Патент USA US2109982код для вставки
March 1., 1938. '2,109,982 H. F. WILDER lLOCAL CORRECTION 0F CABLÉ SIGNALS n Filed April 21, 1937 2 sheets-sheen 1 vvRMQ.R2DIÁ4G9@Q. „wwwAl QN* > , 3mm ` March l, v1938. H. F. WILDER 2,109,982 LOCAL CORRECTION OF» CABLE SIGNALS Filed Apri1r2l, 193'?- 2 .Sheets-Sheet',` 2 lyll jme/MM @am Planned- Mu. 1, ‘193s ~ 2,109,982' ‘ PATENT OFFICE. 2.10am ` . .’ UNITED _ STA-Tas' Loon. coanac'rIoN or CABLE sro‘mms' namur F. wilder.' aIoomI'IeIs, N-.'J., minor tn The Western Union Telegraph Company, Ney»1 York, N. Y., a corporation 'of New York Y Application AprilZl, 1937, Serial No. 138,262 '1 calms. -(cI. 11s-70) '.l'his invention relates to ocean cable telegraph the yduplex bridge and to the shaping networks ` systems andl pertains particularly to-circuit ar- - in the manner shown in my prior application Serial No._90,804,.filed July 15, 1936 and are well understood by engineers. The manner of deter 5 rection circuit -the low frequency components of ' mining the characteristics _oi the cable and the 5 _ , rangements for restoring -the signal waves to their _' -4 proper shape by supplying through a local' cor -ïjlthe telegraph signals which are suppressed in .-,ñlters and ampliilers of the primary receiving _ Eequipment. _ ~ ' proportions' of the shaping and amplifying-ele ments vat the terminal are set forth in said prior application. . , .,It is well knownthat'telegraph signals are at 1_0A tenuatedand distortedin their passage through „ a'cable. due to the resistance, capacity' land in-- ductance of the cable. In recent years the ef-, fect of the capacity ofY the cable conductor to f the sheath and the'earth in attenuating the l5 higher frequency components to a greater ex tent than the lower frequencies has been greatly reduced by continuously “loading" the conduc tor with a materiall which increases the inductive reactance of the line. `The higher frequencies 20 from approximately twice the frequency `of vthe signal reversals to infinity are entirely dissipated ‘ ' » Y . In order to electrically separate the cable from the amplifier and its-associated circuits and also 10 to suppress low frequency interference or induc tion, the amplifier is coupled tothe shaping net- . works by a transformer illi. To suppress high frequency induction and interference due to nat ural potential difierences‘between the terminals l5 l of the cable and from mis-matching oi the ca ble and artificial line impedances- under duplex conditions. as pointed out in said application, a low pass network is introduced between the shap ing networks. These same sources may produce v20' interference at frequencies well below the sig in transmission, but the signal is nevertheless ` nal frequency. although the natural potentials quite suitable for the control of retransmitting or printing equipment. It is necessary, however, ~25 to pass the signals through shaping. networks and. amplifiers before they enter the receiving apparatus. Due 'to the loss oi’ low frequency are usually predominant. _ The introduction of a transformer distorts the signals by suppressing their lower frequency sig-- 25 nal components. During a magnetic storm or a period _in which the earth‘s magnetic fieldv components in the shaping networks and the am plitler, the signal waves aredistorted or are not shifts or changes in magnitude perpendicular to ' »_quency becomes sufficiently low. the current Y minal. upon which thew signals are superposed, ‘ the axis of the-cable. an E. M. F. of a relatively »30 sustained in amplitude and if the signal fre- ' low frequency will appear at the `receiving Vter- 30. -through the receiving impedance may approach thereby causing' the latter to deviate from their \zeroî`and` the entire generated E. _M. F. -will be'-y vs_o-called-zero position. These 'adverse frequen come stored on the‘capacity. 35 _ 'I‘he object of my inventionis to restore the ` signal waves to their normal undlstorted condi cies oi a‘¿ low order' may be' effectively sup pressed or` prevented from entering the receiving 35 apparatus by the interposition of a condenser or,a properly adjusted high pass’filter. The1at-' tenaiso suppresses' low frequency components in Ythe signal waves, _so that the longer signal pulses tion without the presence of low frequencydis~ turbance by returning to the signal wavesl an E. M. F. of the proper shape having frequency com 40, ponents equal in magnitude but opposite in vphase are not sustainedgin amplitude and fall to zero, 40 tothose components suppressed by the local ca- , with consequent distortion and susceptibility to .interferencexas the E. M. F. declines to zero. I . " _ pacitance. In the following' descrIpumi of my Invenn'an Il f It becomes’necessary. therefore. to locally `re shall refer to the accompanying drawings, in store the missing low frequency components thus Y suppressedf- in order to 'reform-the signal to its 45 Figures 1, -2, 3 and- 4' are diagrams illustrating original condition. r,The o_bJectïot my invention , ^ conventionally ;the_ - circuit> _arrangements vof.