US2300942A

US2300942A - Television carrier-signal receiver control system

Info

Publication number: US2300942A
Application number: US372091A
Authority: US
Inventors: Harold M Lewis
Original assignee: Hazeltine Corp
Current assignee: BAE Systems Aerospace Inc
Priority date: 1940-12-28
Filing date: 1940-12-28
Publication date: 1942-11-03
Anticipated expiration: 1959-11-03

Description

H. M. LEWIS Nov. 3, 1942.

TELEVISION CARRIER-SIGNAL RECEIVER CONTROL SYSTEM Filed Dec. 28, 1940 2 Sheets-Sheet 1 oi .0 G 9 u c o. 6 mEuwisE m. Emil! 52:52 $5.58: 653%. 653mm. fi nmw $58532. $5368 292 o o o O 0 0 0 m1 m1 2 2 o: a? 6 01 25.5% wzcfiwzh #56 953 2 .o 9

ATTORNEY H. M. LEWIS Nov. 3, 1942.

TELEVISION CARRIER-SIGNAL RECEIVER CONTROL SYSTEM Filed Dec. 28, 1940 2 Sheets-Sheet 2 QEE BE l u I i ATTORNEY Patented Nov. 3, 19421: i

2,300,942 a p 1 l 'rELavisroN CARRIER-SIGNAL aaon rvnn CONTROL SYSTEM Harold M. Lewis, Great Neck, N. Y.-', assign" to Hazcltine Corporation, a corporation of Delaware Application'December 28, 1940, Serial No. 372,091

8 Claims. (01. m-ss) The present invention relates to a control system for a television signal receiver and, particularly, to a synchronously-operated control system suitable for controlling either a signal-translating characteristic of the receiver or the synchronization thereof or both. While the invention is of general application, it is especially suited for use automatically to control the amplification of the signal amplifier of the receiver in accordance'with the intensity of a received television signal and independent .of itslight-modulation components and for simultaneously controlling the synchronization of the line-scanning and field-scanning generators of the receiver in accordance with the synchronizing components of. the television signal. i

television receivers oonventionally employ a.

rectifier device having a load impedance by which to' derive from a received television carrier sig-' nal a control bias, the magnitude of which varies with the intensity of the television carrier signal and is independent of its light-modulation components. Since, in conventional television slg-g nals, the synchronizing information is represented by the uniform peak amplitude of the unmodulated carrier signal, this characteristic of the televlsion signal has heretofore been takenadvantage of in effecting automatic amplification control. To accomplish this, the load impedance of the automatic amplification control system is given a relatively long time constant to ensure that the derived automatic amplification control bias varies in magnitude only in accordance with the peak amplitude of the latter and is not materially affected by the peak amplitudes representing relatively low-frequency field- 'synchronizing pulses. Such automatic amplification control systems have the characteristics that the automatic amplification control action does -not follow relatively rapidchanges of carriersignal intensity and that a strong noise pulse tends to effect a material and sustained decrease in the amplification of the controlled signal amplifiers, at times partially paralyzing the receiver.

The synchronizing information conveyed bythe television signal conventionally comprises line-synchronizing and field-synchronizing pulses of diiferent frequencies and durations. It

it desirab1e that the synchronizing information be completely separated not only from the imagesignal components but also into its two components to provide individual synchronization of the line-scanning and field-scanning apparatus ofthe receiver. This separation has"heretoiore been accomplished by various synchronizingsignal separating systems the operation of which has been premised in a large part upon the fact that each of two portions of the separating system has been responsive primarily to synchronizing pulses of one typeand only secondarily to synchronizing pulses of the other type. It is desirable that each of these two portions of the separating system be entirely responsive to synchronizing pulses of one typeand not at all responsive to synchronizing pulses of the other type if interaction between the line-scanning and field-scanning systems is to be completely avoided.

It is an object of the invention, therefore, to provide in a television carrier-signal receiver a synchronously-controlled rectifier particularly suitable for use in controlling one or more operations of the receiver, thereby to avoid one or more of the disadvantages and limitations of the prior art systems of this nature.

It is a further object of the invention to pr vide an improved automatic amplification consignal during thetrace intervals thereof.

