US1444605A - Carrier-wave signaling system - Google Patents

Description

Feb. 6, 1923.

R. A. HEI SING. CARRIER WAVE SIGNALING SYSTEM. 7

ORlGiNAL FILED JAN. 21. 2919. 2 SHEETS-SHEET 1.

//1venfar': Raymond H/S/h? R A H E I S l N G.

CARRIER WAVE SIGNALING S YYYY M.

2 SHEETS-SHEET Patented Feb. 6, i923.

UNITED STATES PATENT OFFICE.

RAYMOND A HEISINO, OF MILLBURN, NEW JERSEY, ASSIGNOR TO WESTERN ELEC TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

CARRIER-WAVE SIGNALING SYSTEM.

Application filed January 21, 1919, Serial No. 272,227. Renewed June 23, 1922. Serial No. 570,386.

To all whom it may concern-:-

Be it known that I, RAYMOND A. HEISING, a citizen of the United States, residing at Millburn, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Carrier-lrVave Signaling Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to oscillation generator circuits and'to signaling by means of modulated carrier currents or electromagnetic waves. A

One object of the invention is to associate, in a novel manner, two or more electron discharge oscillation generators.

A further object is to provide simplel transmitting circuitarrangements in which electronic discharge devices are utilized and associated in a novel manner.

In the operation of signaling systems wherein the principle of successive or plural modulation is employed, it is sometimes desirable that direct modulation of the high frequency carrier current by the signal current should be avoided. It is another object of this invention to provide combinations of devices for and methods of signaling through the agency of successively modulated currents, the devices being so designed and associated that the above mentioned or other undesirable modulation is prevented.

Since it is sometimes desirable to trans- -mit a plurality of si nals upon a single high frequency carrier w ave, arrangements for multiplex signaling are also provided. In the operation of these there is produced a high frequency carrier current modulated in accordance with a plurality of intermediate frequency currents, each of which is itself modulated in accordance with a signal or low frequency current.

In the accompanying drawing, Fig. 1 is a diagram of a circuit arrangement adapted for telegraphy; Fig. 2 is a modified form thereof; Fig. 3 is a circuit arrangement adapted for telephony; Fig. 4 shows the manner of duplicating portions of Fig. 3

for multiplex telephony; and Figs. 5 to 8 inclusive are diagrammatic representations of wave forms of currents existing in various portions of the system of Fig. 3.

v Referring to Fig. 1, the system shown comprises a high frequency generating sys tem A and a low frequency generating system B. In system A high frequency oscillations are produced in the antenna circuit 1 by the action of the electronic discharge device G, which is a tube of the audion type comprising suitable electrodes, and an impedance controlling element in a gas-tight, prefer'ably highly evacuated vessel. The frequency of the oscillations generated in the antenna is determined primarily by the tuning of the antenna. In system. B tube G generates oscillations in a tuned circuit consisting of variable capacity 2 and inductances 3 and 4. Capacity '14 is included in the tuned circuit for a reason hereafter stated. A key K ser es to short circuit a portion of inductance 4 for the purpose of changing the frequency generated in system B. By thus changing the frequency signals may be transmitted. Current for the anodecathode circuit of both tubes is furnished by the source 5. Coil 6 is variablycoupled to coils 3 or 4 or both. Coil 7 constitutes ahigh impedance for currents of the frequency generated by the system A, and coil 8 constitutes a high impedance for currents of the frequency generated by the system B. The usual stoppin condensers 9 and resistive leak paths 1 are provided. Capacity 14 prevents the battery 5 from being shortcircuited. A filter or impedance device 11 of any suitable type, which may be a loopresonant circuit tuned to the mean frequency of system B, prevents oscillations generated by the system B from being impressed upon the antenna circuit. Filter 11 is not essential to the operation of the system and may be omitted, if desired.

During operation, the high frequency oscillations of the system A are modulated in accordance with the oscillations of the system B. This is caused by the intercoupling of coils 4 and 6, whereby a voltage corresponding to the low frequency oscillations is impressed upon the space between the anode and cathode of the device G.

