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Патент USA US2124027

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July 19, 1938.
F. CALHOUN
2,124,02 7
SIGNALING‘ SYSTEM
Filed Feb. 17, 19s?
2 Sheets-Sheet 2
TIME
TIME
FIG. 5
INVENTOR.’
„li,f;A
mwM,
„4E
Patented July 19, 1938
2,124,627
UNITED 'STATES PATENT >orner.
2,124,027
SIGNALING SYSTEM
Free Calhoun, Chicago, Ill., assigner to Associ
ated Electric Laboratories, Inc., Chicago, Ill., a
corporation of Delaware
4Application February 17, 1937, serial No. 126,230
18 Claims. (Cl. 179-16)
'I'he present invention relates to signaling sys
tems and more particularly to impulse repeaters
for use in automatic telephone systems.
In conventional forms of automatic telephone
5 systems impulse repeaters of one type or another
are employed in connection with inter-office
trunk lines for the purpose of reducing to a
minimum the number of conductors constitut
ing the trunk line cables and for interrupting the
10 circuits of such trunk lines in accordance with
electrical impulses produced by operation oi’ im
pulsing means or a dialing device embodied in
any substation connected to any calling sub~
scriber’s line. The impulses as thus repeated
15 comprise rapid fluctuations in the. current
through the trunk line conductors, the impuls
ing rate being determined by the dial speed of
the impulsing means, and these current impulses
cause the operation of control means, usually in
20 the form of line relays for selector or connector
switches associated with the trunk lines.
Recent improvements in the design of line re
connecting trunk lines by the impulse repeaters.
If any substantial amount of distortion is intro
duced in the impulses in the transmission path
between the impulsing device and the control
means faithful response of the latter means can- 5
not be obtained. Such distortion may take any
one _of a variety of forms. Thus, if the period
of energization of the control device is greatly
less than the contact make period of the impuls
ing means, the device may have insuiiìcient time 10
in which fully to operate. Conversely, if the pe
riod of -de-energization of the control device is
substantially less than the contact break period
of the impulsing means, the device may have in
suñ‘icient time in which to de-energize and pre- 15
pare for a succeeding impulsing cycle. Again, if
any one of the vline relays in a chain of repeaters ,
is falsely operated more than once during any
one impulsing cycle of the impulsing means, false
operation of the control device may result.
20
In a system of the type indicated, the amount
of impulse -distortion is determined at least in
lays have given rise to the problem of improving part by the relationbetween the circuit constants
the repeater circuits generally. 'I'hese line re
of the line to which the dialing-or impulsing de
25 lay improvements, designed primarily to increase 'Vice is connected, the constants of the elements
the sensitivity thereof to received electrical im
of the repeater associated with the line, the con
pulses, have rendered unsatisfactory those forms stants of any other apparatus associated with the
of repeater circuits such, for example, asthe line as, for example, normally inactive bridged
high impedance bridge type, wherein the repeater ringers on =a party line, the rate of impulsing at
30 relay is, during the operation of the repeater, sub
the impulsing means, and to __alesser extent by
jected to transient impulses which tend to pro
the voltage of the operating batteries and the
duce false operation of the repeater relay. One line constants of succeeding trunk lines and the
, form of repeater circuit which is well adapted to constants‘of the impedance elements associated
meet the requirements of highly sensitive line re
therewith. Usually the circuit constants of the
35 lays is'the well-known repeating coil type. The individual subscribers’ lines and the trunk lines
circuit of this type of repeater includes primary are .ñxed by the physical arrangement of the sys
repeating coils connected in series with the in
tem and cannot economically4 be altered. The
coming line conductors and terminating at a impulsing rate may have any value within a
repeater line relay, the line relay being shunted range, the range usually extending between 8 and
40 by a capacitor for by-passing voice frequency 12 interruptions per'second. »It will be apprecicurrents. These primary repeating coils are in
ated, therefore, that the impulsing characteristics
ductively coupled to secondary repeating coils
connected in series with the conductors of the
trunk line terminating at a distant selector or
45 connector switch, the circuit of the lattertrunk
line being interrupted in accordance with the
transmitted impulses by .means of the repeater
line relay.
`
`~
The satisfactory operation of any impulsing' «ar50 rangement vand more particularly an arrange
ment of the type briefly described above is meas
ured by the ability of the device or -control means
25
3Q
35
40
of the subscribers’ lines associated with a par
ticular group of repeaters will vary over a wide
range and when the impulsing conditions inher
ent in a particular subscriber’s line are particu- 45
.larly unfavorable, the impulse distortion obtained
may, even with a repeater circuit of the type
specified, be so great as to preclude faithful op
eration of the control device to be controlled by
the transmitted impulses. More specifically, a 50
subscriber’s line may be in a condition which is
perfectly satisfactory' for efdcient transmission
to be controlled by .the transmitted impulses of voice currents and yet be in a condition which
faithfully to follow the impulses created at the ‘ is extremely unfavorable to impulse transmission
55 impulsing device and repeated over the inter
thereover. 'I'his usually occurs in cases where 55
2,124,027
2
the subscriber’s line circuit is excessively long so
that the line resistance thereof is high, or where
the shunt leakage resistance between the line
conductors-is extremely low, or by a combina
tion of these two factors.
Under the conditions stated. the forrn of dis
tortion which occurs‘is manifested in a false
energization and de-encrgization of the line relay
included in the iirst repeater of the repeater
chain, causing a.false operation of this relay
which is repeated through the chain of relays to
the control device. As will be pointed out in de
tail hereinafter, the reason for such false ener
gization is that the circuit constants of the calling
re
15 subscriber’s line, the elements of the nr
peater, and any other apparatus associated with
ner by closing the line circuit to energize the first
repeater, before the transient of the impulse has
expired. Hence, the repeater line relay is not
permitted to restore at the expiration of the
transient and double operation of. the repeater
relay during any single impulsing cycle is pre
vented. If desired, the delay may be achieved
entirely through the action of the capacitance
means shunting the voice-frequency by-pass
capacitor of the first repeater. As an alternative, 10
this capacitance means may be so proportioned
that only a portion of the required delay is
achieved thereby, an additional delay being ob
tained due to the operating inertia of the relays
included in the repeater following the first re
repeater line relay during the period of the cycle
peater, such that the combined delay intervals
for each impulse cycle extend well into eachsuc
ceeding cycle. It is pointed out that the term
“repeater” as used herein is a generic designation
intended to connote anydevice or combination of 20
devices for repeating impulses received over one
when this relay is supposed to be interrupted
and corresponding to the interrupted period of
responsive device directly.
the calling subscriber’s line are necessarily so re
lated to each other and to the impulsing rate as
incidentally to cause, in each impulse cycle, a
20 voltage transient across the windings of the ñrst
. the calling subscriber’s line circuit.,r
It is an object of the present invention, there
25
fore, to provide in a system of the character de
scribed an improved repeater capable of operating
in conjunction with any subscriber’s line circuit
having reasonable voice frequency transmission
efficiency in a manner such that impulses trans
mitted over the line may successively be repeated
with tolerable distortion.
