US2250529A

US2250529A - Signal translating apparatus

Info

Publication number: US2250529A
Application number: US255899A
Authority: US
Inventors: Gray Frank; John B Johnson
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1939-02-11
Filing date: 1939-02-11
Publication date: 1941-07-29
Anticipated expiration: 1958-07-29

Description

July 29, 1941.

F. GRAY ETAL 2,250,529

SIGNAL TRANSLATING APPARATUS Filed Feb. 11. 1939 MUL SIGNAL INDIVIDUAL SIGML INDIVIDUAL SIGNAL INVENTORS! F GRAY J. B. JOHNSON BY ATTORNEY Patented July 29, 1941 SIGNAL TRANSLATING APPARATUS Frank Gray, New York, N. Y., and John B. J ohnson, Maplewood, N. J., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application February 11, 1939, Serial No. 255,899

12 Claims. (01. 250-152) This invention relates to signal translating apparatus and more particularly to electronic commutators for multiplex telephone systems such as disclosed in the applications of Frank Gray,

Serial No. 255,897 filed February 11, 1939, and

Serial No. 255,898, filed February 11, 1939.

One'object of this invention is to faithfully commutate a plurality of complex signals such,

for example, as signals corresponding to speech and music.

Another object of this invention is to facilitate the accurate conversion of speech and music into electrical waves.

Still another object of this invention is to prevent electronic cross-talk and distortion in electronic commutators.

A further object of this invention is to improve and to simplify the structure of electronic commutators.

In one illustrative embodiment of this invention, an electronic commutator comprises a plurality of secondary electron emissive targets, a

. collector electrode in cooperative relation with the targets, and means for producing an electron beam whichimpinges upon the targets in sequence and repeatedly at high frequency.

In accordance with one feature of this invention, the targets are made of varying width, for example, sectoral or wedge-shaped, and means,

such as deflector plates, are provided in cooperathe beam deflecting plates for shielding the latter from one another.

In accordance with a further feature of this invention, the several targets are fabricated as a unitary structure. For example, in one specific form, the targets may be spaced radial sections of a disc of good secondary electron emissive material. The portions of the disc intermediate the targets may be treated or coated to prevent secondary emission therefrom.

The invention and the foregoing and other features thereof will be understood more clearly and fully from the following detailed-description with reference to the accompanying drawing in which:

Fig. 1 is a perspective view of an electronic commutator illustrative of one embodiment of this invention, portions of the enclosing vessel,

collector electrode, target electrode and shield electrode being broken away to show details of construction more clearly;

Fig. 2 is a sectional view along line 22 of Fig.-

1 showing the construction of the target electrode;

Figs. 3 and 4 are detail sectional views along lines 3-3 and 3-4, respectively, of Fig. 1,11- lustrating the form and association of the shield and deflecting electrodes; and

Fig. 5 is a circuit diagram illustrating one way of operating the electronic commutator shown in Fi .1.

Referring now to the drawing, the electronic commutator disclosed therein comprises an elongated, evacuated enclosing vessel lil having inwardly extending coaxial stems II and. I2 at op-, posite ends, the stem H terminating in a press I3.

Supported by the stem Ii is an electron beam producing and deflecting structure which may be of the construction disclosed in the aforementioned applications of Frank Gray. This structure comprises a cathode, which may be of the equipotential indirectly heated type, including a heater filament I4 and a cup-shaped or cylindrical sleeve l5 coated on its outer surface with an electron emissive coating. The cathode is supported by leading-in conductors l6 embedded in the press i3. It will be understood, of course, that although a heater type cathode has been shown, other types of cathodes, for example, filamentary, may be employed.

Immediately adjacent the cathode is a concentrating electrode including a cylindrical portion ll coaxial with the sleeve l5, and end flanges l8 and IS. The concentrating electrode may be supported by a plurality of rods or uprights 2U afiixed to the flange I8 and carried by a pair of bands or collars 2| clamped about the stem II. An insulating spacer is mounted on the concentrating electrode and comprises a tubular body portion 22 coaxial with the concentrating electrode, and end flanges 23 and 24, the flange 23 being afiixed to the flange l9 as by rivets or eyelets 25.

An elongated tubular anode 26, of circular or other cross-section, is fitted in the bore in the body portion 22 of the insulating spacer and is provided with a flange or collar 21 seated upon the flange 24. The anode 26 is coaxial with the concentrating electrode and preferably projects into the cylindrical portion I1 thereof as indicated in Fig. 5. The other end of the anode projects into the space bounded by deflector or potential, thousand cycles per second, by oscillators 41 through.transformers- 48, the. two oscillators. be- 7 ing '90 degrees out of .phase so that. the deflector tor sweep plates produce a rotating field. .As175

sweep plates

28 and 29 which are equally spaced from the longitudinal axis of the anode. Each of the deflector or sweep plates, as shown in Fig. 1, comprises a rectangular portion and an outwardly inclined trapezoidal portion, and is supported by a rigid rod or wire 30 afiixed to and carried by the flange 24. Leading-in connection to the deflector or sweep plates may be established through insulated conductors 3| extending from the press I3.

