US2169883A - Television and sound receiver - Google Patents

Description

Aug.` 15, 93.

Filed Nov. 2, 1937 lTELEVISION AND SOUND RECEIVER 70 V/DEO 650/26 PAF/:RA r/l BY g ATTORNEY Patented Aug. 15, 1939 PATENT oFFicE TELEVISION AND SOUND RECEIVER Georg Pairath, Berlin-Sudende, Germany, assignor to Telefunken Gesellschaft fr Drahtlose Telegraphie m. b. H., Berlin, Germany, a corporation of Germany Application November 2, 1937, Serial No. 172,324 In Germany October 17, 1936 Claims.

l For the simultaneous reception ofl sight (video) and sound (audio) signal transmissions, each of which signals is'transmitted on an ultra-short wave, apparatus has been known in the art by which for the image content and for the sound reproduction a respective intermediate frequency amplifier has been provided. whereby these intermediate frequencies are produced by means of a common oscillator. In' such a case the video and audio signals are. transmitted on separate carrier frequencies between which a fixed frequency separation is maintained. When operating such apparatus of this general type it has been found that the frequency variations oi the oscillator are so great, in some instances, that it is necessary to provide a much larger passage range in the intermediate Afrequency amplier for the sound transmission than'would be required in View of the width of the side bands of the sound as such; This again entails the disadvantage that disturbances will also be received which lie outside the frequency range claimed by the sidebands of the sound, and which will be reproduced in the loudspeaker. Furthermore, this arrangement has" the disadvantage that the ampliiication to be attained decreases since, in fact, the amplification per tube stage will be the lower the larger the passage width.

In order to avoid these drawbacks, in accordance with the .invention the frequency variations of the local oscillator are toy be` diminished with the use of an arrangement fory lautomatic sharp tuning. Any sucharrangement for the sharp tuning anyarrangernent commonin the .radio eld can be utilized. `Thus, for instance, two resonant circuits may be coupled to-the output of the intermediate frequency amplier. for the sound reproduction, and whose natural frequencies lie by the same values above and below the desired intermediate frequency and which rectify, and connect in opposition the alternating voltages induced in these circuits, and influence the oscillator frequency in accordance with the difference of these direct voltages. The natural vVariations of the natural frequencies of the oscillatorY are thereby decreased and hence the intermediate sound frequency now varies only within a much smaller frequency'interval so that the passage width in the amplier for the intermediate sound requency can be chosen much smaller than would be possible in an oscillator of the hitherto customary type, i. e. in an oscillator without frequency control.

In accordance therewith the disturbances appearing in the sound reproduction will in conformity with the above be very much smaller than in the known arrangement.

Furthermore, wihen using the invention an additional advantage is that it is possible to use as intermediate frequency amplier the chassis of an ordinary radio receiver, for instance that of a superheterodyne receiver. Under such circumstances it is only necessary that the frequency of the common oscillator be so chosen that the intermediate sound frequencies lie in the range of the radio waves. This is a convenience not only inasmuch as a circuit can. be used for the sound channel which can be manufactured in series thus reducing its cost accordingly. Itis desirable according to this invention that lthe arrangement which is to be used for the sharp tuning of the receiver shall be connected to the audio portion of the receiver. When using the apparatus herein described for pure radio reception the sound channel need only be disconnected from the mixer stage situated in back of the common oscillator, and then connected to the antenna.

The invention has been shown schematically by the accompanying drawing. In the drawing signals are received from suitable transmitting points on the receiver antenna or suitable wire line and directed therefrom to the video and audio signal receiver detector 3. The signals transmitted are sent out from transmitting points in a manner already known in the art. Such transmissions, for example, may be of the character where the video and audio signals are Itransmitted upon separate carrier frequencies and accompanying one of these signals synchronizing signals are also transmitted.

It has been customary in the art to transmit the synchronizing signal upon the same carrier used for the transmission ofthe video signals k although it is naturally within the scope of this invention to transmit the synchronizing signals where desired upon the audio signal carrier.

When the signals are received and directed to the video and audio signal receiver and detector unit 3 the reception. is substantially as shown by the reissued Carlson Patent #20,700, dated April 19, 1938, for example and a local oscillator 5, Whose output is supplied to the receiver detector 3, produces the desired intermediate frequency signals. The video intermediate frequency signals are then passed to an intermediate frequency amplifier 1, as also described in the Carlson patent, and the output from this amplifier controls the operation of the suitable image reproducing apparatus. Such image reproducing apparatus,

Il il" although not shown, is preferably of the cathode ray type, although naturally, any other type of image reproducing device, such as so-called mechanical and electro-mechanical types, may be utilized.

synchronizing signals for controlling the spacial position at which the video signal reproduction takes place are derived by connections to the terminal points S and these signals are usually separate signals developed for synchronizing each line and each frame or field of the produced electro-optical image.

