Патент USA US2404939код для вставки
Juiy 3o, 1946. W. F. BARES” TELEVISION SIGNAL-TRANSLATING SYSTEM Filed. Feb. 27', 1942 ¿404,939 Patented Julyv 30, 1946 2,404,939 UNITED STATES PATENT OFFICE 2,404,939 TELEVISION SIGNAL-TRANSLATING SYSTEM William F. Bailey, Port Washington, N. Y., as signor, by mesne assignments, to Hazeltine Re search, Inc., Chicago, Ill., a corporation of Illi nois Application February 27, 1942, Serial No. 432,669 8 Claims. 1 This invention relates to a television signal translating system and, more particularly, to a video-frequency signal-translating system having 2 sired video-frequency signals, in spite of the aforementioned expedients. As a still further expedient, it has been pro an improved characteristic effective in compen sating for shading effects in the reproduced pic posed to minimize the shading component in the ture. able, artiñcal compensating signal which may be inserted in the video amplifier. It has been found In video-frequency signal-generating systems, especially those in which a camera tube having a output signal of a camera tube by utilizing a suit that such an artificial signal having a saw-tooth, target electrode comprising a mosaic plate is em exponential or parabolic Wave form may in some Dloyed as the video-frequency signal generator, 10 cases be effective to reduce, to a limited extent, there is produced, in addition to the desired the undesired shading effect. In some instances video-frequency signals corresponding to the the compensating signal is a composite signal image to be translated, an undesired, spurious comprising a combination of these Wave forms, signal, commonly known as a shading signal. and having frequency components related to the This undesired signal is produced, at least in part, 15 scanning frequencies of the signal generator. by secondary electrons emitted from the target This method of compensating has the disadvan electrode during the scanning operation. The tage that it requires elaborate and extensive emitted secondary electrons rain back upon the equipment which is both difficult and inconven ient to operate successfully. target electrode but, in general, this rain is not uniform over the area of the target so that the 20 It is an object of the present invention, there several elements of the target do not assume po fore, to provide an improved television signal tentials accurately representative of their respec translating system Which is not subject to one or more of the above-mentioned disadvantages. tive degrees of illumination, Consequently, the output signal of the cameraV tube includes an un It is still another object of vthe invention to desired component resulting in a shading effect 25 provide a television signal-translating system having an improved arrangement for removing, in the reproduced picture. Since the shading at least in Dart, from the signal translated there effect is produced in part by the scanning opera by an undesirable component introduced into the tion, the shading signal contains frequency com signal in the signal generator and normally eiïec ponents related to the scanning frequencies of the system. The amplitude of the undesired signal 30 tive to produce a shading effect in the reproduced picture. under consideration is generally of a greater order It is a still further object of the invention to of magnitude than that of the desired video-fre provide an improved method and means for quency signal so that it is necessary to delete translating television signals substantially free from the composite output signal of the camera tube those components which correspond to the 35 from components related to the scanning fre quencies of the translating system and normally undesired shading signal if high-quality image effective to produce a shading effect in the repro translation is to be attained. duced picture. For the purpose of minimizing shading effect of the type under consideration, it has been pro 40 A specific object of this invention is to provide in a television signal-translating system an auto posed in the past to include a collector ring in the camera tube having a circular shape symmetrical with respect to the mosaic and particularly adapted for collecting the secondary electrons. It has also been proposed to use small values of beam current in the camera tube to reduce the shading effect. Another expedient resorted to for the same purpose is to avoid scanning the edges of the mosaic Where the variations in the rain of electrons back to the mosaic are the greatest. However, systems in which these DI‘OIJOSEÚS have been utilized are subject to the disadvantage that a substantial shading effect remains and that the amplitude of the undesired shading signal pro duced is generally greater than that of the de 55 matic means for shading correction which means does not require the services of an operator re gardless of the shading wave form. In accordance with the invention, a television signal-translating system includes a signal translating channel having an input circuit and an output circuit, and means for applying to the input circuit a composite signal derived by scan