The concentrating electrode l1, anode 25 and. sweep or

deflector plates

28 and 29 constitute an electron lens system which has a focal point just inside the end of the anode '26 opposite the cathode l and whichproduces an image of this point on the targets to be described hereinafter.

An annular target electrode 32 is supported coaxial with the anode 25 by leading-inconductors 33 sealed in the side of the stem [2. This electrode may be a disc of a material, such as nickel or beryllium, having. goodsecondary electron emission properties, and, as shown clearly -in Fig. 2, the surface thereof toward the deflector or sweep plates may have thereonequally spaced radially extending coatings34 of a material, such as graphite, which does not emit secondary electrons. The remaining wedge-shaped or substantially sectoral portions 35 of this surface constitute secondary electron emissive targets.

- Alternatively, the targets 35 may be coatings of a secondary electron emissivematerial, such .as matrices including silver oxide, caesium, oxide and some free caesium.

An annular or cylindrical collector electrode 36 is disposed in juxtaposition to the targets 35 and is supported coaxial with thedisc32 .by a leadingin conductor 3'! sealed in the stem l2.

Disposed in circular formation about an. axis coincident with that of the electrode 32 and I collector electrode 33 area plurality of curved trapezoidal deflector plates 38, each of .Whichis supported opposite a corresponding one .of the targets 35, as by a leading-in conductor 39 sealed in the stem [2, and is slightly inclined, as illustrated in Fig. 5, with respect to the. stem..l2.

shown in Fig. 5, the sweep or deflector plates are maintained at a positive potential, for example, of the order of three hundred volts, by connections from the mid-points of the secondary windings of the transformers 48 to the battery 45 so that these plates serve as a second anode. If desired, the deflector or sweep plates may be biased at a potential higher than that upon the anode 26, for example, at a potential of the order of three times the potential on anode 26.

The target electrode 32, the shield electrode 40 and the deflector plates have applied thereto the same potential as the sweep or

deflector plates

28 and 29 and the collector electrode 36 is maintained at a positive potential, for example, of the order of fifty volts, with respect to the target electrode, as by a battery 49 in series with a resistance 50.

Individual signal channels 5|, for example, telephone lines, are connected between the shield electrode 4.0 and the deflector plates 38 as through The deflector plates 38 are encompassed by a one another.

During operation of the electronic commutator, the heater filament I4 is energizedas bya battery 15, and the concentrating electrode is maintained at a suitable potential, positive .or

negative, with respect to the cathode as by a.

battery 46. The anode '23 is maintained ,at a high positivepotential, for example of the order of six hundred volts, with respect tothe cathode as by a battery 43. The deflector or sweep plates 28and 29 have applied thereto a high frequency for example, of .the order of six transformers .52.

.The battery 49 and resistance Snare bridged across the input circuit 53 of an amplifier,

a suitable blocking condenser .55 being provided as shown. The output circuit of the amplifier 54 maybe connected .toa common transmission channel.

When the electronic commutator is operated, the electrons emanating from the cathode l5 are concentrated into a beam focussed upon the targetelectrode 32, the beam being rotated at. high frequency by the field produced by the deflector or sweep plates .28 and, 29 so that it impinges upon the targets 35 in succession. The impinging electrons cause the emission of secondary electrons and, consequently, a current will flow from each of the targets 35 to thecollectorelectrode 36. Each secondary electron current may be modulated in accordance with the signal from the corresponding individual signal channel through the actionof the corresponding deflector plate .38. That is to say, eachdeflector plate will deflect the electron beam radially substantially along an axis such as X-TX shown for onetarget 35 in Fig. 2. Hence, ,the time of travelof the electron beam along each target and the area of .the target energized will be varied in accordancewith the potentials of the deflector-plates and the .currentsto the collector electrodewill correspond to the individual signals.

Acomplex current, it will .be apparent, composed of the several modulated currents .will flow through. thev common resistance .50 and. corresponding variationsflwill be producediinthe potential of the grid orcontrol electrode of the amplifier 54. Hence, the output of theamplifierwillbe, a multiplexed signal having, components corresponding to the severalindividual signals.

The multiplexed signal may .be transmitted over a common transmission channelto ,areceiving distributor and thereanalyzedasde- .scribed in the application Serial No.;255,89'7,. fi led February 11, o 1939, ofFrank Gray.

