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Патент USA US2405620

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Aug. 23, ‘19%.
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R.‘ TAYLOR ETAL
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ZAQS?ZQ
TELEPHONE SYSTEM
Filed Aug. 19, 1943
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INVENTORS
5 v REGINALD TAYLOR
eeone; THOMAS BAKER
ATTORNEY
' Au‘ 3» i»
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R. TAYLOR ETAL.
,5,
TELEPHONE SYSTEM
-Filéd_ Aug. 19, 1945
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lNVENTORS
REGINALD TAYLOR
GEORGE TH OM§$ KER
Patented Aug. 13, 1946
2,405,620
UNITED STATES PATENT OFFICE.
2,405,620
TELEPHONE SYSTEM
Reginald Taylor and George Thomas Baker,
Liverpool, England, assignors, by mesne assign
ments, to Automatic Electric Laboratories, Inc.,
Chicago, 111., a corporation of Delaware
Application August 19, 1943, Serial No. 499,194
In Great Britain September 17, 1942
18 Claims.
1
The present invention relates to telephone or
like systems and is more particularly concerned
with systems in which it is desired to effect the
setting of automatic switches or the like by
trains of impulses transmitted over considerable
distances.
( Cl. 179-27)
2
which serves to e?ect the operation of a grid
controlled gas discharge tube which is adapted
to be intermittently operated subsequently in re
sponse to the transmission of numerical im
pulses.
According to another feature of the invention,
in a telephone or like system having signals
transmitted over a. junction by the intermittent
control is e?ected by repeatedly interrupting the
completion of a direct current circuit thereover,
?ow of direct current over the control circuit, dif 10 the equipment at the incoming end includes a
?culties are experienced as the length of line in
grid-controlled gas discharge tube which oper
creases owing to the distorting effect produced by
ates in response to each numerical impulse to
the inductance and capacity of the line. Another
control the repetition of that impulse to an au
di?iculty which arises under long line dialling
tomatic switch and also operates in response to a
conditions is due to the impulse distortion pro 15 signal indicating that impulse sending is com
duced by speech transmission condensers in asso
pleted to introduce speaking conditions in the
ciation with impedances which are connected to
incoming equipment.
the speech conductors. The removal of these
The invention will be better understood from
reactive elements from the line prior to ‘and dur
the following description of one method of carry
ing dialling out has hitherto involved consider 20 ing it into effect which should be taken in con
able circuit complexity as well as impulse storage
junction with the accompanying drawings com
and regeneration. The chief object of the in
prising Figs. 1 and 2, which should be arranged
vention is to provide improved arrangements
with Fig. 1 on the left. Fig. 1 shows the equip
enabling direct current impulsing to be used
' ment associated with an operator's sleeve control
satisfactorily over very long lines by taking suit
position at the outgoing end of a long junction
able steps to minimise the distortion which would
line, while Fig. 2 shows the corresponding receiv
otherwise be produced.
In arrangements of the type normally em
ployed in automatic telephone systems in which
According to one feature of the invention, in a
telephone or like system having‘ connections set
ing equipment at the incoming end.
The general arrangements are similar in some
respects to those described in our application Se
up over a junction in response to impulses trans- 30 rial No. 446,900, ?led June 13, 1942, where another
mitted from an operator’s position, at the in
coming end of the junction the circuits are nor
mally conditioned for the reception of impulses
solution of the general problem is disclosed, this
however involving the use of mechanical regen
erator at the. receiving end which is not neces
sary with the arrangements according to the in
an operation performed by the operator on the 35 vention. The setting up of a normal call will
completion of impulse sending.
and speaking conditions are set up in response to
According to another feature of the invention,
in a telephone or like system having connections
set up over a junction in response to numerical
impulses transmitted from an operator’s posi
tion, each impulse is transmitted by the mo
mentary completion of a direct current circuit
?rst be traced through briefly.
When the line in question is free, relay SLR,
Fig. 1, will not be operated and will co-operate
with similar relays associated with other lines to
complete a chain circuit for giving a visual indi
cation of the next line to be used. If this is
the line shown, when the operator inserts her
over the junction while the establishment of cur
plug to seize the line, no circuits are completed
rent ?ow over the junction in the opposite direc
over the line conductors but battery applied to
tion in response to an operation performed by‘ 45 the sleeve of the jack J operates relay SR which
the operator on the completion of impulse send
in turn at its contacts. srl energises its relief
ing serves to introduce speaking conditions in the
relay SS. Thereupon at contacts ssl a circuit is
incoming equipment.