> is‘to provide _in_ieans embodying thermionic vac equipment embodying my invention which may ' uum tubes _for thus 'locally restoring -these -miss- f ` .45 Ivhich-4 , , be employed at the receiving end oi' a~cable. .ing components to- the receiving equipment. « For the> purposeV of explaining my method of 50 60 Figure 5 illustrates the' graphs of voltages devel oped by'rthe signal waves and the voltages de-l restoring ‘the missing components by local `cor rection. I will- refer to the circuit ,arrangement`~ veloped in the local correction ‘circuits and‘show 1 ing the' .manner of combining, these voltagesdto - produce a perfect signal wave for retransmission. 55 The receiving end of the cable is connected to of Fig. 1,v and >the explanatory diagrams of Fig. 5.v A two-'stage vacuum tube signal-'shaping tele graph amplifier shown. , The ampliñer is con- 65 - 2 3,109,982 nected to the shaping network and cable by means of the transformer I0. A resistance capacitive pressed in the primary receiving equipment are restored to the signal waves, with particular ref coupling having a relatively high time constant. , erence to the circuit arrangement of Fig. 1. The operation of the other modifications shown in A in the order of twenty seconds, is employed be tween the stages of the amplifier. By means of Figs. 2, 3 and 4 will be obvious without further detailed description. « an extra biasing winding I2“, on the retransmit ting relay I2, the D. C. component of the plate _ Certain types of four-elementv high mutual current of the vacuum tube 2, is neutralized, to conductance vacuum tubes, the UX48 for exam allow the relay to be freely operable by the sig ple, oii'er the desirable possibility of very efiicient 10 nal A. C. component. Assuming that a negative signal pulse modu lates the grid oi' vacuum tube I., the plate cur and powerful operation of a magnetic relay when rent Im will be decreased, thereby causing point a to become more positive, since the battery B1 is 15 opposed by a smaller IR drop in resistance Rx.. The consequent positive charging current into condenser Ca and to ground through resistance Ri will raise the potential ofthe grid ofvacuum tube 2, causing a positive pulse of current to flow 20 through the operating coil of relay I2. ' ` The signal voltage wave developed across the resistance R1 is of the form shown at Fig. 5-a. Resistances Rz and Ra are made equal and con ' stitute a potentiometer, dividing the signal volt 25 age approximately in half. The signal voltage developed between the points g and b’ is thus l ' shown at Fig. 5-b. The operation of the arma. ture of relay I2 applies a voltage from battery »to the input terminals of the local correction net 30 work. Ultimately this potential, assumed to be the coils of the latter are connected as in the push-pull output circuit of Flgure.2. The local correction current is supplied by modulating the grids of the tubes by means of the symmetrical grid circuit and low pass filter. - In cables of less attenuation anl amplifier hav ing tubes of the type above mentioned in push pull arrangement, may be, employed and con nected as indicated in Fig. 3. In this case a transformer Il is introduced between the local correction network and the potentiometer grid bridge circuit. This arrangement also permits the station generator I0 to be utilized as a sup ply both for the push-pull tube circuit and for the local correction network. The transformer may also be equipped with a tertiary winding forthe purpose of introducing an opposing oscilla tory voltage to compensate for undershoot in the ` signal'as is sometimes desirable under conditions of severe interference ln the high frequency end ~ 7.5 volts, will appear .across the resistance Rs but of the signal spectrum. In Fig. 4, I have shown another modification the rate at which the maximum is reached is con trolled by the electrical constants of the correc loi? this invention which maybe advantageously tion network to be an inverse function of employed` under certain conditions. 