It is a further object of the invention to provide in" a television carrier-signal receiver a synchronously-controlled rectifier systenrfor deriving from a received television carrier signal a pulsating unidirectional potential, the wave form and amplitude characteristics of which are suitable for use in simultaneously controlling synchronizing apparatus and translating characteris'tics, respectively, of the receiver.

In accordance with one embodiment of the invention, a television carrier-signal receiver includes a synchronously-controlled rectifier system comprising an input circuit adapted to have applied thereto a television signal having periodlcally-recurrent peak amplitudes and rectifying means coupled to the inputcircuit for deriving a v unidirectional potential from the television sigml which varies in magnitude with the peak amplitude thereof. The television signal is subject to sporadic peak amplitudes which may undesirably affect the magnitude of the derived unidirectional potential. An output circuit is coupled to the rectifying means to utilize the derived unidirectional potential. There is also included a means for reducing the effect of the sporadic peak-signal amplitudes on the magnitude of the derived unidirectional potential, the last-named means comprising a source of periodic potential effectively of pulse wave form and having a period equal to the period of the recurrent peak amplitudes of the television signal, and means for stabilizing the periodic potential to derive a periodic unidirectional bias and for applying the bias to the rectifying means to render the latter unresponsive to the television signal during the intervals between the recurrent peak amplitudes thereof.

In accordance with a preferred form of the invention, the peak amplitudes of the television carrier signal are representative of periodic linesynchronizing and field-synchronizing pulses and the synchronously-controlled rectifier system includes rectifying means coupled to the input circuit thereof for deriving from the television system a pulsating unidirectional potential varying with the peak amplitude thereof and having a period of pulsation equal to the period of one kind of the synchronizing pulses and having a wave form including the complete wave form of said one kind of synchronizing pulses. A synchronizing circuit is coupled to the rectifying means which is responsive to the derived unidirectional potential for controlling the period of the periodic potential, and there is also provided means for reducing the effect of the amplitudes of the television signal during the intervals between the one kind of synchronizing pulses on the wave form of the derived potential. This last-named means comprises a source of periodic potential effectively of pulse wave form and having a period equal to that of said one kind of synchronizing pulses. There is provided a means for maintaining a predetermined phase relationship between the periodic potential and said one kind of synchronizing pulses and means responsive to the periodic potential for rendering the rectifying means unresponsive to the television signal during the intervals between said one kind of synchronizing pulses.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

Referring now to the drawings, Fig. 1 is a circuit diagram, partly schematic, of a complete television carrier-signal receiver embodying the invention; Fig. 2 is a graph-comprising curves representative of voltage variations occurring at certain points in the arrangement of Fig. l and is used as an aid in explaining the operation of the invention; and Fig. 3 is a circuit diagram of a control system, per se, embodying a modified form of the invention.

radio-frequency amplifier I having its input circuit connected to an antenna system H, l2 and having its output circuit connected to an 05011- output circuits comprises an automatic amplification control or A. V. C. circuit which is connected to the input circuits of one or more of the tubes of the radio-frequency amplifier Hi, the

oscillator-modulator l3, and the, intermediatefrequency amplifier M in conventional manner.

The other output circuit comprises a synchronizingsignal circuit and is connected to the input of an intersynchronizing-signal separator 2| to the output of which are coupled a line-scanning system 22 and a field-scanning system 23.

It will be understood that the various units just described may, with the exception of the'synchronously-controlled rectifier system 20, be of a conventional construction and operation, the details of which are well known in the art, rendering detailed description thereof unnecessary. Considering briefiy the operation of the television receiver as a whole, and neglecting for the moment the operation of the rectifier system 20 presently to be'described, a desired television carrier signal is selected and amplified by the radio-frequency amplifier l0, converted to an intermediate-frequency carrier signal in the oscillator-modulator i 3, amplified in the intermediate-frequency amplifier I4, and detected by the detector l 5, thereby to derive the video-frequency modulation components. The video-frequency components are, in turn, amplified in the videofrequency amplifier I 6 and are applied to the input electrodes of the image reproducer IT to modulate the cathode-ray beam thereof. The intermediate-frequency carrier signal is also applied to the rectifier system 20, where the synchronizing-signal components of the television signal are separated from the video-frequency components thereof, as described in detail hereinafter, and are applied to the intersynchronizing-signal separator 2|. The line-synchronizing and fieldsynchronizing signals are separated from each other by the separator 2| and are applied to the respective line-scanning system 22 and fieldscanning system 26:. The line-scanning system 22 applies a scanning wave of saw-tooth wave form to the line-deflecting elements of the image reproducer l1, while the field-scanning system 23 applies a scanning Wave of saw-tooth wave form to the field-scanning elements of the image reproducer, thereby to deflect the cathode-ray beam of image reproducer I! in two directions normal to each other, visually to reproduce the received television image. y