A further feature of the invention is that in a
telephone or like system having signals trans
mitted over a junction by the intermittent com
pletion of a direct current circuit thereover, the
equipment at the incoming end is initially pre
pared for operation by the momentary comple
tion of a direct current circuit over the junction
' completed for relay SLR which alters the visual
idle indicator circuits so as to mark the next line
as free, While at contacts ss2 ?icker earth over
lead It! is connected up over the low resistance
upper winding of relay SE to ?ash the operator’s
supervisory lamp, thereby indicating that the
equipment is ready for further operation. Relay
SR remains operated under this condition and in
2,405,620
3
fact remains operated until the operator subse
quently removes her plug from the jack,
When the operator throws thedial key, a high
resistance is included in the sleeve circuit and
resistance battery is connected to both line con
ductors so that relay RR is operated after a short
interval. Relay A does not operate under this
condition owing to high resistance of the resists .
ance battery feed to line.
Relay RR in operate “
4
(on the grid of the tube GTA and triggering this
tube into operation, whereupon relay PD is ener
gised. ‘This relay then at contacts poll connects
the discharged condenser QH in series with its
winding whereupon the tube is at once extin
guished by the substitution of negative for posi
tive potential and as the condenser becomes
charged the current falls until relay PD can no
longer remain operated. With this arrangement
the period of operation of relay PD may be read
ing, at contacts rrl brings up‘ relay RP which
ily adjusted by suitable choice of the value of
at contacts rpé and M25 completes a battery feed
condenser QI-I. Relay PD also at contacts 11:12
ing circuit over the junction including resistances
completes a circuit for relay KO which looks up
YK, YL, YH and YJ, contacts mrB and mrl,
over its contacts kol, completes a, loop forward
windings of relay RS, inductance Tl which with
condenser QD and resistance YG forms a low 15 to the incoming ?rst selector at its contacts 7e02,
prepares circuits at contacts 7e04, R05 and bot
pass ?lter, and the primary winding of trans
for relays PS, PB and KN and at contacts 7:03
former T2, Fig. 2, at the distant exchange. Re
completes a circuit for relay CD. Relay CD is
lay RS operates and at contacts rsl completes a
slow-to-operate
and consequently contacts cd2
circuit for relay DT to the earthed contacts ss3,
do
not
complete
a circuit for relay KN at this
while at contacts 1'32 it holds relay vRP independ 20
time since relay PD will'have released before
ently of relay RR. Relay DT in operating, at
relay CD, operates. No further changes occur
contacts dtl and (1253 completes locking circuits
until
the operator commences to dial.
for itself and for relay RP and at contacts c2152
When the dial is moved off-normal, the bat
disconnects the flicker earth from the jack sleeve
and prepares a circuit for relay MR. This relay 25 tery connection to the T and R lines at the oper
ator’s position is removed and these line con
cannot operate owing tothe high resistance in
ductors are left directly connected together over
troduced in the sleeve circuit at the operator’s
the dial springs. When these springs first open,
position, but the resistance of relay MR is sum
cient to extinguish the operator's supervisory . relay A releases and at contacts 0.! removes the
lamp. Relay DT also at contacts dill shuntsvout 30 shunt across the battery connected to the junc
tion line circuit so that line current again ?ows.
relay RR and at contacts dt5 connects battery
This has the effect of reducing the negative po
via resistance YE to the other winding of relay
tential on the grid of tube GTB and since its
A which now operates. Relays A and .DT to
gether at contacts a1 and CH6 shunt. the battery... anode circuit is now completed by the operation
connection to the junction so that current falls 35 of relay KO, it strikes and operates relay PS.
rDhis in turn at contacts psi brings up relay PB
to zero in the winding of the distant transformer
which at contacts pbl connects relay P2 to the
anode of tube GTA in place of relay PD, at con
The tubes GTA and GTB in the incoming equip
tacts pbZ locks up, at contacts @173 releases relay
‘ ment are gas discharge tubes of the type in which. _
a grid controls the striking of the tube but‘ there 40 PS and extinguishes tube GTB, at contacts p124
repeats the impulse by opening the circuit to the
after exercises no further control, the tube being
?rst selector, and at contacts pbS transfers relay
extinguished only by a change in the anode cir
CD
to the P conductor extending back from this
cuit. These tubes are preferably of the hot cath
switch so that it is held up by the guard earth
ode argon-?lled type. It will be noted that a
circuit is normally completed for the ?laments 45 which was connected thereto when the loop was
extended forward.
of the tubes in series in a circuit including re
When the impulse springs again close, relay A
sistances YN, Y0 and YR. The grids of the
reoperates and battery is again shunted off the
tubes are connected to separate windings of
T2.