'I'hus if the 35 the decay of the “tail” of the arrival ratio of transformation of the transformer is great the high internal impedance of the sec-l curve. This local- correction (abbreviated CXN) voltage developed between the points c and d is ondary may prevent the loading of the latter ' symbolically shown at Fig. 5-c. ' 'I'his local correction network voltage transient 40 will in turn develop a potential of 2.5 volts across R1, 2.5 volts across Rz and 2.5 volts across Ra and the sum of the drops across R1 and Rz is 5 volts which is,`> in the~steady state condition, exactly -equal to the maximum peak deflection of the 45 signal transient, also between‘points g and b'. The voltage transient developed between the points g and b' by the local correction network is represented at Fig. 5-d. Hence the combined effect of the signal voltage at ’point 0' with the local correction _voltage at said point g produces a resultant operating pulse which is maintained at steady state value throughout its extent, as illustrated at Fig. 5-e. , The operation of my local correction system of sa cable signals -as above described is theoretically correct. In practice it has been found helpful to shunt the resistance R; with a series capacity resistance network R4 C: to compensate for the eii'ect of the initial charging current to the con denser Cs through the tube' plate impedance Rpi and the tube load resistance Rr. in parallel. As the local correction voltage begins to appear -across R1, the effect ofthe condenser C: and the preceding tube plate circuit -is to lowerI for a brief charging interval, the eii'ective resistance between ithe points (lf-b. The shunt R4 C: is adjusted t0 .lust compensate ‘for this interval by passingV tothe 'resistance Rés an extra current component during the time that C: is being charged and thus prevents‘the voltage ratios in the signal-correc tion` mixing network from being momentarily changed from theirif-steady state ratios. I have disclosed in detail my method of apply l ing a local correction to the received cable sig' rs. nais whereby the low frequency components sup with even a resistance grid potentiometer of sev eral megohms. 'I'he secondary is split and the correction E. M. F. is introduced between the two half windings by the _transformer Il. As the primary of I4 is shunted by a low resistance, in the order of several hundred ohms, the impedance looking into the transformer I4 from the sec ondary is approximately the same for a Iratio of >transformation yof unity and the'introduction of this impedance is, therefore, negligible. In order that the low frequency correction cur rents shall pass through the correction trans former Il without distortion, the ratio of the pri mary inductance of the transformer to the re 50 sistance of the primary winding, plus the reflected' secondary load resistance, plus the resistance of the correction network shunted across the pri mary, should be kept high as possible. Ratios of L/R of 4 and 6 have been found satisfactory for the majority oi' signal circuits. A transformer so constructed is large physically but quite prac tical and is in general use in cable signaling equip ment. - In order to more completely disclose this in vention I have shown several circuit arrange ments which may be employed to suit different conditions but it will be evident to engineers that various other modifications may be made and that any combination of the circuits for amplifying 65 and correcting may be made to best suit :the power sources available, without departing from this inventionor from the scope of my claims. i. In a communication system having a receiv 70 ing terminal providedwith signal shaping and amplifying means which distort the received sig-nals by suppressing the lower frequencyv com ponents of the received signal impulses, the method ofrestoring to normal amplitude the dis 75 3, 2,109,982 torted portions’oi’ the signal impulses, which con sists in initiating the local generation of a volt age impulse by the operation of a received 4dis l`correction voltage., whereby-the repeating relay > torted signal impulse, shaping anddeveloping said generated impulse to` correspond to van inverse » _ forth in` claim 4, said correction means compris function of the decay'of-_ said- distorted imp and electrostatically controlling that' lof 'a siènar impulse bythe conjoint action jo ,sein `fs'tic‘s'which produce; voltage transients embody ng components V,corresponding to»¿_the low fre transmits undistorted signals. „_ 5. Av repeating orrelaying apparatus as set `nega. low pass -filterï network having character 5 quency components o! the received signals sup distorted ‘impulser and said generated impulse. ï ',press'ed in the shaping and amplifying means. 