be clear that it is necessary that the two synchronizing signals coincide following the scanning of the same relative field, that is to say, that they must coincide following the scanning of the odd fields, as well as the even fields. Provision is made for insuring this feature by my method and apparatus.

Moreover, in order to safeguard against opercal circuits.

Another object of my invention is to provide 1 a new and useful method and apparatus for synchronizing -the synchronizing generators of a television transmission system.

Another object of my invention is to provide a new and useful method and apparatus for maintaining the synchronism and phasing of a plurality of television synchronizing generators with the additional feature of supplying an alternative control in the event that synchronizing signals from one of the generators should fail.

Another object of my invention is to provide new and improved synchronizing method and' apparatus which permits the selection for transmission of one or more individually generated video signals without producing "drop-outs or tearing of the received image.

Still another object of my invention is to provide a method and apparatus for synchronizing generators to give improved lap dissolve and superimposed or composite picture eifects.

Other objects of my invention will become clear upon reading the following detailed description taken together with the drawings.

In the drawings, Figure 1 shows in block diagram form an overall television system wherein provision is made for transmittingfrom a main transmitting point programs originating from diiferent sources; Figure 2 shows in block diagram form a portion of the system with further details; Figure 3 sho/ws in block diagram form the details embodying my method and apparatus for synchronizing diierent synchronizing generators with each other; Figure 4 shows a detailed circuit diagram of the phase shifting apparatus and synchronizing control circuit; and Fig. 5 is a schematic circuit to show one form of automatic control.

Turning now to Figure 1, I have shown the elements of a television system in which there is provided a studio pick-up I, a remote unit 3 for picking up programs from the field, and a lm scanner 5 for providing pictures from motion picture lm. At the master control position, generally located adjacent the studio pickup I, is a master control selector I3 which enables the operator to select one of the three programs. The output of the selector is fed to a line amplifier I5 for suitable amplification and thereafter the signals are used to modulate the transmitter I1 for transmission in the antenna I9. Diagrammatically there is shown the synchronizing generators l, 9, II for synchronizing the nlm scanner, the studio pick-up, and the remote unit, respectively. It will be appreciated that in practice two or more equipments may actually use the same synchronizing generator, but for purposes of illustration each of the video camera chains has been shown as being controlled by a separate generator.

It will be. observed that in view of the fact that the remote unit 3 and the lm scanner 5 are controlled from diierent synchronizing generators', that when the switching operation takes place at the selector I3, the transmitted signals, received at the -antenna 2I and rectified at the receiver 23, actuate the reproducer 25 with an abrupt change in the relative timing of the synchronizing impulses, since, in general, the synchronizing generators 1, 9, II will not be supplied from the same power supply. Moreover, even if the three synchronizing .generators were supplied from the saine power supply, due to the diierent times of transmission and different time constants of the locking circuits for the remote unit 3 as compared with that of the studio pick-up I, the line synchronizing signals will be displaced with respect to each other. At the receiver there would result a tearing out of the picture, since the receiver blocking oscillator can not follow the appropriate change in phase displacement of the two synchronizing signals following the switching operation. To avoid the tearing out of the picture with a resultant deterioration of reception, it is necessary to provide some means of so synchronizing the various pick-up points with each other such that the switching operation will not disturb the line synchronizing signals. With such provision being made, it will readily be appreciated that no tearing out of the picture will take place at the reproducer 25, since the receiver 23 is unable to determine the time that switching is taking place. While the diiculty induced by the different times of transmission through the various chains may be overcome by using a circuit arrangement shown schematically in Figure 2, this arrangement does not solve the problem entirely.