,
,
'
.
line. Tube GTA is now triggered into action
transformerT2 in such manner that one tube
with the result that relay PZ operates and at
60
is caused to strike by a fall in the line‘ current
contacts p22 effects the release of relay PB. Re
and the other tube by a rise in the line current.
lay PB again closes the loop to the ?rst selector
The purpose of the arrangement shown whereby
the negative bias of the tube GTA is derived by
at contacts 12b4, transfers relay CD to its orig
inal circuit at contacts M25, and at contacts pbl
way of resistance YN which equals the hot re
and p173 again prepares circuits for relays PD
sistance of the ?lament of either tube GTA or
and PS, tube GTA being extinguished and relay
GTB is to ensure that the standing negative grid
PZ releasing on the opening of the contacts pbl.
bias on each tube with respect to its ?lament
In response to the next break, relay PS is again
and therefore the striking voltage will be sub
operated and brings up relay PB and when the
stantially the same in spite of the fact that the
loop
is again closed relay PZ operates and brings
60
?laments being in series are at slightly different
down
PB. This operation continues during the
potentials. The purpose of the condensers QF
di?erent trains of impulses which are according
and QG and associated resistances YM and Y?
ly repeated to the ?rst and subsequent selectors
and the position at the end of dialling is that
. operation of relay RP at the outgoing end pro 65 only relays K0 and CD remain operated in the
incoming equipment, relay KO being locked over
duces a momentary voltage in the secondary
contacts ski! and 7001 and relay CD being held
windings of transformer T2, the effect of which
locally over contacts 7e03, p126 and 7on3.
isto reduce the negative bias on the grid of the
The operator now restores the dialling key,
tube GTB but it does not strike at this time owing
whereuponv
the high resistance introduced into
70
to the fact that its anode circuit is not yet closed.
the sleeve circuit at her position is short-circuited
Shortly thereafter when relays A and DT oper
will be dealt with later.
The initial closing of the line circuit on the
ate, the current in the line circuit is again re
duced to zero and a pulse is then produced in
and this causes the operation of relay MR. This
relay thereupon locks up over contacts mrZ to
battery via resistance YB, prepares answering
the ‘opposite direction by the transformer T2.
This has the eifect of reducing the negative bias 75 supervisory circuits at contacts mr3, mrll and mr5,
5
2,405,620
opens the circuit of relay DT at contacts mrl,
reverses the battery connections to the junction
at contacts mr? and mi‘? and opens the shunt
at contacts mr8 so that current ?ow over the
junction now takes place but in the reverse direc
tion to that previously flowing.
Consequently, at the distant end, the impulse
generated by transformer T2 at the distant ‘ex
change is in the same direction as that previously
produced by cessation of current flow over the
line, that is to say, in the sense to cause the op
eration of tube GTA. As a result relay PD is
again operated and since relay CD is energised
at this time, a circuit is now completed for relay
KN from earth over contacts
cd2 and lco?.
Relay KN locks up at contacts .‘cnl dependent
upon relay KO, opens the circuit of relay CD at
contacts 7:713 and at contacts 7on2 completes a
shunt across the speaking leads by way of re
sistance YS to prevent the release of the estab
lished connection during the changeover opera
tion. On the release of relay CD after its slow
period, relay SK is operated over contacts ccZ'l
and 1on3 and thereupon locks up over contacts 0031,
p126 and $703 to the P conductor. At contacts ski
and slc2 it disconnects the primary winding of the
transformer T2 and switches the line through,
while at contacts sled it opens the circuit of relay
KO. This relay releases after its slow period
and in turn releases relay KN. The speaking
leads are then switched straight through at the
incoming relay set and the only relay remaining
6
for through supervision purposes. The operator
now releases her cord circuit speaking key so as
to cause a through circuit to be provided in the
cord circuit between the calling and called parties,
and vconversation now proceeds.
