US1519626A - Two-way high-frequency signaling - Google Patents

Description

Dec. 16, 1924. 1,519,626

H. W. N|CHOL$ TWO'WAY HIGH FREQUENCY SIGNALING Filed Sept. 26, 1919 Arr 3 Patented Dec. 16, 1924.

UNITED STATES PATENT oFl-lca.

HAROLDW. NICHOLS, 0F MAPLEWOOD, NEW JERSEY, ASSIGNOR 'IO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A. CORPORATION OF NEW YORK.

TWO-WAY HIGH-FREQUENCY SIGNALING.

Application filed September 28, 1919. Serial No. 826,498.

To all whom it may concern:

Be it known that I, Hnnow W. N narrow, a citizen of the United States resi'dln at Maplewood, in the countyof lissex', tate of New Jersey, have invented certaln new and useful Improvements in Two-Way High-Frequency Signaling, of WhlCh the following is a full, clear, concise, and exact description.

The present invention relates to the twoway transmission of currents for signallng or other purposes, and particularly to the two-way transmission of signals by means of high frequency currents or waves.

By two-way transmission is meant, for the purpose of the present specification, transmission between two separated stations wlth substantially equal facility in each direction, so that if the signaling system be a high frequency telephone system, for 1nstance, conversation may be carried on between stations, as in the case of the ordinary wire telephone systems employing only voice frequencies.

By high frequency is meant a frequency above the limits of audibility or at least,

near the limit of audibility as distinguished from frequencies that are easily heard such as those comprised in the voice frequency range. The high frequency currents or waves herein referred to are commonly called carrier currents or waves as distinguished from the low frequency signaling currents or waves by WhlCh the carrier wave is modulated.

Two-way transmission by means of high.

frequency currents or waves has always presented a difiiculty, in that the high frequency currents or waves must be acted upon by the signal waves, such as volce waves, in the process of transmitting, and the received high frequency waves must again be acted upon in a different manner in order to render the signal currents or waves discernible. It has been the practice heretofore, to provide one set of apparatus for transmitting, including a modulator for transforming low fre uency currentsv into variations of the high frequency currents or Waves and a separate set of apparatus for receiving, including a detector, or demodulator, for transformin the high frequency variations into low requency currents to be received. It has been the practice in radio systems for two-way communication to provide switching means for associating one or the other sets of apparatus with the antennae according as the user wishes to transmit or to listen. In wiretransmission systems for signaling by high frequency, it has been customary instead of providing switches for the purpose stated, to employ a balancing circuit so that the receiver is unaffected by the local companion transmitter but is affected by the distant transmitter. In word-to-word conversation, the switching back and forth between transmitter and receiver and the line or antennae is very cumbersome and unsatisfactory. The party who is transmitting does not hear either his own or the distant partys voice in his receiver, and it is im- POSSIblG for the receiving party to interrupt the transmission for any purpose such as to have a word repeated. The balancing circuit which is commonly used on wire lines for high frequency transmission has the disadvantage of not permitting the transmitting party to-hear his voice in his own receiver, which is not essential, but is convenient as an indication that the transmitter is working properly. Practical tests have shown that the balancing circuit for twowa signaling, such as is used on lines, is di cult to adapt to radio transmission, and the method of switching with its inherent disadvantalges has been quite generally adopted. 11 addition to the objections just pointed out, the necessity of providing a set of transmitting apparatus and a separate set of receiving apparatus adds to the expense anddbulk of the two-way systems heretofore use An object of the present invention is to dispense with switching arrangements and balancing circuits in a two-way high fre quency signaling system and to employ a single set of apparatus for both transmitting and receiving.

A feature of the invention is the use of the same discharge device in a novel manner for both transmitting and receiving.

A further feature of the invention is the use of a discharge device as a three-element device for amplifying or modulating and as a two-element device for detecting.

A still further feature of the invention is the use of a discharge device for partially detecting the signal being transmitted so that it may be heard in the-local receiver, and for detecting the signal being received so that it may be heard in the same receiver.

Other features of the invention will appear from the following description of the embodiment of the invention which is illustrated in the drawings, in which Figs. 1and 2 illustrate applications of the invention to a radio telephone system. Fig. 3 illustrates the invention as a lied to a carrier current transmission line, 1g. 4.- illustrates a slightly diflerent circuit arrangement and Fig. 5 discloses a modification which may be emloyed in any of the systems of the other gures.

