US2230854A - Signal reproducing means - Google Patents

Description

Feb. 4, 1941. w. c. WELLMANN SIGNAL REPRODUCING MEANS Filed 'March 15, 199 2 Sheets-Sheet 1 im; :100-05m Malena-015m apano/7m /qmmaifm 5711; anmaim d www fw. mi m M Feb. 4, 1941. w c, WELLMANN 2,230,854

SIGNAL REPRODUCING. MEANS .FledMarCh l5, 1939 2 Sheets-Sheet 2 Patented Feb. 4, 1941 UNITED STATES PATENT OFFICE 8 Claims.

This invention rela-.tes to signal reproducing means.

An object, among others, of my invention is to provide improvements in means for reproducing sound from sound recording means.

Another object is the provision of means whereby a standard radio set may be used in conjunction with a sound projector for reproduction of sound from sound film.

More particularly, an object, among others, of my invention has been the provision of means whereby a sound projector for sound lm may be connected up to a standard radio so that the radio may be used to reproduce sound recorded on sound film.

Still another obje-ct of my invention has been the provision of means for eliminating hum in signal reproducing means.

2 Another object has lbeen the provision oi `means for regulating various tones such as high and low tones in signal reproducing means.

Another object has been to provide for preliminary heating of the filaments of the rectifier tubes by any electrical current prior to energizing the whole circuit, so as to make possible the operation of the lament circuit on direct current which provides for the reduction of hum throughout the whole circuit, including the exciter lamp.

Another object has been to provide improvements in respect of various features of signal reproducing means.

Other objects include the production of the above means at radically low cost and with improved eihciency.

By means of my invention, one advantage among others is that the ordinary radio in a home, for example, may be used by a person desiring to project sound from a sound iilm and also to give improved sound reproduction at radically low cost.

Other objects and advantages will appear hereinafter and be brought out more fully in the following specification, reference being had to the accompanying drawings, wherein;

Fig. 1 is a diagrammatic View of a circuit arrangement embodying the features of the invention and showing the receiver set directly connected to detect the audio waves;

2 is a fragmentary view of an alternate 'form of connection with a radio receiver detecting the low frequency audio waves carried and transmitted by the high frequency carrier Waves of the circuit as a pick-up from an antenna;

Fig. 3 is an elevation showing the different components of the equipment, including a talking picture projecting machine, sound adjunct to a radio and radio receiver adapted to be coupled, as shown in Fig. 1; and

Fig. 4 is a diagram showing a graph illustrating the result of the use of the circuit or wiring lo diagram as schematically shown in the ligure.

Referring to the drawings, I designates a plug adapted to be connected to an ordinary wall socket of the house wiring for supplying current, the same being connected by a lead wire 15 2 to a resistor 3 which may be variable if desired. The respective electrical values of the elements of this circuit are designated adjacent thereto, by way of example, especially in connection with the equipment designed for home 20 or local use and as explanatory thereof.

This resistor is connected to a contact 4 of a double pole double throw switch 5, one terminal of the switch being connected 'by a lead 6to a conductor 'I and then through the heating iila- 25 ment of one or more rectier tubes. As shown, the lead is taken through the laments of two rectifier tubes 8 and 9 connected in series as shown and then to a resistor I0. Connectionis then made at II back to the switch 5 through 30 a contact I2, constituting the other pole of the blade or knife of the switch opposite that from which lead 6 extends, and through a Contact I3 opposing the contact 4, to a junction I4 to the iilament I5 of an oscillator or oscillation unit 35 shown as a screen grid tube, it being understood that all o-f said tubes, heretofore referred to may be of any preferable type. Connection is then made in series to the heating filament of an amplifier tube, one or more of which can be used. As shown, connection is made to nlaments I6 and I1 of two amplier tubes and then through the lead I8 from the iilament I'I to the ground I9 and a suitable control switch 20 back to the source at the plug I. 45

The wire 22a. is connected to a contact 2| of the switch 5 opposite the contact 4 with an interposed iilter choke 22 arranged and connected, as will -be later described. The other contact 23 of the switch 5 opposite the contact 2l is con- 50 nected to an interposed filter condenser 24 applied to the circuit and operated when the blade of the switch 5 spans or engages the contacts 2l and 23.

