Television system

Oct. 22, 1935.

V. K. ZWORYKIN

TELEVISION SYSTEM Original Filed March 17, 1924

2,017,883

SheetS-Sheet 1

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Oct. 22, 1935. v. κ. zworykin 2,017,883

TELEVISION SYSTEM Original Filed March 17, 1924 3 Sheets-Sheet 2

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V V . ’ wiTNFSSt-s- INVENTOR

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Oct. 22, 1935. v. κ. zworykin 2,017,883

TELEVISION SYSTEM Original Filed March 17,. 1924 3 Sheets-Sheet 3

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WITNESSES: INVENTOR

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Patented Oct. 22. 1935

2,017,883

UNITED STATES PATENT OFFICE

2,017,883 TELEVISION SYSTEM Vladimir K. Zworykin, Haddonfield, N. J. Application March 17, 1924, Serial No. 699,630 Renewed June 27,1931

Claims.

My invention relates to television systems.

One of the objects of my invention is to provide a system of television that shall be suitable for, use in conjunction with a telephone system.

Another object of my invention is to provide a system of the above indicated character in which the amount of equipment at a subscriber’s substation is a minimum, and the other equipment Is common to all the subscribers and is 10 located at a central office.

A further object of my invention is to provide a “duplex” method for the transmission and reception of images or pictures by television.

There are other objects of my invention which, 15 together with the foregoing, will be described in the detailed specification which is to follow.

While in the drawings I have shown my invention applied to a telephone system, it will be understood that It is not limited to this use, but 20 it may be arranged to secure the transmission and reception of television over an ordinary power circuit or in other places, as will be obvious.

In practicing my invention, I provide, in addi25 · tion to the ordinary telephone equipment at each substation, transmitting and receiving apparatus for transmitting the image of the party calling to the receiving apparatus at the substation of the called telephone subscriber. The 30 television transmitting apparatus associated with the substation of the called subscriber causes the image of this party to be reflected by the television receiving apparatus at the calling subscriber’s substation.

Referring now to the drawings, comprising Figures 1 to 3, inclusive, I have shown by means of conventional diagrams, circuits and apparatus for connecting one substation A with another substation A'.

The apparatus shown in Fig. i is associated with the subscriber’s substation A and comprises the transmitting and receiving television apparatus. In Fig. 2, a portion of the apparatus at the central office is shown comprising means for connecting the substation A to the substation A'. The apparatus shown in Fig. 3 is associated with the substation A' and comprises television And transmitting apparatus.

The substation A is of the ordinary type of 50 subscriber’s telephone station, having the usual talking instrumentalities. At the substation A, the line conductors I and 2 are connected through a transformer 3, with a detector triode 4. The filament of the detector triode 4 is also ¢5 connected tp the fllament 5 of a cathode-iray (CI. 178—6) tube 6. The cathode-ray tube 6 is somewhat similar to an ordinary cathode-ray oscillograph, being provided with a hot cathode, a diaphragm 7, a tubular anode 8 and plates 9 and 10. .

A portion 11 of the cathode-ray tube 6 is sepa- ₆rated from the other portion by means of a composite plate (2. This plate is formed first of a thin layer of aluminum foil 14 about .0003 inch in thickness, upon which is placed a layer of aluminum oxide IS about ,0001 inch in thick- χθ ness. Upon the aluminum oxide 15 is placed a layer of photoelectric material which may be an alkali metal 16, such as potassium hydride. In front of the composite plate is placed a grid 40. The cathode-ray tube is filled with an atmos- 15 phere of argon at low pressure.

A lens 18 is held in place before the cathoderay tube by means of a container 19. This lens is adapted to project light upon the surface of the photoelectric material. A mirror 20, having 20 a small hole cut therein, is positioned before the cathode-ray tube 6. Through this opening, the lens 10 focuses the image from the other side upon the surface of the photoelectric globules.

A cathode-ray tube 23 is positioned on the other 25 side of the mirror. 20, in the manner shown. The cathode-ray tube 23 is similar to an ordinary cathode-ray oscillograph, being provided with a hot cathode 24, a grid 25, a tubular anode 26, plates 27 and 28 and a fluorescent screen 29. 30' The plate circuit of the detector triode 4 is connected with the grid 25 of the cathode-ray tube 23.