ning continuous lines of an image to be translated which signal comprises video-signal components Within a predetermined frequency range corre sponding to images to be translated in the system and undesirable shading components having fre quencies within this range and related to a fre quency of scanning of the image. |Also included 2,404,939 3 a power amplifier 24, and an antenna system 25, 2G ; all, with the exception of the translating stage in the system are means having a frequency char acteristic related to the above-mentioned scan ning frequency for effectively removing from the compo-site signal at least one lower frequency 2li which embodies the present invention as will be described more fully hereinafter, are con structed and arranged in accordance with con component of the shading components and for translating to the output circuit the resultant sig nal which includes video-signal components hav ing frequencies below the above-mentioned lower frequency component and is substantially free from each removed shading component. ventional practice. Line-synchronizing pulses and held-synchronizing pulses are derived from line-frequency generator I3 and field-frequency generator lli, respectively, and supplied to the video-frequency amplifier 2l for translation with the video-frequency signals generated in unit I0. In accordance with a preferred embodiment of the invention, a repeater circuit including a plu Suitable means (not shown, but which may be considered as included in the signal generator l0) are also provided for developing a unidirectional rality of trap circuits is coupled in the signal translating channel. rI‘he trap circuits, which background-illumination voltage and for insert ing it into the developed video-frequency signal. may be either series or parallel arrangements of , inductors and capacitances, are resonant at the fundamental and at least one harmonic of the line-scanning frequency and are effective to re move from the translated signal components of Neglecting for the moment details of opera tion of the signal-translating stage 26, the sys tem just described comprises the elements of a television transmitter of conventional design and the various parts thereof, which are illustrated schematically, may be of well-known construc tion, rendering a detailed description of their op eration unnecessary. Brieiiy, however, the im those frequencies which correspond to shading ~ components. A coupling circuit, which comprises a stabilizing device coupled to the repeater circuit, is provided and is effective to suppress shading components related to the held-scanning fre quency. To this end, the coupling circuit has a time constant which is short with respect to the age of a scene to be transmitted is focused on the target of the signal generator I0 and scanning field-scanning frequency and rejects components currents are applied to the scanning elements Il and I2 of the generator l0 to supply electro-mag of the translated signal at that frequency. For a better understanding of the invention, netic fields which serve to deflect the scanning together with other and further objects thereof, 30 ray in two directions normal to each other, there reference is had to the following description taken by to scan successively a series of ñelds of par in connection with the accompanying drawing allel lines upon the target. The de?lecting cur and its scope Will be pointed out in the appended rents, and hence the scanning fields, are of saw tooth wave form providing relatively slow linear claims. In the accompanying drawing, Fig. 1 is a circuit trace and rapid retrace scansions. Block-out im pulses developed by generator I5 are applied to diagram, partly schematic, of a television trans mitting system including a circuit arrangement the signal generator Iû to suppress or block out the scanning beam during retrace portions of the embodying the present invention; Fig. 2 is a cir scanning cycles. The timing impulses developed cuit diagram of a modification of the arrangement of Fig. 1; Fig. 3 comp-rises a graph representing by the generator I6 are applied to generators I3 certain operating characteristics of the circuit of |5, inclusive, to lock these generators in synchro Fig. 2; and Fig. 4 is a circuit diagram of a further nism. The photosensitive elements of the target of modification of the arrangement of Fig. 1. the signal generator IEI are electrically affected Referring now more particularly to Fig. l of to an extent dependent upon the varying values the drawing, there is illustrated a television transmitting system comprising a signal gener of light at the corresponding elemental areas of the image focused thereon so that, as the cath ator Ii), which may be of conventional design in ode-ray beam scans continuous image lines of cluding a camera tube of the cathode-ray type, the image on the target, Video-frequency signals having a mosaic type target electrode and scan ning elements Il and I2. For the purpose of i of correspondingly varying amplitude, and having a frequency range determined by the images to developing scanning currents for the signal gen be translated, are