The rectifier system 20 also derives an automatic amplification control or A. V. C. bias from the television carrier signal. as described in detail hereinafter, which is effective to control the amplification of one or more of the units I0, l3, and M to maintain the signal input to the detector l5 within a relatively narrow range for a wide range of received signal intensities.

The sound-modulated carrier signal accompanying the desired vision-modulated carrier sigof the system embodying the present invention,

the synchronously-controlled rectifier system 2|] includes an input circuit comprising a winding 24 coupled to the intermediate-frequency amplifier I4. The input circuit is adapted to have applied thereto a television signal having periodicallyrecurrent peak amplitudes representative of periodic line-synchronizing pulses which vary with the intensity of the television signal carrier and independent of its light modulation components. There is provided a peak-rectifying means coupled to the input circuit for deriving from the television signal a unidirectional control potential varying in magnitude with the peak i system 20 from the line-scanning-system 22.

amplitude thereof comprising a rectifier device 25 and

load impedance

26, 21 which are inductively coupled through a winding 28 to the input circuit winding 24. The unidirectional control potential is developed across the load impedance,

26, 21. To avoid the undesirable effect of sporadic noise pulses of peak amplitude on the magnitude of the derived unidirectional poten-' tial, there is provided means for deriving from the line-scanning system 22 a periodic potential bias includes the complete wave form of the linesynchronizing pulses. The last-named means comprises a second rectifier device 29 coupled-to the line-scanning system or source of periodic potential 22 through a condenser 30, the rectifier device 29 having a load impedance 3i, 32 for developing thereacross a unidirectional biasfrom the periodic potential. The rectifier system 26 has an output circuit coupled to the rectifying means 25, 26, 21, 28 for utilizing the derived unidirectional potential to control a translating characteristic of the receiver. This circuit comprises the automatic amplification control circuit previously referred toand includes a filter net-. work comprising a series resistor 33 and a shunt condenser 34.

There is also provided in the rectifier system 20 a synchronizing-signal separator comprising a rectifier device 35 and load impedance 36 which are coupled through a transformer 31-to the output of the intermediate-frequency amplifier I4. The load impedance 36 is a low-pass filter network comprising. a series-inductance arm 36,

shunt-condenser arms 4|, 42, and shunt

termihating resistors

39, 40. The anode of the rectifier device 35 has applied thereto through a resistor 43 a selectable portion of the unidirectional voltage derived across the load impedance 2'6, 21 of the first rectifier device 25. -The output of the tudes of the television signal as represented by curve I of Fig. 2 and the magnitude of the uniload impedance 361s coupled to the input of the intersynchronlzinz-signal separator 2|.

In considering the operation of the circuit just described, reference is made to Fig. 2 in which curve A presents the image modulated intermediate-frequency carrier signal ap from the output of the intermediate-frequenc amp;

fier l4 to the input circuit of the rectifier system n. The television carrier signal has periodically-recurrent peak amplitudes a representing linesynchronizing pulses and recurrent at linescanning frequency, peak amplitudes b representing equalizing pulses, and peak amplitudes c representing field-synchronizing pulses, only a portion of one group of which is shown but which periodically recur at field-scanning frequency. The television carrier signal also includes imagesignal components a and is subject to sporadic peak amplitudes e which may be caused by undesirable noise disturbances arising from a source external to t e television system.