It is a further object of the invention to pro
vide in a signaling system an impulse repeater
35 arrangement, comprising a plurality of tandem
connected repeaters, which is capable of produc
ing faithful response of the impulse controlled
means in accordance with impulses transmitted
by impulsing means_through the repeaters, and
in which at least one of the repeaters is adapted
to be connected to any one of a number of sub
scribers’ lines having a wide variety of impulsing
characteristics.
More particularly, it is an object of the inven
tion- to provide an improved repeater of. the
general type described which is capable of re
peating substantially without distortion impulses
received over a line having highly unfavorable
impulsing characteristics.
In brief, the objects as set forth above are
realized in accordance with the present invention
by associating with at least one of the repeaters
included in the repeater chain, reactance means
for altering the circuit constants of the network
between the impulsing device and the control
55 means, thereby to reduce the impulse distortion
in the impulse transmission path of the network
to a tolerable value. More specifically, capaci
tance means is‘included in the first repeater of
the repeater chain, in shunt with the voice fre
quency current by-passing capacitor and so pro
portioned relative to the circuit constants of a
line having unfavorable impulsing characteris
tics. the elements of the associated repeater, and
any other apparatus associated therewith that the
electrical transient which occurs in each impulse
cycle is delayed, following the interruption of the
circuit of the line over which the impulses are
transmitted, and the duration of the transient
70 is increased.
As a result, and for any reasonable
impulsing rate, the circuit of this line is closed,
during any one impulsing cycle,`before the ex
piration of the transient of the preceding im
pulsing cycle. In other words, each open cir
cuit impulse perlod is ended in the normal man
line to 'a second line or to a controlled impulse
The novel features believed to be characteristic
of the invention are set forth withparticularity 25
in the appended claims. The invention itself,
however, both as to its organization and method
of operation, together with further objects and
advantages thereof, will best be understood by
reference to the specification taken in connec 30
tion with the accompanying drawings in which
Figure 1 illustrates in partially schematic form
an automatic telephone system constructed and
arranged in accordance with the present inven
tion; Fig. 2 illustrates a portion of the system of 35
Fig. 1 reduced to its simplest form; and Figs. 3
to 5, inclusive, are graphs illustrating the operat
ing characteristics of typical installations.
Referring now more particularly to Figure 1
of the drawings, there is illustrated in partially 40
schematic form a telephone system of the auto
matic type comprising a plurality of ofllces or
exchanges ladapted to be inter-connected by
trunk lines individually having associated there
with an impulse repeater for the purpose briefly 45
described above. The system comprises four
oilices or exchanges indicated at I0, Il, I2, and
I3, respectively, with trunk lines extending be
tween the oflices'in the conventional manner so
that any subscriber’s line terminating at one 50
oilice may selectively be connected to any other
subscriber’s line terminating at the same or at
any of the other omces by means of the usual
line, selector and connector switches. This ar
rangement of elements for a connection between 55
a subscriber’s line Il, comprising conductors Ii
and I6, terminating at the ofñce I, and a sub
scriber’s line terminating at the bank contacts of
the connector switch included in the oilice I3
may comprise, connected in tandem, in the order
named, a line switch I1, an intra-office three
conductor cable I8 including conductors I 9, 2II
and 2l, a first selector switch 22, an impulse re
peater indicated generally at 23, a two-conductor
inter-oi’ñce trunk cable 24 comprising conductors
25 and 26, a second selector switch 21, a second
impulse repeater 28, a second two-conductor in
ter-office trunk cable 29 comprising the conduc
tors 30 and 3|, a third selector switch 32, a third
repeater 33, a. third inter-office two-conductor 70
trunk cable 3l comprising conductors 35 and 36
and, ñnally, a. connector switch indicated gen
erally at 31. It will be understood that the
enumerated selector- switches, trunk lines, re
peaters and the connector switch individually 75
2,124,027
represent a number of similar elements located
in and inter-connecting the various ofñces. The
line, selector and connector switches may be of
any desired type, although preferably the line
switch is of the rotary type and the selector and
connector switches are of the well-known Strow»
ger type embodying a contact selector element
adapted to be translated vertically and then -ro
tated in response to the selective and repeated
10
operation of vertical and rotary control magnets,
respectively. Sin'ce these switches are entirely
conventional in form, they have been indicated
only schematically in the drawings.
The line | 4 is shown as being of the party line
type having a plurality of subscribers’ substa
tions connected thereto, one of -which is shown
in detail at 39 and another of which is shown`
schematically at 40. Each of these substations
is of the well-known booster type embodying se
lective harmonic ringers. Thus, the station 39
comprises a ringer circuit including a ringer 4|
and a condenser 42 connected in series across the
line |4. This circuitis connected in shunt with
a winding 43 of the booster transformer through
' the upper contact 44 of a hook switch 45, a
transmitter 46, contacts 41 and 48 of impulsing
means-in the form of .a dialing device 49, and the
lower contact 59 of the hook switch 45. A re
ceiver 5| is provided which is connected between
30 one terminal of the transmitter 46 and the junc
tion point between the ringer 4| and the con
denser 42 through the second winding 52 of the
booster transformer. Gif-normal springs indi
cated at 53’ are also provided which are adapted
to short circuit the transmitter 46 and receiver
5| during the transmission of impulses. It is
pointed out here that the words “impulsing cycle”
.as used herein denote the cycle of opening the
contacts 41 and 48 for a predetermined period
40 determined by the rate of impulsing to interrupt
the circuit of the subscriber’s line I4, and the
closing of these contacts for a predetermined
period, also determined by the rate of impulsing,
thereby to close the circuit of the line I4.