An oscillatory circuit 3 f, including the primary windings of the transformers 32 and 33, is con- 35 nected to the line conductors I and 2 through the transformer 30.' The secondary winding of the transformer 32 is connected to a detector triode 34, while the secondary winding of the transformer 33 is connected to another detector 40 triode 34^a. The transformer 32 is resonant to the carrier current that is modulated at a predetermined operating frequency, while the transformer 33 is resonant to the carrier current that is modulated at another predetermined operat- 45 ing frequency.

The output circuit of the detector 34 is connected to the coils 35 and 36 and 37 and 38. These colls 35 and 36 are associated with the cathode-ray tube 23 and are so disposed with 60 respect thereto that the magnetic field that they may set up is parallel to the electrostatic field that may be set up by the plates 27 and 28. The coils 37 and 38 are disposed in a like relation to the .cathode-ray tube 6. 80

3,017,888 ·

The output circuit of the detector triode 34® is connected to the plates 27 and 28 and 9 and 10 in the cathode-ray tubes 23 and 6, respectively. These plates are adapted to set up an alternating 6 electrostatic field to deflect a cathode beam in one direction, while the magnetic field set up by coils 35 and 36 and 37 and 38 deflects the cathode beam at right angles to that set up by the electrostatic fields.

The grid 40 in the portion 11 of the cathoderay tube 6 is connected to an amplifier triode 41. The output circuit of the amplifier triode 41 Is connected through a transformer 42 to the modulator triodes 43 and- 44. A circuit including an •15 oscillator triode 46, that is adapted to oscillate at a predetermined frequency, is connected to the modulator triodes, 43 and 44 through a transformer 45. The output circuits of the modulator triodes 43 and 44 are connected to an amplifier 20 triode 48 through a transformer 47. The output circuit of the amplifier triode 48 is connected through a transformer 49 to the line conductors I and 2.

The normal operation of the oscillating cur25 rent in circuit, including the oscillator triode 46, does not apply a high carrier current to the line conductors I and 2, by reason of the fact that this carrier current is neutralized by the action of the modulator triodes. 43 and 44. The only 30. manner in which the carrier current can be broadcasted is by a change in the primary winding of the transformer 42 which causes a pure modulated high frequency current to traverse the conductors I and 2 in accordance with the cur35 rent in the primary winding of the transformer.

The high-voltage current applied to the anodes 26 and 8 of the cathode-ray tubes 23 and 6, respectively, is obtained from a rectifier 52 that is connected to the source of alternating current 53. 40 The line conductors I and 2 of the substation A terminate at the exchange in an answering jack J, as shown in Fig. 2. Ordinary line and cut-off relays 60 and 61 are associated with the jack J at the exchange. A line relay 60 is adapt45 ed to control a line lamp, 62. The line of the substation A may be extended by means of a cord circuit O.

The cord circuit O is of the usual type, having - · an answering plug P and a calling plug P—I. 50 The cord circuit O is also provided with an answering key K and a ringing key K—I. The plug p— I of the cord circuit O may be inserted into any one of the multiple jacks, such as J—I, leading to the desired subscriber’s telephone. By 55 means of a transformer 65, the cord circuit O is associated with an amplifying circuit that includes an amplifying triode 66.

Modulator triodes 67 and 68 are associated with the amplifying circuit through a transformer 69. 60 . A circuit, including an oscillator triode 70 that is adapted to generate an oscillating current, is associated with the modulation circuit through a transformer 71. By means of a transformer 72, an alternating-current generator 73 is associated 65 with the modulating circuit including the modulator triodes 67 and 68. An alternating-current generator 74 is also associated with the modulating circuit through a transformer 75.

The oscillating current generated by the os70 cillator triode 70 is not normally applied to the cord circuit, by reason of the fact that, by the action of the modulator triodes 67 and 68 and the primary winding of the transformer 69, the output of the oscillator triodes is neutralized. The 75 generator 73 is adapted to generate an alternating current of a relatively high frequency, for example 1000 cycles, while the generator .74 generates an alternating current of a relatively low frequency, of about 10 cycles. The alternating current from the alternators 73 and 74 is adapted 5 to modulate, through the transformer 72, the high-frequency carrier current generated by the oscillating circuit including the oscillator triode 70. This modulated frequency current is amplified by the amplifier triode 66 and applied to all iu the cord circuits in the system through transformers, such as 65. The equipment including the triodes 68, 67, 68 and 70 and the alternators 73 and 74 is common to the exchange.

