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Патент USA US2135609

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Nov. 8, 1938.
E. K. VAN TAssEL
l
LOADED TRANSMISSION LINE
2,135,509
-
Filed Aug. 27, 1956
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Patented Nov. 8, 1938
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>UNITED STATES
PATENTOFFICE
2,135,609
`
LOADED TRANsMissroN' LINE Í'
Earl Kenneth Van Tassel, GreatfKills‘, >N. '.Y.,îas
signor to Bell TelephoneLaboratories’, Incor
porated, New York, N. Y.,'a corporation of -New
York
Application August 27, 1936; sen-a1 1~r0.19s,`1-'11y
(c1. Y17a-45)
This invention relates to electricaltransmis
ancre-temperature ,cîoeflicient> of which is the
'sionr>` lines landv particularly to means for load
.
.
-
.
v
6-
Claims.
saine as thaty of 'transmission pair I0. Resist
ing'such
M
lines,A
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It' is known that the transmission character
‘135 istics of a; line may be improved by providing
loadingI such as leakage paths between they con
ductors of the line at intervals along its length.
The 'amount of leakage to be provided depends
A upon the spacing of the paths, thev top frequency
@T0 'to bek transmitted, and the chosen compromise
between perfect transmission and perfect -tem
perature correction. One method of providing
these 'leakage-paths consists in inserting shunt
resistances at 'the proper points along av-line.
.11:vi Since'- these resistances are placed at' particular
points along a line they are not affected by the
same’v temperature variations’as the »remainder
of the line and hence their compensating effects
‘are not accurate.A This means that the trans
?29 mission `loss at any given frequency cannot be
accurately predicted and hence the signal might
be distorted.
'I'he object of this invention is to provide im
proved loading for a transmission line.
#25
In its preferred form this invention comprises
Aav loop-of. resistance wire connected across the
line and distributed throughout the cable so that
vit is> subjected to the same temperature varia
tions 'as- the cable itself. These loops _may be
'1.3.0 of any length, but it is preferred, thatfthey'be
of the same length as a reel of cable.
A trans
missiony line incorporating thisv invention, there
' fore, may consist of pairs of wires connected
together at each splicing of a reel and connect
35 ed across the transmission pair at the opposite
end of each reel.
In the drawing which accompanies this spec
iiication and forms a part thereof, Fig. 1 shows
how the novel loading may be applied to a cable
40 and Fig. 2 shows an equivalent transmission net
work.
Referring now to Fig. 1, I0 is a pair of con
ductors forming a transmission line. This pair
may be one of several hundred incorporated in
45 a single cable. Transmission pair I Il may be
twisted to provide a certain amount of induc
. tive loading as is customary in such construc
tion. Since transmission lines are made up, in
general, of a number of relatively small sec
50 tions, i. e., of a number of reels, these sections
'fmust be spliced at intervals to form
‘ous line. Two sections, I2 and I3,
vspliced to transmission pair I0 at
respectively. Within cable sheath Il
65 cluded a pair of resistance wires I 6,
a continu
are shown
I4 and l5
is also in
the resist
yance pair I6‘Yis connected across transmission
pair II'Iv atfthe cable splice I4 and the opposite
end yI'l l is short-circuited.r Transmission pairs
I2 and I3 likewise are shunted by resistance
pairs I 8 and v,I 9" respectively.
Sincel the v"resistance wirey is distributed
_throughoutf'the' cable instead of being wound
on the customary support and located approxi- 10
mately at yone point, it is subjected to exactly
the same temperature variation as the trans
mission pair and hence temperature effects upon
the transmission >characteristics of the cable may
be eliminated." This, however, lis predicated upon
the assurntionr that a resistancey wire is available
which has the correct 'resistance value for the
length employed and‘at fthe same time has the
same'resistance temperature coefficient as the
transmission pair.' ,If sucha wire is not avail N)
able, a compromise >must be made. It 4will beV
necessary to choose between a perfect transmis
sion characteristic and a good temperature cor
rection on ‘one hand, and a perfect temperature
correction and a nearly flat transmission char- 25
acteristic'on' the other. It is of course possible
to obtain compromises between these two ex
tremes.-
'
~
j
f
v
1
g
`~ f If desired, the resistance pairs may be incor
poratedjin~ a separate cable located> adjacent the 30
transmission line. ~
`
l
The equivalent transmission network for the
loaded cable-of Fig. 1 is'shown in Fig. 2. It may
be considered as a balanced'line having series
inductances 20 and resistances 2I and shunt re- 35
sistances 22 and capacitances 23. The resistance
loading may be considered to be a similar net
work 24 shunted across the line at predetermined
intervals. For a complete discussion of such
networks reference may be made to K. S. John- 40
son’s book entitled “Transmission Circuits for
Telephonie Communication”,
Company, 1924.