An exciter lamp 25 is directly connected with 55 the resistance I8 and the contact I2 on one side at the junction II and with the filament I5 of the oscillator and contact I3 on the other side. This short circuits the eXciter lamp when switch 5 is in the heating circuit so that the exciter lamp will not burn out with the heating circuit surge. This exciter lamp is employed in connection with a condenser lense or lens system 26 through which the light from the exciter lamp passes and it in turn throws a very narrow beam of light on the sound film 21, that is, a film with a sound track or sound on film which may be combined with a picture film. The sound lm is shown passing around the usual guide or gate, and window and a light sensitive cell or photoelectric tube 23. Light passes through the film 21 allowing the film to modulate the light, and the modulated light falling on the photo-electric cell 28 produces an alternating current exactly similar to the original sound on the film. This is in turn impressed on the grid 29 of the amplifier tube nearest thereto, having the filament II, through a condenser resistor network A, the purpose of which is to compensate for any lack of low or high notes in the original recording. This network includes a resistance 38 of suitable resistance to lower the overall gain Vto a desirable point connected to the photo-electric cell 28 with a series condenser 3| of such value as to pass all useful frequencies without attenuation, and having connected thereto in parallel, on the outside of the resistance 38 and condenser 3I, a low-capacity condenser 32 of suitable value to reduce the reactance above a suitable reference frequency, decreasing in reactance the higher the frequency. This allows an increasing frequency characteristic for the high freouencies to the point where vthe grid cathode and plate cathode capacities prevent any further increase in high response. The low notes below a suitable reference frequency are adjusted by the increased reactance of a resistor capacity network B including a medium capacity condenser 33 which is connected between the condenser resistor network or unit A on one side. and `the grid 29, directly to the cathode 'I3 of the amplifier tube of the latter, with an interposed resistance 34 as will be more fully described. The condenser 33 is interposed between the resistance 34 and a resistance 35. Condenser 33 is in effect in parallel with the resistor 35, and a resistance 36 and a condenser 31 are interposed in the connection to the cathode '53. The rst va cuum tube ampli,- iier 38 having the filament I'I and the control electrode or grid 29 is connected through its annode plate 39 with a similar resistor network corresponding to condenser resistor .network A and the resistor network B or unit just described, Resistor network unit C includes a. condenser M. condenser` M. resistance 42. all in parallel with the circuit. Resistance 43, 43a. 44, and 44a and a condenser 4.5 are connected to the control electrode or grid 45 of a second vacuum tube amplier 41 which latter is connected with the amplifier tube 38. The filaments IB and i'I constituting the heating elements thereof are connected in series. The current is then passed through a conventional resistor network D including a condenser 48 and resistors 49, 58 and 5I of suitable resistance or reactance and as previously pointed out, all or any of which may be variable, if desired.

There is also a resistance 52, connected to the cathode of tube 4'I corresponding to the cathode of the tube 38, corresponding to the resistance 3B, and another resistance 53 is connected to the cathode 55 of an oscillator tube 54 constituting part of the oscillation unit E which receives the amplified current from the tubes 38 and 4'I. The oscillator tube 54 may be in the form of a heptode tube and has one grid 55 thereof connected to the amplifier 4'I through the condenser 43, .The grid 5'I is connected through a variable condenser 58 with an inductance 59 in parallel with an anode inductance 60 which is connected to the anode plate 6I of the oscillator tube 54 for the development of radio frequency oscillations which are modulated by the previous amplifier and picked up by a radio as designated at 62 or with an antenna 63 having an interposed condenser 64 as a safety precaution. This antenna produces vibrations in the ether which can be received by a radio without direct connection thereto and spaced at a distance therefrom. The screen grid 65 of the oscillator tube 54 is connected to the plate supply through a resistor 66 which is bypassed by a condenser 61 to ground 68. The inductancev 59 having the variable condenser 58 connected thereto is also connected to another resistance 69 and a condenser 'Ill connected in parallel and in turn connected to ground I9.