At the end of conversation if the called party
hangs up ?rst, relay D will release and at contacts
(ll will re-light the operator’s supervisory lamp,
while at contacts d2 the resistance battery poten
tial will be removed from the R conductor so as
to give through supervision to a distant originat
ing operator in cases where the incoming call has
arrived over a junction.
The sleeve control op
erator may now wait for clearing supervision
15 from the originating exchange and when she
withdraws her plug from the jack J the sleeve
relay SR will be released and will bring about the
release of relays SS and MR. Relay MR in re
leasing at contacts mr5 opens the loop via relays
20 D and I to the outgoing junction thereby initiat
ing the release of the automatic switch train in
the distant exchange. When this has been ef
fected earth is removed from the P conductor to
allow relay SK to release, whereupon both the
25 outgoing and incoming equipment is ready for
further use.
In case the Wanted subscriber is found to be
busy, busy tone and ilash is returned over the
speaking leads from the ?nal selector and relay I
30 ?ashes in response to the busy ?ash signals, and
at contacts i2 ?ashes the sleeve control position
operator’s
battery
viasupervisory
resistance lamp,
YF iswhile
intermittentlyv
at contactsap
operated is relay SK which is locked up to the P
conductor.
plied to the R conductor so as to bring about the
At the outgoing end, relay DT, in releasing in 35 flashing of the calling supervisory lamp of the
response to the operation of relay MR, at con
originating A operator in cases where the call has
tacts diZ further prepares a circuit for giving
arrived over a junction. The calling party is
called party supervision to the operator. At con
then advised and the connection is taken down,
tacts (its the short-circuit is removed from relay
whereupon release of the outgoing and incoming
RR, which however cannot re-operate since the 40 equipments shown is effected in the manner al
battery connection to the T and R lines was
broken when the dial key was restored. At con
tacts dt3 one looking circuit for relay RP is
opened and the continued holding of this relay
is now dependent on relay RS. When relay SK
at the incoming end operates and initiates the
release of relay KO, during the slow release of
relay KO there will be no loop holding circuit for
relay RS at the outgoing end, and this relay will
thereupon release and in turn bring down relay
RP. At contacts we and M05 relays D and I are
now connected across the outgoing loop and on
release of relay KO at the incoming end relay I
will operate in series with the battery feeding
relay of the ?nal selector at the distant exchange.
Relay I in operating at contacts 2'! energise the
polarising winding of relay D, at contacts 12 ex
tends full earth back via the upper low resistance
winding of relay SR to the sleeve circuit so as to
ready described.
The case must also be considered in which the
desired call is not set up as just described, but
is prematurely released by the sleeve control op~
eratc-r withdrawing the plug before completing
dialling.
In this case relays SR and SS are re
leased by the disconnection of the sleeve circuit,
while relay DT which is held from the earthed
contacts 883 commences to release slowly. Relay
A also releases but relay RP remains held during
the release time of relay DT over contacts dtt and
mi. On the release of relay A, current is again
allowed to ilcw out through relay RS and over
the outgoing loop to the transformer T2 so that
relay
re-operates and maintains the circuit of
relay RP independently of relay DT. The cur
rent flow over the loop produces an impulse in
transformer T2 in such direction as tocause tube
GTE to strike
at the beginning of a normal
light the operator’s supervisory lamp and indicate 60 dialled impulse, whereupon relay PS operates and
that connection has been made with the called
party but that he has not yet answered the call,
while at contacts 13 the battery connection via
resistance YF and the right hand winding of relay
in turn brings up relay PB. Relay; PB looks over
its contact pbfé and at its contacts gobs opens the
loop to the selector train. Since this condition
persists, the automatic switch train is released
A is removed from the R conductor, this arrange 65
in due course earth is removed from the P
ment being used as will be later described for
conductor. Relay CD has been previously held
through supervision purposes
cases where the
up over this circuit via contacts @735 and E03 and
originating call has arrived over an incoming
it will now commence to release slowly and when
junction.
it falls away a circuit is completed over contacts
When the called party replies, battery reversal
and cell for relay SK. Relay SK in operating
takes place over the line from the distant ?nal
at contacts ské opens the holding circuit of relay
selector, whereupon relay D operates and at con
KC and when this relay releases after its slow
tacts dl extinguishes the operator’s supervisory
lamp and at contacts d2 restores the connection
of resistance battery potential to the R conductor
period it brings down relay PB at contacts 7e05,
whereupon the circuit for relay SK is opened at
contacts
and it also releases.
