US2477679A - Television and pulse modulated sound system - Google Patents

Description

Aug. 2, 1949. N. H. YOUNG, JR 2,477,679

I TELEVISION AND PULSE MODULATED SOUND SYSTEM Filed April 24, 1946 2 Sheets-Sheet 1 INVENTOR. NORMIQN H. Yoq/vaJR.

1949- N. H. YOUNG, JR V 2,477,679

TELEVISION AND PULSE MODULATED SOUND SYSTEM Filed April 24, 1946 2 Sheets-Sheet 2 RECEIVER W959 AMPUFER, 2" DETECTOR 2| 2 i SYNCHRONIZING VERTlCAL 0 smum. sEPAmoR SCANNING UTPUT CIRWIT osuLLAToR.

28 men-a 'ruueo Z3 FILTER TUNED souuo AUDIO 3 T0 HORIZONTAL DEMWULN AMPUFIER PULSE FREQ. $11M Fun. wma RECTIFIER 2o HORRONTAL 8 5w aims? SHAPER OSCILLATOR INVEN TOR. NORMAN H. YOUNG, JR.

AT TORNEY Patented Aug. 2, 1949 UNITED STAT TENT OFFICE TELEVISIGN AND PULSE MUDULATED SOUND SYSTEM Delaware Application April 24, 1946, Serial No. 664,482

2 Claims. 1

This invention relates to a television transmission system and, more specifically to a television arrangement for communication involving composite video signals which include sound, picture and synchronizing signals.

My Patent No. 2,401,384 issued June 4, 1946, describes both method and means for producin in a television system composite video signals in which there are super-positioned upon each of the horizontal blanking pulses a horizontal synchronizing pulse and a sound pulse modulated in time displacement with respect to the horizontal synchronizing pulses in accordance with the instantaneous value of an audio-signal. The present invention is directed to television transmission systems wherein time-modulated sound pulses are also transmitted on blanking pulses, as described in the aforementioned applications, but wherein horizontal synchronizing pulses are not included in the composite video wave. The transmitter arrangement employed for the proposed transmission system is simplified by virtue of the feature that horizontal synchronizing signals need not be super-positioned on the blanking pulses or be radiated from the transmitting location. Receiving apparatus for such a televlsio communications system is necessarily somewhat different, however, since it is essential that horizontal synchronizing pulses be made available at the receiving position even though these are not included as components of the video signals. The advantages of the arrangement to be disclosed herein should be apparent when it is emphasized that rather than a plurality of pulses, only a single sound pulse is positioned on each horizontal blanking pulse; hence, slightly wider sound pulses might be employed, greater time deviation of the time-modulated sound pulses is made allowable, and the horizontal blanking intervals may be considerably reduced.

It therefore becomes one object of the invention to provide a television transmission system utilizing a composite video signal in which the sound program is included as time-modulated pulses super-positioned upon the blanking pulses and in which transmission of horizontal synchronizing pulses is not required.

A second object is to provide a television transmission system wherein a composite video signal including time-modulated sound pulses super-positioned on the blanking pulses is transmitted and wherein, in the absence of horizontal synchronizing pulses upon these blanking pulses, horizontal blanking pulse intervals of duration merely sufiicient to accommodate the time-modulated pulses may be employed.

Another object is to provide a television transmission system, utilizing a composite video si nal in which the sound program is included as time-modulated pulses super-positioned upon blanking pulses, wherein the sound pulses may be slightly wider and the time deviation of the time-modulated pulses may be somewhat greater than in systems which transmit two pulses during each of the blanking pulse intervals.

Receiving equipment associated with this transmission system may provide horizontal synchronizing pulses by extracting a second harmonic, or line frequency, component of the incoming train of pulses and shaping it into the desired pulses suitable for tripping a horizontal scanning oscillator whose output is delivered to a cathode ray tube. The horizontal synchronizing signals are thus in fact derived from the video signal; and the base or time reference wave, which must be provided when certain types of modulators for the sound channel are employed, may be furnished from the same harmonic component which is utilized to yield the horizontal synchronizing pulses.

A further object of this invention therefore, is to provide a television receiver, for use in a television system in which horizontal synchronizing pulses are not transmitted and in which timemodulated sound pulses are super-positioned on the horizontal blanking pulses, wherein horizontal synchronizing pulses are produced from a harmonic component of the received train of pulses and wherein this harmonic component may also be used as the base or time reference wave in the sound demodulator section of the receiver.

