March 15, 1932. T_ D, DUTTQN 1,849,141 TRANSMISSION REGULATOR SYSTEM Filed March 11, 1930

"1 J.

BY §_ ATTORNEY Patented Mar. 15, 1932 0' f 11,849,141‘

‘ UNITED "STA/res 'PATENTYOFFICE‘ “ 'rnoivms nnur'roiv, or CHEVY CHASE Gnmmns, MARYLAND, 'ASSIGNOR 'ro 'mnnIoAN :. TELEPHONE AND TELEGRAPH COMPANY, A oonromvrroiv or new YORK ’ "mmsmssm 313G111, ATO'R .VSY-STEM Application ?led Marcli- 11,’ 1930. Serial No. 435,000.‘ This invention relates to signaling systems temperature causes an increase in the‘ trans- . and particularly to those employing repeat-' mission loss and, conversely, a- decrease in - ' ers to adjust the magnitude of transmitted temperature. causes - a’ decrease in the trans signals. More‘ particularly, this invention mission loss. . I > _ The pilot W1 isiconnected: in series .' 55 5 relates to arrangements for automatically adjusting the gain of a repeater in‘ order to circuit whichincludes a B1 anda re compensate for variations in the transmission sistance R1. vIt will be‘ apparent that‘ as the equivalent of one or more conductors form temperature of the pilot wire increases, its _ ing a circuit when the temperature of. these resistance increases and, consequently,'the flow of current from battery 131 through the‘ 10v conductors changes under varying ‘atmos pheric conditions. resistance Rlwill decrease. Conversely, a In’ ‘signaling systems employing cable cir decrease 1n temperature wlllcause a greater cuits for the transmission ofenergy in whic h ?ow of current from battery B1? through the ampli?ers are located at repeater points for resistance R1. . ' A designated Vl includes three? 65' 15 increasing the level of the transmitted energy so as to overcome the attenuation of the con , a- grid 91, a plate elec- ~ ductors, it has been determined that variable trode p1 and a ?lament electrode f1. , The grid temperature is an important factor in~chang~ electrode is connected to the filament electrode ing the effective attenuation ‘of the‘ circuit. through the resistance Rlf anda battery-1B2. '20 At high temperatures, the attenuation ‘is A battery B3 is connected across the ?lament quite large and, conversely, it is low at low electrode 7‘, and one side'of: this battery is temperatures. A pilot wire is often‘ set aside. grounded. The plate ‘electrode 101, and the ' in a cable andthis wire forms a. circuit which ?lament electrode _/"1 are: connected ina'cir is connected to a repeater so that the gain of -.cuit1 which includes, in addition to theseele 25' therepeater may be changed in accordance ments, a battery B4, ‘a resistance R2,;a- battery“ 75 with variations in the temperature of the. B5 and ground. The resistanceRz is shunted . pilot wire. It is the purpose of they arrange by a condenser G.’ ‘ ‘ ' ' - ' ' ment to increase the gain of the repeater when 1. The‘ reference character .Vg designates a the resistance changes by virtue of‘ an in vacuum tube which includes four elements,‘ I30, crease in temperature and to decrease its gain . a plate electrode p2, a ?lament electrode 7%, 80 a grid electrode 92 and a. screen gridv elec- . with a decrease in temperature. 7 , _ .. - It is an obj ectofthis invention to provide trodes. The grid electrode 92 is connected a pilot wire-regulating system intended for to‘the' ?lament electrode f2 through a wind use with the repeaters of signaling systems to ing'L; and a battery B6, this battery being -35 automatically adjust the gain of each repeater . employediior biasing the .grid electrode 92‘ ‘so as to take care of temperature ‘changes at a suitable negative potential with ‘respect which bring about variations in the transmis to the. ?lament electrode f2. The plate elec sion equivalent of the conductors forming ‘trode p2 is connected to the ?lamentielectrode ' ' the signaling circuit. This obj ect may becar f2 through a winding L2and a battery B-,,'the ‘ 40 ried out with the‘ apparatus‘ shown in the battery l37 providing a suitable positive po-' ‘90 drawing, details of which willnow be de tential for the plate electrode 102. The ?la- I ment f2 is connected to a battery B8, one ter scribed.Referring , to the drawing,p the- reference -minal of which is grounded. The screen grid character W1 designates two’ conductors electrode 8 is connected to the negativepter '45 forming a cable pair or circuit. Such a pair minal‘ of battery Bé through a'choke coil K1. or'circuit is known as a “pilotwire”. It may This screen grid electrode may be maintained be saidof this pilot wire, aswell as otieach of at a positive potential and the magnitude of the other conductors of the cable, that its re this positive potential may be ‘changed in " sista-nce changes in‘ accordancelwith temper order to correspondingly vary the. gain of the 50.. attire.’ It is well- lmown 'that‘an increaseiin .vacuum; tube V2. i V .The- mannerin which: the"? 100’ I 2 1,849,141 gain of the vacuum tube may be controlled through the resistance R2 which is in the will be described in greater detail herein plate circuit of the vacuum tube V1 changes after. in accordance with the temperature of the A winding L3 is connected to a source of pilot wire “71. An increase in temperature signals El and the signals that reach the brings about a decrease in the current ?owing 70 winding L3 may be of the voice frequency through resistance R2 and a decrease in tem type or carrier current modulations corre perature produces an increase in the ?ow sponding to voice frequency signals or of of current through resistance R2. any other type. , Windings L1 and ‘L3 are in The screen grid electrode 8 of the vacuum 10 ductively related to each other and the wind tube V2 is'connectedin series with choke coil 75 ing L1 transmits the currents impressed upon K1, resistance R2, battery B5 and ground. the winding L3 through the circuits associ The battery B5 and the magnitude of the cur ated with the vacuum tube V2 to a winding rent ?owing through the resistance R2 deter L4. The winding L4 is inductively related to mine the effective potential of the screen grid winding L2 and, moreover, it transmits the electrode 8. When the current flowing 80 signals ampli?ed by the vacuum tube V2 to through resistance R2 increases as a result of an output circuit E2. ' ' a decrease in the temperature of the pilot wire The degree of ampli?cation of the vacuum W1, the potential difference established by re tube V2 is determined by the relative poten sistance R2 will be increased and the poten .20 tial of its screen grid electrode 8. As the tial of the screen grid electrode 8 will be. 85 positive potential of the screen grid electrode dropped below its normal value. Similarly,a increases, the ampli?cation of the vacuum decrease inthe ?ow of current through re tube will increase and upon a decrease in the sistance R2 as a result of an increase in the positive potential of the screen grid electrode temperature of the pilot wire W1, will in 25 8, the ampli?cation of the tube will be corre crease the positive potential of the screen grid 90 spondingly decreased. Thus, it will be appar electrode 8 above its normal value. Thus, ent that the gain in the signals transmitted 7 the gain of the repeater which includes the from the source E1 to the circuit E2 may be vacuum tube V2 will be increased when the changed by any desired amount merely by the temperature of the pilot wire increases and 30 control in the size of the potential impressed the gain will decrease as the temperature of 95 upon the screen grid electrode 8. - . the pilot wire decreases. Under normal conditions of temperature, The screen grid electrode of another vacu the ?ow of current from battery B1 through um tube V’2 is connected in series with the resistance R1 will produce a potential dif resistance R2, battery B5 and ground. The 35 ference across resistance R1 which opposes gain of the repeater which includes this vac; 100 the voltage established by the battery B2. uum tube will be effected by temperature Under normal conditions, the voltage of the changes of the pilot wire W1 in the same man battery B2 is greater than the potential di?er ner'as the repeater which includes the vacu ence across the resistance R1 and the differ um tube V2 is effected. The conductor W2 40 ence between these voltages determines the may extend to other repeaters or groups of‘ 105 negative potential impressed upon the grid repeaters. ' electrode 91 of the vacuum tube V1 with re The choke‘ coil connected in series with each spect to the ?lament electrode f1 of that tube. screen grid electrode is employed to prevent The vacuum tube V1 is operated on the alternating currents from being impressed 45 straight line portion of its plate current-grid upon these electrodes. These choke coils 110 voltage characteristic curve in order that any together with the condenser C substantially change in the effective potential of grid elec eliminate crosstalk between repeaters.