Telephone systems are illustrated and below described, not because the invention is limited to telephony but because telephony is the more highly developed type of signaling, and in view of prior art, it will be obvious how to substitute, in the systems herein described, a source of high frequency waves controlled in accordance with telegraph or other signals or for other purposes in the place of the source of high frequency waves modulated in accordance with the voice.

In Fig. 1, speech-modulated radio frequency waves from the modulator M are impressed upon the antenna 1 through the amplifier A as is the usual practice. The modulator M, which may be of any suitable type, is shown as a single thermionic tube having its input circuit supplied with radio frequency waves from the generator, diagrammatically indicated at 2. This generator may as a thermionic oscillator, an arc generator or other source for furnishing a continuous wave of radio frequency, and is shown coupled to the modulator input at 3. Also coupled to the input of the modulator M is a circuit containing the microphone 4 and battery 5. When speech is directed against the microphone 4, potential variations corresponding to the voice vibrations are produced in the input circuit of the modulator M, and by the well-known action of the modulator, these currents produce corresponding variations in the amplitude of the wave from source 2, that is transmitted by the modulator. The modulated radio frequency wave is amplified at A and is impressed upon the transmitting antenna 1. The amplifier A is of the well-known thermionic type but its output circuit in addition to being coupled to the transmitting antenna 1, contains a receiver 6 preferably in series with the source 7 of the space current. Receiver 6 is an audible-frequency receiver and is preferably shunted by a'condenser 8 to by-pass the high frequency current. As

shown, the condenser shunts both the receiver 6 and the battery 7. It is an experimental fact that with the voltages of space be of any suitable type such' current battery 7 and grid battery 9 suitably adjusted, the low frequency component of the modulated high frequency wave is heard in receiver 6. In the circuit, as shown,

for instance, speech directed against the microphone 4 is heard in receiver 6 due probably to a certain rectifying or detecting property of the amplifier A. Incoming signal modulated waves intercepted by the antenna 1, produce corresponding voltage variations which are superimposed on the circuit of amplifier A, including the filament 10 and the anode or plate 11, and generally termed the output circuit. The amplifier A then acts similarly to a two-electrode detector enabling the audio frequency modulation component to be heard in receiver 6. The radio-frequency wave from source 2, although a certain amount of it is being transmitted through the amplifier A to the antenna 1 continuously, as explained, has no effect upon the receiver 6, so long as it. is unmodulated, and its presence in the out-- put circuit of amplifier A does not interfere with the reception of incoming signals from antenna 1 by means of receiver 6, as de' scribed. The operator therefore, in talking into transmitter 1 hears his own voice at receiver 6, although receiver 6 is in position to receive signals from the distant station without the necessity of operating any switching device or the like.

WVith the circuit arrangement as shown in Fig. 1 there is a possibility of some of the voice frequency currents from the microphone circuit being transmitted directly as voice frequency currents through the modulator M and amplifier A to the receiver 6, instead of being entirely represented as high frequency modulations. This might tend to make the signals heard in the receiver unduly loud during the time that speech is being transmitted, or might confuse the sig nal that is heard in the receiver6 under these circumstances. To prevent the passage of currents of voice frequency, the cir' cuit of Fig. 2 may be employed, in which the numeral 12 indicates most of the circuit of the oscillator and modulator of Fig. 1, as will be clear from a comparison of the two figures. Between the modulator and the amplifier A there is inserted a high-pass filter 13, designed (preferably in the manner described in the U. S. patent to G. A. Campbell No. 1,227,113, granted May 22, 1917) to suppress practically completely all currents of the voice frequency range but to transmit freely to the amplifier A the modulated radio frequency currents. Voice currents, due to speech directed against the microphone 4:, will still be heard in the receiver 6, however, due to the detecting action of the amplifier A.

In Fig. 3, a simple two-way two-station, high frequency carrier telephone system for a wire line is indicated. The line 15 may be multiplexed for any desired number of independent conversations by applying other high frequency sets similar to those shown, but the system will be understood from considering merel two such stations, S and S which may assumed to be arranged for inter-communication. However, taps 20 and 21 are shown to indicate that other-stations may be connected to the line 15 as may be desired. The microphone 4, modulator M, amplifier A and receiver 6 may be the same as those already described. The nerator 2 of this fi are preferably has a requency of several t ousand cycles, but is preferably not of such frequency as would ordinarily be em loyed for radio transmission. The ampli er A is coupled by means of coils 17 to the line branch 18, which includes band filter 19 of the type described in the Campbell patent above referred to, capable of transmitting only a limited range of frequencies. If only the two stations S and S are present on line 15, no filter 19 is necessary but if the line is multiplexed for independent conversations there will be a plurality of high frequencies set apart for the different communication channels as is well understood by those skilled in the art, and it is necessary to connect each stat-ion to the line through a filter such as 19 which will pass only the frequencies intended for that station. It should be noted that no balancing circuits are needed for the high frequency line 15 in the present system and that one filter 19 serves to transmit all the frequencies with which station S is concerned, in