It will be noted in Figure 2 that the synchronizing generator 3l serves to synchronize the film scanner 33 and the studio pick-up 35, while the synchronizing generator 4I serves to synchronize the remote unit 43. Between the film scanner 33 and the selector 35 is providedV a phase shifter 3l. Similarly, between the remote unit I3 and the selector 33 there is provided a phase shifter 45. By appropriate adjustment of the

phase shifters

31 and 45, assuming no drift between the two line frequencies, the total transmission time through the chains can be adjusted so as to be equal to the time of transmission throughv one of the chains or equal to the time of transmission through one of the chains plus an integral number of frame time intervals. Under these conditions both the line synchronizing and vertical synchronizing impulses will have the same relative phase position. It must be noted that the phase position is important, since in an interlace system it would be possible to have the frame synchronizing signal of an even eld coincide with the frame synchronizing signal of an odd eld, and under these conditions the reproduced picture would suier from missynchronization. In addition, because the synchronizing generators 3| and 4I, in general, run from different power supplies, there is no assurance that they would be of the same frequency and again mis-synchronization might take place. To avoid this mis-synchronization, I. have provided by my invention the method and means of deriving from oneof the camera chains synchronizing impulses which are used to control the synchronizing generator of a 'second chain. This provision locks the two synchronizing generators together so that theemitted signals, regardless of the switching position, always transmit line and eld synchronizing impulses which have the same relative phase position. This enables rapid switches to be made without destroying the asaasso quality of theprogramby having the picture dropoutmommtarllyortotclrout.

Inll'lgurelhaveshownsnmewhatmoredetailed features of my invention which prothestabilityofoperatlonwhichissodebyitsgeneratorll andtransmiiting the video and synchronizing signalthroughantennallto areceivingantenna l1. '111e receiving antenna is considered tobe located in the promity of the studo equipment1l. Thesignalsfromtheantenna i1 are rectified by the receiver detector 5S and the output is fed over two paths. one running to the switching position 85-41 to be passed on to the line amplifier and t equipment for on A portion of the output travels over a second path to a D; C. inserter 6|. The D.C.inserteril maybeofanyoftheconventionalD.C.inserters,suchasarewellknownin the art and generally embodying a diode connected across the grid cathode circuit of athermionic amplifying tube to reinsert the direct current component representative of the average brightness of the picture which is generally suppressed during the transmission. The reason for inserting the direct current component is to counteract the effects oi.' any'inadvertent lowfrequency noise or hum which may be picked up dung the transmission and reception of the signal. The output of the D. C. inserter is fed to the skimmer 53 which is a threshold amplifier which tendsto give zero output for all signals supplied to it below a certain predetermined value and which gives substantially constant output for all signals exceeding the said predetermined value. 'I'he threshold level corresponding to the predetermined value is generally set to operate only upon the receipt of the synchronizing signal. The skimmer therefore serves to separate the synchronizing signal from the picture signal, assuming blacker-thanblack transmission, and the limiting feature of the skimmer, when taken together with the D. C. insertion, serves to counteract any fading which mayhavebeenpresentsoastoinsurestability of synchronization. The output of the skimmer 63, it will be appreciated, will therefore have the wave form of square-top waves. These waves are then passed to a wave shaper 65 which converts the square waves to substantially a sinusoidal wave. The sinusoidal wave output of the wave shaper i5 is thereafter fed to a phase splitting network 61. The purpose of the phase splitting network is to produce a three-phase sinusoidal output from the single phase energy and this is accomplished by a number of parallelly .connectedreactancecircuitssochosenastogivc since by continuous rotation of the Selsyn motor rotorthephaseanglecanbemadeaslargeas desired,whereasthesinglephasetypeofphase shifterwhichcanbeoonvenientlyusedhasarestrictedmaximmnangleofphaseshift. TheV doubling-the frequency of the sinusoidal wave passed through the phase shifter 1I: The output of the frequency doubler may be fed through the switch SI to the local synchronizing generator 1i to synchronize the master oscillator thereof, which is assumed to run at double line frequency, The studio pick-up equipment 13 is synchronized by its local synchronizing generator 1l. 'fhe generator 15 may be controlled through the switch 93 from one of the two (S0-cycle supplies I3 and 19. Under ordinary circumstances the switch 95 is thrown to the position S! so that the Gli-cycle supply 83 is fed through the switch S3 to the synchronizing generator 15 to control the frequency of the master oscillator by means of a differential biasing circuit. One form of a dierential biasing circuit that may be used is that described in considerable detail in the above referred to publication by Smith and Bedford. A phase shifter 8 I which may take any form, but for simplicity in practice is usually a Hartshorn circuit, is provided in order to facilitate the initial adjustment of the diiferential biasing circuit. The phase shifter Il may also be activated by remote control from a film studio, for example, in order to properly phase the film scanner with vthe film projector which also operates on the 60- cycle supply. When the switch $5 is thrown to the position 91. vthen the three-phase 60-cycle supply 19 serves to control the synchronizing generator 15. The phase shifter 11 of the Selsynv motor type provides means for obtaining as large a phase shift as desired, since each revolution of the rotor of the Selsyn motor adds 2 radians, since the number of revolutions which may be made is unlimited. It will be readily appreciated that the phase angle may be made any desired value, which is not true of the phase shifter operated at Il, since the Hartshorn circuit only provides a phase shift of degrees. It will be appreciated, therefore, that the phase of the vertical synchronizing pulse will be determined by the settings of the phase shifter 11 or lL-and, moreover, aids in reducing the amount of phase shift necessary to be introduced by the phase shifter 69.