developed in the generator I0. erator III there are provided a line-frequency The terms video signal or video-frequency signal, saw-tooth wave generator I3 and a field-fre as employed in the specification and claims, are quency saw-tooth wave generator M, the output circuits of these generators being connected to ; intended to designate a conventional picture sig nal which is generated by the usual scanning scanning elements II and I2, respectively, of the operation. This terminology therefore excludes signal generator IB in the usual manner. In or a generated picture signal, the wave form of der to block out the scanning ray of the generator which is modified by interrupting the scanning lil during retrace scanning periods, there is pro vided a block-out wave generator I5 having an beam by suitable means at a high frequency so output circuit suitably connected to the signal generator I0. that the picture signal, in effect, modulates the developed interrupting wave, this latter wave be For the purpose of synchronizing the genera tors there is provided a timing-impulse generator I5 coupled to the input circuits of the generators I3-I5, inclusive. Timing-impulse generator I6 is preferably stabilized by means of a connection i'l ing in the nature of a carrier wave. image to be translated as in customary scan ning practice. At the same time as the conven to a suitable source of periodic voltage, for exam tional video-frequency signals are generated, due ple, the power-supply circuit or the synchroniz ing-voltage source of a motion-picture mecha nism where such is employed. The inter ruption of the scanning beam in the foregoing manner therefore effectively prevents the beam from scanning continuous image lines of the 70 to the above-mentioned secondary-electron ef Connected in cascade to the generator I il, in the order named, are a signal-translating stage 2S, a video-frequency amplifier 2|, a modulator 22, an associated carrier-frequency oscillator 23, 75 fect, shading signals having components related to the line-scanning frequency and field-scanning frequency and included within the frequency range of the video-frequency signals are also developed in the generator Ill. These developed 2,404,939 5 signals comprise a composite signal derived by cuit of the signal-translating stage includes a load resistor 4| and is suitably coupled to the input terminals of video-frequency ampliñer 2|. Operating potentials for tubes 21 and 28 are sup the generator I0 and the unidirectional back ground-illumination voltage which is developed by suitable means included in the generator IG is inserted in this signal. Thus, the video-fre Ul plied to their screens from suitable sources indi -quency and shading-signal components, block cated -l-Sc and to their anodes from suitable out components, and unidirectional-background sources indicated -l-B. components are all derived from the signal gen In considering the operation of the circuit of erator I0 and applied to the signal-translating Fig. 1, it will be assumed that composite signals stage 29, wherein they are translated in accord 10 comprising video-signal components Within a ance with the present invention and from which predetermined frequency range corresponding to they are applied to the video-frequency ampli the images to be translated and undesired shad fier 2|. synchronizing impulses derived from ing components having frequencies within the generators I3 and i4 are mixed With the video range and related to the line-scanning and field signal components in the combining video-fre scanning frequencies of the signal generator l0 quency amplifier 2| and the resultant signal is are applied negatively, that is, with the black thereupon supplied to the modulator 22 wherein level of the composite signal more negative than it is impressed upon the carrier wave generated the white level thereof, by way of coupling con by the oscillator 23. The modulated carrier sig denser 29 to the input circuit of the signal-trans nal is then delivered to the power amplifier 2d. 20 lating channel and to tube 21, The time constant for amplification and is impressed upon the an of condenser 2S and grid-leak resistor 3G is such tenna system 25, 2'5 to be radiated. that the signal is not stabilized about its positive Referring now more particularly to the signal peaks in the input circuit of tube 21. The trap translating stage 2Q embodying the :resent in circuits included in the cathode circuit of tube vention and provided for the purpose of remov 21 are effective to render the tube degenerative ing shading components from the composite sig to applied signal components of the fundamental nal to be translated, this stage comprises a pair frequency and the second harmonic, respec of vacuum tubes 21 and 23, which are preferably tively, of the line-scanning generator whereby of the pentode type, coupled in cascade to pro components of the composite signal at these fre vide a signal-translating channel having an in quencies, which correspond to components of the undesired shading signal, are effectively removed and do not appear in the repeated signal which put circuit connected to