The called substation A', shown in Figs. 2 and 3, is is similar to the substation A previously described, and its line, comprising conductors 80 and 8.1, terminates at the exchange in an answering jack (not shown) and in multiple jacks, such as J—I and J—2. 20

The line conductors 80 and 81 are also connected by means of a transformer 82 (Fig. 3) with a detector triode 83. The filament of the detector triode 83 is connected to the filament 84 of a cathode-ray tube 85. The cathode-ray tube 85 25 is similar to the cathode-ray tube 6 at the substation A, previously described, having a hot cathode 84, a diaphragm 86, a tubular anode 87, plates 88 and 89 in a container 90. The container 90 is divided into two portions by means 30 of a composite plate 91 that is made up of a layer of aluminum foil 92, a layer of aluminum oxide 93 and a layer of photoelectric material 94. Disposed in front of the composite plate is a grid H6. The cathode-ray tube contains an 35 argon vapor at low pressure.

A container 96 holding a lens 97 is placed over the end of the cathode-ray tube. A mirror 99 is placed at an angle of about 45° in front of the lens 97. The mirror 98 has a hole 99 cut therein 40 through which the lens 97 reflects the image on the screen 94.

The plate circuit of the detector triode 93 is connected with a grid 109 in a cathode-ray tube 101. The cathode-ray tube 101 is similar in all 45 respects to the cathode-ray tube 23, having a hot cathode 102, a tubular anode 103, plates 104 and 105 and a fluorescent screen (06, the whole being enclosed in an evacuated container (07.

An oscillatory circuit ((( is connected to the gg line conductors 80 and 9(, through a transformer ((0. The detector triodes 1(2 and 113 are associated with the oscillatory circuit (11 by the transformers (14 and ((5, respectively. The transformers, ((4 and (15, are resonant to current 55 of certain frequencies, as before described in connection with the equipment at the substation A.

The grid 116 of the cathode-ray tube 85 is connected to the grid circuit of an amplifier triode 117. . The output circuit of the triode 117 is con- qq nected through the transformer 118 with modulator triodes 119 and 120. The circuit including the oscillator triode 121, that is adapted to generate a current of a definite frequency, is connected to the modulator circuit through a trans- _βδformer (22. The output circuits of the modulator triodes are connected through a transformer. 623 with the grid circuit of an amplifier triode 124. In turn, the output circuit of the triode 124 is connected to the line conductors through a γθ transformer 12*. Ordinarily, unless there is a change in the current flow in the primary winding of the transformer III, the alternating current generated by the circuit including the triode 121 is not applied to the line conductors 80 and 81. T*.

2,017,883

In the drawings, the various triodes and cathode-ray tubes at the substations A and A', respectively, are in an energized condition. However, this has only been done in order to simplify the ₆ drawings, it being obvious that it is quite possible to render the various circuits at each substation inoperative until the receiver thereat is removed from the switch hook.

Having briefly described the apparatus shown in 10 the drawings, I will now explain its detailed operation. For this purpose, it will be assumed that the subscriber at substation A desires to call the subscriber at substation A'. In order to accomplish this result, the subscriber at substation A 15 will remove his receiver from the switch hook, shown in Fig. 2. As a result of this operation, a circuit is closed for the line relay 60 on the line circuit at the exchange.

The line relay 60, upon being energized, at 20 armature 150 closes a circuit for the line lamp 62. By the lighting of this lamp, the operator’s attention is drawn to the fact that the subscriber at substation A desires a connection. Therefore, she will insert the plug of an idle cord circuit, 25 which, it will be assumed, is the plug P, of the cord circuit O into the jack J. As a result of the insertion of plug P in the jack J, a circuit is completed extending from battery, through resistor 151, lamp 152, sleeve of the plug P, sleeve of the jack J and 30 the winding of the cut-off relay 61 to ground.

The cut-off relay 61 is energized over this circuit and operates to attract its armatures 153 and 154. By the latter operation, the circuit of the line relay 60 is opened, and this relay is deener3ό gized to extinguish the calling signal 62. The supervisory lamp 152 would also be energized over the above circuit were it not for the fact that there is a circuit completed over the two-line conductors in series for the supervisory relay 155.

The relay 155, upon being energized, at its armature 156, shunts out the answering supervisory lamp 152. The operator will now operate key K, in order to associate her head set with the cord circuit, and will ask the subscriber at sub45 station A what number he desires. Upon hearing the number, the operator will test the line of the called substation by touching the tip of the plug P—I to the sleeve of the jack associated with the particular line desired. If the line is idle, the 50 operator will insert the plug into the line jack and will then operate a ringing key K—I.