The contacts 2| and 23 are connected through a condenser unit F with the ground I8. The return wires of the circuits leading from the various resistances are connected with another resistance 'II also connected to ground through a condenser unit G interposed in the circuit including the amplifier tube 4'I while another condenser unit H is connected to the amplifier tube 38. A resistance I2 is connected to the lead from the photo-electric tube having connection with the control electrode or grid 29 thereof and to the cathode T3 thereof with an interposed condenser 14 and resistor capacity network or condenser unit B corresponding to the aforesaid condenser units including the elements 33, 34, 35, 35 and 31 previously described. The cathode of the photo-electric cell or photo-electric tube is thus directly connected to the cathode of the frst amplifier tube instead of through a resistance and condenser network as used in connection with conventional circuits through ground. This has the advantage of reducing hum and increasing efficiency. Connection is also made through a resistance 15 with an adjustable resistance 'I6 on either side of the connection with the condenser unit H and a resistor TI from which connection is made through a resistor I8 with ground '19.

Interposed in the circuit to the exciter lamp 25 is an adjustable resistance serving the purpose of a rheostat to vary the intensity of the lamp, thereby varying the signal volume.

While the talking picture projecting machine, including the case, film carrier reels, projecting lamp, lens and film gate, as Well as the sound mechanism heretofore described and adapted to be plugged into the house wiring at line voltage may be permanently associated together, they are shown as separate units in which the various wiring connections may be coupled at the plugs 8| and 82 through the medium of the coacting terminals 83, 84, 85, 86, 8'i, 88 and 89, which connect with the sockets 83a, 84a, 85a, 86a, 81a, 88a, and 89a and which render the parts capable of physical as well as electrical disconnection. An ordinary radio receiver is also illustrated at 62 as heretofore described, the same being preierably of the heterodyne type with a plurality of stages of amplication, and including a plug 9U for connecting to the house wiring. However, as previously explained, instead of the physical connection or mutual indu-ctance permitting the elements to be plugged one into the other, the audio waves may be detected and picked up by means of the usual aerial or antenna fromthat of the signal reproducer and transmitter to reproduce and transmit signals. While particularly explained in connection with audible signals or sound, it is to be understood that the principle is capable of application for all signals and particularly those reproduced from an electrically recorded record such as sound on film and adapted for any'electronic use.

Thus, in the operation of the circuit in the application of D. C. on the filaments, starting at the plug I, electrical current flows along the lead 2 to the resistor 3. This resistor makes up the difference in voltage between the D. C. output of the rectier tubes 8 and 9 and the line voltage. The current continues along into contact 4 and through switch 5 and lead 6 to I and from 'I through the filaments 8a and 9a of the rectifier tubes to the resistor I which reduces the voltage to the required voltage of the balance of the tubesl and other load in the circuit. Continuing to the point Il, the current from there is led back to the contact I2 of the switch 5 and through the contact i3, when the switch is in the up or heating position, to the junction I4 leading to the filament I5 of the screen grid tube or 0scillator Unit 54, to filaments I6 and I1 directly through lead I8 to the ground I9 and through control switch 2li to the source or plug I connected to the house wiring or otherwise. This represents the starting procedure of one embodiment of the application of the invention heretofore described. After reasonable time for the heating of the filaments 8a, 9a, I5, I6 and I1, the switch 5 is thrown in the opposite or down position to engage the contacts 2| and 23, which is the D. C. position. The current now flows through the tubes of the filaments 8a and 9aappearing at I as a pulsating D. C. current and then iiowing through the switch 5 and contact 2| and through the choke 22 to the various parts of the circuit as already described. The filter condenser 24 isI connected to the contact 23 and, in the formy of the unit F is applied to the circuit to smooth the D. C. pulsations appearing across the exciter lamp 25 and tube filaments.