It will be appreciated that to shift synchronizing control from one of the local supplies to that of the remote unit by opening the switch 93 and closing the switch 9|, it is exceedingly difficult to make the switching operation at precisely the right instant to cause the generator 1l to lock in on the right line because the impulses from the frequency doubler 1I and those of the synchronizing generator drift by each other. Thus, some shifting of the phase of the controlling double frequency pulses will be required in order to line up perfectly the two generator outputs. The maximum correction which would be required is a shift comparable to the number of lines in one field, /which occurs when vertical impulses are perfectly lined up with each other, but, in one case, the first equalizing pulse starts one line after the leading edge of the preceding horizontal pulse, while, in the case of the other generator, the rst equalizing pulse occurs one-half line after the leading edge of the pre-l ceding horizontal pulse, that is to say, the even fields from one source and the odd fields from the other source have their vertical synchronizing pulses matched. To correct for thiscondion in a S25-line picture, for example, requires a phase shift of 262% lines, or 189,000 degrees in terms of the double frequency controlling pulse.

Hence the Selsyn motor continuous phase shift arrangement.

This extreme condition can be avoided, however, if prior to the operation of the switches 9| and 93, switch i95 is thrown into position 91. By observing, through the aid of monitors, the relative position of the controlling signals from 1| and the signals from the generator 15, the phase shifter 11 may be operated to bring the two groups of controlling signals into approximate alignment, i. e., 21r radians of rotation on phase shifter 11 is the equivalent of 2621/2 times 21| radians of rotation on phase shifter B9. Following this, the opening of the switch 93 and the closing of the switch 9| can be effected, and the maximum amount of correction needed will then be only on the order of 3 or 4 lines. Correction by rotating the phase shifter 69 is not noticeable by the observer, except insofar as the received picture is free from tearing-out effect when the switch is made. The use of the three-phase 60-cyc1e phase shift will be understood in the light of the operation of the system when lm transmission is used in addition to the studio pick-up 13. In the case of film transmission, the local generator must be synchronized with the local power supply and a certain amount of phase shift is needed to properly align the generator pulses with the frame lines on the lm. If the phase shifter 8| were used to align the generator 15 with that of the generator 5|, the phase shifter 8| would have to be returned to approximately its normal position each time after the two generators were disconnected from each other in order to insure the lm scanner having proper phase relation with the lm projector. From the operational point of view, it is preferable to supply a supplementary phase control so that when the local generator 15 is released from remote control, it can be immediately placed in position for lm transmission by the operation of va switch rather than having to set carefully the control to a predetermined position. Moreover, the supplementary 60cycle phase control 11 has a large enough phase shift to correct easily and quickly for any previous misalignment condition of even elds with one generator and odd fields from the other, whereas the phase shifter 8| does not provide the ran-ge necessary to accomplish this easily.

More specifically, the method of providing the supplementary phase shift is shown in Figure 4, together with a more detailed showing of the phase splitting network 61, the phase shifter 69, and the frequency doubler 1| of Figure 3. Figure 4 the (iO-cycle .supplies |12 and |86 correspond to the

supplies

19 and 83 of Figure 3. The three-phase supply connected to the terminals |12 are fed to three transformers |13, |15, |11,

lwhich have their primaries each tied between one side and neutral.