45
The control means or device which, in the sys
tem shown, is to be controlled by the impulses
transmitted by the impulslng means 49 com
prises the connector switch 31 and, more par.
ticularly, a line relay 53 which is connected to
50 the trunk conductors 35 and 36 when this par
ticular connector switch is seized. The relay 53,
as is well known, controls, through a system of
interconnected relays, the operation of the ver
tical and rotary stepping magnets of the con
55 nector to cause the selector element to select the
proper set of bank contacts leading to the called
subscriber’s line. Since the manner of connect
ing such relays and their mode of operation is
well known,. they have been omitted from the
60 system in order to simplify the drawings.
Each of the repeaters 23, 21 and 33 included
in the transmission path between the subscriber’s
line |4 and the connector switch 31 is preferably
of the well-known repeating coil type with the
65 exception of the repeater 23 which is modified by
the addition of means for reducing to a tolerable
value distortion of the impulses in the manner
described in detail hereinafter. For this reason,
the repeater 23 only, has been shown in detail.
70 It comprises the usual repeating coil transformer
56, including primary windings 51 and 58 and
secondary windings 59 and 60 serially connected,
respectively, in the cable conductors extending
from the selector switch 22 and the cable con_75 ductors 25 and 26 comprising the trunk line 24.
3
The windings 51 and 58 are connected in series
with the windings of a repeater line relay 10
through the contacts 3| and 82 of a battery re
versing shunt relay 80. A capacitor 63 is ‘pro
vided in shunt with the windings of the relay 10
for by-passing voice-frequency currents -around
these windings and additional capacitance'means
comprising the capacitor 64 shunting the wind
ings of the relay 10 ls also provided for reducing
impulse distortion to a tolerable value in the 10
manner to be described in detail hereinafter.
Also shunting the upper winding of the relay 10,
during the circuit interruption period of each
impulse cycle, is 4a priming resistor 65 which
functions partially to energize the relay 10 and
to render it more sensitive to received impulses.
In order to repeat these impulses over the trunk
line 24 the relay 10 is provided with a front ar
mature 1| and associated contact 12 which are
inserted in the conductor 25. The relay 10 is»
also provided with an armature 13 and associated
contacts 14 and 15 for controlling a slow-to-re
lease relay 90 and for removing the resistor 65
from in shunt with the windings of the relay
10 during the closed circuit period of each im 25
pulse cycle. One of the windings of the shunt
relay 80 is connected in' series with the second
ary windings 69 across the trunk line conductors
25 and 26 and is shunted by a voice-frequency by
pass condenser 66. The other winding of the;
relay 80 is adapted to be energized from the
common battery at the contact 9| of the slow-to
release relay 90, so that when the called sub
scriber lifts his receiver the relay 90 becomes
fully energized to operate its battery reversing
armatures and contacts 8346, inclusive in the
usual manner.
'
The slow-to-release relay 99 is also provided
with contacts 92 and 93 and an armature 94 for
removing negative battery from the guarding .40
conductor I9' when the relay ßis operated and for
substituting guarding ground. An additional
armature 95 and associated contact 95 are in
cluded in this relay which are connected in the
circuit of the resistor 65.
Neglecting for the -present the additional ca
pacitance means 64 and ~its function, the system
as generally described above is entirely conven
tional in form and its operation is well under
stood in the art. In brief, a call from the sub- _,
scriber’s substation 39 to a subscriber’s line ter
minating in the bank contacts of the connector
switch 31 is initiated by lifting the receiver at the
substation 39 to operate the hook switch 45 and
close the contacts at 44 and 50, thereby causing 55
the line switch |1 to select in the usual manner
an idle ñrst selector switch, as, for example, the
ñrst selectorl switch 22. _This operation also
places ground on the control conductor I9 in the
usual manner, which ground extends over this.
conductor by way oi' the line switch contacts tothe associated connector bank contact to busy
the line |4 and thereby prevent its being seized
due to an incoming call thereto. In response
to successive operations of the impulsing means 65
or dialing device, the selector switches 22, 21 and
32 are successively operated in the usual manner
individually and successively to select idle trunks
as, for example, the trunk lines 24, 29, and 34,
extending between the oillces |, 2, 3, andf4. Dur 70
ing these dialing operations, contacts 41 and 49
are periodically opened and closed to send elec
trical impulses over the line |4, which impulses
are repeated over the trunk circuits by the re
peaters 23, 29 and 33. Thus, at the conclusion
0
4
2,124,027
of the operation of the first selector 22 to select
the idle trunli:- I8 in response to the dialing of
the nrst digit, the contacts 41 and 48 are closed
to energize the repeater line relay 10 over an ob
vious circuitand thereby to condition the re
peater 23 to repeat the impulses of the second
digit to the second selector switch 21. The op
eration of the relay 10 causes the operation of
the slow-to-release relay 80 over the circuit ex
10 tending from ground at the armature- 18, the
contact 14, the winding of relay 80 to battery, and
also closes the circuit of the trunk line 24 at the
contact 12. When the slow-to-release relay 80
operates, it places guarding ground on the con
15 ductor I8' at contact 82, completes the circuit
for partially energizing the relay 80 at contact
8| and prepares the circuit for the shunt prim
ing resistor 85 at contact 88. The circuit of the
priming resistor 65 is held open during the pe
riods when the contacts 41 and 48 are closed by
the relay 10 at back contact 15. It is pointed out
that the windings of shunt relay 80 are so poled
relative to each other that during the calling op
eration the fluxes thereof are additive and the
relay remains de-energized. However, when a
call is completed and the called party lifts his re
ceiver, the current through the winding in series
with the repeater coils 58 and 80 is reversed,
causing the relay to operate, thereby to reverse
the polarity of potential applied to conductors I5
tively.. Other elements of the circuit are identi
fled by the same reference characters as are used
in the circuit of Fig. 1.
operation of the impulsing device including the
contacts 41 and 48, depends upon the‘relation
between the rate of impulsing, the circuit con
stants of the line, and the impedance elements
associated therewith. Thus, with a normal im
pulsing rate within the range of from 8 to 12 in
terruptions per second and an extremely long line
wherein the values of the resistors |00 and |0| are
high, the current through the relay windings |01
and |08 may be insumcient to cause the relay 10
to operate. This problem is obviated by the use
of the relay priming resistor 05 as noted above
which effectively shunts, during the open circuit
period of each impulse cycle when the relay 10 20
is restored, a sui'llcient amount of current from
around the loop circuit so that when the contacts
41 and 48 are closed, the added current through
the windings |01 and |08 causes positive oper
25
ation of the relay.