In the modified form of Fig. 2 the inductance 3 instead of inductance 4 has a small portion which may be short-circuited by key K. A terminal of coil 6 is connected to the point 13 between coil 4 and the large condenser 15. The coupling of coils 6 and 4 thus serves to impress the voltage enerated by the system B upon the anode-c thode circuit of system A. Coil 6 also serves to perform the function of coil 7 in Fig. 1

which coil is therefore omitted. Fig. 2 contains no element corresponding to coil 8 in Fig. 1. Instead of an antenna 1, a tuned circuit 1 is used. The transmission line 12 is coupled to circuit 1 This adapts the arrangement to signaling over conductive line wires and any system shown herein may be so adaptedby a corresponding change.

The parts of Fig. 3 correspond to those of Fig. 1 to which similar reference characters are attached. For telephony, however,

additional elements are provided in the form of means to modulate the oscillations of the system B in accordance with speech or other sound waves. The key K is omitted but could be utilized to short-circuit a small portion of coil 4 in case it is desired to carry on both telegraphy and telephony by the same system.' The means to modulate the oscillations of system B comprise a speech frequency system, generally designated at C, in which a vacuum tube V, having a space current path in parallel with tube Gr with respect to the low frequency choke 15, is provided. The choke 15 tends to keep the sum of the space currents through the tubes V and Gr constant." Variations of current in microphone circuit 17 vary the potential of the grid of tube V which changes the impedance of tube V and causes corresponding changes of potential difference across tube G whereby the oscillations generated thereby are varied in amplitude. Coil 16- is designed to offer a high Impedance to oscillations of the frequency generated by system B, but a low impedance to variations induced in system C. Microphone circuit 17 acts upon the tube V. through the input circuit 18 thereof.

Speech frequency variations of voltage across the tube Gr will therefore be caused by the action of the microphon in circuit 17 Condenser 14 prevents short circuiting of source 5 and also prevents speech frequency variations of material amplitude in the anode circuit of tube G Furthermore, any speech frequency variations existing in the plate circuit of system B are impressed upon coil 6 only to a negligible extent, since coils 4 and 6 are not adapted to transfer energy of this frequency. The filter 11 serves to prevent the modulated intermediate frequency oscillations from being impressed upon the antenna and thereby radiated.

The oscillations existing in various parts of the system of Fig. 3 will now be explained in connection with Figs. 5, 6, 7 and 8. In Fig. 5, thecurve a represents a singlecycle of a low frequency variation of impedance across the vacuum tube V. Although in general, for speech the curve a will be of a highlycomplex wave form, for purposes of illustration it may be assumed to be a simple sine wave, and the same principles may be taken to apply to more complicated wave forms. In Fig. 6, the curve 6 represents the unmodulated intermediate frequency current generated by the system B in the tuned circuit 2, 3, 4; while in Fig. 7, the curve 0 will represent the oscillations of the system B when modulated in accordance with the curve a. The envelope (Z of the curve 0 will have the general wave form and the same frequency as the curve a: The more perfect the apparatus the more nearly similar will be curves-a and (Z.. In Fig. 8, the curve 6 represents the high frequency oscillations generated in the antenna 1 of the system A when modulated in accordance with the oscillations represented by the curve 0. The envelope f of the curve d is seen to have the general wave form and the same frequency as the curve a. If a high frequency current corresponding to the curve 6 has been produced by an efficient modulating system and is detected by an efficient detector of any ordinary type, the output of the detector will contain no component corresponding to the curve a and hence the signal transmitted by a system of thetype described cannot be received by a system employing a single detector. It is considered, of course, that the filter 11 prevents transmission of the intermediate frequency corresponding to the system B because it will be obvious that if oscillations of this frequency are radiated, a single detection thereof will be suflicient to reproduce the signal impressed upon the system C. In

general, the frequency generated by the system B may, be practically completely eliminated from the antenna 1 by the filter 11. F urthermore, this frequency may be low as compared to that of the high frequency of the system A, so thatit would be radiated comparatively inefiiciently.