Curve B of Fig. 2 represents the periodic voltage of pulse wave form applied to the rectifier This voltage is preferably derived by differtiation of the saw-tooth scanning currentsvdeyeloped by the line-scanning system 22, whereby the voltage wave has relatively large negative peaks during the retrace intervals and relatively small positive amplitudes during the trace intervals. Condenser 32 by-passes currents of intermediate frequency but is not'of suificiently large value to affect the wave form of this periodic potential applied through the condenser 30 to the rectifier system. The rectifier device 29 is so poled that the negative peaks of the periodic potential are rectified to develop across the load impedance 3| a positive unidirectional bias potential having the magnitude of ear, curve B. The bias as applied to the cathode of rectifier device 25 is thus that represented by curve C of Fig. 2 and has such polarity that rectifier device 25 is rendered unresponsive to the television signal except during the portions of the retrace intervals corresponding to the negative pulses of curve B. I

Thus the potential applied to the rectifier device 25 is that represented by. curve D of Fig. 2 whereby the rectifier device 25 Deak-rectifies the recurrent peak amplitudes of the television carrier signal corresponding to the line-synchronizing pules to develop across its load impedance 26, 21 a unidirectional potential. The magnitude of the unidirectional potential is determined by the time constant of the

load impedance

26, 21. If the time constant is long, the condenser 21 does not discharge appreciably between the recurrent peak amplitudes of the television carrier signal and the magnitude of the derived unidirectional bias is thus'ez of curve D. If the time constant is short, condenser 21 may discharge appreciably between the recurrent peak amplidirectional potential thus has a value as. Intermediate values of the time constant of the load impedance permit the condenser 21 to discharge a lesser amount as represented by curve I, and provide intermediate values of unidirectional potential, as the value c; of Fig. 2. Since the rectifier device 25 is not responsive to the television carrier signal during the trace intervals occupied by the image-signal component d, the magnitudeof the derived unidirectional potential is not affected by such noise disturbances e as occur during these periods, but it is only affected by noise disturbances occurring during the retrace interval which is only about 10 per cent. of the line-scanning period.

The rectifier device 29, therefore, is included in a means for reducing the effect of the sporadic peak-signal amplitudes on the magnitude of the derived unidirectional potential, and the abovementioned device is also included in a means which is responsive to the periodic potential for rendering the rectifying means including the rectifier device 25 unresponsive to television signals during the intervals between the line-synchronizing pulses. The pair of rectifying

devices

25 and 29 and their

load impedances

26, 21 and 8!, 32, respectively, are provided for the input circuit of the rectifying system 20. Winding 28 is included in a means for connecting the first one of the rectifier devices and the first one of the load impedances in series with the input circuit for deriving across the load impedance a unidirectional potential varying in magnitude with the peak amplitude of the television signal. The condenser 30 is included in a means for coupling the second of the load impedances, namely impedance 3!, 32, and its associated rectifier 2t, to the source of periodic potential 22 for stabilizing the periodic potential derived from unit 22 and to derive a unidirectional bias across the second load impedance. The second load impedance is connected in series with the first rec tifying device 25 for applying thereto a unidirectional bias to render the first rectifying device developed across the

load impedance

26, 27, thereby to render the device responsive only to the synchronizing pulses of the television signal. The synchronizing pulses are thus effectively separated from the television signal and are applied through the load impedance 36 of the intersynchronizing-signal separator 2|. In the event that' the time constant of the load impedance 2!, 2'! is made so short that the magnitude of the derived unidirectional potential is insufficient adequately to bias the rectifier device 25, an additional unidirectional potential, not shown, may be included in the circuit of device 35 in a wellknown manner to make up the deficiency in the required total bias.

Fig. 3 is a circuit diagram representing a modified form of synchronously-controlled rectifier system of the invention essentially similar to the arrangement of Fig. 1, similar circuit elements being designated by the same reference characters, except that the function of separating the 25 unresponsive to the television signal during.

plied to the rectifier system 20 from the line-- scanning system 22 should increase, or merely be chosen larger, as shown by the broken line curve 9 of Fig. 2, the operation of the rectifier device 25 is unailected since the rectifier device 29 then produces a larger unidirectional potential e5, whereby the bias as applied to rectifier device 25 is es, Fig. 2, during the trace intervals but, as before, is zero during the retrace intervals; that is, the bias potential applied to rectifier 25 is always stabilized on the zero value of its pulse component.

It is preferable that the negative peaks of the potential represented by curve B should'begin at or slightly before the occurrence of a line-synchronizing pulse a and should end before the end of the line-retrace interval.