The light from the exciter lamp 25 passes through the condenser lens or lens system 26 which in turn throws a very narrow beam of light on the sound film 2l. This' light passing through the film 2l allows the .film to modulate the light and the modulated light falling on the photoelectric cell 28 produces an alternating current exactly similar to the original soundv on the film, and is impressed on the grid or control electrode 29 through the condenser resistor network A, the purpose of which 'is to compensate for any lack of low or high notes in the original recording which it does in this manner. The audio frequencies are reduced to a certain proportion of their original amplitude by the resistance 30, condenser 3i being of such value as to pass all useful frequencies without attenuation. Condenser 32 is of suitable value to reduce the reactance above a suitable reference frequency, decreasing in reactance, the higher the frequency. This allows an increasing frequency characteristie for the high frequencies to the point Where the grid cathode and plate cathode capacities of the amplifier tubesy prevent any further increase in high response. ble reference frequency are adjusted by the increasing reactance of the condenser 33 so that the effective value of resistor 35 increases with the increasing reactance ciy condenser 33. The current is then amplified by the rst vacuum tube 38 and is passed through a similar resistance network C corresponding to the resistor network A, to the second vacuum tube II. The current is passed through a conventional resistor network D to the oscillator tube 54 in which the radio frequency is modulated. These radio frequency oscillations may then be transmitted to the radio receiving set by an antenna or by a direct wire from the oscilla-tor to the radio set as already described, or by the use of alternating or direct current light power supply lines.

From the foregoing, there will be observed that with the signal reproducing and transmitting circuits or a sound adjunct combined with sound on film or other electrically produced or recorded record such as light produced vibrations, for radio receiving sets herein disclosed for reproducing and projecting or transmitting recorded audible or visual signals or whereby signals or sound with or without pictures is produced and amplified for any electrical use, such as by means of a talking picture machine or a moving picture machine with sound on film or sound track nlm, in combination with or as an adjunct to a radio receiving set by direct connection thereto 4or by pick-up reproduction of thesignals economically without hum at the loud-speaker, with more amplincation and less light source, is possible. However, although the equipment is adapted for application to other methods of signal or sound recordation and reproduction, especially electrically as distinguished from purely mechanically produced records ysuch as a phonograph record, an importantffeature is the use of the equipment and circuit in connection with the sound track of a film or using the light passing through the lm to modulate the light falling on the photo-electric cell to produce an alternating current corresponding to the original sound on the lm and then amplifying and modulating radio frequency oscillations and the modulated output including the high frequency carrier waves and the low frequency audio waves which are picked up on the radio.

The normal circuit or circuits employed and the combination of a recorded signal transmitter circuit for reproducing signals particularly by light or sound on film and the amplifying and rectifying circuit employed whereby the equipment may be plugged into the ordinary line voltage of the house wiring or otherwise on either direct cr alternating current and receiving such signals within the audible hearing range .0n an ordinary receiver preferably of the heterodyne type is of particular advantage. By this means, the signals of the signal or sound reproducing circuit will be received and amplified as well as economically reproduced in such a way as to eliminate the necessity for a high powered audio amplifier and complicated and expensive equipment ordinarily required. Moreover, while one electronic use is shown, it is to be understood that the invention embraces the circuits and arrangements or combinations for other electrical uses where electricity or magnetic energy is used as an intermediary or means to effect such reproduction or transmission of signals either audible or visual or both. The apparatus will The low notes below a suitaf be simple, inexpensive and embodied in small units capable of being readily transported or moved from place to place and constitutes animportant adjunct in a home or wherever it is desired to reproduce certain signal records as desired. Moreover, the signals will be free of hum, crackling sounds or other interference and render possible the use of `more amplification with less light source and current consumption.

