US1537099A - Carrier-current system - Google Patents

Description

May 12, 1925 v 3,537,099

' H. J. VENNES Y CARRIER CURRENT SYSTEM Filed Dec. 21, 1920 Patented May'l2, 1925 UNITED STATES PATENT OFFICE.

HARALD J. VENNES, OF NEW YORK, N. Y., ASSIGNOR WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

CARRIER-CURRENT SYSTEM.

Application filed December 21, 1920. Serial No. 432,816.

To all whom. it may concern:

Be it known that I, HARALD J. VENNES, a citizen of the United States, residing at New York, in the county of Bronx, State of New York, have invented certain new and useful Improvements in Carrier-Current Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to carrier current systems and more particularly to means for improving the quality of the signal supplied to a transmitting circuit.

It is a well-known fact that the frequency supplied by a vacuum tube oscillator, such as is used in carrier current systems, is to a considerable degree dependent on the impedance of the load circuit connected to the oscillator.

It is also a fact that when an alternating voltage, impressed on the input circuit of a vacuum tube device, has an amplitude suflicient to make the grid positive with re s ect to the filament, a grid current will ow 'andhence lower the input impedance of the device. Hence, when in a carrier telea h system the output of an oscillator o e s into the input of an amplifier, it is obvious that the impedance-of t ese circuits when connected to other will depend upon the amplitude of the oscillations to be impressed on the am lifier. This amplitude may be determined y using apotentiometer to interconnect theamplifier and oscillator but when the potentidmeter setting is changed the output impedance will be changed and as a result the frequency of the oscillations will be caused to vary.

Again, in such systems whonsignals are being transmitted, the sending relay connects a low impedance path across the output circuit of the oscillator with the result that a sur e will occur at the beginning and Y end of eac signal. This seems to be caused by a suddenchange of frequency at these points in the signal periods: hence, sharp si a1 efl'ects are impossible.

e primary object of'this invention is to provide means whereby sharp signal effects may be obtained.

Another object of this invention is tov provide means which will stabilize the frequency of the oscillations produced by an oscillator.

A further object is to rovide an arrangelt" ment in which the impe ance of the circuit external to the oscillator circuits will be maintained substantially constant.

These objects and others which 'will. appear as the nature of the invention is disclosed, may be accomplished by inserting a large resistance in the circuitexternal to the oscillator, so that the impedance chan es in said circuit due to the adjustment of t e potentiometer or transmission of signals will not introduce material changes in the impedance of the output circuit of the oscillator. In this manner, the tendency of impedance changes in the external circuit to react upon the oscillator and change the frequency of the oscillations produced thereby is avoided.

Different circuit arrangements embodying the invention are shown in the two res of the attached drawings, wherein F1g.,1 shows an arrangement in which the oscillator is connected to theamplifierthrough .a potentiometer and Fig. 2 shows an arrangement in which the oscillator connected to the amplifier.

Referring to Fi 1 an oscillator of the type, described by V. L. Hartley in his patent for oscillation generators, No. 1,356,763, issued October 26, 1920, isillustrated. Thi's oscillator comprises a space discharge device 1 having its grid or control electrode and its anode connected to the opposite terminals of an inductance 3, and its cathode connected to an intermediate point thereon. In shunt to this inductance 1s a variable condenser' 4 which cooperates with inductance 3 to constitute a tuned circuit adaipted to determine the frequency of the osci ations generated. By varying the inductance 3, condenser 4, or both, the he is directly quency of the oscillations may be varied.

ductance to revent short-circuiting of the oscillations t rough thesources 5 and 6.

Condensers 7 and 8, designed to impose an infinite impedance to the flow of direct current but to permit alternating current to pass without ap reciable attenuation, are in- :serted in the temating current paths of the oscillator circuits which connect the filament heating source 5 to the midpoint of .the inductance 3 and the plate source 6 to tensity of the electromotive force supplied to the grid circuit of the amplifier 10 may be regulated by adjusting the contact 11 associated with the resistance 9. Included in the circuit connecting the adjustable .contact 11 and the grid of the amplifier 10 is a resistance 12, which will-be referred to later, and associated with said circuit between the resistance 12 and the grid is a path 13 adapted to be grounded to eflect si al transmission. A condenser is inserte in this path to prevent the flow of direct current from the grounded sources therethrough, while permitting the flow of oscillations when this circuitis completed.