As disclosed in the above mentioned Carlson patent the intermediate frequency audio signals are passed from the output of the video and audio signal receiver detector 3 to the audio intermediate frequency amplifier II and the resultant signals appearing in the output of this intermediate frequency amplifier Il are supplied from terminal points |3-l3 to suitable detector and sound reproducing apparatus. Connected with the output of the audio intermediate frequency ampier unit Il is also an automatic frequency control unit l5 whose output energy is connected from the terminal points Il thereof to control the local oscillator unit 5. Such automatic frequency control unit, for example, may be of the general type disclosed by Round U. S. Patents Nos. 1,642,173 and 1,712,051 or, for example, of the general type disclosed by Travis, U. S. patent application, Serial No. 4,793 filed February 4, 1935.

From the above description it will be apparent that the automatic frequency control unit x, serving to control the local oscillator 5 controls it in accordance with the departure of the receiving system from resonance for the range of signals occupying a relatively narrow frequency band as spectrum as do the audio signals. With a Xed separation maintained between the video carrier frequency and the audio carrier frequency, as is customary in the art, it is apparent that it is possible to obtain sharp tuning of the video signal reproduction by controlling the local oscillator in accordance with the audio signals. In this way a relatively narrow frequency band serves to control the tuning over a relatively wide frequency band, over the latter of which it is difficult because of the spectral width of frequencies received to tune with greatest sharpness of tuning.

While one of the various embodiments which the invention may assume has been shown by the drawing and described hereinabove, it is, of course, apparent that various modifications may be made provided such modifications fall clearly within the spirit and scope of the hereinafter appended claims.

What I claim is:

1. A system for simultaneously receiving sight and sound signals comprising a receiver detector unit, an oscillator connected with the receiver detector unit to produce separate intermediate frequency signals for both the received sight and sound signals, and means for controlling in accordance with the produced intermediate frequency sound signals the tuning of the oscillator for maintaining predetermined tuning for the receipt of both of the signals.

2. A system for simultaneously receiving sight and sound signals transmitted upon different car rier frequencies with fixed and predetermined separation comprising a receiver detector unit, an oscillator connected with the receiver detector unit to produce separate intermediate frequency signals for both the sight and sound signals, and means for lcontrolling in accordance with the produced intermediate frequency sound modulated signals the tuning of the oscillator for obtaining correctness of tuning for the receipt of both of the signals.

3. A system for receiving video and sound signals wherein the video signals occupy a relatively wide frequency band with respect to the sound signals and wherein the video and sound signals are transmitted upon separate carrier frequenn cies maintained with fixed spectral separation comprising a receiver unit for receiving both of the signals, a local oscillator for producing from both of the received signals separate intermediate frequency bands representing video and audio signals, and means for controlling the local oscillator from the intermediate frequencies developed from the signals occupying the narrow frequency band for obtaining correct tuning for both produced intermediate frequencies.

4. 'I'he method of receiving video and audio signals transmitted upon separate carrier frequencies with predetermined spectral spacing therebetween which comprises receiving simultaneously the video and audio signals transmitted upon both carrier frequencies, developing locally electrical oscillations of a predetermined frequency, heterodyning each of the received signals with the locally developed frequency for producing a plurality of separate intermediate frequency bands representing each of the transmitted signals, and controlling the frequency of the locally developed frequency in accordance with the intermediate frequencies developed from the received audio modulated signals.

5. A system for simultaneously receiving sight and sound signals comprising a receiver detector unit for receiving a plurality of pairs of carrier frequencies, one carrier of each pair being modulated by video signals and the other carrier of each pair being modulated by audio signals, the said video modulation frequencies being of the order of at least hundreds of times the audio frequency modulations, local oscillator means to produce from the received video and audio modulated carrier frequencies separate intermediate frequency signals for the video and the audio signals, and means for controlling the frequency of the local oscillator means in accordance with the departure from normal of the produced intermediate frequency signals occupying a relatively narrow band of frequencies for tuning the oscillator means to obtain at all times correct ness of tuning for both video and audio signals received.

GEORG PAFFRATH.

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