2,405,620
Meanwhile at the outgoing end the operation of
relay It? with relay SS normal has the effect that
at contacts m2 the busying battery via resistance
YA maintains relay SLR and at contacts m3 bat.
tery via resistance Y0 and contacts ss5 is applied
to the jack sleeve for engaged test purposes in case
this should be required. When relay SK at the
incoming end operates, contacts skl and ski? open
the holding circuit for relay RS at the outgoing
'8
said trunk line at such times thereby to char
acterize said trunk line as busy.
3. In a telephone system wherein call-directing
impulses are transmitted from an operator’s posi
tion in one exchange over a two-conductor trunk
line to another exchange, and wherein said other
exchange has numerical switching equipment, cir
cuits in said other exchange normally conditioned
to receive said impulses from said one exchange
end, and since relay RP is dependent upon relay 10 and to control said equipment in accordance
therewith, and means in said other exchange con
RS,‘ this relay also releases and the outgoing
trolled by an operation performed at said op
equipment is completely restored to normal. At
erator’s position after said impulses have been
the incoming end when relay SK releases after
sent for preparing circuits in said other exchange
having released relays K0 and PB in turn, this
for the transmission of speech.
equipment also is ready for further use.
4. In a telephone system, two exchanges inter
It will be understood that if for any reason
connected by a trunk line, an operator’s position
the automatic switches do not release so that
in one of said exchanges, means under the control
earth is maintained on the P conductor, relay CD
of said position operated to transmit direct cur
will remain held, relay SK will not be operated,
rent impulses of a certain polarity over said trunk
and current will continue to ?ow over the loop to
lineto the other of said exchanges and then op
maintain relay RS and in turn relay RP at the
erated to transmit a direct current impulse of the
outgoing end. Relay RP then maintains relay
opposite polarity over said trunk line to said other
SLR operated so as to prevent the line being in
exchange, means in said other exchange for re
cheated as idle, while the engaged test battery is
ceiving the impulses of said certain polarity and
maintained on the jack sleeve. Moreover, at con
directing the extension of a connection in ac
tacts 7113 the circuit for relay SR is held open so
cordance therewith, said connection including a
that if the operator should re-insert the plug
normally disabled speech circuit, and means in
after only a momentary withdrawal, this relay
said other exchange controlled by the impulse of
cannot re-operate until the equipment at the dis
said opposite polarity for enabling said speech
tant end has released and permitted relay RP to
fall away.
With regard to the paired condensers and re
sistances QF, YM and QG, ‘YP which are asso
circuit.
‘
-
5. In a telephone system, two exchanges inter
connected by a trunk line, an operator’s position
in one of said exchanges, means under the control
ciated respectively with the tubes GTA and GTB,
these serve to integrate the effect of impulses from 3: of said position operated to transmit numerical
impulses over said trunk line to the other of said
the windings of transformer T2 so that satis
exchanges, a pair of grid controlled gas discharge
factory operation from non-steep-fronted re
tubes in said other exchange associated with said
ceived signal waves can be obtained without in
trunk line and ?red alternately by said impulses,
volving false operation due to parasitic line volt_
ages of equivalent instantaneous value. These 40 means controlled by said tubes for repeating said
impulses thereby to~ control the extension of a
arrangements are dealt with more fully in the
connection in accordance therewith, said connec
speci?cation previously referred to.
tion including a normally disabled speech circuit,
It will be appreciated that the impulsing ar
means responsive to an operation performed at
rangement shown whereby battery is shunted off
said position after the transmission of said im
the line is preferable to the more useful method
pulses for again ?ring the tube last ?red by said
of opening the line as it permits the rise and fall
impulses, and means controlled by said tube for
of current to follow substantially similar curves
thereupon enabling said speech circuit.
and thus enables the two gas discharge tubes to
6. In a telephone system, two exchanges inter
operate under substantially identical conditions.
connected
by a trunk line, means in one of said
It will be seen also that with the arrangement
exchanges operated at will to complete a direct
shown the ratio of the impulses supplied to the
current circuit over said trunk line, an interrupter
automatic switches is dependent on the ratio of
in said circuit at said one exchange then oper
the dialled impulsesrbut that this ratio is not ap
ated to transmit impulses over said trunk line, a
preciably distorted since the factors which pro
grid controlled gas discharge tube associated with
duce distortion with relay repetition are not op
said trunk line in the other of said exchanges,
erative on the improved circuit.