The secondaries, for the purpose of illustration, are shown connected in delta, the sides |19, |8l, |83 corresponding to the three windings of a Selsyn stator. The rotor |85 of the Selsyn motor is grounded at the mid-tap and the outer terminals connect to the contacts |93 of the switch |89. The 60-cycle supply fed to the terminals |86 corresponding to the 60-cycle supply 83 of Figure 3 is fed through a transformer |81 to the terminals |9| of the switch |89. The output terminals of the switch |89 connect to a phase shifter comprising `the serially connected condenser |95 and variable resistor |91, the phase shifter being of the Hartshorn i other, which is required for three-phase. oper,- ation. The rotor |3| of the Selsyn motor |21 willk therefore supply a sinusoidal voltage whose phase" angle compared with that of the energy supplied.-

type well known in the art. The circuit comprising the diodes |99 and 20| and the time constant circuit 203 and the transformer 204 and condenser 201 comprise the differential biasing circuit, the transformer' 204 being fed on the primary side with 60-cycle pulses derived from the frequency divider of the synchronizing generator. This circuit is shown and described in detail in the above referred to publication by Bedford and Smith. It will be readily appreciated, therefore, that the differential biasing circuit, by throwing the switch |89 either in the rst position, or second position will utilize the 60-cycle supply fed to the terminals |8| or vthe three phase supply connected to the terminals |12 as a standard against which the impulses fed to the transformer 204 are compared. The output of the differential biasing circuit is fed to the grid |1| of the tube |61, which tube serves as the frequency control tube of the double line frequency master oscillator tube |68 by being connected across the resonant circuit of the oscillator.

To control the master oscillator tube |68 directly, sinusoidal wave energy of horizontal line frequency is fed to the terminals I0 'Ihis horizontal line frequency energy is derived, as explained in connection with Figure 3, from the output of the wave shaper 65. The energy fed to the input terminals |0| is then fed to three parallel paths, each path constituting one phase of a three-phase phase splitter. The energy from |0| is rst of all fed to the tube |2| by means of capacity resistance coupling. The value of capacity of the condenser ||3 is made very large, while the resistance ||5 across the grid circuit of the tube 2| is likewise made large. Since the line frequency is relatively high, substantially no phase shift, or at most only a very little phase shift, takes place in the voltage across the grid of the tube |2| compared with the voltage fed in the terminals |0|, the condenser |03 also being a very large value'. The output of the tube |2| is fed to the delta winding |29 of the Selsyn motor |21.

The input Voltage is likewise fed to the tube ||9 through capacitor |09 and across the resistor The capacitor |09 and the resistance are so chosen as to introduce a phase shift of voltage which leads the input voltage by substantially 60 degrees. The output of the tube |9 is thereafter fed to the tube |25, the output of which is likewise connected to the delta winding |29.

Tube ||1 is fed with energy from the input through the resistor |05 across the condenser |01. The resistor |05 and condenser |01 are so chosen as to produce a voltage which lags the input voltage by substantially 60 degrees. The output of the tube ||1 is then ted to the tube |23, the output of which is connected to the delta winding |29. It will be noted that because the output of the tube |2| is fed directly to the delta winding, while tubes ||1 and 9 have an inverting stage connected between them and the delta winding, that the additional tube introduces a further shift of 180 degrees. The result is that across the delta winding there will appear three voltages spaced degrees from each at the terminals |0| will be determined by the relative mechanical position of the rotor |3| with respect to the stator |29. Rotation of the rotor v|3| will therefore increase the phase angle or decrease the phase angle, dependent upon the direction of rotation.