It was further pointed out above that one form
of impulse distortion which occurs in the impulse
transmission path is caused by the voltage tran
sient which occurs following the opening of the
contacts of the impulsing device 48 at the end of 30
the closed contact period of eachl impulse cycle.
'I'his transient is caused by the rapid demagncti
zation oi' the relay 10 and functions to raise the
line voltage between the conductors I5 and I8 to
a value which may be several times the normal 35
line voltage. The polarity of this voltage tran
sient is opposite' that of the station battery' but so
relay 80 at contact 14. The latter relay', how
ever, being s'iow to release, stays operated until
greatly predominates thereover, that the capac
itors |08, |08, and 88, shunting the line are
charged to a high potential. It is pointed out that 40
the distributed capacitance |03 of the line is of
the relay 10 is again operated during the next im
pulse cycle. Further impulse cycles produced at
the contactsof the dialing device cause alternate
operation and restoration of the line relay 10,
thereby repeating these impulses over the circuit
of the trunk line 24 at the contact 12. Follow
such a value as to have practically no eñect on
the magnitude or duration of the transient. The
voltage transient in each impulse cycle reaches its
peak at about the instant the relay 10 restores. 45
ing the operation of the selector switches and the
45 connector to select the called subscriber’s line,
_the usual operations of applying ringing poten
tial to the called subscriber’s line, guarding the
Following the charging interval,- the capacitors
|08, |08, and 88 discharge through the relay wind
ings I01 and |08 and cause the relay to re-operate.
Such spurious or false re-operation of the relay
is somewhat momentary but if the series resist 50
ance |00, |0I is high, corresponding to a long line,
the duration of the transient- may be sufficient
to cause re-operation of the distant control
means which, in this case, comprises the line relay
58 of the connector switch I8. Such re-operation
of the relay 58 may result in the controlled ver
tical or rotary magnets taking two steps in each
called line against seizure, and the like, are car
ried out in the conventional manner by means of
apparatus, not shown, and forming no part of
the invention. Since the system- as thus far
described is entirely conventional it is belieìfeld
0 _
' that the restoration of the apparatus shown,
lowing the termination of a call, will be ap
parent to those skilled in the art and for that
reason a description thereof is unnecessary.
Referring now more particularly to Fig. 2 of
the drawings, there is illustrated the circuit of
Fig. l in diagrammatic form, with the circuitim
pedances of the subscriber’s line I4 and the asso
ciated impedance elements shown in detail. Thus,
the series resistance of the line is represented by
the resistors |00 and |0|; the shunt leakage re
sistance between the conductors I5 and I8 is in
dicated by the dotted line resistor |02; the capac
itance between the line conductors I5 and I8 is
shown by the dotted line capacitor |08; the im
all the ringer circuits of the line are indicated by
the serially connected condenser |08 and indue-_
tor |05, and the windings of the _line repeater
'Il relay 10 are indicated at |01 and |08, respec
‘
ceived over the line |4 and occasioned by the
and i8 at the armatures 84 and 86. At this stage
of the operation and when the contacts 41 are
opened for the nrst time during the dialing of the
second digit, the line relay 10 is deenergized to
open at contact 1| the circuit of the trunk line
24 and to open the circuit for the slow-to-release
pedance of the elements » of substation 89 in
70 series with the contacts of the impulsing device is
indicated by the inductor |04; the impedances of
.
As was pointed out above, the faithfulness with
which the line relay 10 responds to impulses re
impulse cycle.
The above described phenomenon is, among
other factors, dependent upon the value of the 60
shunt resistance of the line |4 including the leak
age resistance |02 across the conductors ’In and |8
of the line circuit |4, and also upon the value of
the combined capacitance of the l:apacltors 68
and 84. Thus, with the resistor i' , chosen to pro
'
65
vide the greatest sensitivity of the relay 10 or of
a value of approximately 2,000 ohms, a shunt
leakage resistance of the order of 10,000 ohms to
infinity, and the usual value of two microfarads
for the voice-frequency by-pass capacitors 88 70
there is insufllcient damping of the transient, with
the result that the voltage transient as above de
scri d occurs and is of suillcient duration to
c
false operation followed by a restoration of
e line relay 18. The magnitude of this tran 75
2,124,027
sient also depends upon the voltage of the com
mon battery in the oiiice I0 since the voltage
across the windings of the relay 10 determines
the rate of demagnetization thereof. Thus, if, in
Points F and G or vune B indicate the instan
at which the current impulses in the circuit o_f
the trunk line 24 produced by false operation4
of the relay 10 begin and end. andthe distance
a given case, the voltage is reduced from 56 to 52 between these lines indicates the duration of the
volts, false operation of the relay 10 may be en
transient causing such false operation. The
tirely eliminated. With a 4low shunt leakage re-v points H and Il indicate respectively the instants
sistance between the line conductors, of the order when the distant line relay of the second-selector
of 5,000 to 10,000 ohms, the transient which oc
10 curs is sufliciently damped so that false operation . switchl closes and opens its back contacts. It will
be observed that, during each impulse cycle and
of the relay 10 due to the cause described above shortly after the contacts at 41 open at the ln l0
is eliminated. Under these conditions, however, a stants D, a current surge F-G occurs in the cir
seconïi'and equally undesirable transient results cuit of the trunk line 24 which causes a spurious
in each impulse cycle. This latter transient is or false operation of the distant relay at the
15 caused by the opening of the circuitof the trunk
second selector switch. Such false operation is 16
line 24 at contact 12 when the line relay 10 re
probably the result of the transient caused by
stores in the usual manner. As this trunk circuit capacitor discharge, although the graph does not
is opened, a current transient occurs in the sec
distinguish between the two causes'as described
ondary coils of the repeater transformer 56 above. As will be noted from the first impulse
20 which causes a voltage transient across the pri
I-H of the line C, this false operation takes the
mary windings 51 and 58 of this transformer. form of a complete energization and re-opera
'I'his voltage transient aids the potential supplied v tion ofthe relay 10 followed by a complete re
by the battery through the priming resistor 65 to
the winding |01 in the sense that it flows through
25 the shunt leakage resistance |02 in series with the
line resistance |00, |0|, and thereby increasing
the current through the windings |01 and |08 of
relay 10.