The foregoing objects and features should be clarified and others should become apparent and the invention itself best understood from the follOWil'lg discussion and description of arrangements utilized in a particular embodiment of this invention, reference being had to the drawings, in which:

Fig, 1 is a block diagram which represents a portion of the transmitting apparatus required for producing the synchronizing blanking, and sound pulses which are to be components of a composite video signal;

Fig. 2 shows a sketch of a complete television signal waveform typical of those produced by the proposed system; and

Fig. 3 is a block diagram of a portion of a television receiving arrangement suitable for operating in accordance with the principles of this invention.

The system illustrated in Fig. 1 is similar to that already described in my aforesaid application, Serial No. 545,291, and produces horizontal synchronizing and blanking pulses, vertical synchronizing and blanking pulses, and time-modulated sound pulses all under control of the sine wave output of a single oscillator, I. As described in detail in the last mentioned application, the output of the multivib-rator 2, which is triggered by the output signal from oscillator I, is shaped into horizontal blanking pulses .by shaper 3 and into horizontal synchronizingj pul'ses by shaper 3. Likewise, by conventional means, vertical synchronizing and blanking pulses may be produced in the pulse producer.

Time-"modulated sound pulses are generated in the arrangement comprising a frequency divider 3 to which is applied the sinusoidal output wavea form of oscillator], a .olls'per modulator l, to which are applied the butputof th'e divider 6 and the audio signaisfrom amo'dul'ating' signal source 3, and a pulse shaper 'amplifierQ, fed by the output of the modulator 1, and delivering narrow time-modulated pulses to the mixer ill. The cusper modulator operates on a push-pull principlewhich 'causesfrectification of the sine wave output of 'thedividerf'fi, about an offset axis, the voltagelevel' of this axis being determined by the instantaneous values ofthe audio modulating signal. A further understanding of this type of pulse time-modulation may be obtained by reference to the patent of E. Labin and D. D. Grieg No. 2,416,329, issued-February 25, 1947. The frequency dividers, is employed in order that the numberof pulses produced by the modulator a will be of the number required for the combination of one sound pulse with each horizontal blanking pulse. i

In the mixer lo, the iso'und'pulses from shaper amplifier 9 are super-positioned upon blanking pulses from the horizontal blanking pulse shaper 3. In addition, verticalsynchronizing and blanking pulses from pulse producer are delivered to the mixer and are thus included in the composite wave in the output thereof. Video signals and possibly equalizer pulses may also be provided, and thesemight be applied to the mixer from apparatus, not shown in Fig. 1. The composite video wave which would then appear at the mixer output connection II, would thereafter be applied to a transmitting apparatus for radiation at a, desired carrier frequency. Camera equipment, I la, is also shown in Fig. l with voltages applied thereto from horizontal synchronizing pulse shaper 4, horizontal pulse shaper 3, and vertical synchronizing and blanking pulse producer 5.

The television signal Waveform may be observed in thesketch of Fig, 2. Horizontal blanking pulses l2 separate the picture signal lines 13; and superimposed on the. blanking pulses l2 are time-modulated. sound pulses i l. The sound pulses are time-modulated in that they vary in time displacementfromacertain position on each of the horizontal blanking pulses, Components of the frame retracing interval which may be required, in certain television systems are represented on the sketch also, there being, in addition to the sound pulses 14, equalizing pulses l5, and vertical synchronizing pulses I6. It should be noted that the shaping of the vertical synchronizing pulsesis such tha tmnsmission'of this energyduring horizontal blanking intervals containing time modulated pulses, IE, is not required.

Composite video signals transmitted in ac cordance with the above-revealed principles may be received and translated in apparatus such as that of Fig. 3. The television signals are received and detected in the receiverl'l and the picture signal output component is delivered to the cathode ray tube 18 after amplification by video amplifier l9. Output signals from receiver ll are also delivered to synchronizing signal separator circuit Zdwhich in turn applies vertical synchronizing pulses to the vertical scanning oscillator 2|. Scanning voltage from this oscillator is amplified by output amplifier 22 and is thereafter applied to the cathode ray tube I8.