Across the stator 3| a potentiometer |33 is provided to supply energy of controllable amplitude to the tube |35. The amplied energy from the tube |85 is fed to a symmetrical clipper comprising the tubes |31 and |39. The symmetrical clipper tubes operate by being biased to cut-off and overdrivingv the grid circuits of the tubes, as is well known in the art. Under these conditions, non-linear amplification takes place with the result that one side ofthe output energy wave has substantially a flat top. Passing this wave through a second stage, as |39, ilattens out the other side and by an appropriate adjustment of the circuit constants, the resultant wave can be made symmetrical. The output of the tube |39 is fedthrough a differentiating tube com-l prising the condenser |45 and the resistance |41. By making the value of resistance |41 relatively small compared to the reactance of the condenser |45 only the high frequency components of the square wave will be passed. The result is that a sharply peaked wave is produced at the output of the tube |4|, the peaks corresponding f to the substantially vertical sides of the square wave. The outputs of the tube |4| are fed to the two tubes |43 and |44 which have their output circuits made common across the resistor |53. The tube |43 has its grid circuit energized from the plate circuit of the tube |4|, while the grid circuit of the tube |44 is-actuated by the drop i produced across the ycathode resistor |49 of the tube |4| so as to provide an essentially pushpush stage. The common output of the tubes |43 and |44. is consequently a series of pulses which are of double frequency compared to the frequency of the pulses supplied by the output of the tube 4|. The double frequency pulses across the common output resistor |43 are fed by capacity resistor coupling to the terminal |63 of the switch |59. When the switch |59 is thrown in position to make contact with |6|, the double frequency impulses are fed directly to the grid circuit of the' double line frequency master oscillator tube |68. It will be noted that under these conditions the output from the tube 20| ,and condenser 201 is short-circuited so that the frequency control tube |61 becomes inactive to control the frequency of the master oscillator |68. When the switch is, however, thrown to the psition |63, then the output from the tubes |43-|44 is short-circuited and bias from the tube and condenser 201 is fed to the control grid of the tube |81 to control the frequency of the master oscillator.

In order to facilitate an understanding of the operation of the frequency doubler I have shown,

above each tube, representative plate circuit wave shapes to indicate the output of each of the tubes. Thus, the output of tube |35 is shown as a sinusoidal wave at 2| while the output of the tube |31 has a wave form shown in 2 |3 in which one side is at and the other is sinusoidal. The output of tube |39 is shown as a square wave at 2|5, while the output of the differentiating tube |4| shows the peaked impulses produced whenevfr the voltageA changes appropriately, and, finally, the output appearing across the common resistor 2|9 in which the negative pulse of 2|1 is inverted. It will thus be appreciated by manipulation of switch |59 control may be had either locally from one of two 60cycle supplies or by fed from the frequency doubling tubes |43-|44.

the remotely generated synchronizing signals It also is desirableto prcvide means for automatically returning the equipment to local control lin the event that the remote signals are controlling the synchronizing generator and the -remotely generated synchronizing signals are interrupted by reason of a failure. One means of providing such automatic control is shown schematically in Figure 5. In Figure 5 relay 289 normally has one of its armatures 291 in contact with contact 295, which short-circuits the output from the'frequency doubler 21|, the equivalent of the common output from the resistor |53 in Figure 4. 'I'he local control output from the tube 20| is connected to the contact 293. Contact 29| is connected to the relay winding and also to a push-button 285 which is normally biased tocut-oif, and an integrating circuit 213 `through action of the local Abattery 281.

comprising a resistance and a condenser. The circuit 213 is likewise fed with double frequency pulses from the frequency doubler 21|. When frequency pulses from the frequency doubler 21| are present, momentary closure of the push-button 285 pulls both of the

armatures

283 and 291 toward the contacts 29| and .293, respectively, The opening of the push-button 285 following its momentary closure, however, leaves the relay armatures in their closed position, due to the fact that current from the tube 285 now flows through the armature winding of 'the relay 289, The cut-off bias from battery 215 is overcome by the positive potential built up across integrating circuit 213. To switch back to local control it is` only necessary to momentarily open the pushbutton switch 28|, which breaks the holding current of the relay 289 and permits the armature 283 to open, as well as throwing the armature 291 back to the short-circuiting position 295. Likewise, any failure to receive double frequency pulses from the frequency doubler 21| removes the potential across the integrating circuit 213 so that the current of tube 211 is cut off, and consequently no current flows through the winding of the relay 289. Control is thus automatically returned to the local control energy source of the 60cycle supply.

Various alterations and modications of the present invention may become apparent to those skilled in the art and itis desirable that any and all such modifications and alterations be considered within the purview of the present invention except as limited by the hereinafter appended claims.

Having now described my invention, what I claim is: y

1. The method of operating a television system having a remote television camera and a local television camera which includes the steps of generating master control synchronizing im pulses at the local television camera, normally controlling the frequency of the generated impulses by locally generated energy, receiving composite video and synchronizing signals fromv synchronizing signals from the received conrposite signals, converting the segregated signals into control impulses, and selectively switching control of the frequency of the generated impulses by the locally generated energy to control by the control impulses.