both directions between the line 15 and station S The same is, of course, true of the filter at station S,., which filter is in every respect similar to that at statlon S The operation of the system of Fig. 3 is similar to that described in connection with Fig. 1. Modulated high frequency currents from the modulator M are amplified at A and impressed on the line 15. During this transmission of the modulated high-frequency current, voice current or the other signal current that may be employed to modulate the high frequency current, appears as detected current at the receiver 6 and may be heard. The modulated current is also impressed on line 15, is selectively received through filter 19 at station S and produces detected signal indications in the receiver 6 at that station. In the same manner speech or other signals are transmitted from station S to station" 8,, the apparatus diagrammatically indicated at station S being entirely similar to that shown more in detail at station S,. It is understood that a filter such as 13 may be inserted at the corresponding point in the circuit of Fig. 3 for the same purpose that is explained in Fig. 2. It may be noted, however, that less attention need be. iven to reducing the loud- I:

ness of the 'soun in receiver 6 in the s stem of Fig. 3 during the transmission than in the case of the system of Fig. 1, since the ratio between the energy transmitted and that received is much smaller in a wire transmission s stem than in a radio system.

In ig. 4 the speech modulated carrier wave is impressed upon the transmission circuit without the intervention of amplifier A, as shown in the preceding res, between the modulator M and tIIHlSIlLlSSlOIl circuit.

Referring now to Fig. 5, there is shown the amplifier A such as might be employed in any of the circuits that have been described. Instead of the receiver 6 being inserted directly in the circuit of the battery 7, however, the primary of a transformer 22, suitable for speech frequencies, is inserted at the point occupied byreceiver 6 in the other figures, and the secondary of the transformer 22 is connected to an amplifier 23 in the output of which the receiver 6 is placed. The action as regards amplifier A 1s the same as that hereinbefore described, but by the use of the amplifier 23, as is obvious,.stronger signals are obtained in the receiver 6.

In cases where it may not be necessary to use the amplifier A for increasing the ener of the transmitted wave, the receiver 6 or t e transformer 22 of Fi 5 may be inserted in 'the output circuit of the modulator M as derstood that the invention is not limited to the particular arrangements that have been illustrated and described for the pur-' pose of disclosing the features and ob'ects of the invention but only by the scope o the appended claims.

What is claimed is:

1. In a two-way signaling system, a threeelectrode discharge device for both transmitting and receiving signals, a. circuit connected between one electrode and a second electrode of said device for controlling the device as a. three-electrode device in transmitting and a circuit connected between said first-mentioned electrode and a third electrode of said device for controlling said device exclusive of said first mentioned electrode as a two-electrode device in receiving.

2. In a two-way signalin circuit, a discharge device having a cat ode, an anode and an impedance controlling element, for

both transmitting and receiving signals, circuits for impressing energy upon said cathode and impedance controlling element for transmitting, and upon said cathode and anode exclusively of said impedance controlling element for receiving, and a receiver associated with said cathode and anode.

A discharge device having an input circuit and an output circuit, a source of sending Waves connected to said input circuit,

a circuit for received waves connected tosaid output circuit, and a receiver. connected to said output circuit and actuated by the energy of said received Waves.

4. In a two-way signaling circuit, a discharge device having a cathode and an anode and a control element, a source of signalin waves for transmission associated with said cathode and control element, a two-way signal-transmission circuit associated with said cathode and anode, and a receiver associated with said cathode and anode for separately and independently responding to waves transmitted from said source and Waves received from said transmission circuit.

5. A discharge device having a circuit including a discharge'space, a control circuit for influencing the impedance of said discharge space, and a source of transmitting signal waves associated with said control circuit, a circuit for impressing received signal waves upon said first mentioned circuit exclusively of said control circuit, and a receiver-associated with said first mentioned circuit.

6. In a two-Way signaling circuit, a discharge device having an input circuit and an output circuit including a space current source, a signal transmission circuit associated with said device, means associated with said input circuit for controlling the current in said output circuit for transmitting signals, and means associated with said transmission circuit for controlling the current in said output circuit exclusively of said input circuit for receiving signals.