A high-Q filter 23, tuned to the horizontal pulse frequency, derives a harmonic component, for example the second harmonic which is the line frequency, from the train of pulses in the output of separator circuit 293 which may be shaped into pulses suitable for tripping a horizontal scanning oscillator 24 "flhe --oscillator tripping pulses are fproduced by full wave "rectifying theoutput of filter 23in "wave rec'- tifier 25 and then applyirig the'reetifiejd 'wayejto the cusper and pulse shaperfifi'wherein by wellknown processes the de sir'ed pulses may be 'obtained for delivery to the"horizontalbscillator An output amplifier "2'7 is-alsolindicatedfih the output circuit of'this oscillator 'pri'or to the application of the scanning voltageto-the cathode raytube l8. i M

Another nportant' fallllfelQftlflQ'IQB'lVBI section of this invention is that t'hef'output wave-or the tuned filter 23 may beemplp' edas the base ref wave in g the sound *demjo'dulatorfsystern liich als'oha's appiied toitthe outputjof the receiver i? The'connecti'qn indicated by line would be requiredwith'such an arrangement. This demodulator 'syst mgconsists of means ior selecting the tir'n'e-modulatedfsound pulses from the receiver output and means for producing an audio voltage which varieswiththe'instantaneous values of the time intervals between thes'ouhd pulses and the'occurrence'ofc'ertaln characteristic positions on the referenceiwave. Audioamplifier amplifies the demodulator system outputv'oltto a value ,suiilcien't't'o operatethe sdurid reproduce? 'Any fdesire'dftype ofdih dulator System. my w be u and the present invention is not to be consideredlirn'i ted by the above-described arrangement. v

In the television reo'eive'r'system shown 'in Fi'g. :3 it will be foundby analysis thattw'ic'e' theneeded number of horizontal 'synchronizing puls'es are producer. Most types "of horizontal scanning oscillators are not aidverselyhffectejdby this phenomena, but if it 'sho'uld terounwnece'SSar to eliminate the "unwanted. pulses, these ma be readily removed by a blocking circuit located at any convenient point in the fsystemwith'out affectingthe' desired'operation ofthe system. "Also, it may be required 'to'includefa blanking wave which will prevent the interactiorrnf thevertical synchronizing signals "on "theftim'ing -of the'li'ne signals, but if ot'nersiitncaser -effectively s parating the line and frame'sigrials can be included this will not be needed.

An important advantage" of this television system which shouldnow be"-understand'able is that disturbances. of timing ofithe lin'esby impulse type noise will begreatly reducedbec'auseof'the essentially narro-wband character of the channel through which the line syn chronizing'signalsare filtered. This-same high flQ filter in'addition may provide a very good waveform for use as a base from the principles or scope of this television system. Means other than those described for the production of time-modulated pulses in Fig. 1 or for demodulating the time modulated sound pulses in Fig. 2 may be employed as well as other means for producing horizontal synchronizing pulses from the output of the high-Q filter in Fig. 3.

Figure 2 shows equalizer pulses and vertical synchronizing pulses in a composite video wave suitable for use in certain television arrange- L ments, but it should be recognized that this invention cannot be viewed as restricted by such factors as the presence or absence or number of equalizing pulses or by the particular type of vertical synchronizing system it may be preferred to utilize.

Therefore, although the present television system has been diagrammed and described with particular reference to specific embodiments of preferred equipment, it should be clear that this has been done merely by way of illustration and should not be construed as limiting the scope of the invention.

I claim:

1. A television communication system, comprising transmitter means for producing and transmitting composite video signals in which timemodulated sound pulses are superpositioned on horizontal blanking pulses and in which horizontal synchronizing pulses are excluded, means for receiving and detecting said composite video signals, means for separating the horizontal blanking and vertical synchronizing signals from said composite video signals, means for deriving from said blanking signals a base wave having a frequency equal to the desired horizontal synchronizing pulse frequency, means for producing horizontal synchronizing pulses from said base wave, means utilizing said base wave for demodulating said sound pulses, means for reproducing the sound signals, and picture reproducing means controlled in operation by synchronizing, blanking, and video signals derived from said composite video signals.

2. In a system for receiving a composite signal having a picture component, a vertical synchronizing component, a horizontal blanking compo nent and a sound component, the method of operation which comprises receiving and detecting the composite signal, separating the synchronizing and blanking components from the detected composite signal, separating the blanking signal from the synchronizing signal, developing from the blanking signal a base wave, utilizing the base wave as a time reference base for demodulating the sound component of the composite signal,

a and deriving from the base wave horizontal synchronizing pulses.

NORMAN H. YOUNG, JR.

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

UNITED STATES PATENTS

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