signal generator Hi and an output circuit connected to video-frequency amplifier 2|. The input circuit of the signal-translating channel includes the signal-input electrode of tube 21 and is coupled to the output circuit of signal generator |ß by way of a coupling con denser 29 and a grid-leak resistor 3d. Tube 21, which functions as a signal repeater, is pro vided with means having a frequency character' istic related to one scanning frequency of the signal generator lll to render the tube degener ative to applied signal components of predeter mined frequencies for attenuating from the com posite signal applied thereto components having a frequency related to the saine scanning fre quency and corresponding to shading compo nents in the signal output of generator it. Spe cifically, there is provided in the cathode circuit of repeater 21 a pair of parallel-resonant trap circuits connected in series. The ñrst trap cir is derived from the output circuit of tube 21. Due to the phase-reversing characteristic of tube 21, the repeated signal is applied positively, that is, with the black level of the signal more posi tive than the white level thereof, by way of cou pling condenser 3i) to tube 28 wherein the signal is stabilized through grid rectification at the most positive peaks of the signal. The time-constant circuit comprising condenser 39 and leak resistor 4l! is effective to remove from the signal applied to tube 28 components at the ñeld-scanning fre quency which also correspond to components of '. the shading signal. Thus, a composite signal from which the undesirable shading components have been removed is derived from the output circuit of the signal-translating channel 2|) and applied to video-frequency amplifier 2| for fur cuit comprises a parallel combination of an in ductor 3|, a condenser 32, and a damping re sistor 33, and this trap circuit is tuned prefer ably to the fundamental frequency of the line lll A, frequency generator |3. The second trap circuit comprises the parallel combination of an induc tor 34, a condenser 35, and a resistor 36, and this trap circuit is tuned preferably to the sec ond harmonic of the line-scanning frequency. (SO The damping resistors 33 and 3S are provided in order to broaden the attenuation characteristics of the trap circuits. The output circuit of tube 21 is provided with a load resistor 31 and is coupled to the input circuit of tube 23 through a time-constant circuit which comprises coupling condenser 39 and grid-leak resistor 40. The time constant of the circuit coupling tubes 21 and 28 is proportioned with respect to another scanning frequency of the generator lll and, preferably, the circuit is arranged to have a time constant short with respect to the period of the ñeld frequency generator I4 so that the coupling cir cuit has a frequency characteristic related to the field-scanning frequency. The output cir 75 ther amplification. Therefore, it may be seen that the unit 20 is effective to remove undesired shading compo nents from a composite signal comprising both desired video-signal components and undesired shading components within the frequency range of the video-signal components and related to a frequency at which the image to be translated is scanned, whereby the video-signal components supplied to amplifier 2| are thus substantially free from shading components caused by the scanning operation at the signal generator. In Fig. 2 there is disclosed a repeating network embodying a modification of the invention which may be substituted in the television transmit ting system of Fig. 1 for the signal-translating stage 20 by connecting the terminals indicated C and D to the corresponding terminals of Fig. l. The network includes a pair of vacuum-tube re peaters 50 and 5| which preferably are of the pentode type. The input electrode of tube '50 is coupled through a coupling condenser E2 and a grid-leak resistor 53 to the output circuit of gen erator I0 and the signal output from tube 50 is derived from a cathode load resistor 54 so that the output signal has the same polarity as the '2,404,939 7 8 input signal. The input circuit of tube 5| is coupled in parallel with that of tube 50 and in ing the fundamental, second, and third harmonics of the line-scanning frequency which correspond to shading components which are particularly troublesome, whereby the video-signal compo cludes a coupling condenser E5 and a leak re sistor 5l. Also included in the input circuit of tube 5l is a low-pass filter network comprising series resistors E8 and SQ and shunt condensers 59 and (il. The output signal of tube 5l is de rived from an anode load resistor 62 and, due to nents of the composite signal are translated to the output circuit of the signal-translating chan nel substantially free from shading components of frequencies related to the line-scanning fre the phase-reversing characteristic of the tube, quency. the signal derived therefrom has a polarity oppo 10 In the modification of the invention disclosed site to that of the signal-input thereto. A con in Fig. 4, the means provided for attenuating denser 63 is connected between the anode of tube