Any suitable tone control means may be employed or inserted in the circuit. In addition, by my circuits and arrangement or equipment, the equipment required for radio reception, and also as distinguished from pure audio amplification without radio reception, is reduced more than one-half and the weight thereof is also reduced at least one-half.

It should be noted that the cathode of the photo cell 28 is connected directly to the cathodes of the first amplifier tube. In Fig. 4 of the drawings, a graph or diagrammatic illustration of the respective characteristic curves of different control systems are shown. The curve A-A represents the characteristic curve of the present circuit for tone compensation in which zero in decibels and 400 cycles per second represent the desired mean ratios in the tone compensation between high and low frequencies or tones above or below a suitable reference frequency which is the desired useful frequency and tone. It will be seen that both the low and high notes are so compensated for by the use of condenser resistor networks A and B, with each amplifying unit and particularly in the first stage of amplification where a flow of alternating current similar to the original sound record is produced, whereby each represents a gain in tone cornpensation and faithful reproduction without attenuation and without undue attenuation in either high or low frequencies or tones beyond that of audible value. This gain, while represented so as to build up the lows and'the high, has the effect of flattening or rendering more uniform the sound frequency curve toward a constant value and to compensate for any lack of low or high notes in the original recording so that the audio frequencies are rendered properly audible and tone quality improved. The curve B--B represents the characteristic curve of a resistance coupled amplifier with tone control at minimum while the curve C-C represents the characteristic curve of a resistance coupled amplifier with tone control at maximum and it will be noted from this that all desirable tone qualities are retained in my circuit, in properly amplified audible form so that the reproduction is greatly perfected, as shown by curve A-A.

In lieu of supplying D. C. to the filaments of the rectifier tubes, a transformer may be used to heat the filaments of the rectifier tubes to supply direct current for the filaments of all other tubes or lamps used, where only A. C. is available but this is not nearly as desirable and is eliminated by the present circuit together with the hum and other harmonic effects usually present from the employment of one or more transformers.

While I have illustrated and described the preferred form of construction for carrying my invention into effect, these are capable of variation and modification without departing from the spirit of the invention. I, therefore, do not wish to be limited to the precise details of construction setI forth, but desire to avail myself of such variations and modifications as come within the scope of the appended claims.

I claim:

1. In signal reproducing means, a source of illumination, a. photo cell, a photographic record of sound, means to cause said record to travel between the source and the cell, a rectifier lncluding one or more rectifier tubes having filaments connected in series and through a resistance to the source of illumination for supplying the latter with current at line voltage, a plurality of amplifying tubes having filaments connected in series, an oscillator tube having a filament connected in series therewith, condenser, resistor and filter means in the circuit and a switch in the circuit adapted in one position to supply A. C. or D. C. to the filaments until heated and in the other position to supply D. C. current to said tubes for energizing the whole circuit.

2. In an electrical circuit for reproducing signals from an electrically produced sound record, a rectifier tube, a light source, an electrically produced sound record, a photo cell adapted to receive the light from said source modulated by the record, one or more amplifier tubes having a cathode directly connected to the cathode of the cell with interposed means to build up the low and high notes and render more uniform the sound frequency curve toward a constant value including resistor condenser net works at least one of which is free of direct connection with thesupply line to the light source and cell and at least one of which has direct connection with said line to the cell, means for receiving the audio frequencies thus produced and to convert the same into radio frequencies for reception by a radio receiver and means for supplying D C. to the filaments of all the tubes.