7. In a two-way signaling system, a discharge device having input and output circuits, a. circuit for operating on said input circuit to control transmission of signals, and a circuit for operating on said output circuit exclusively of said input circuit to control reception of signals.

8. In a two-way signaling system, a discharge device having input and output circuits, a circuit for-operating on said input circuit to control transmission of signals, a circuit for operating only on said output circuit to control reception of signals, and a receiver connected Withsaid output circuit.

9. In a two-way signaling system, a transmission circuit, a discharge device having an input circuit and an output circuit, a

transmitter and a receiver associated with saiddevice, means for transmitting signals I 10. In a two-way signaling system, a dis" charge device having input and output circuits, a circuit for impressing modulated high frequency currents upon said, input circuit, a circuit for impressing modulated iigh frequency-currents upon said output circuit, and a low frequency receiver associated with said output circuit for receiving a modulation com onent of either of said modulated high requency currents independently of the other. a

11. A discharge device having a control circuit and a power .circuit, a source of variable currents associated with said control circuit for controlling said power, circuit to transmit variable currents, a circuit for impressing other variable currents upon said power circuit, and a receiver connected to said power circuit for responding to the detecting action of said discharge device upon bothof said kinds of currents, respectively.

12. A discharge device having a circuit including a discharge space and an element for controlling said circuit by modifying a characteristic of said discharge space, a receiver associated with said circuit, a source of variable currents associated wth said derice for acting upon said elementfito 'a-tfect said receiverby controlling said circuit, and a source of currents for acting upon said circuit to affect said receiver through the medium of said discharge space exclusive of said element.

13. A discharge device, a circuit including elements of said device and a signal indicator, a control circuit including another element of said device for controlling said circuit including said indicator, a source of waves associated wit-h said control circuit for controlling said first mentioned circuit to affect said indicator; and a circuit for reacting upon said first mentioned circuit to control said indicator through the medium of said discharge device.

l4. A source of outgoing variable highfrequency waves, a source of incoming variable high-frequency waves, a receiver for waves from both sources, a discharge device for modifying said variable high frequency waves to render them capable of'afi'ectiug said receiver, circuits operatively associated with both of said sources, said device having an electrode included in both of said circuits, and an electrode respectively connected to each of said circuits whereby said device is controlled to affect said receiver in accordance with the transmitted and the received waves, respectively.

15. A discharge device having a source for giving off electrons, an anode and a control element, a control circuit including said source of electrons and said control element, an anode circuit including said source of electrons and said anode, a receiver asso; ciated with said anode circuit, means for affecting said receiver comprising a source of waves for acting upon said control circuit, and other means for controlling said receiver comprising a source of waves for acting upon said anode circuit independently of said first mentioned source of waves.

16. A discharge device for transmitting and receiving high frequency waves modulated by signal currents having a cathode and an anode, and a control element, a source of transmitting signal waves connected to its cathode and control element, a signaling circuit connected to .its cathode and anode. a condenser in the circuit of said cathode and anode, and a signal receiver in shunt of said condenser for receiving signal currents due to the action'of said device on the waves from said source, and for receiving other signals due to the action of said device on the waves in said signaling circuit.

17 In a two-way circuit for transmitting signals by means of high frequency currents, a l1ne connecting separated stations, means at each station for impressing modulated high frequency currents on said line and for receiving modulated high frequency currents from said line including a discharge device, a source of transmitting high frequency waves therefor, and a signal receiver in the circuit of said discharge device for indicating signals impressed on said line, and received from. said line. Y

18. A two-wlay circuit for transmitting signals by means of high frequency currents oomprlsing a line for transmitting high frequency currents, a source of high frequency currents for said line and a source of signaling currents for modifying said high. frequency currents,- a discharge device having an input circuit operatively associated with said sources and its output circuit operatively associated with said line, and a receiver for signaling currents connected to said output circuit.

19. In a two-way signaling system, a high frequency. transmission circuit, a discharge device having an output circuit operatively associated with said transmission circuit and an input circuit, means including said input circuit for transmitting high frequency currents to said output circuit, other means including said transmission circuit for trans mitting high frequency currents to said output circuit to the exclusion of said input circuit, said discharge device acting to said high frequency currents to low frequency currents, and a low frequen receiver connected to said output-circuit.

20. A signal transmission circuit for transmitting and receiving signals, a source of slgnahng currents for said circuit, a dis charge device for transmitting currents from said source to said circuit, an amplifier havmg its input circuit connected to said discharge device and having a receiver in its output circuit for registering both transmitted and received signals.