In order that the automatic amplification control action shall be fast, thereby to ensure adequate response to rapid changes of intensity of the television carrier signal, it is preferable that the

load impedance

26, 27 have a relatively short.

time constant. In this event, the magnitude of the derived unidirectional potential is still proportional to thepeak amplitude of the television carrier signal, but is unaffected by the peak amplitudes representative of the field-synchronizing pulses or by the instantaneous magnitudes of the image-signal comrxment of the signal which might fall within the amplitude range of the rectifier.

In a standard television signal of the present day, the amplitude of the synchronizing pulses is a predetermined proportion, at the present time 20 per cent., of the peak amplitude of the television signal. Advantage is taken of this fact to bias the rectifier device with a corresponding proportional part of the unidirectional potential synchronizing-signal components from the imagesignal component of the television signal and from each other is performed entirely by the rectifier system 20. In this modification, the periodic potential effectively of pulse wave form derived from the line-scanning system 22 is applied to rectifier system 20 through a delay circuit' M having a time delay slightly shorter than the period of the line-synchronizing pulses of the television signal, thereby maintaining a predetermined phase relationship or predetermined constant phase delay between the periodic potential and the line-synchronizing pulses. The load impedance of the rectifier device 25 is a low-pass filter 55, uniformly to develop and translate all frequencies in the video band, comprising a seriesinductance arm 46, shunt-condenser arms 49, 50,.

and shunt terminating resistors 41, 48, whereby there is developed in the input circuit of the band-pass filter 45 a pulsating unidirectional potential having a wave form similar to curve D of Fig. 2. The output circuit of the filter 45 is coupled to the input circuit of the line-scanning system 22. The low-pass filter 45 thus is included in a synchronizing circuit coupled to the rectifier device 25 and responsive to the wave form characteristic of the derived unidirectional potential for utilizing the derived potential to control the period of the periodic potential applied from the line-scanning system 22 to the rectifier system 20.

The rectifier system 20 also includes a synchronizing-signal separator system 5| by which the field-synchronizing pulses are separated from the television carrier signal. The system 5| comprises an input transformer 52 connected to the output of the intermediate-frequency amplifier M, a rectifier device 53 and a load impedance 54 coupled to the input transformer 52, and a rectifier device 55 and a load impedance 56, 51 which synchronously control the operation of the rectifier device 53. A periodic potential having a period equal to that of the field-synchronizing pulses of the television signal is derived from the fieldscanning system 23 and applied through a delay circuit 58 and a coupling condenser 59 to the

rectifier devices

53 and 55. The load impedance 54 is a low-pass filter comprising a series-inductance arm 65, shunt-condenser arms BI, 62, and shunt terminating resistors 63, 64. The output circuit of the load impedance 54 is coupled to the input circuit of the field-scanning system 23.

The operation of this modified form of the inarrangement except that the periodic potential applied from the line-scanning system 22 to the rectifier system is-delayed in phase by the delay circuit 44 with respect to the line-synchronizing pulses of the television signal to ensure that each negative peak of the periodic potential begins a short time before the beginning of a corresponding line-synchronizing pulse. Thus the entire wave form of the synchronizing pulses is preserved and the wave form of the pulsating unidirectional potential derived from the television carrier signal by rectifier device in-.

cludes the complete wave form of the line-synchronizing pulses. The wave formof the derived unidirectional potential is preserved by the network 45 and is effective to synchronize the line-scanning system 22. In this modification, the output circuit comprising the filter network 33, I4 is responsive to the amplitude characteris tic of the derived pulsating unidirectional potential and derives therefrom a relatively steady automatic amplification control bias, the magnitude of which is directly proportional to the intensity of the received television carriersignal and independent of its light-modulation components.

- The field-synchronizing pulse separating sysslmilar fashion, the periodic potential derived from the field-scanning system 23 and applied to interaction between the line-scanning and field scanning systems of the receiver.