The system shown in Fig. 4 is an adaptation for multiplex telephony of that of Fig. 3 and contains an additional pair of systems B and C, which consist of an intermediate frequency generator G and a tube V to modulate the oscillations of the corresponding intermediate frequency in accordance with speech. Any number of additional pairs of systems B andC may-beprovided. Each pair of systems B and C will be identical except that they are adjusted to produce different intermediate frequencies. The oscillations produced by the system A will thus be modulated in accordance with each of the modulated intermediate frequencies. The filter 11 may be suitably designed to exclude the plurality of intermediate frebe embodied in other forms of apparatus than those shown herein. Certain features of the invention may be utilized in other than signaling systems, as for example, in systems for operating mechanism at a'distance.

lVhat is claimed is:

1. In combination, a tuned circuit, an electronic discharge tube'conductively connected thereto for generating oscillations therein, an anode-cathode circuit for said discharge tube, a space current source in said circuit, means for producing oscillations modulated in accordance with other oscillations, and means for applying to the anode-cathode circuit of said tube a potential which varies in accordance with the modulated oscillations.

2. In combination, a tuned circuit, an electronic discharge device for generating oscillations in said circuit, a second electronic discharge device for generating other oscillations, means whereby the first oscillations are modulated in accordance with the second, a third electronic discharge device, means whereby. the oscillations of the second device are modulated in accordance with potential variations across said third device, a common source of operating space current for said devices, and means forpre venting direct action of said third-mentioned device upon the first-mentioned.

3. In combination, a tuned circuit, an electronic discharge device for generating oscillations in said circuit, a second electronic discharge device for generating other oscil lations, means whereby the first oscillations are modulated in accordance with the sec-- ond, a third electronic discharge device, means whereby the oscillations of the second device are modulated in accordance with potential variations across said third device, a common source of operating space current for said devices, and meanstending to prevent oscillations generated by said second device from being impresed upon said oscillation circuit.

4c. In combination, a tuned circuit, an electronic discharge device ,for generating oscillations in said circuit, a second electronic discharge device for generating other osc1l-' lations, means whereby the first oscillations are modulated in accordance with the second, a third electronic. discharge device, means whereby the oscillations of the second device are modulatedin accordance-with potential variations across said third device,

I and means tending to cause the sum of the currents supplied te said second and thirdmentioned devices to remain constant.

- p 5. In a signaling system, an electronic device for generating high frequency oscillations, a-

plurality of electronic discharge devices for generating low frequency oscillations, means for modulating the oscillations produced by each of said last mentioned devices in accordance with respectively different signals, a space current circuit for saidfirst mentioned device, inductive means for impressingthe oscillations generated by said plurality of devices upon said space current circuit, and a common source of space current for all of said discharge devices.

6. In a signaling system, a source of space current, a pair of electronic discharge devices, and an impedance device substantially opaque to variations of all frequencies within the range of audible sound waves, said discharge devices being in circuit with said source and with said impedance device, an impedance device" opaque to intermediate frequencies, one of said discharge devices being also in'series with said device opaque to intermediate frequencies, an impedance device opaque to high frequencies, and a third electronic discharge device in'series with said source and said device opaque to high-frequencies.

' 7 In a signaling system, an electronic dis- I cillations generated by said first-mentioned device, and means for preventing the transmission of oscillations generated by said second-mentioned device.

8. In combination, a source of current, a

.plurality of groups of space discharge devices supplied thereby, each group comprising a plurality of devices having separate input circuits, and means for maintaining 0on stant the current of each group independently of variations in current to the other group.

9. In a signaling system, a space discharge device having plate, grid, and filament electrodes, circuit arrangements whereby said device functions to produce carrier oscillations, circuit arrangements whereby said device functions to modulate said oscillations in accordance with lower frequency oscillations, and circuit arrangements whereby said device functions to modulate other oscillations in accordance with the produced modulated oscillations.

In witness whereof, I hereunto subscribe my-name this 15th day of January, A.'D.,

RAYMOND A; HEISING.

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