3. In signal reproducing means, an exciter lamp, a photo-electric tube, a photographic record of sound, means vto cause said record to travel between the source and the cell, a rectifier including one or more rectifier tubes having filaments connected in series and to the source of illumination, one or more amplifying tubes, an oscillator tube having a filament connected in series therewith, a condenser, resistor and filter means in the circuit, a switch in the circuit adapted in one position to supply A. C. to the filaments until heated and in the other position to supply D. C. current to said tubes for discharge as a pulsating D. C. current and means to smooth the D. C. pulsations appearing across the exciter lamp.

4. In signal reproducing means, an exciter lamp, a light sensitive tube, a photographic record of sound, means to cause said record to travel between the lamp and tube, a rectifier including one or more rectifier tubes having filaments connected in series for supplying the tube with current, one or more amplifying tubes having filaments connected in series, an oscillator tube having a filament connected in series therewith, condenser, resistor and filter means in the circuit and means in the circuit to supply A, C. to the filaments until heated and then to supply D. C. current to said tubes for energizing the whole circuit.

5. In signal reproducing means, a source of illumination, a photo cell, a photographic record of sound, means to cause said record to travel between the source and the cell, a rectifier including one or more rectifier tubes having filaments connected in series and through a resistance to the source of illumination for supplying the latter with current at line voltage, a plurality of amplifying tubes having laments connected in series, an oscillator tube having a filament connected in series therewith, condenser, resistor and filter means in the circuit and means in the circuit adapted in one position to supply A. C. or D. C. to the filaments until heated and in the other position to supply D. C. current to said tubes for energizing the whole circuit.

6. In signal reproducing means, a source of illumination, a photo-electric cell, an electrically produced record of sound, means to cause said record to travel between the source and the cell, a rectifier including one or more rectifier tubes having laments connected in series and through a. resistance to the source of illumination for supplying the latter with current, an oscillator, a resistance in the circuit between the oscillator and source of illumination, a plurality of amplifying tubes connected in series with the oscillator and means to automatically compensate for any lack of high or low notes in the original recording with an increasing frequency characteristic for the high notes and automatic adjustment of the low notes below a suitable reference frequency free of transformers and manual control, including a condenser resistor network having a low capacity condenser ccnnected thereto in parallel on the outside and an additional resistor condenser network in the circuit on the outside of the first condenser and resistance to prevent any further increase in high response and to adjust the low notes below a suitable reference frequency by increasing reactance of one of said condensers so that the effective value of the resistor increases with the in-creasing reactance thereof.

7. A signal reproducing means including a signal record eiected by light, means including a light sensitive cell to produce a pulsating current corresponding to the original record by passing light through the record and modulating the same for action on said pulsating current producing means, a condenser resistor network having a series condenser connected with the light sensitive cell, a low capacity condenser connected to the cell in parallel on the outside of the resistance and condenser of suitable value to automatically compensate for any lack of high or low notes in the original recording and reduce the audio-frequencies at or above a suitable reference frequency to a certain proportion of their original amplitude and to amplify normally attenuated low and high notes which are indistinct to a greater degree than the reference frequency so that the notes that are imperfect in the original recording toward a mean ratio and reference frequency between high and low frequencies are compensated for and means for amplitying and converting such frequencies with a gain in both high and low notes to render thel same capable of detection and reception by a radio receiver.

8. A sound motion picture projector comprising a motion picture film bearing a sound tract, optical means to project the motion pictures from said nlm and means for reproducing sound from said sound tract including a source of light to illuminate said sound track, a source of direct current to supply said source of light including one or more rectifier tubes to receive A. C. current at line voltage, and an adjustable resistance between the rectifier tubes and the source of light, a photo-electric cell adapted to receive light modulated by said sound track, one or more amplier tubes having a cathode directly connected to the cathode of the photo-electric cell, means interposed to build up the low and high notes and render more uniform the sound frequency curve toward a constant value and to automatically compensate for lack of both high and low notes including a resistor condenser network and means for receiving the audiofrequencies thus produced and to convert the same into radio frequencies.

WALTER C. WELLMAN.

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