shading components comprises a pair of shunt 5l and the cathode of tube 53 whereby the tubes connected series-resonant trap circuits coupled are connected in phase opposition. in the signal-translating channel, The ñrst trap Tube 50 has a substantially uniform gain char circuit includes an inductor "55? and condenser 'li acteristic over the frequency range of the video and is tuned, preferably, to the fundamental of signal components while the filter 58 to @l causes the line-scanning frequency, while the second the tube 5I to have a gain characteristic related trap circuit includes inductor 'i2 and condenser to a frequency at which the image to be trans 'i3 tuned, preferably, to the second harmonic of lated is scanned. Specifically, the low-pass nlter the line-scanning frequency. The circuit of Fig. 58 to 6| is arranged to reject frequency compo 4 may be substituted for the signal-translating nents of the applied signal which are of a fre stage 2e in Fig. `l by connecting terminals C and quencsr equal to or greater than the third har i) to the correspondingly designated terminals monic of line-frequency generator i3. The cou of Fig. l. When this substitution has been pling circuit associating the output circuits of effected the composite signal applied to terminal the repeater tubes 5t and lil has a frequency C is translated and applied to video-frequency characteristic related to another lfrequency at amplifier El, but components of the signal hav which the image to be translated is scanned and, ing frequencies corresponding to the first and specifically, the coupling circuit is arranged to second harmonics of the line-scanning frequency have a time constant which is short with re 30 and ccrresponding to shading components are spect to the frequency of the field-scanning gen attenuated by the trap circuits. erator I4. It is appreciated that in utilizing the principles In considering the operation of the circuit of and concepts of the invention, certain desired Fig. 2, it will be seen that the composite signal, picture components may be removed from the defined above, is derived from signal generator translated signal; that is, in attenuating fre l0 and applied to tube 59 and that a signal of quency components related to the undesired shad the same polarity is developed across its cathode ing signals components of the desired video sig load 5e. The signal output of generator ! 0 is also nals of the same frequency are simultaneously applied to the input circuit of tube 5I, but the attenuated. However, the deletion of such small components of the signal having a frequency 40 portions of the relatively wide frequency band equal to or greater than the third harmonic of representative of the video signals to be trans the line-scanning frequency are rejected by the lated does not appreciably affect the picture con low-pass filter 5B to Si and, therefore, do not tent of the signal, That is, the frequency com appear in the output circuit of tube 5i. Signal ponents which are removed are of relatively low components of the lower frequencies, however, frequencies which control the shade of the pic are translated in repeater 5l to substantially ture rather than the picture details and, hence, the same extent that these components are trans the sharpness of the reproduced picture is not lated in repeater The signal output of tube adversely affected. At the same time, removal 5| developed across the anode resistor 62 is of of the shading components, particularly those opposite polarity to that developed across cathode related to the line-scanning frequency which are resistor 54 of the tube 50 so that these outputs most pronounced, enables the reproduction of a when coupled together through condenser S3 translated image which is sufficiently improved tend to cancel one another for the frequencies over the reproduction of images wherein the under consideration. Due to the above-defined shading components have not been removed to time constant of the coupling circuit, however, coupling condenser 63 is effective to block com ponents of the repeated signal of tube 5| of a fre quency less than the fundamental of the line scanning frequency and, since only components of the applied signal having frequencies up to the third harmonic of the line-scanning frequency appear in the output circuit of the tube 5l, a band of frequencies extending substantially from the fundamental to the third harmonic of the line-scanning frequency is effectively suppressed in the output circuit of tubes 5l) and 5l . The out put characteristic of the repeating network is represented in Fig. 3 wherein f1, f2, and f3 indi cate the fundamental, second, and third har monics, respectively, of 'the line-scanning fre quency. Consequently, it may be seen that the repeat ing network of Fig. 2 is effective to remove from the composite signal applied thereto or appre ciably to attenuate a band of frequencies includ more than compensate the inherent loss of nat uralness in the reproduction caused by the dele tion of a portion of the video signals. There has been included in the above-described embodiments of the invention means for remov ing