US1432863A - Transmission system - Google Patents

Description

K. S. JOHNSON. TRANSMISSION SYSTEM. APPLICATION FILED JULYAI. IsIe.

1,432,863. Patented 001;. 24, 1922.

F/ 7 y I 7 Y 7 i T Patented @ct. 24, 1922.

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KENNETH S. JOHNSON, OF JERSEY CITY, NEW JERSEY, ASSIGNOR T VJESTERN ELEG- TRIC GOMBANY, INCORPORATED, OF NEW YORK, N. Y., A.CORPOP,ATIN 013 NEW YORK.

Application filed July 1,

To all whom it may concern.

Be it known that I, KENNETH S. Jonnsoiv', a citizen of the United States, residing at Jersey City, in the county of Hudson, State of New Jersey, have invented certain-new and useful Improvements in Transmission Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to transmission systems, more particularly it relates to means for improving the quality oftransmission from an incoming line to a vacuum tube repeater.

It is wellknown inthe art of telephony, that the proper functioning of a transmission system depends, to a great'extent, on the relative proportioning of the electrical impe'dances of the component elements of the system. Thus it has been found that the voltage impressed by a transformer from an incoming line on a repeater varies considerably with the frequency, thereby impairing the quality. In accordance with this invention, it has been found that the quality of transmission in'such a circuit may be considerably improved .by shunting an impedance across theinputside of the trans former. On a one-way repeater circuit the value of the impedance may be varied between considerable limits, although in general, a resistance of the orderv of the effective resistance of the line has been found quite satisfactory. In two-way repeater circuits where accurate balancing between the lines and the artificial networks is required, the value of the impedance across the input side of the transformers should be equal to onehalf the impedance of the incoming line. That this value should hold for two way repeater circuits will be apparent from the detailed description of this invention.

Previous to this invention it has been known that the quality of transmission could be improved by connectingzacross the terminails of the secondary winding of the input transformer a resistance equal to the value of the effective resistance of the line multiplied by the square of the ratio of turns of the transformer, but such an arrangement necessitates the use of a very high and more costly resistance compared with that employed in this invention. For good repeater operation, it is also preferable to have as little apparatus as possible associated with the input circuit of a repeater, because of TRANSMISSION SYSTEM.

1918. Serial No. 242,797.

less liability for cross-talk between neighboring repeater circuits. Experiment has furthermore shown that a greater amplification may be obtained from a repeater having the resistance across the input side rather than the output side of the transformer.

This invention will be better understood by reference to the detailed description of the drawings, in which Figure 1 shows this invention in connection'withan incoming line inductively associated with a vacuum tube repeater for one-way operation, while Figure 2 shows this invention in connection with a two-way repeater circuit.

Referring to the drawing, 3 is an incoming line which terminates in the primary winding 4 of a transformer 5, the secondary 6 of which is connected betweenthe grid 7 and cathode S of a vacuum tube repeater 9. Signals impressed upon the input circuit of the tube 9 by the line '3 are therefore reproduced in amplified form in the output circuitof the tube and the amplified signals may be impressed upon an outgoingline 10 by a transformer 11.

In order to prevent the voltage impressed by the transformer 5 on the amplifier 9 from varying with the frequency, it is desirable to insert a resistance 12 in shunt to the primary winding. From a quality standpoint the smaller the value of this resistance the better the quality, but it is apparent that making the resistance very small would improve the quality only at considerable expense to the transmission efficiency of the system.

' In general it will be found that for transmission lines a value of the resistance 12 of the order of the effective resistance of the incoming'line will be quite satisfactory.

In Figure 2, 15 is a vacuum tube for repeating signals from the line 16 to-the line 17 while 18 is a vacuum tube for repeating signals in the opposite direction. 19 is an artificial network for simulating the impedance of the line 16 and should have an impedance equal to the impedance of the line.