Van
Nostrand
_ As an illustration of the application of this
invention to a specific cable construction, a re- 45
sistance of 105 ohms at 1° F. having the same
temperature coeflicient as a 16 gauge pair com
monly used for transmission, and shunted across
such a pair at 18,000 foot intervals, will result
in a practically constant transmission loss for 50
frequencies from 0 to 8,000 cycles. In addition
to this leveling effect upon the transmission loss,
changes in the loss due to temperature changes
in the medium surrounding the transmission
pair and shunt will be materially reduced. If 55
2
2,135,609
it is desired to maintain the same transmission
3. A transmission line comprising a plurality of
loss for frequencies above 8,000 cycles, it is nec
essary to increase the resistance of the shunt
and decrease the distance between shunts. For
Ui example, spacings of 3,000 feet would result in
spliced lengths of four-Wire lead, each length
comprising tWo parallel conductors of good con
maintaining a substantially constant loss for a
frequency range of 0 to 60,000 cycles, and a still
further reduction in spacing, ‘such "as one .shunt
of 3,850 ohms at 1° F. »for each reel length,` i. e.,
about 500 feet, would extend the upper Vlimit to
about 200,000 cycles.
Y'
Thus from the design shown in Fig. v1„»it is >a -
parent that the load resistances are inthe `same
thermal medium as the transmission Vline ’and
15 hence will follow very closelyY the ‘temperature’
variations in the line. In 1‘addition Ito this «desir
able feature, the resistance pair will have a
smooth impedance characteristic which may -ibe
changed by altering the position of the Wires in
the cable. A flatter frequency characteristic -Will
result by making the impedance Aslightly induc
tive. This system of loading approaches very
closely the ìdeal’continuous .loading and .resul-ts
in cheaperlcable carrier .systems since smaller re
peaters may kbe used. vIts applicability` is not
limited to long Ãlines for .message Aand broad band
systems, but it may Íbe fused for short local -cir
cuits designed for any-Wide band transmission,
and when vso used, greatly reduces phase-.distor
30 tion, >the equalization necessary and the-effect ofv
temperature on theoverall transmission.
It >is understood that the foregoing description
is merely -illustrative of the invention and -that
the scope of the invention is not to be determined
i
thereby, .but by the appendedvclaims.
What >is claimed is:
,
1. AV transmission :line comprising a cable, a
sheathing therefor, and shunt Aresistances WithinY
the sheathing .for loading said line, »said resist
40 ances comprising Wires which extend substantial
ly the entire length of the »cablefbetweenpointsof
connection to the line.
`
2,. A transmission-system comprisinga plurality
of reel lengths of cablejspliced togethezgfeach reel
45 length of cable including a'reel length of -line and
a `pair of resistance wires having substantial-ly
the same resistance-temperature ycoefficient as the
line, the Wires of said pair being connected to
gether at one end of the .reel length of 'cablezand
50 connected across the line at .the `@.Dllosite end of
ductivity and one loop conductor of low conduc
tivity, said loop conductor permanently connected
across the said parallel conductors at one end of
said lengths, and the temperature-conductivity`
characteristic of said -loop adapted to provide
loading for said parallel conductors.
‘
4. A transmission line comprising a plurality of 10
A‘spliced lengths of four-Wire lead, each Vlength
-comprising two parallel relatively high conduc
tivity conductors and one pair of relatively low
.conductivity yconductors permanently connected
»together at'oneend to form a loop conductor, the 15
A'temperature-conductivity characteristic of said
loop adapted to provide loading for said parallel
conductors, and the `said loop permanently con
nected across said parallel conductors so as to
provide equally spaced loadsalong said trans
missionline.
Y
Y
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n
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“
r5. VA Wide frequency :range transmission system
comprising a plurality of spliced equivalentcable
lengths each comprising a cable sheath enclosing
»one or :more transmission lines laid up -:together
with anV equal number of loops of resistance Wire
coextensive With said 4transmission lines, the yends
-of each of said resistance wire loops permanently
‘connected `across its associated transmission -line
Iand the speciñc resistivity and resistance-tem
,perature coeiiicient of each of saidresistance -wire
»loops »adapted to provide compromise loading
means
for` 4its >associated vtransmission
line
throughoutthe designed rangeof operating tem
peratures and of frequency, transmission «of said 35(
transmission line.
,
l‘6. A .transmission line comprisingîa plurality of
»equal lengths of four conductor leads, one pair-of
>said leads of >higher conductivity andíspliced
length »to »length to 'formthe `main channel .-o'f the
«transmission line, the other low'conductivity pair
cross-connected at one end of said length to :form n
a loop and a-t the other end connected :in shunt
across said high conductivity pair so that ateach
splice :of the .high conductivity .pair there is ’i5
shunted the loop of the »low conductivity pair, vand
.the temperature resistance coeiiicient of fthe :10W
conductivity .loop substantially> equivalent Íto ¿the
>temperature resistance coefiicient rof the `high
conductivity pair.
'
the reel length of cable to form ashuntîresistance
load whichiscoextensive with the reellength of
-line and subject :to thesame temperature varia
tions as >the reel llength of line.
EARL
VAN ' .TASSEL
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