‘ trode 91 will cause a corresponding change in The repeater'regulating system employed the between the ?lament in this invention is automatic in operation .50 electrode f1 and the plate electrode 391 of the and has. a great many advantages over those' 115 tube V1. When there is a decrease in the tem regulating systems known in the art. It perature of the pilot wire l/V1, the potential employs no relays or moving parts and, con di?'erence determined by resistance R1 will sequently, there can be no trouble due to the be increased and, therefore, the ?ow of cur sticking of contacts or due to dirty ‘or cor ,7 55 rent in the plate circuit of the tube V1, which roded contacts. The complete absence of ‘120 has been described hereinabove, will be in moving parts eliminates ‘mechanical di?icul ' creased. Similarly, an increase in tempera ties. Moreover, changes in the gain of the re ture will decrease the potential di?’erence peaters are made gradually and not step by ~ across resistance R1, correspondingly increas step. Furthermore, the cost of installation 60 ing the negative potential of the grid elec as well as the cost of maintenance will be con 125 trode 91 of the tube V1 with respect to its ?la siderably smaller than that of any repeater ment' electrode f1 and correspondingly de regulating arrangement now used in the art. creaslng the ?ow of current in the plate cir While this invention has been shown in a ‘ cuit ofthe tube V1. . certain particular arrangement merely for 65 So, it will be seen that the flow of ‘current the purpose of illustration, it will beunder-i 12d 1,849,141 stood that the general principles of this in vention may be applied to other and widely varied organizations Without departing from the spirit of the invention'and the scope of‘ the appended claims. What isclaimed is: 1. A gain control system including a ?rst ~ tube having plate, ?lament and grid elec trodes, a second tube having the same‘ elec 10 trodes as the ?rst tube and in addition a screen grid electrode, a ?rst'resistance, ?rst and second sources of direct current potential connected in series With said ?rst resistance between'the plate and ?lament electrodes of 15 the ?rst tube, the screen grid electrode of the second tube being connected to the plate elec trode of the ?rst tube through the‘ second‘ source of direct current potential, a second re sistance connected between the grid and ?la 20 ment electrodes of the ?rst tube, and a source supplying direct current potentials which. vary in accordance with temperature, the lat ter source being connected in series with said second resistance. 25 2. A gain control system including a ?rst tube having plate, ?lament and grid elec trodes, a ?rst resistance connected between the grid and ?lament electrodes of said tube, a second vacuum tube having plate, ?lament, 30 grid and screen grid electrodes, the ?lament ‘ electrodes of both tubes having a common connection, an input circuit connected be tween the grid and ?lament electrodes of said second tube, an outputcircuit connected be tween the plate ‘ and ?lament electrodes of said second tube, the screen grid electrode of the second tube being connected to the plate electrode of the ?rst tube, a second resistance, a source of potential connected in series with 40 said second resistance and the plate and ?la ment electrodes of the ?rst tube, and a pilot wire connected in series with the ?rst resist

ance. V 3. A gain control ‘system for a plurality of 45 repeaters each of which includes a tube hav ing plate, ?lament, grid and screen grid elec trodes, including a three-element tube hav ing plate, ?lament and grid electrodes, a ?rst resistance connected between the plate and 50 ?lament electrodes of said three-element tube, all of the screen grid electrodes being con nectedto the ?lament electrode of said three- 1 element tube through said ?rstresistance, a ' second resistance connected between the grid 2 55 and ?lament electrodes of said three-element ‘ tube, a pilot wire, and a source of potential connected in series with said pilot wire and said second resistance. ‘ ' V ' In testimony whereof, I have signed my 60 vname to this speci?cation this 4th‘ day of March, 1930. . THOMAS D. DUTTON.

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