When the plug P—i is inserted in the jack J—(, a circuit is completed for the cut-off relay (57 over a path extending from battery through re55 sistor 168, supervisory lamp 159, sleeve of plug P—I, sleeve of Jack J—I and the winding of cutoff relay 181 to ground.

The cut-off relay, upon being energized, at armatures 160 and 161, disconnects the line relay 60 (62 from the line circuit. The supervisory lamp 158 is also energized over the above circuit.

When the ringing key K—I is operated, ringing current from the generator (63 Is applied to the line conductors 80 and 01 of the calling line. As 55 a result of this operation, the bell at the substation A—I is operated.

When the calling subscriber removes his receiver, a circuit is completed over the line con70 ^duc^^0rs and 01 in series for the supervisory relay 164. The supervisory relay (64, upon being energized, attracts armature 865 and shunts out the calling supervisory lamp (09, whereby it is extinguished. By this operation, the operator is 15 Informed that the connection has been completed.

The subscriber may converse over the circuit shown in heavy lines in the drawings.

As soon as the plug P is inserted into the jack J of the calling line, the carrier current modulated by the current from the generators 73 and 14 is 5 transmitted over the line conductors I and 2 and through the transformer 30. By the operation of the transformer 32, the carrier current that is modulated by current from the low-frequency generator 74 is applied to the detector 34. By ιθ the operation of the detector 34, the high-frequency carrier current is eliminated and an alternating current of a frequency the same as that generated by the generator 14 is applied to the coils 35 and 36 of the cathode-ray tube 23 and the 15 coils 37 and 38 of the cathode-ray tube 6. By the operation of the transformer 33, the carrier current modulated by the current from the highfrequency generator 13 is applied to the detector 34α. The output of this circuit is connected to 20 the plates 27 and 28 of the cathode-ray tube 23 and to the plates 9 and (0 of the cathode ray tube 6.

By reason of the fact that the coils 35 and 36 of the cathode ray tube 23 are so disposed with 25 respect to the plates 27 and 28 that the magnetic field generated by these coils lies parallel to the electrostatic field generated by plates 27 and 28, the cathode beam in the tube is caused to be deflected in one plane which is at right angles to 30 the magnetic field set up by the coils. In a like manner, the operation of the coils 9 and 10 of the cathode-ray tube 6 is deflected in one plane. By the application of alternating current of operating frequency to the plates 27 and 28, the cathode- ₃₅ray beam in the tube 26 is deflected in a plane at right angles to the one before mentioned and by its application to the plates 9 and 10 the cathoderay beam in the tube 6, is similarly deflected.

The resultant action of the magnetic and elec- .θ trostatic fields is such that the cathode beams ⁴cover the whole area of the fluorescent screen 29 and the composite plate (2. By reason of the frequency of the currents used, the whole area of the screen 29 and the plate (2 is covered in 1/20 of a second.

As the cathode-ray tubes 6 and 23 are so disposed close to the telephone that, when the calling subscriber removes his receiver, he will be within the objective of the lens 18 and his image will be projected upon the photoelectric material (6 of ⁰the composite plate 12. For each particular point of the image on the photoelectric globules, there will be a certain electron emission from the globules in accordance with the intensity of the light. _β5This electron emission ionizes the argon gas in the container ί I and gives a connection of varying resistance between the grid 40 and various portions of the photoelectric material in accordance with the light from the party telephoning. However, the latter is without effect, except at. a certain point at which the cathode beam is located, as will be explained.

At the point that the cathode beam impinges on the composite plate, it will be of sufficient _β5velocity to penetrate the aluminum foil and alu- ⁰⁰minum oxide, thereby making a connection from the grid of the amplifier triode 41 to the filament of said triode, and the amount of current flow in this circuit will be directly proportional to the ₇₀intensity of the light falling upon the photoelectric globule that is covered by the cathode beam, that is governed by the light intensity of the image of the party calling.

Thus, as the cathode beam covers the whole T5

2,017,888 area of the composite plate In 1/20 of a second,' the carrier current, generated by the circuit including the oscillator 46, will be modulated in accordance with the image of the party point by 5 point in a definite sequence. This takes place in 1/20 of a second. That is, when there is current flowing in the grid circuit of the amplifier triode 41, this current is amplified and transmitted to modulator triodes 43 and 44, whereby the high10 frequency current generated by the oscillator 46 is modulated in accordance with this current and transmitted by means of transformer 41 to amplifier triode 48. The output of the amplifier triode 48 flows through the transformer 48 and over 15 the line conductors I and 2.