'I'his added current causes a false re
operation of the line relay 10 which is repeated
30 over the trunk conductors of the line 24. It is
pointed out that, if the leakage resistance of the
line is high, this second effect is prevented due to
the discharging of the capacitors at about the
time the transient caused by the opening of the
35 trunk circuit occurs, since the polarities ofthe
two transients are opposite. lUnder these condi
tions, however, the transient caused by the capac-y
itor discharge is so greatly predominant that the
transient produced by opening of the trunk cir
40 cuit does not prevent the above described false
operation of the line relay 10.
'I’he exact nature of the impulse distortion
which occurs is well illustrated in the graph of
Fig. 3 which is an oscillographic record of the
45 operation of a typical installation. 'I‘his graph
was taken on a system embodying a single re
peater and having the following circuit constants
for the elements of Fig. 2:
Resistance of resistor 65 ________ __ohms__
2000
I0 | _________________________ __ohms--
0000
Resistance of resistor |02 _______ „ohms“
5000
50 Combined resistance of resistors |00 and
Series resistance of trunk line 24___ohms__
'150
Shunt resistance of trunk line 24__ohms__ 10000
55 Combined capacitance of capacitors 63 and
64 ____________________ __microfarads__
-
6
Station battery voltage __________ __volts-Impulsing rate ________________ __I. P. S__
56
8
No. substations on line |4 ______________ __
1
In this graph, the line A represents the current
through the winding |08 of the line relay 10, the
line B represents the current in the circuit of
the trunk line 24, and the line C indicates the
65 opened and closed periods of the back contacts
of the line relay associated with the second selec
tor switch 21. When this last-mentioned line
relay is deenergized these back contacts are c-losed
and vice versa. In the line A, the points D and E
70 denote respectively the instant when the 'circuit
of the subscriber’s line |4 is interrupted at the
contacts 41 and 48 and the instant when this
line circuit is completed by these contacts during
an impulsing operaticn and the distance D-D
75 or E-E represents one `complete impulsing cycle.
storing thereof. It is to be noted further that
such false operations occur during each of the
impulsing cycles. In the particular graph oi' this
figure the false operation is of suiiicìent dura.
tion to cause the control device, which may com
prise the vertical or rotary magnets of the selector
switch, to take a false step in the manner pointed
out above, thus resulting in improper trunk line
selection.
As previously pointed out, the rate of impulsing
is another factor which partially determines
whether or not distortion in the form of false
operation of the first repeater line relay will
occur. This is strikingly~ emphasized by the
graph of Fig. 4 which shows the operating char
acteristics of a system having the same character
istics as those for Fig. 3 with the exception that
the combined capacitances of capacitors 63 and
64 were in this case 8 microfarads as contrasted
with 6 microfarads for the system having the
operating characteristics shown in Fig. 3. The
same reference characters are used in Fig. 4 as
in Fig. 3 to identify the same curves and the
various points thereon. From Fig. 4 it will be 45
observed that during the first impulse cycle and
with an impulsing rate of exactly 8 interruptions
per second no false operation of the relay 10
occurs. However, by the beginning of thev second
impulse cycle the impulsing rate had decreased
to 7.7 I. P. S. with the result that a false opera
`tion of the relay 10 occurs. During the third
impulse cycle the impulsing rate was still less with
the result that the false operation of relay 10
was still more pronounced. From this graph it 55
is apparent that, for a given set of system char
acteristics, the impulsing rate cannot be de
creased below a predetermined value without
causing the form of impulse distortion noted.
In accordance with the present invention, the
distortion as described above, namely, spurious or
false operation of the relay 10, is prevented or
reduced to a tolerable value by including in the
repeater 23 reactance means comprising the ad
ditional capacitance means 64 for delaying, during
each impulse cycle, the occurrence of the tran
sient for an interval after the contacts at 41 and
48 have opened to interrupt the circuit of the
subscriber’s line I4, and for increasing the dura 70
tion of the transient sufliciently to permit the
contacts at 41 and 48 to close and energize the
relay 10 in the normal manner for the next im
pulse before the transient expires and the relay
restores as a result of such expiration.
This ad
6
2,124,027
relays of the repeaters following the nrst re
ditional capacitance means is connected in shunt
peater Il'. Each of these relays has a certain
with the voice-frequency by-pass capacitor il y operating
and restoring inertia such that a time
and the windings of the relay 1t, and its purpose interval elapses between energization and opera
in the network is to increase the time constant tion and between de-energization and restora
of the network so that the -current surge through tion. The total operating interval representing
the relay windings |01 and i0! is delayed in
the sum ot the individual operating lags of the
building up to a value sufilcient to cause opera
when added to the instant when false op
tion of the relay, and the duration of the surge relays
eration
of the relay 1l occurs gives the instant
is increased to hold the relay operated for a when false
energization of the distant control de
10 greater time interval which overlaps the instant vice occurs. Moreover, the interval correspond
of reclosure of the contacts at 4l and 48, initi
ating the next impulse cycle. Thus, referring ing to the combined restoring lags of these relays
an increase in the interval during which
again to Ii‘lg.- 4, it will be seen that during the effects
the
distant
control means is falsely operated,
nrst half impulse cycle D-E, the transient as thereby insuring
that the false’ operation for each 15'
15 indicated by the current of the line 24 during the impulse cycle will continue weil into the succeed
interval F-G overlaps the instant E when the ing cycle. It was found that such operating and
contacts 41 and 48 are reclosed to initiate the next restoring lags caused a change in the ratio of the
succeeding impulse cycle. Hence, when the tran
sient is over and the relay 10 would normally open-circuit period to the closed-circuit period 20
impulse received at the distant control
tend
to restore, it is held energized by virtue »of for each
20
fromthe ratio of these intervals as origi
the reclosure of its energizing circuit in the usual device
nally transmitted at the impulsing device, but not
manner. It is pointed out here that the oper
ating inertia of the relay 10 assists in increasing to an extent sufficient to cause undesired opera
tion of the device ultimately to be controlled.
the operated time interval of the relay to make 'I‘his
effect is well illustrated by the graph of Fig.
this interval overlap the reclosure instant E. In
5 which is similar to those of Figs. 3 and 4 but
regard to the second impulse wherein the im
shows the operating characteristics on a system
pulsing rate has decreased to '7.7 I. P. S. the including
three repeaters connected in tandem
transient occurs at the same instant in the im
over
trunk
lines. The characteristics of the sys
pulse cycle as for the ilrst half cycle but the
30
delay in the reclosure instant E of the second tem were as follows:
42
impulse cycle caused by the decrease in impulsing Operating voltage at all stations__volts__
12
rate permits the transient F-G-to expire and Impulsing rate______________ ___I. P. S__
the relay 10 to restore before the instant E Subscriber’s vline series resistance_ohms__.