from the composite signal frequency com ponents corresponding to the fundamental, sec ond, and third harmonics of the line-scanning frequency, as well as components corresponding to the fundamental and one or more harmonics (55 of the field-scanning frequency. It is, of course, to be understood that any desired combination of frequency components related to scanning fre quencies and corresponding to an undesired shading signal may be similarly removed by re arranging or increasing the number of the trap circuits employed. The specific embodiments disclosed are merely illustrative of some possible combinations. Although the invention has been disclosed in 75 connection with a television transmission system, 2,404,939 9 10 it is to be further understood that the principles and embodiments of the invention may be applied With equal facility to a television receiving sys tem to accomplish the purposes accomplished by the invention when applied to a television trans 4. A television signal-translating system com prising, a signal-translating channel having an input circuit and an output circuit, means for applying to said input circuit a composite signal derived by scanning an image to be translated mission system. and comprising video-signal components with in a predetermined frequency range correspond While there has been described what is at pres ing to images to be translated in said system and ent considered to be the preferred embodiment undesirable shading components having a fre of this invention, it will be obvious to those skilled in the art that various changes and modifications 10 quency within said range and related to a fre quency of scanning of said image, a repeater cir may be made therein without departing from cuit in said channel, and a trap circuit included the invention, and it is, therefore, aimed in the in said repeater circuit and resonant at said fre appended claims to cover all such changes and quency within said range for attenuating fre modiñcations as fall within the true spirit and quency components corresponding to said shad scope of the invention. ing components, said repeater circuit being What is claimed is: adapted to translate to said output circuit the 1. A television signal-translating system com resultant signal including video-signal compo prising, a signal-translating channel having an nents having a frequency below the fundamental input circuit and an output circuit, means for applying t0 said input circuit a composite signal 20 frequency of said scanning frequency and sub stantially free from said shading components. derived by scanning continuous image lines of an 5. A television signal-translating system com image to be translated and comprising vvideo prising, a signal-translating channel having an signal components within a predetermined fre input circuit and an output circuit, means for quency range corresponding to images to be trans applying to said input circuit a composite signal lated in said system and undesirable shading derived by scanning an image t0 be translated components having frequencies within said range and comprising video-signal components within and related to a frequency of scanning of said a predetermined frequency range corresponding image, and means in said channel having a fre to images to be translated in said system and quency characteristic also related to said scan ning frequency for effectively removing from said 30 undesirable shading components having a fre quency within said range and related to a fre composite signal at least one lower frequency quency of scanning of said image, a repeater component of said shading components and for circuit in said channel comprising a vacuum translating to said output circuit the resultant tube repeater having a cathode circuit, a paral signal Which includes video-signal components lel-resonant trap circuit included in said cath having frequencies below said lower frequency ' ode circuit and resonant at said frequency with component and is substantially free from each in said range for attenuating frequency compo said removed shading component. 2. A television signal-translating system com prising, a signal-translating channel having an input circuit and an output circuit, means for 4 0 applying to said input circuit a composite signal derived by scanning an image to be translated and comprising video-signal components with in a predetermined frequency range correspond ing to images to be translated in said system and undesirable shading components having a fre quency within said range and related to a fre nents corresponding to said shading components, said repeater circuit being adapted to translate to said output circuit the resultant signal sub stantially free from said shading components. 