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Патент USA US2109982

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March 1., 1938.
'2,109,982
H. F. WILDER
lLOCAL CORRECTION 0F CABLÉ SIGNALS n
Filed April 21, 1937
2 sheets-sheen 1
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March l, v1938.
H. F. WILDER
2,109,982
LOCAL CORRECTION OF» CABLE SIGNALS
Filed Apri1r2l, 193'?-
2 .Sheets-Sheet',` 2
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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.
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