0
arrives. Thus, false operation of the relay occurs Subscriber’s line leakage shunt ' resist
35
ance
nhms
5,000
35 during this and succeeding impulse cycles.
From the foregoing discussion with reference Series resistance of each trunk line
ohms__
250
to Fig. 4, it will be apparent that for an impulsing
rate above 8 interruptions per second and with Leakage shunt resistance of each trunk
line
nhmg__ 10, 000
the additional capacitance means 64 having a
value of 8 microfarads, the latter element is so Primings resistor 65 in ñrst repeat
proportioned relative to the circuit constants of
er __________________ __ ____ __ohms__
2,000
Capacitance shunting line relay windings
the line I4 and the constants of the other imped
ance elements associated with this line, including
of rlrst repeater ______ __microfarads-8
the elements of repeater 23, that the transient Substations on Subscriber’s line _______ .__
6
causing the false operation of the relay 10 holds
In the graph the line A’ represents the current
the relay operated, during each impulse cycle, through
the negative winding of the first repeat
until the reclosure instant E occurs. It is point
er line relay, the curve B' represents the current
ed out that the circuit parameters given above through the windings of the distant control de
for the system, upon which the operating char
vice which in this case was the line‘relay 53 of
acteristics of Fig. 4 are based, represent extreme
connector switch Il, and the curve C' repre
ly unfavorable impulsing conditions and that any the
sents the open and closed contact periods of the
line having more favorable impulsing character
control device. The distance D’--E' indicates
istics will operate perfectly satisfactorily in con
junction with the repeater as described above the open contact interval of the impulsing de
vice 49 and the distance H'--I’ indicates the cor
and having the present invention embodied there
55 ‘ in. It is further pointed out that the shortening responding interval during which the distant
control device is de-energized. Likewise the dis
of the period representing the restored condition tance
is a measure of the closed contact
of the control means.. due to the false operation of period E'-D'
of the impulsing means and the distance
the relay 10, is not sufllcient to have any adverse I’-H’ is a measure of the corresponding interval
eiïect on the operation of the control means. In during which the control device is energized.
other words, the ratio of the restored period of This graph strikingly illustrates the effect of the
the control means to the energized period of the inertia of the relays in delaying the response of
control means is well within the range which per
the control device. Thus, during the iirst impulse
mits -complete operation and restoration of this cycle, operation of the control device occurs al
_means during each impulsing cycle.
most at the end of the ñrst half of the ilrst im
In the system as described above impulse dis
pulse of the impulsing means as shown by the
tortion in the form of false operation of the ñrst
distance, along the time axis, between D' and H'.
`- repeater line relay is entirely eliminated by de
It will be understood that if the impulsing con
laying, andvincreasing the duration of, the elec
ditions of the trunk lines, as for example the lines 70
trical
transients
causing
false
operation
of
the
70
first impulse repeater line relay 10. If desired, 24 and 29, interconnecting the various repeaters
are particularly unfavorable it may be necessary
andin those arrangements such as that illus
to employ additional capacitance means in each
trated wherein a number of repeaters are con
of the repeaters in the manner described above
nected in tandem, at least a portion of the re
75
quired delay may be supplied by the repeater line
for preventing false operation of the control
75
7
2,194,097 ‘
means at- the distant oilice or station. *In most
instances, however, the trunk line characteristics
are more favorable to impulse transmission than
the subscribers’ lines and consequently the ex
pedient mentioned is unnecessary.
'
.
In practicing the invention as described above,
the capacitor 63 and the additional capacitance
means 64 may consist of two separate elements or
they may be combined in the form of one ca~
‘
-
l
_
’
impulses received over said line to additional re
is 8 microfarads,v satisfactory operation is ob
incidentally to produce false operation of said
15 tem having the following characteristics:
Priming resistor- 85 ___________ __ohms-2,000
Series resistance of subscriber's lin
14...r ______________________ _-ohms-- `04,250
20 Shunt leakage resistance of line 14
,
`
ohms-infinite resistance--
ated with said line are necessarily so related as
repeater following the interruption of the circuit
o_i' said .line during an impulse cycle, which false 15
operation Ais repeated by the other repeaters of
the system, the method of operation which com
prises, delaying said false operation of said re
peater for a time interval- after the interruption '
5,000
Series resistance of each trunk line
ohms each__
Shunt leakage resistance of each trunk
0-750
line_____ „ohms-infinite resistance--
10,000-
Impulsing rate ______________ __I. P. S-- l
8-12
of said line circuit, delaying in said additional 20
repeaters and for a. further time interval the
eil'ect of said false operation on the last of said
repeaters, and starting the next impulse cycle
before the combined timeintervals have expired.
4. In a signaling system comprising a line, 25
Station battery voltage ________ __volts-- ' 42-56
impulsing means on said line and a repeater
Number of substations on line 14 ..... __ '
adapted to be connected to said line to repeat
electrical impulses received over said line to ad
ditional repeaters adapted to be connected in
tandem with said first-named repeater over ad 30
ditional lines, and wherein the circuit constants
oi' said line, the associated repeaters and other
apparatus associated with said line are neces
sarily so related as incidentally to produce elec
1-6
Number of trunk lines in tandem with
line 14_..__'_..__ _____________________ __.
1-3
Number of repeaters in tandem ______ __
1_3
The above parameters and physical characteris
tics of the system shown are given by way of `ex
ample only since many other relationships be
tween the various factors. involved may be used
~ without departing from the invention herein dis
closed.