6. A television signal-translating system oom prising, a signal-translating channel having an input circuit and an output circuit, means for applying to said input circuit a composite sig nal derived by scanning continuous image lines of an image to be translated and comprising video-signal components within a predetermined quency of scanning of said image, a trap circuit frequency range corresponding to images to be in said channel resonant at said frequency with in said range for attenuating frequency compo 50 translated in said system and undesirable shad ing components having a frequency within said nents corresponding to said shading components, range and related to a frequency of scanning of and means in said channel for translating to said image, a repeater network in said channel, said output circuit the resultant signal includ a pair of repeaters in said network adapted to ing video-signal components having a frequency below the fundamental frequency of said scan 55 produce output signals of opposite polarity, one of said repeaters having a substantially uniform ning frequency and substantially free from said gain characteristic over the frequency range of shading components. said video-signal components and the other of 3. A television signal-translating system com said repeaters having a gain characteristic over prising, a signal-translating channel having an input circuit and an output circuit, means for 60 said range related to said scanning frequency, output circuits for said repeaters, and means for applying to said input circuit a composite signal coupling said output circuits so that frequency derived by scanning an image to be translated components of said composite signal correspond and comprising video-signal components within ing to said shading components are removed in a predetermined frequency range corresponding to images to be translated in said system and 65 said repeater network, said repeater network being adapted to translate to said output circuit undesirable shading components having a fre of said channel the resultant signal substan quency within said range and related to a fre tially free from said shading components. quency of scanning of said image, and a series 7. A television signal-translating system com resonant trap circuit connected in shunt to said channel and resonant at said frequency within 70 prising, a signal-translating channel having an input circuit and an output circuit, means for said range for attenuating frequency compo applying to said input circuit a composite signal nents corresponding to said shading components, derived by scanning continuous image lines of said channel being adapted to translate to said an image to be translated at a plurality of scan output circuit the resultant signal substantially 75 ning frequencies and comprising video-signal free from shading components. 2,404,939 lll components within a predetermined frequency range corresponding to images to he translated in said system and undesirable shading com ponents having frequencies in a given band with in said range and related to one of said scan ning frequencies, a repeater network in said channel, a pair of repeaters in said network adapted to produce output signals of opposite polarity, one of said repeaters having a sub stantially uniform gain characteristic over the frequency range of said video-signal components and the other of said repeaters having a gain characteristic over said range related to one of 12 of an image to be translated, said scanning being effected in one direction at a predetermined line-scanning frequency and in another direc tion normal to said mst-mentioned direction at a predetermined field-scanning frequency and said composite signal comprising video-signal components within a predetermined frequency range corresponding to images to be translated in said system and undesirable shading _com ponents having frequencies within said range and related to said line-scanning and said ñeld scanning frequencies, means in said channel hav ing a frequency characteristic related to said said scanning frequencies, output circuits for line-scanning frequency for effectively removing said repeaters, and a coupling circuit having a time constant short with respect to the period cf another of said scanning frequencies for cen~ necting said output circuits of said repeaters so from said composite signal shading-signal fre quency components related to said line-scanning that frequency components within said band of frequency, and means in said channel having a frequency characteristic related to said field scanning frequency for effectively removing from frequencies are effectively removed from said 20 said composite signal shading-signal frequency composite signal, said repeater network being components related to said field-scanning ire adapted to translate to said output circuit cf said quency and for translating to said output circuit channel the resultant signal substantially free the resultant signal including video-signal com from said shading components. ponents having a frequency below the funda 8. A television signal-translating system corn 25 mental frequency of said line-scanning fre prising, a signal-translating channel having an quency and above the fundamental frequency of input circuit and an output circuit, means for said held-scanning frequency and substantially applying to said input circuit a composite sig free from said shading components, nal derived by scanning continuous image lines WILLIAM F. BAILEY.