While there have been described what are at present considered to be the preferred embodiments 'ofxthis invention, it will be obvious to those skilled in the art that various changes and modi-' fications may be made therein without departing from*the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1 In a television carrier-signal receiver, a synchronously-controlled rectifier system comprising, an input circuit adapted to'have'applied thereto a television signal having periodicallyrecurrent peak amplitudes, rectifying means coupled to said input circuit for deriving from said television signal a unidirectional potential varying in magnitude withthe peak amplitude thereof, said signal being subject to sporadic peak tem 5! of the rectifier system 20 operates in amplitudes which may undesirably affect the magnitude of said derived unidirectional poten tial, an output circuit coupled to said rectifying means to utilize said derived unidirectional potential, and means for reducing the eflfectof said sporadic peak-signal amplitudes on the magnitude of said derived unidirectional potential comprising a source of periodic potential efie'ctively of pulse wave form and having a period equal to the period of the recurrent peak amplionly during the field-retrace interval, thereby to develop across the input circuit of the load impedance 54 from the field-synchronizingpulses of the television signal a pulsating unidirectional potential, the wave form of which includes that of the complete field-synchronizing pulses. The wave form of the derived unidirectional potential is preserved by the load impedance 54 and is, therefore, effective accurately to synchronize the field-scanning system 23. l v

From the above-described operation of the invention, it will be apparent that a television carrier-signal receiver embodying the invention has the advantage that the unidirectional potential derived from the television signal by the synchronously-controlled rectifier system is unaffected by sporadic peakamplitudes of the television signal, such as may be caused by noise disturbances, during the relatively longtrace intervals thereof. Moreover, the time constant} of the rectifier systeinmay be so short thaiiithely unidirectional potential is effective to provide an automatic amplification control action 'sufiiciently rapid that it responds to relatlvely rapid changes of carrier-signal intensity, this action being entirely unaffected either by the imagesignal component of the television signal, by the field-synchronizing pulses, or by sporadic peak amplitudes thereof. The invention has the ad= ditional advantage that the line-synchronizing and field-synchronizing components are eflectively separated from the image-signal compo nent of the television signal and are completely tudes of said television signal and means for stabilizing said periodic potential to derive a' periodic unidirectional bias and for applying said bias to said rectifying means to render the latter unresponsive to said television signal during the intervals between the recurrent peak amplitudes thereof. i

2. In a television carrier-signal receiver, a

synchronously-controlled rectifier system com-,

prising, an input circuit adapted to have applied thereto a televisionsignal having periodicallyrecurrent peak amplitudes, means including a rectifier device and load impedance coupled to said input circuit for deriving across said load impedance from said television signal a unidirectional potential varying in magnitude with the peak amplitude thereof, said signal being subject to sporadic peak amplitudes which may undesirably affect the magnitude of said derived unidirectional potential, an output circuit coupled to said rectifying means to utilize said derived I unidirectional potential, and means for reducing the effect of said sporadic peak-signal amplitudes, on'the magnitude of said derived unidirectional potential comprising a source of periodic potential eflectively of pulse wave form and having a period equal to the period of the recurrent peak amplitudes of said television signal and a second rectifier device and load impedance coupled to said source for stabilizing said periodic potential to derive a periodic unidirectional bias and for applying said bias to said first-named rectifier device to render the latter unresponsive to said television signal during the intervals betweentthe recurrent peak amplitudes thereof.

3. In a television carrier-signal receiver, a synchronously-controlled rectifier system comprising, an input circuit adapted to have applied thereto a television carrier signal having peak amplitudes representative of periodic line-synchronizing 'pulses which vary with the intensity I of said television carrier signal and independent separated from each other, whereby there is no ot its light-modulation components, rectifying;

means coupled to said input circuit for deriving from said television signal a unidirectional potential varying in magnitude with the peak amplitude thereof, said signal being subject to sporadic peak amplitudes which may undesirably affect the magnitude of said derived unidirectional potential, an output circuitcoupled to said rectifying means to utilize said derived unidirectional potential, and means for reducing the effect of said sporadic peak-signal amplitudes on the magnitude of said derived unidirectional potential comprising a source of periodic potenintervals between said one tial effectively 01' pulse wave form and having a period equal to thatof said line-synchronizing pulses and means responsive to said periodic potential for rendering said rectifying means unresponsive to said televisionsignal during the intervals between said line-synchronizing pulses.

4. Ina television carrier-signal receiver, a synchronously-controlled rectifier system comprising, an input circuit adapted to have applied thereto a television carrier signal having peak amplitudes representative of periodic line-synchronizing pulses, rectifying means coupled to said input circuit for deriving from said television signal a unidirectional control potential varying in magnitude with the peak amplitude,

of said line-synchronizing pulses, said television signal being subject to sporadic peak amplitudes during the intervals between said line-synchronizing pulses which may undesirably affect the magnitude of said derived unidirectional potential, a control circuit coupled to said rectifying means to utilize said unidirectional potential for controlling a translating characteristic of said receiver, and means for reducing the effect of said sporadic peak-signal amplitudes on the pulses.