While there has been described vwhat is at pres
ent considered to be the preferred embodiment of
40 the invention it will be understood that various
modifications may be made therein and it is
aimed, therefore, to cover in the appended claims
all such modifications as fall within the true spirit
45
line:
3. In a signaling system comprising a line, im
pulsing means on said line and a repeater adapt
ed to be connected to said line to repeat electrical
In either case it has been found that if the total
capacitance across the windings of the relay 10
pacitor having the appropriate capacitance value.
tained when the repeater is operated in a sys-
30
said
peaters adapted to be connected in with said
first-named repeater over additional lines. and
wherein- the circuit constants of said line, the 10
associated lrepeater and other apparatus associ
10
25
and starting the next impulse cycle before said
transient expires by completing the circuit of
andscope of the invention.
I claim:
i
1
-
1. -In a signaling system comprising a line, im
pulsing means on said line and a repeater adapt
ed to be connected to said line to repeat electrical
impulses received over said line to a second line
50 and wherein the circuit constants of said line,
the associated repeater and other apparatus
associated with said line are necessarily so re
trical transients following the interruption of
the circuit of said line during an impulsing cycle
thereby to cause false operation of said first re
peater, which false operation is repeated bythe
other repeater or repeaters, the method of oper
ation which comprises delaying the occurrence
of said transient for a time interval after the in
terruption of said line circuit, increasing the du
ration of said transient, delaying insaid addi
tional repeaters and for a further time interval.
the effect of the resulting false operation of the
first-named repeater, and starting the next im
pulse cycle before the combined delay intervals
have expired.
5. In a signaling system, a line, impulsing
means for causing electrical impulses to be trans,
mitted over said line, an impulse repeater adapted
to be connected to said line and responsive to said
lated as incidentally to produce false operation - impulses,
said repeater being operative to repeat
oi‘ said repeater following the interruption of the said impulses over a second line, said first-named
55 circuit of said line during an impulse cycle, the
line, impulsing means and repeater necessarily
method of operation which includes, delaying having included therein and associated there 55
said false operation for a time interval after the with impedances which tend to produce false im-interruptionof said line circuit, and starting the pulsing of said repeater, and reactance means
next impulse cycle by completing the circuit of
said line before said interval expires.
'
2. In a signaling system comprising a line,
impulsing means. on said line and a repeater
adapted to be connected to saidline to repeat
electrical impulses received over said line to a
65 second line and wherein the circuit constants of
said line, the associated repeater and other ap
paratus associated with said line are necessarily
so related -as incidentally to produce an electrical
transient which causes false operation of said re
70 peater following the interruption of the circuit
of said line during an impulsing cycle, the meth
od of operation which includes delaying the oc
currence of said electrical transient for a time
interval after the interruption of said line cir
75 cuit, increasing the duration of said transient,
associated with said repeater and so proportioned
relative to said impedances as to prevent said false 60
impulsing.
6. In a signaling system, a line, impulsing
means for alternately closing and interrupting the
circuit of said line at a predetermined rate to
transmit electrical impulses thereover, an impulse 65
repeater adapted to be connected to said line and
including a relay energized when the circuit of
said line is closed and de-energized when the
circuit of said line is interrupted, said relay op~
erating to repeat said impulses over a second line, 70
means necessarily included in and associated with
said first-named line for incidentally producing
false energization of said relay during the time
interval of each impulsing cycle when the circuit
of said line is interrupted, and reactance means 75
l
.
2,124,027
8
associated with said relay for preventing, during
each impulse cycle, thede-energization of said
relay after its false energiaation.
7. In a signaling system, a line, impulsing
means for valternately closing and interrupting
the circuit of said line at a predetermined rate
to transmit electrical impulses thereover, an im
pulse repeater adapted to be connected to said
line and including a relay energized when the
circuit of said line is closed and de-energized
10 when the circuit of said line is interrupted, said
relay operating to repeat said impulses over a
second line, means necessarily included in and
associated with said mst-named line for inci
dentally producing, during the period of each im
15 pulse cycle when the circuit of said line is in
terrupted, an electrical transient which causes
false energlzation of said relay, and reactance
means associated with said relay for delaying,
during each impulsing cycle, the occurrence of
said transient following the interruption of the
circuit of said line and for increasing the dura
tion of said transient, whereby the circuit of said
line is closed during any one cycle before the ex
piration of >the transient of the preceding cycle.
8. In a signaling system, a' line, impulsing
means for alternately closing and interrupting
the circuit of said line at a predetermined rate
to transmit electrical impulses thereover, an im
pulse repeater adapted to be connected to said
line and including a relay energized when the
circuit of said line is closed and deenergized when
the circuit of said line is interrupted, said re
peater being operative to repeat said impulses
over a second line, means necessarily included in
and associated withl said iirst-named line for in
cidentally producing, during the period of each
impulse cycle when the circuit of said line is in
terrupted, an electrical transient which causes
false energization of said relay, a resistor adapt
40 ed to shunt the winding of said relay to increase
the sensitivity thereof to received impulses and
incidentally to increase the sensitivity of said
relay to said transient, and capacitance means
shunting said resistor for delaying, in each im
45 pulse cycle. the occurrence of the transient i'ol
lowing the interruption of the circuit of said
line and for increasingv the duration of said tran
sient, whereby the circuit of said line is closed
during any one impulsing cycle before the ex
50 piration or the transient of the preceding im
pulsing cycle.
9. In a telephone system, a line, impulsing
means on said line for transmitting electrical im
pulses thereover, an impulse repeater adapted to
55 be connected to said line and including repeater
windings for transmitting voice frequency cur
rents over a second line, a relay included in said
repeater having windings connected in series with
a portion of said repeater windings, said relay
being operative to repeat said impulses over said
second line, the circuit constants of said first
named line, the elements of said repeater, and
any other apparatus associated with said nrst
named line necessarily being so proportioned as
65
incidentally to cause intolerable distortion of the
repeated impulses, and capacitance means shunt
ing the windings of said relay and so proportioned
relative to said circuit constants that said dis
70 tortion is reduced to a tolerable value.
l0. In a telephone system, a line, impulsing
means on said line for transmitting electrical
~ impulses thereover, an impulse repeater adapted
to be connected to said line and including wind
75 ings for transmitting voice frequency currents
over a second line, a relay included 1n said re
peater having windings connected in series with a
portion of said repeater windings, said relay be
ing operative to Irepeat said impulses over said
second line, resistance means adapted to shunt
the windings of said relay, the circuit constants
of said first-named line, the elements of said re
peater including said resistance means, and any
other apparatus associated with said first-named
line necessarily being so proportioned as inci
dentally to cause intolerable distortion oi the
repeated impulses, and capacitance means shunt
ing the windings of said relay and so proportioned
relative to said circuit constants that said dis
15
tortion is reduced to a tolerable value.