A key has been herein shown to control the ground path. Any other means, for

example,' a line relay controlled by a distant or local operator, may be'u'sed for this purpose.

When no signals are being transmitted, the oscillations impressed upon the grid circuit of the amplifier will cause current variations of the same frequenc in the plate current of the amplifier. This variable current is supplied to the tuned circuit constituted by the adjustable condenser 15 and the primary winding of the transformer 16,

the secondary of which may be connected either to a transmission line or the antenna of a radio system, whereby oscillations of definite frequency will be transmitted to the distant receiving station.

When it is desired to transmit a message to a remote station, the ground path 13 is closed and opened in accordance with any desired code to shunt the oscillations from the amplifier input circuit, thus suppressing the flow of variable current in its output circuit and hence the transmission of energy to the distant station.

Plate current is supplied to the output circuit of the amplifier 10 by a source 17 through a retard coil 18, which serves to prevent the flow of the oscillations through the source 17 while permitting the flow of direct current from the source through the plate circuit of the amplifier.

A blockin condenser 19 is inserted between the p ate source and the tuned circuit to prevent direct current supplied by the source 17 from reaching tuned circuit 1516, though offering substantially no impedance to the flow of alternating curing conditions stated above.

Referring to Fig. 2 the invention is shown applied to a system employing metallic or ungrounded circuits. In this gure the oscillator is of the same type as that shown in Fig. 1, but is directly connected to the amplifier 10 through the resistance 12. The signal path 13 is connected across the input circuit of the amplifier at a point between resistance 12 and the grid, and the potentiometer 911 is placed in the alternating current output circuit of the amplifier to control the amplitude of the current supplied to the transformer 16 and therethrough to the load circuit.

In the arrangement shown in both of these figures, the operation of the system is the same. Normally an alternating current .of frequency largely determined by thenatural period of the tuned circuit 2 is supplied to the load circuit. Upon completion of the signal circuit 13, the supply of alternating-current is cut off so that silent and active intervals follow one another in any desired order determined by the open- .ing and closing of the signaling circuit;

hence, signals or spaces may be represented by either silent or im ulse receiving intervals in accordance with the code decided upon.

In an arrangement. which did not include the resistance 12, .the completion of the signal path 13 caused a lowering of the impedance of the out t circuit of the oscilator, sincethe por ion, of the inductance 3 in the input circuit of the tube'l was thereby shunted through a portion of the resistance 9, in Figure 1 or short-circuited in Figure 2. When this occurred, the tuning of the oscillatory circuit was subjected to variations due to the above mentioned change in the impedance across a portion of the inductance 3 and surges occurred both upon the opening and closing of the signal path. Resistance 12, by eliminating surges, sharpened the signal periods.

Since the form of carrier current supply is immaterial from an operative viewpoint it will be apparent that any other type of oscillator or source of supply may be utilized. Again complete wire circuits may be used in the arrangement shown in Fig. 1 and. ground connections willbe equally effective in thedesign shown in Fig. 2. The circuit changes necessary in either case being evident it is believed to be unnecessary to describe them further.

While the particular form of devices utilized and circuit connections em loyed have been described inorder to clearly and completely set forth the invention, it is to -be understood, that this invention is not limited to these specific features but only by the scope of the appended claims.

What is claimed is 1., A signal system comprising a source for continuously generating a current of.

carrier frequency, said source including a tuned frequency determining circuit, a work circuit connected thereto including an amlifier, means to shunt the carrier current 2'0!!! said amplifier in accordance with signals and means to maintain substantially constant impedance conditions in said work circuit irrespective of the operation-of said shunting means.

2. A signal system comprising a source for continuously generating a current of carrier frequenc said source including a tuned frequency etermining circuit, a work circuit connected thereto including anamplifier, means to divert the carrier current from said amplifier in accordance with signals and means between said source and diverting mean's to maintain substantially constant impedance conditions" in said work circuit irrespective of the operation of said diverting means.

3. A signal system comprising a source for continuously generating a current of carrier frequency, said source including a tuned frequency determining circuit, an amplifier connected thereto, means to interrupt the flow of carrier current to said amplifier in accordance with signals and means to prevent changes in impedances external to said source from reacting upon said frequency determining circuit.