2. In a communication system havin'git` receiv f- Av"6.„Ifn a communication system having a receiv ing terminal provided with_ signal _shaplngï‘aridv y _ ,ing terminal provided with signal shaping and amplifying means which distort the received sig- ' amplifying means which distort the received sig ‘nals `by suppressing the lower frequency co'mg-- - nals by suppressing the lower frequency com _' ponents of the received signal impulses',v` `the ; ponents of the received signal impulses, a resist method of restoring to normal amplitud'e‘thedis-Ú s ance connected across the output of said am torted portions of the signal impulses, _which con-f plifying means, a repeating or. relaying circuit sists in locally generating a voltage -impulse, connected in shunt to said _resistance and having shaping and developing said impulse as an in ' a pair of high resistance. potentiometers,- a pair verse function4 of the decay'A of the- distorted re of thermionic vacuum tubes having anode, cath , ceived signal impulse, .and retransmitting an un j ode and- grid elements connected at mid-points distorted signal impulse under the vjoint‘elec respectively- of said potentiometers and in in trostatic control of said distorted impulse and - verter arrangement, means for' locally generating said locally generated impulse'. voltages in synchronism and phase with the... 3. In a communication system having 'a receiv received signals and embodying components cor ing~ terminal provided with _signal ‘shaping vand responding to the suppressed components ofthe amplifying means _which distort the received sig received signals, means for subjecting the grids nals by suppressing the lower frequency com of the tubes 'tothe conjoint control of the volti- ` ponents of the/received signal impulses, the meth ages of the received signals and the 'locally gen“- ‘ od of restoring to normal amplitude the distorted erated voltages and vmeans controlled by the out -portions of the signal impulses, which `consists -`putr of the tubes, for repeating signals corre 30 in initiating the local generation of voltagesby>> spending to the original undistorted signals into . the >operation of the received distorted signal> . _a recorder or transmission line. impulses', shaping said generated'voltages `in lin verse _ratio to the decay of said distorted voltages, « ’ _" '7.,In acommunication system having a recelv- ' j ing terminal provided with signal shaping and _ combining the distorted and locally generated ’ amplifying means which distort the received sig-fl voltages to produce resultant sustained voltages Vnais by vsuppressing the-lower frequency com ‘ and electrostatically applying said sustained volt ages to control the transmission I' of undistorted ponents of the received signal impulses, a 'repeat-ing or relaying arrangement connected to the output. of >said amplifying means embodying a 4. vIn a' communication system having- a rect-.fiv-l ` vtransformer and a pair of thermionic vacuum 40 ing terminal provided withsignalsliaping and ' tubes having anode, cathodeand grid elements,amplifying meanswhich distort 'the received sig '_said tubes being connected in inverter arrange signals. . ` > nals icy-suppressing the lower vfrequency com . ponents of the received signal impulses, a repeat ing or relaying apparatus embodying a circuit _ arrangement havinga thermionic vacuum tube provided with anode, cathode and grid elements, a current source, a relay for repeating or relaying signal impulses from said source to a recorder or _ transmission line, said relay having its operating ment with their grid elements connected to the lsecondary of the transformer, a source of elec- ` trical energy, a rcorrection network having char-_ acteristics whic transmit only ¿frequency corn-l ponents corresponding to said suppressed com ponents of the received signals, means for con necting said network to saidsource in synchro nism with the received signals,I means for sub 50 coil in the output of said tube, means for ¿pro - jecting >said tubes to thel conjoint control of the _ ducing a correction voltage having characteristics received signals and the output of said network, which are an inverse function of the decay of the and means'in the output of the tubes for repeat distorted received signal voltages, and means to ing signals into a recorder or transmission line@ subject the grid of said tube 'tc the conjoint- control of the received distorted'voltage -and the ' HAROLD F.` wnnna.