2. The method of operating a television system having a remote television camera and a local television camera which includes the steps of generating' master control synchronizing impulses at the local television camera, normally controlling the frequency of the generated impulses by locally generated energy, receiving composite video and synchronizing signals from the remote television camera, segregating the synchronizing signals from the received composite signals, converting the segregated signals into control impulses, selectively switchv ing control of the frequency of the generated impulses by the locally generated energy to control lby the control impulses, and controlling the operation of the local television camera by the generated impulses.

3. I'he method of operating a television system having a remote television camera and a local television camera which includes the steps of generating master control synchronizing irnpulses at the local television camera, normally controlling the frequency of the generated impulses by locally generated energy, receiving composite video and synchronizing signals from the remote television camera, segregating the synchronizing signals from the received composite signals, converting the segregated signals into control impulses, shifting the phase of the control impulses a predetermined amount determined by the phase of the locally generated energy, selectively switching control of the frequency of the generated impulses by the locally generated energy to control by the control impulses, and controlling the operation of the local television camera by the generated impulses.

4. 'I'he method of operating a television system having a remote television camera and a local television camera which includes the steps of generating master control synchronizing impulses at the' local television camera, normally controlling the frequency of the generated impulses by locally generated energy, receiving composite video and synchronizing signals from the remote television camera, segregating the synchronizing signals from the received composite signals, converting the segregated signals into sine Wave energy, converting the sine Wave energy into wave energy of twice the frequency of the sine wave energy, selectively switching control of the frequency of the generated impulses by the locally generated energy to control by the Wave energy of double frequency, and controlling the operation of the local television camera by the controlled generated impulses.

5. The method of operating a television system having a remote television camera and a local television camera. which includes the stepsl of generating master control synchronizing impulses at the local television camera, normally controlling the frequency of the generated impulses by locally generated energy, receiving composite video and synchronizing signals from the remote television camera, segregating the synchronizing signals from the received composite signals, converting the segregated signals into control impulses, selectively switching control of the frequency of the generated impulses by the locally generated energy to control the control impulses,

controlling the operation of the local television camera by the generated impulses, and returning the frequency control of the generated impulses to the locally generated' energy uponfailure to receive synchronizing signals from the remote television camera.

6. A television system comprising a. remote television camera and a local television camera.'

means for generating master control synchronizing impulses at the local television camera, means for normally controlling the frequency of the generated impulses by locally generated energy, means for receiving composite video and synchronizing signals from the remote television camera, means for segregating the synchronizing signals from the received composite signals, means for converting the segregated signals into control impulses, and means for selectively switching control of the frequency of the generated impulses by the locally generated energy to control by the control impulses.

7. A television system comprising a remote television camera and a local television camera, means for generating master control synchronizing impulses at the local television camera, means for normally controlling the frequency of the generated impulses by locally generated energy, means for receiving composite video and synchronizing signals from the remote television camera, means for segregating the synchronizing signals from the received composite signals, means for converting the segregated signals into control impulses, means for selectively switching control of the frequency of the generated impulses by the locally' generated energy to control by the control impulses, and means for controlling the operation of the local television camera by the generated impulses.

8. A television system comprising a remote television camera and a local television camera, means for generating master control synchronizing impulses at the local television camera, means for normally controlling the frequency of the generated impulses by, locally generated energy, means for receiving composite video and synchronizing signals from the remote television camera, means for segregating the synchronizing signals from the received composite signals, means for converting the segregated signals into control impulses, means for shifting the phase of the control impulses a predetermined amount determined by the phase of the locally generated energy, means for selectively switching control of the frequency of the generated impulses by the locally generated energy to control by the control impulses, and means for controlling the operation of the 'local television camera by the generated impulses.

9. A television system comprising a remote television camera and a local television camera, means for generating master control synchronizing impulses at the local television camera. means for normally controlling the frequency of the generated4 impulses by locally generated energy, means for receiving composite video and synchronizing signals from the remote television camera, means for segregating the synchronizing signals from the received composite signals, means for converting the segregated signals into sine wave energy, meansl for converting the sine wave energy into wave energy of twice the frequency of the sine wave energy, means for selectively switching control of the frequency of the generated impulses by the locally generated energy to control by the wave energy of double frequency, and means for controlling the operation of the local television camera by the controlled generated impulses.