Although the electron beam has been, described as rotated by an electrostatic field, it may be rotated also by a magnetic fieldproduced forexample,.by external coils. It wil1 be,understo0d also that, although. a specific embodiment of this invention has been shown and described, various modificationsmay be made therein withoutdeparting from the scope and spirit of this inven- ,tion as,,defined inntheappended c aim .What; is claimed is:

1- Signal translating apparatus comprising means for producing an electron beam, a plurality of similar, secondary electron emissive targets each target being of varying width from the beam axis outwardly, a single collector electrode in cooperative relation with all of said targets, means for deflecting said electron beamto impinge upon said targets in sequence, and means for controlling the secondary electron current from each of said targets including means for deflecting the electron beam in directions substantially normal to the width of said targets.

2. Signal translating apparatus comprising means for producing an electron beam, a plurality of similar, secondary electron emissive targets, each target being of varying width from the beam axis outwardly, a collector electrode in cooperative relation with said targets, means for deflecting said electron beam to impinge upon said targets in sequence, and means for controlling the secondary electron current from each of said targets including means for deflecting the electron beam in directions substantially normal to the width of said targets, said targets being wedgeshaped and mounted in circular formation about an axis coincident with the longitudinal axis of said collector electrode.

3. Signal translating apparatus comprising means for producing an electron beam, a plurality of similar secondary electron emissive targets, each target being of varying width from the beam axis outwardly, a collector electrode in cooperative relation with said targets, means for deflecting said electron beam to impinge upon said targets in sequence, and means for controlling the secondary electron current from each of said targets including means for deflecting the electron beam in directions substantially normal to the width of said targets, said controlling means comprising a plurality of deflecting plates, one for each of said targets, each deflecting plate being in alignment with a corresponding one of said targets.

4. Signal translating apparatus comprising a collector electrode, a plurality of secondary electron emissive targets mounted in a circular boundary coaxial with said collector electrode, means for producing an electron beam, means for rotating said beam so that it impinges upon said targets in succession, each target varying in dimension normal to the direction of the trace of said beam thereon, means for varying individually the area of each target impinged upon by said beam including means for deflecting said beam along radii of said circular boundary.

5. Signal translating apparatus comprising a collector electrode, a plurality of secondary electron emissive targets mounted in a circular boundary coaxial with said collector electrode, means for producing an electron beam, means for rotating said beam so that it impinges upon said targets in succession, each target varying in dimension normal to the direction of the trace of said beam thereon, and means for varying the area of each target impinged upon by said beam including means for deflecting said beam along radii of said circular boundary, said deflecting means comprising a plurality of deflecting electrodes mounted in a boundary coaxial with said collector electrode, each of said deflecting electrodes being in cooperative relation with a corresponding one of said targets.

6. Signal translating apparatus comprising a collector electrode, a plurality of secondary electron emissive targets mounted in a circular boundary coaxial with said collector electrode, means for producing an electron beam, means for rotating said beam so that it impinges upon said targets in succession, each target varying in dimension normal to the direction of the trace of said beam thereon, means for varying the area of each target impinged upon by said beam including means for deflecting said beam along radii of said circular boundary, said targets being radially extending wedge-shaped portions of an annular member, and non-emissive coatings upon the portions of said member intermediate the wedge-shaped portions.

'7. Signal translating apparatus comprising a collector electrode, a plurality of secondary electron emissive targets mounted in a circle coaxial with said collector electrode, means for producing a rotating electron beam impinging upon said targets in succession, the dimension of each target in the direction of the trace of the beam thereon varying outwardly with respect to the center of said circle, a plurality of beam deflecting electrodes, each in alignment with a corresponding one of said targets, and. shield members between successive deflecting electrodes.

8. Signal translating apparatus in accordance with claim 7 comprising a shield electrode encompassing said deflecting electrodes.

9. Signal translating apparatus comprising a collector electrode, a plurality of secondary electron emissive targets mounted in and along radii of a circular boundary coaxial with said collector electrode, each of said targets varying in dimension normal to the corresponding radius of said' boundary, a plurality of deflector plates, one for each of said targets and in alignment therewith, said plates being mounted in a boundary coaxial with said collector electrode, a hollow electrode encompassing said deflector plates, coaxial with the boundary thereof, and defining a substantialiy annular passageway therewith, means for producing an electron beam, and means for rotating said beam in said passageway to impinge upon said targets in succession.

10. Signal translating apparatus in accordance with claim 9 wherein said hollow electrode comprises a base having therein a plurality of apertures, one for each of said targets, each aperture being in alignment with the corresponding target.

11. Signal translating apparatus in accordance with claim 9 comprising shields for screening said deflector plates from one another.

12. Signal translating apparatus in accordance with claim 9 comprising a plurality of radially extending vanes integral with said hollow electrode, each vane projecting between two successive deflector plates.

FRANK GRAY. JOHN B. JOHNSON.