11. In a telephone system, a line, impulsing
means on said line for transmitting electrical
impulses thereover, an impulse repeater adapted
to be connected to said line and including re
peater windings for transmitting voice frequency
currents over a second line, a relay included in
said repeater having windings connected in series
with a portion of said repeater windings, said re
lay being operative to repeat said impulses over
said second line, the circuit' constants of said
first-named line, the elements of said repeater,
and any other apparatus associated with said
first-named line necessarily being so proportioned
as incidentally to cause false operation of said
relay during each impulsing cycle, and capaci
tance means shunting the windings of said re
lay and so proportioned relative to said circuit
constants that said false operation of said relay
is prevented from causing false repeated im
pulses.
^
-
l2. In a telephone system, a line, impulsing
means on said line for transmitting electrical
impulses thereover, an impulse repeater adapted
to be connected to said line and including wind
ings for transmitting voice frequency currents
over a second line, a relay included in said re
peater having repeater windings connected in
series with a portion of said repeater windings,
said relay being operative to repeat said impulses
over said second line, a resistor adapted to shunt
the windings of said relay, the circuit constants
of said first-named line, the elements of said re
peater including said resistor, and any other ap
paratus associated with said first-named line
necessarily being so proportioned as incidentally
to cause false operation of said relay during each
impulsing cycle, and capacitance means shunting
the windings of said relay and so proportioned
relative to said circuit constants that said false
operation of said relay is prevented from caus
ing false repeated impulses.
' 13. In a telephone system, a line, impulsing
means on said line for alternately closing and in
terrupting the circuit of said line to transmit
electrical impulses thereover, an impulse repeater
adapted to be connected to said Iline and
including repeater windings for transmitting
voice frequency currents over a second line, a
relay included in said repeater having a. winding
connected in series with a portion of said re» 05
peater windings, said relay being energized when
the circuit of said first-named line is closed and
deenergized with the circuit of said first-named
line is interrupted, and being operative to repeat
said impulses over said second line, a resistor
adapted to shunt the winding of said relayI the
circuit constants of said first-named line, the
elements of said repeater, and any apparatus as
sociated with said first-named line being neces
sarily so proportioned as incidentally to cause M5
2,124,027
a voltage transient across said relay windings
suflicient to cause false energization and opera
tion of said relay during the period of each im
pulse cycle when the circuit of said line is
Ul interrupted, and capacitance means shunting
said relay windings and so proportioned relative
to said circuit constants that said voltage tran
sient is delayed and the duration thereof is in
creased, whereby said relay is not de-energized
following the expiration of said transient.
14. In a signaling system, a line, impulsing
means for transmitting electrical impulses over
said line at a predetermined rate, an impulse
repeater adapted to be connected to said line and
including a relay for repeating said impulses over
a second 1ine,»the circuit constants of said ñrst
named line, the elements of said repeater and
any apparatus associated with said ñrst-named
line necessarily being so related to each other
20 and to said predetermined rate of impulsing as
incidentally to cause intolerable distortion of the
-repeated impulses, and reactance means con
nected in circuit with the windings of said relay
and so proportioned relative to said circuit con
9
said line, said additional lines, the elements of
said repeaters and any other apparatus asso
ciated therewith being necessarily so related to
each other as incidentally to cause intolerable
distortion of the impulses received at said control
means, and an impedance element associated
With at least one of said repeaters and so pro
portioned relative to said circuit constants that
said distortion is reduced to a tolerable value.
17. In a signaling system, a line, impulsing
means for transmitting electrical impulses over
said line at a predetermined rate, control means
adapted to be controlled by said impulses, a plu
rality of impulse repeaters and additional lines
adapted to be connected in tandem to inter-con 16
nect said line and said control means, the circuit
constants of said line, said additional lines, the
elements of said repeaters and of any other ap
paratus associated therewith being necessarily
so related to each other and to said impulsing 20
rate as incidentally to tend to cause false oper
ation of said control means, and means compris
ing reactance means included in 'at least one of
said repeaters for preventing false operation of
25 stants and said predetermined rate of impulsing
said control means.
25
that said distortion is reduced to a tolerable value.
18. In a signaling system, a line, impulsing
15. In a signaling system, a line, impulsing .means for transmitting electrical impulses overmeans for transmitting electrical impulses over said line, control means adapted to be controlled
said line at a predetermined rate, an impulse by said impulses, a plurality of impulse repeaters
repeater adapted to be connected to said line and and additional lines adapted to be connected in 30
including a relay for repeating said impulses over tandem to inter-connect said line and said con
a second line, the circuit constants of said first
trol means, each of said repeaters including a
named line, the elements of said repeater, and
any other apparatus associated with said ñrst
35 named line being so related to each other and to
said predetermined impulsing rate as incidental
_ly to cause intolerable distortion oi' the repeated
impulses, and capacitance means connected in
shunt with the windings of said relay and so
40 proportioned relative to said circuit constants
and said predetermined rate of impulsing that
said distortion is reduced to a tolerable value.
16. In a signaling system, a line, impulsing
means for transmitting electrical impulses over
45 said line, control means adapted to be controlled
by said impulses, a plurality of impulse repeaters
`and at least one additional line adapted to be
connected in tandem to inter-connect said line
and said control means, the circuit constants of
relay for alternately interrupting and closing the
circuit o-f its associated line in response to said
impulses, whereby said impulses are transmitted 35
to said control means, the circuit constants of
said line, the elements of said repeaters, said
additional lines and other apparatus associated
therewith necessarily being so related to‘each
other as incidentally to cause intolerable dis 40
tortion of the impulses received at said control
means, the operating time interval of each of
said relays being eiïective to reduce said dis
tortion, and capacitance means included in at
least one of said repeaters in shunt with the
ywindings of the associated relay and so propor-l 45
tioned relative to said circuit constants that said
distortion is further reduced to a tolerable value.
FREE CALHOUN.
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