At the receiving station, by the action of the detector triodes i 12 and 113, the cathode beams in the cathode-ray tubes 85 and 101 are deflected in synchronism with the cathode-ray beams in 20 the tubes 6 and 23 at the calling substation. That is, these beams are all in the same relative position at the same time.

By the operation of the transformer 82, the high-frequency current which is modulated in ac25 cordance with the varying intensity of light is transferred to the detector 83, whereby the carrier frequency is eliminated and the current is applied to the grid 100 of the cathode ray tube tOI. By the varying potential upon the grid, the 30 intensity of the cathode ray which strikes the fluorescent screen is regulated in accordance with the intensity of light falling upon the particular portion of the composite plate at which the cathode beam in the transmitting tube 6 is striking at 35 that particular instant. Thus, the intensity of the light given off by the fluorescent screen 101 at that particular point is relatively, to other spots thereon, the same as the Intensity of the light falling upon that particular point from the 40 object at the transmitting station.

Tn a like manner, all the various pointe of the object are transmitted and recorded in varying Intensity of light for a particular point. Thus, the image of the party calling is reproduced on 45 the fluorescent screen 108 in 1/20 of a second. This image is reflected to the eye of the observer by means of the mirror 98.

The transmitting tube 85 at the receiving station is operated in a like manner and causes the 50 carrier frequency generated by the circuit, including the oscillator triode 9 i, to be modulated in accordance with the intensity of the light falling upon the photoelectric material 04 at a particular point at which the cathode beam is impinging.

As the cathode beam in the receiving tube 23, at the substation A is in the same relative position, by the action of the detector triode 4, a certain potential is placed upon the grid 25 of the receiving cathode ray tube 21, and the intensity 60 of the cathode beam striking the fluorescent screen 29 is modulated in accordance with the intensity of light at that particular point on the screen at the substation A'. As this takes place in l/20 of a second, the whole image will be re65 produced in that time and reflected to the eye of the calling party by means of the mirror 20.

By reason of the high frequency at which the image is transmitted, any movement of the person at either the substation A or substation A' 70 will be reproduced at the other substation, and the party thereat will be able to see such movement.

It will be seen that the high voltage applied between the anodes and the cathodes in the 75 cathode-ray tubes at the substation A is obtained from a source of alternating current 53 through the operation of the rectifier 52. This gives a unidirectional pulsating current. As this potential governs the speed of the cathode rays, the cathode beam is made up of a number of im- 5 pulses in accordance with the alternations in the alternating current supply. This action is intensified by reason of the fact that the potential on the grids of the cathode ray receiving tubes is supplied from a rectified alternating current 10 by the action of the detector triodes. The cathode beam is thus made up of what corresponds to a number of impulses, and the tendency of the fluorescent spots to spread is minimized. The same arrangement holds true for the substa- 15 tion A'.

When the conversation is terminated, the subscribers at substations A and A' will replace their receivers upon the respective switch hooks: Upon the replacement of the receiver at substation A, 20 the circuit of the supervisory relay 155 in the cord circuit O is opened, and this relay is deenergized to remove the short-circuit from the supervisor signalling lamp 152. The operation of this lamp serves to apprise the operator of the replacement 25 of the receiver at substation A.

The replacement of the receiver at substation A' causes the deenergization of the relay 164 and. the lighting of the lamp 159, whereby the operator is apprised that the receiver at substation A' has 30 been replaced. The operator will now withdraw the plugs P and P—I from the jacks J and J'. The connection is released in the above manner.

In the event that the called line is busy when the operator attempts to connect thereto, there 35 will be a battery potential upon the sleeve of the jack and a click will be produced in the operator’s ear, when she tests it with the tip of the calling plug. She will then inform the calling subscriber that the line is busy. 40

From the above, it will be seen that I have provided a system whereby it is possible to simultaneously transmit and receive vision over a single pair of wires, and that any movement of the objects under observation at either station will cause 45 a corresponding movement in the reproduced image.

It is, of course, obvious, that as many views of the object may be transmitted as desired by regulating the frequencies of the synchronizing cur- 50 rents.

My invention is not limited to the specific arrangement of the apparatus illustrated, but may be variously modified without departing from the spirit and scope of my invention, as set forth in 55 the appended claims.