.
What we claim as new and desire to secure by
said tube operated initially by the completion of
said circuit and reoperated by each of said im
Letters Patent is:
pulses, equipment conditioned by said initial op
1. In a telephone system, two exchanges inter
eration of said tube and thereafter controlled by
60
connected by a trunk line, an operator’s position
the reoperations of said tube to direct the exten
in one of said exchanges, means operated under
sion of a connection in accordance with said im
the control of said position to transmit call di
pulses.
recting impulses over said trunk line to the other
7. In a telephone system, two exchanges inter
of said exchanges, circuits in said other exchange
normally conditioned to receive said impulses and 65 connected by a trunk line, means in one of said
exchanges operated to transmit direct current im
to control the extension of a connection in ac
pulses over said trunk line to the other of said
cordance therewith, said connection including a
exchanges, a gas discharge tube associated with
normally disabled speech circuit, and means for
said trunk line in the other of said exchanges and
enabling said speech circuit responsive to an op
eration performed at said position after the trans 70 operated intermittently by said impulses, means
controlled by said tube for directing the extension
mission of said call directing impulses.
of a connection in accordance with said impulses,
2. In a telephone system as claimed in claim 1,
said connection including a normally disabled
wherein said connection is maintained at times
speech circuit, means in said one exchange oper
after said trunk line has been released at said po.
ated
after said impulses have been transmitted
75
sition, a relay in said one exchange operated over
2,405,620
10
to transmit a further'impulse over said trunk 1ine,
and means operated by said tube responsive to
said further impulse to enable said speech circuit.
8. In a telephone system, two exchanges intere
connected by a trunk line, means in one of said
exchanges operated at will to complete a direct
necting said receiving equipment from said trunk
line and connecting to said trunk line the ex
tended speech path.
14. In a telephone system, a line, means for
current circuit over said trunk line, an interrupter
in said circuit at said one exchange then oper
ated to transmit impulses over said trunk line, a
pair of gas discharge tubes in the other of said 10
exchanges, means whereby one of said tubes but
not the other operates responsive to the comple
tion of said circuit and said two tubes thereafter
operate respectively at the beginning and end of
each impulse, equipment conditioned by the ini 15
tial operation of said one tube and thereafter con
trolled conjointly by said two tubes to direct the
extension of a connection in accordance with said
impulses.
\
9. In a system as claimed in claim 8, wherein
each of said tubes has a grid and a cathode, a cir
cuit for heating said cathodes including both said
cathodes in series, and means for normally apply
ing to the two grids a slightly different bias to
compensate for the di?erence in mean potentials
of said cathodes, whereby said tubes require sig
nals of substantially equal strength to be applied ‘
impressing direct current impulses upon said line,
impulse receiving equipment normally connected
to said line, said equipment including a ?rst gas
discharge tube operated responsive to the begin
ning of each impulse and a second gas discharge
tube operated responsive to the end of each im
pulse, meanscontrolled conjointly by said tubes
to direct the extension of a speech path, means
operated after the last of said impulses to impress
upon said line such a potential as to reoperate
said second tube without ?rst reoperating said
?rst tube, and means thereupon controlled by said
second tube to disconnect said impulse receiving
equipment from said line and to connect said
speech path to said line.
15. In a telephone system, two exchanges inter
connected by a trunk line, means in one of said
exchanges operated to transmit direct current
impulses of a certain polarity over said trunk line
and then operated to transmit a direct current
impulse of the opposite polarity over said trunk
line, a gas discharge tube in the other of said
exchanges, means whereby said tube operates in
to their respective grids to bring about the opera
termittently responsive to the impulses of said
tion of said tubes.
certain polarity and causes a connection to be
10. In a telephone system, a line, means for 30 extended in accordance with said impulses, said
impressing direct current impulses upon said line,
connection including a disabled speech circuit,
a pair of grid controlled gas discharge tubes so
associated with said line that one of said tubes op
erates responsive to the beginning of each impulse
and the other operates responsive to the end of ‘
each impulse, means controlled conjointly by said
and means whereby said tube operates responsive
to the impulse of said opposite polarity thereby
to enable said speech circuit.