4. signal system comprising a vacuum tube oscillation generator, a load circuit connected'thereto including an amplifier, a controlled shunt path for the oscillations supplied by said generator, and reaction suppressing means included in said load circuit between said generator and the path.

5. Asignal system comprising a vaccum tube oscillation generator, 9. load "circuit connected thereto including a resistance and an amplifier, a controlled shunt circuit con nected to said load circuit adjacent'to said amplifier, and means to control said shunt circuit.

6. A signal system comprising a vacuum tube oscillation generator, a load circuit connected thereto including a resistance and an amplifier, a controlled shunt circuit connected to said load. circuit between the resist-ance'and amplifier, and means to control said shunt circuit.

7. A signal system comprising a source of carrier current, a load circuit connected thereto including an impedance and an amplifier, a ground circuit connected to said oad circuit between the impedance and amplifier, circuit.

8. A signal system comprising a source of carrier current, a circuit connected to said source including reaction suppressing means and an amplifier, and means to ground the terminal of the reaction suppressing means which is adjacent to the amplifier.

9. A signal system comprising a vacuum tube oscillation generator, a circuit connectand 'means to control the ground ed thereto including reaction suppressing.

means and an amplifier, and means to ground the terminal of the reaction suppressing means which is adjacent to the amplifier.

' 10. A signal system comprising a vacuum tube oscillation generator, a circuit connected thereto including a resistance and an amplifier, and means to ground the terminal of the resistance which is adjacent to the amplifier.

11. The combination of a generator for continuously producing a current of carrier frequency, frequency determining circuit, a transmission circuit to which oscillations are to be supplied by said generator, means for shunting said transmission circuit to control the application of oscillations thereto in accordance with signals, and means connecting said generator to said transmission circuit trans-- ant upon signaling from affecting the char- I actor of the oscillations produced by saidgenerator.

12. The combination of a generator for continuously roducing a current of carrier frequency, said generator including a tuned frequency determining circuit, a transmission circuit to which oscillations are who supplied by said generator, means for shunting said transmission circuit to control the application of oscillations thereto in accordance with Y signals, a one-way conductin circuit connecting said generator to' sai transmission circuit transferring oscillations therebetween which substantially prevents any change in the impedance of said transmission circuit attendant upon signaling from affecting the character of the oscillations produced by said generator.

13. The combination of a generator for continuously producing a current of carrier frequency, said generator including a tuned frequency determining circuit, a transmission circuit to which oscillations are to be supplied by said generator, means for shunting said transmission circuit to'control the application of oscillations thereto in accordance with signals, a circuit including a series resistance, connecting said generator to said transmission circuit transferring oscillations therebetween, said resistance having such magnitude as to substantially prevent any change in the impedance of said transmission circuit attendant upon signaling from afieco ing the character of the oscillations produced by said generator.

14. The combination of a generator for continuously producing a current of carrier frequency, said generator including a tuned frequency determining circuit. a transmission circuit to which oscillations are to be supplied by said generator, means for shunting said transmission circuit to control the application of oscillations thereto in accordance with signals, and means connecting said generator to said transmission circuit transferring oscillations therebetween which substantially prevents any change in the impedance of said transmission circuit at tendant upon signaling from changing the frequency of the oscillations produced by said generator.

15. A generator for continuously producing a current of carrier frequency, an impedance to which said generator supplies current, a load circuit, means for shunting said load circuit in accordance with signals and a circuit including a series resistance connecting said load circuit to' said impedance eleme t, said resistance having such magnitude as to efiectively prevent any tendency tashort-circuit said impedance e ement. g y

16. The combination of an oscillator, for continuously producing oscillations, which includes a tuned frequency determining circuit and an oscillating current output branch, a transmission circuit, means for connecting said output branch to said transmission circuit, and a fixed resistance adapted to substantially prevent changes in the impedance of the circuit external to said output branch from afi'ecting the character of the oscillations produced by said oscillator.

17. The combination of an oscillator, for continuously producing oscillations, which includes a tuned frequency determining circuit and an oscillating current output branch, a transmission circuit, and means for connecting said output branch to said transmission circuit including a fixed resistance adapted to substantially prevent changes in the impedance of the circuit external to said output branch from affecting the character of the oscillations produced by said oscillator.

In witness whereof, I hereunto subscribe my name this 16th day of December A. D.. 1920.

HARALD J. VENNES.

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