21. In a two-way signaling system, an electron discharge device hiaving a dischar spare and a cathode, an anode and a grid or impedance control element, means for utilizing the grid to control the characteristics of said discharge space to transmit signal waves, and means to control the characteristics of said discharge space solely by potentials applied to said anode and cathode for receiving signals.

22. In a two-way signaling system, a twoway transmission circuit, a one-way repeating device of the audion type associated therewith having grid and anode circuits, a

source of signaling waves for transmission (onnectcd to the grid circuit, said grid circuit and transmission circuit being associated only through the medium of said device, and a signal receiver in the anode circuit for responding to both the signals transmitted from said source and the signals received over said transmission circuit.

23. In a two-way signaling system, a twoway transmission circuit, a three-electrode discharge device having an impedance-control or grid circuit and an anode circuit a source of transmitting waves associated w1th said grid circuit, said device and circuits being arranged to transfer waves between said grid circuit and said transmission circuit only in the direction from said grid circuit to said anode circuit and a receiver connected to said anode circuit for responding both to the presence of transmitting waves in said anode circuit from said source and to waves in said anode circuit impressed from said transmission circuit.

24. In a. two-way wave signaling system, an electron discharge device having a cathode, an anode and a grid or impedancecontrol element, a grid circuit and an anode circuit, a. two-way wave-transmission circuit connected to said anode circuit, means for impressing waves on said grid.- circuit to be transmitted, said transmission circuit being arranged to impress received waves on said anode circuit exclusively of said grid circuit, and a signal receiver connected to said anode circuit for responding to transmitted and received signals.

25. In a two-way repeatin s stem, a discharge device having a ca 0 e, an anode and a grid or impedance controllin element, a receiver connected to said ano e and cathode, means for applying waves representing signals between said cathode and grid for actuating said receiver, and other means for independently applying waves representing other signals between said cathode and anode for actuating said receiver.

26. In a two-way high frequency signaling system, a three-electrode discharge device for both transmitting and receiving, means for sup lying high frequency currents modified y signal currents to control said device as athree-electrode device for transmission, means for supplying high frequency current modified by signal currents to control said device independently of said first mentioned means as a two-electrode device for reception, and a receiver for signal currents associated with said device.

27. In a two-way high frequency signaling s stem, a three-electrode discharge device or both, transmitting and receiving, an input circuit and an output circuit for said device, a source of modulated hi h frequency currents of variable amplitu e associated with said input circuit, a transmission circuit for supplying variable amplitude high frequency currents to said output circuit for operating said device as a twoelectrode device, and a receiver for low frequency currents of variable amplitude as sociated with said output circuit.

28. In a two-way high frequency signaling system, a transmission circuit, a threeelectrode discharge device for both transmitting and receiving, an input circuit and an output circuit for said device, a source of high frequency currents modified in accordance with signal currents of variable amplitude coupled to said input circuit to control said device as a three-electrode device for transmission, a source of high freuency currents modified in accordance with signal currents of varying amplitude coupled to said output circuit to control said device as a two-electrode device for reception, and a receiver for signal currents associated with said output circuit.

29. A two-way circuit for transmitting signals comprising a high frequency transsame frequency modulated in accordance with variable amplitude signal currents to said output circuit, said discharge device acting to change said carrier currents to low frequency currents and a low frequency receiver associated with said output circuit.

30.,A two-way circuit for, transmitting signals comprising a high frequency transmission circuit, a dischar e device having an output circuit associate with said transmission circuit, an input circuit therefor, means for supplying carrier currents modulated in accordance with variable amplitude signal currents to said input circult, and other means including said transmission circuit for supplying carrier currents of the same'frequency modulated in accordance with variable amplitude signal currents to said output circuit, said discharge device acting as a three-electrode discharge device for transmission and as a two-electrode discharge device for reception to change said carrier currents to low frequency currents, and a low frequency receiver connected to said output circuit.

31. A two-way circuit for-transmitting signals comprising a transmission circuit, a source of high frequency currents for said circuit and a source of signal currents for modifying said high frequency currents, a three-element discharge device having an input circuit operatively associated with said sources to be controlled thereby as a three-element device for transmitting and an output circuit associated with saidtrans mission circuit for operating said device as a two-element device for receiving, and a a receiver for signal currents connected to said output circuit. 0

In witness whereof, I hereunto subscribe my name this 25th day of September A. D., 1919.

HAROLD W. NICHOLS.

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