Similarly the network 20 should simulate the impedance of the line 17. In accordance with this invention the fiiinpedance of the circuit at the point 23 should be the same looking in either dircction, and since the incoming circuit for the transformer comprises in parallel the line 16 and the artificial line 19, the effective resistance at the terminals 23- look ing in the direction of the incoming circuit is one-half the elfective resistance of the line 16-. The value of the resistance 26 should then be equal to one-half the resistance of the line 16. Similarly, resistance 28 across the primary winding 29' should equal one-half the effective resistance of line 17 With' such- Values for resistances 26 and 28,.

the balance conditions necessary for no local circulation of power in the repeater station are obtained.

The resistances 26 and 28 will in some cases provide a sufficiently accurate simulation of the impedance of lines 16 and 17. In case that these lines have an appreciable amount of reactance as well as resistance, the reactance component of the impedance may be simulated by reactances such as condensers 30 and 3-1 in shunt'to the resistances 26 and 28 respectively. The circuit or mesh provided by resistance 26 and condenser 30, andby resistance 28 and condenser 31 iscommonly called a network or artificialline.

Although this invention has been described above in connection withcircuits employing, vacuum. tube repeaters, it is evi e dent that it is'also applicable tocircuits in which other types of. repeaters such as mechanical re eaters are employed.

It is obvlous that the principles above setforth maybe embodied i systems widely different from that described herein without departing. from the spirit of the inventionv as defined. in the appended claims.

What is claimed is: v

1.. In combination, an incoming line, a translating device a transformer-having aprimary winding connectedwith said line, and a secondary winding connected with. said. device, andanimpedanceconnected to the primary .side of said transformer and havi-n an impedance closely approximating thee ective impedance of said line.

2. In combination, an incoming line, a; transformer having, its primary winding connected with said line, a repeater forsaid line connected with the secondary winding of said transformer, and a resistanceelement connected in shun-t to the terminalsotfi said primary winding for improving the" quality of transmission from. said line to said repeater, said element having a resistance closely approximating the; resistance of. said incoming line.

3; The combinationwith-an incoming cir cuit,-of a transformer having its primary my name this connected to said line, a vacuum tube associated with the secondary winding of said transformer, and a resistance connected across the terminals of said primary, said resistance having avalue closely approximating the resistance of said circuit.

4. A two-way repeater circuit comprising .an actual line, an artificial line and a circuit connected between said lines comprising a transformer, an artificial line con nected at the primary 0t said transformer, and arepeater connected to the secondary of said transformer.

5-. A two-way repeating. systemv comp-rising. anv incoming. line, an outgoing line, a

6. A two-way repeater circuit comprising two lines, avacuum tube for repeating signals from one of said linesto the other of said lines, a second vacuum tube for repeating in the opposite direction, a transformer connecting the input of each of saidrepeaters with one of said lines, and an artificial network. in shunt to the primary of each of said transformers.

7. In combination, an incoming line, a translating device, a transformer having a primary winding connected with said line and asecondary winding connected with said device, and an impedance inshunt to said primary winding, said impedance having such a value that the impedance between the points across said line adjacent said impedance, looking inthe direction of said 1111- pcdance and said transformer, closely approximates the impedancelooklng from said points in the direction of said incoming line.

.8. A two-way repeating system comprising two line sections, a balancing network for each of said line sections, a uni-directional path for repeating, in one direction between said lines, a second uni-directional path for repeating inthe opposite direction between said lines, each of said paths comprising a vacuum tube amplifier, a trans-.

former for coupling said amplifier to one of said lines, anda' resistance element'in shunt to the primary winding of said transformer for causing the voltage impressed onthe amplifier to be substantially constant over a wide rangeof frequencies, said resistance. having a value closely approximat ing the resistance of one of said lines and itsbalancing network connected in parallel.

In witness whereof, I hereunto subscribe 24th of June A'. 1)., 1918. KENN TH s; JOHNSON.

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