10. A television system comprising a remote television camera and a local television camera, means for generating master control synchronizing impulses at the local television camera, means for normally controlling the frequency of the generated impulses by locally generated energy, means for receiving composite video and synchronizing signals from the remote television camera, means for segregating the synchronizing signals from the received composite signals, means for converting the segregated signals into control impulses, means for selectively switching control of the frequency of the generated impulses by the locally generated energy to control by the control impulses, means for controlling the operation of the local television camera by the generated impulses, and means for automatically returning the frequency control of the generated impulses to the locally generated energy upon failure to receive synchronizing signals from the remote television camera.

1l. 'I'he method of transmitting composite television pictures formed by scenes picked up by a local television camera and a remote television camera which includes the steps of transmitting composite video and television signals from the remote television camera, generating master synchronizing impulses at the local television camera, controlling the operation of the local television camera by the generated master synchronizing impulses to produce video signals at the local television camera,v receiving at the local television camera the composite video and synchronizing signals -from the remote camera,

segregating the synchronizing signal and the video signal from the received composite signals,

controlling the frequency of the master synchronizing impulses by the segregated synchronizing signals, combining the segregated video signals with the produced video signals of the local television camera, and transmitting the combined video signals.

12. A television system comprising a local television camera, a remote television camera, means for transmitting composite video and television signals from the remote television camera, means for generating master synchronizing impulses at the local television camera, means for controlling the operation of the local television camera by the generated master synchronizing impulses to produce video signals at the local television camera, means for receiving at the local television camera the composite video and synchronizing signals from the remote camera, means for segregating the synchronizing signal and the video signal from the received composite signals, means for controlling the frequency of the master synchronizing impulses by the segregated synchronizing signals, means for combining the segregated video signals with the produced video signals of the local television camera, and means for transmitting the combined viedosignals.

pulses at the local television camera, normally controlling the frequency of the generated impulses by locally generated energy, receiving signalling energy from the remote point to provide local control signals, selectively switching control of the frequency of the generated impulses from the locally generated energy to control by the control signalsdependent upon the energy received from the remote source, and controlling the operation of the local television camera by the generated impulses.

14. The method of operating a television sys- I tem having a remote television camera and a local television camera which includes the steps of generating master control synchronizing impulses at the local television camera, normally controlling the frequency of the generated impulses by locally generated energy, generating control impulses at the remote point which are received at the local point, converting the signals received at the local point into control impulses, selectively switching control of the frequency of the generated impulses by the locally generated energy to control by the controll impulses developed from the received signals, and controlling the operation of the local television camera by the generated impulses.

15. The method of operating a television system comprising local and remote television cameras which includes generating master control synchronizing impulses at the local point for all of the local cameras, normally controlling the frequency of the generated impulses by locally generated energy, simultaneously generating control synchronizing impulses at the remote point for controlling the remote camera devices, receiving at the local point the remotely generated synchronizing impulses transmitted from the remote point, converting the received impulses into controlling impulses, then selectively switching the control of the frequency of the generated master control synchronizing impulses by the locally generated energy to control by the control impulses derived from the remote source, and controlling the operation of the local camera by the said generated impulses.

16. A synchronizing control for a television system including remote and local television pickup cameras which includes a local source for generating master control synchronizing impulses for all local cameras, means for normally controlling the frequency of the locally generated impulses by locally generated energy, remotely positioned means for generating control synchronizing impulses for controlling the remote camera devices, receiving means at the local point for receiving the remotely generated synchronizing impulses transmitted thereto from the remote 13. The method of operating a television system having a remote television camera and a local television camera which includes the steps of generating master control synchronizing impoint, signal converting means to develop control impulse energy from the received impulses derived from the remote source, selective switching means to control the frequency of the generated master control synchronizing impulses from the locally generated energy to a control by the control energy impulses derived from the remote source, and camera control means for controlling the operation of all local cameras by the generated impulses.

JAMES RUSSELL DE BAUN.