6. In a television" carrier-signal receiver, a

synchronously-controlled rectifier com-Q to said derived unidirectional potential for controlling the period of said periodic potential, and 'means'for reducing the effect of the amplitudes of said television signal during the intervals between said one kind of synchronizing pulses on the wave form of said derived potential comprising a. source of; periodic potential eiIGO V Y-M pulse wave form and having a period equal to that of said one kind of synchronizing pulses, means for maintaining a predetermined constant phase delay between said periodic potential and said one kind of synchronizing pulses and means responsive to said periodic potential for rendering said rectifying means unresponsive to said television signal during the intervals between v said one kind of synchronizing pulses.

7. In a television carrier-signal receiver, a synchronously-controlled rectifier system comprising, an input circuit adapted to have applied magnitude of said derived unidirectional potential comprising a source of periodic potentials eiiectively of pulse wave form having a period equal to that of said line-synchronizing pulses and means responsive to said periodic potential for rendering said rectifying means unresponsive to said television signal during the intervals between said line-synchronizing pulses.

5. In a television carrier-signal receiver, a synchronously-controlled rectifier system comprising, an input circuit adapted to have applied thereto a television carrier signal having peak amplitudes representative of periodic line-synchronizing and field-synchronizing pulses, recti-.

riving from said television signal a pulsating unidirectional potential varying with the peak amplitude thereof and having a period of pulsation equal to the period of one kind of said synchronizing pulses and having a wave form including the complete wave form of said one kind oi synchronizing pulses, a synchronizing circuit coupled to said rectifying means and responsive to said derived unidirectional potential for controlling the period of said periodic potential, and means for reducing the effect of the amplitudes of said television signal during the intervals between said one kind of synchronizing pulses on the wave form of said derived potential comprising a source of periodic potential effectively of pulse wave form and having a.

period equal to that of said one kind of synchronizing pulses, means for maintaining a predetermined phase relationship between said periodic potential and said one kind of synchronizing i pulses and means responsive to said periodic potential for rendering said rectifying means un responsive to said television signal during the fying means coupled to said input circuit for dethereto a television signal having peak amplitudes representative of periodic line-synchronizing pulses, rectifying means coupled to said input circuit for deriving from said television signal a pulsating unidirectional potential varying with the peak amplitude thereof and having a period of pulsation equal to the period of said linesynchronizing pulses and having a wave form including the complete wave form of said linesynchronizing pulses, a synchronizing circuit coupled to said rectifying means and responsive to said derived unidirectional potential for controlling the period of said periodic potential, and means for reducing the eflect of the amplitudes of said television signal during the intervals between said line-synchronizing pulses on the wave form of said derived potential comprising a source of periodic potential effectively of pulse wave form and having a period equal to that of said line-synchronizing pulses, means for maintaining a predetermined phase relationship between said periodic potential and said linesynchronizing pulses and means responsive to said periodic potential for rendering said rectifying means unresponsive to said television slgnal during the intervals between said line-synchronizing pulses.

8. In a television carrier-signal receiver, a synchronously-controlled rectifier system comprising, an input circuit adapted to have applied thereto a television signal having periodicallyrecurrent peak amplitudes, a pair of rectifier devices and load impedances therefor, means for coupling a first one of said rectifier devices and a first one of said load impedances in series to said input circuit for deriving thereacross from said television signal a unidirectional potential varying in magnitude with the peak amplitude thereof, said signal being subject to sporadic peak amplitudes vvhich may undesirably affect the magnitude of said-derived unidirectional potential, an output circuit coupled to said rectifying means to utilize said derived unidirectional potential, and -.means for reducing the effect of said sporadic peak-signal amplitudes on the magnitude oi said derived unidirectional potential comprising a source of periodic potential effectively 0! pulse wave form and having a period equal to the period 01' the recurrent peak amplitudes oi said television signal, and means said first rectifier device for applying theretosaid unidirectional bias torender said first rectifler device unresponsive to said television signal during the intervals between the recurrent 10 peak amplitudes thereof.

HAROLD M.