16. In a telephone system, two exchanges inter
tubes to direct the extension of a connection in
connected by a trunk line, means in one of said
exchanges operated at will to complete a direct
accordance with said impulses, said connection
current circuit over said trunk line, an inter
including a disabled speech circuit, means oper
rupter in said circuit at said one exchange then
ated after the last of said impulses to impress 4.0 operated to transmit impulses over said trunk line,
upon said line such a potential as to reoperate
a pair of gas discharge tubes in the other of said
said other tube without ?rst reoperating said one
exchanges, means whereby one of said tubes op
erates responsive to the completion of said cir
tube, and means thereupon controlled by said
other tube to enable said speech circuit.
cuit and thereafter operates responsive to the
11. A telephone system as claimed in claim 10,
end of each impulse, means controlled by the
wherein said tubes are inductively connected to
initial operation of said one tube for conditioning
said line so that any particular change of current
the other of said tubes for operation whereby
in said line causes potentials of opposite polarity
said other tube thereafter operates responsive to
to be impressed simultaneously upon the grids of
the beginning of each impulse, and equipment
said two tubes.
conditioned by the initial operation of said one
' 50
12. In a telephone system as claimed in claim
10, wherein said one tube has a normally open
anode circuit and said other tube has a normally
tube and thereafter controlled conjointly by said
two tubes to direct the extension of a connection
in accordance with said impulses.
17. In a telephone system, two exchanges inter
closed anode circuit, means for controlling said
other tube over said line before said impulses are 55 connected by a trunk line, means in one of said
exchanges operated at will to complete a direct
impressed upon said line, thereby to cause said
current circuit over said trunk line, an interrupter
other tube to energize its anode circuit, and means
in said circuit at said one exchange then operated
controlled by said energization of the anode cir
to transmit impulses over said trunk line, a trans
cuit of said other tube for causing the anode cir
cuit of said one tube to be closed, thereby to pre 60 former in the other of said exchanges having its
pare said one tube to respond to the beginning
primary winding connected to said trunk line, a
of each impulse.
grid-controlled gas discharge tube having its grid
connected to a secondary winding of said trans
13. In a telephone system, two exchanges inter
former so that said tube is brought to its critical
connected by a trunk line, said trunk line com- I
prising not more than two conductors, an oper 65 grid potential responsive to the completion of
ator’s position in one of said exchanges, means
operated under the control of said position to
transmit call directing impulses over said trunk
said circuit and also responsive to the end of each
impulse, another grid controlled gas discharge
tube having its grid connected to a secondary
winding of said transformer so that said other
line, impulse receiving equipment in the other of
said exchanges normally connected to said trunk 70 tube is brought to its critical grid potential re
sponsive to the beginning of each impulse, each
line for responding to said impulses and causing
tube effective to operate when brought to its criti
a speech path to be extended in accordance there
cal grid potential, equipment conditioned by the
with, and means operated responsive to an opera
tion performed at said position after the trans
operation of said ?rst tube responsive to the ini
mission of said call directing impulses for discon 75 tial completion of said circuit and thereafter con
trolled conjointly by said two tubes to direct the
2,405,620"
11
extension of a connection in accordance with said
12
ing a discharged condenser and, in series there~
with, a, source of potential so poled with respect
'
to'said ?rst source as to aid said ?rst source in
18. In combination, a circuit including in series
charging said condenser through the winding of
a source of potential, the winding of a relay and
relay, the condenser charging current hence
a, gas discharge tube, said tube normally prevent C1 said
maintaining said relay operated for an interval
ing said source from causing current to ?ow over
after the discharge through said tube has ceased,
said circuit, means for momentarily applying to
and
said relay eifective to restore to normal when
said tube such a potential as to initiate the dis
the condenser charging current ceases to ?ow due
charge thereof, thereby to cause current to flow
over said circuit and operate said relay, a circuit 10 to the condenser becoming charged.
connected by said relay upon operation in bridge
REGINALD TAYLOR.
of the discharge path through said tube thereby
GEORGE THOMAS BAICER.
to extinguish said tube, said bridge circuit includ
impulses.
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