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Oct. 8, v1946.
F_ A, MQRRl‘s
2,409,145
CONTROL AND TRIGGER CIRCUIT FOR TELEPHONE SYSTEMS AND >'.l‘I-IEÈ LIKE
Filed sept. 2e, i944
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Í. â, ì946.
F, A_ MORRlS
2,409,145
CONTROL AND. TRIGGER CIRCUIT FOR TELEPHONE SYSTEMS AND THE, LIKE
Filed Sept. 26,> 1944
4 sheets-sheet 2
INVEN TOR.
FFH/VK H MORE/5
Oct. 8, 1946.
F. A_MoRRls
2,409,145
CONTROL AND TRIGGER CIRCUIT FOR TELEPHONE SYSTEMS AND THE LIKYE1
Filed Sept. 26, 1944
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. 8, 1946.
2,409,145
F. A. MORRIS
CONTROL AND TRIGGER CIRCUIT FOR TELEPHONE'SYSTEM‘S AND THE LIKE
Filed Sept. 26, 1944
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Patented Get. 8, 1946
UNTE
2,409,145
STATES FATENT OFFICE
2,409,145
CONTROL AND TRIGGER CIRCUIT FOR
TELEPHONE SYSTEMS AND THE LIKE
Frank A. Morris, Rochester, N. Y., assignor to
Stromberg-Carlson Companyyltochester, N. Y.,
a corporation of New York
'
Application September 26, 1944, Serial No. 555,850
20 Claims. (C1. 179-4752)
1
2
rlîhis invention relates to stopping, triggering
and testing circuits which are particularly useful
in telephone systems and the like.
In such systems and especially in automatic
telephone systems, it is important that the auto
generalized application than the speciñc arrange
ment shown in Fig. 3.
The novel control circuits herein shown, are
applicable to many fields of use, but for con
venience in disclosure they are shown incorpo
rated in an automatic telephone system. This
system is herein illustrated as being of a size em
matic switch means employed therein be prompt
ly stopped as soon as a given switching connection
ploying only ñnder and connector switches.
has been effected. Also in such systems, it is nec
However, the number of lines served by the sys
essary to test certain equipment, such as lines,
trunks or allotters to determine whether or not 10 tem can be increased by the addition of selector
such equipment should be seized for use. Such
switches in the >manner well known.
'
The finder and connector switches herein ln
testing should be effected in a reliable manner
dicated, are of the construction disclosed in the
and in an inñnitesimal period of time. Further
patent to Lienaen No. 2,148,824, granted Febru
more, both in automatic telephone systems and in
manual systems as well, trigger circuits are es 15 ary 28, 1939, although other types of switches
sential especially for tripping the ringing current
having primary and secondary selecting move
when the called subscriber answers.
The main feature of the invention relates to
ments may be used instead. The allotter herein
indicated may be of the so-called ball-selector
type, disclosed in the patent to Blomberg No.
control circuits generally, wherein electric dis
charge devices contribute to the reliability and 20 2,127,322, although other types of allotter
switches may alternatively be used.
markedly prompt action thereof.
With this brief reference to the switch con
Another feature of the invention relates to
struction, it is believed that the invention will
novel control circuits incorporating therein elec
best be understood by describing the method of
tric discharge devices, which circuits determine
establishing a telephone connection from a tele
the availability for use of telephone equipment,
phone subscriber’s line, indicated at A, to a called
govern the action of telephone switching appa
subscriber’s line, indicated at B. When the sub
ratus, and trigger the operations of telephone
apparatus.
The various features and advantages of the in
vention will appear from the detailed description
and claims when taken with the drawings in
which Figs.
2 and 3. when arranged in the or
der named, illustrate the novel circuits of this in
vention incorporated in an automatic telephone
system. Fig. l shows two typical telephone lines
and duplicate allotter control means. Fig. 2 il
lustrates an allotter and a portion of aline ñnder,
certain of the brushes oi which are shown at the
lower right of this ligure. At the left hand side
of Fig. 3 there` are shown the remainder of the
finder brushes, while at the center and at the
right hand portion of this figure, there is shown
the connector switch circuit. Fig. 4 is a schematic
circuit arrangement illustrating in somewhat
simpler form a low voltage “ñring” circuit for a
gas-filled arc discharge device utilized to stop the
finder switch in the system of Figs. l, 2 and 3.
Fig. 5 is a simpliñed disclosure of the testing ar
scriber at substation A removes his receiver from
its switch-hook, a circuit is completed for ener
30 gizing the group line relay 5 which is common to
a group of ten lines in the same tens group. This>
circuit extends from ground, winding of the relay
5, upper back contact and armature of the cut-off
relay 6, upper side of the calling line, thence,
35 through the calling substation and over the low
er side of the calling line, lower` armature and
back contact of the cutoiî relay 5, resisto-rs l and
8 in series to the negative side of battery. Con
denser S is connected in parallel with the resistor
.40 8 so that the drop across resistor 8 charges the
condenser 9, thereby putting an identifying con
dition on the calling line hunt terminal I0, in the
terminal of the group of finder switches serving
this line. The operation of the common line re
45 lay .'ê serves to start an allotted ñnder to search
for the calling line, and also serves to place an
identifying ground on the group level ll (Fig. 1)
in the line under banks. It will be noted that the
upper armature of the line relay 5 is provided
rangement employed in the mentioned system,
two links being shown to indicate the condition 50 with two contact springs I2 and I3 which close in
sequence. This insures that the identifying
prevailing when a busy line is tested. Fig. 6 is
ground will be applied to the group level Contact
a modified form of ringing trip arrangement or
li in the line finder bank, before the line finder
starts to move. The start of the line ñnder is
used in the connector circuit of Fig. 3. Fig. ’7
illustrates a trigger circuit of somewhat more 55 elîected from ground at the upper armature of
trigger circuit which can be substituted for that
'
2,409,145
3
group relay 5 and front contact I2 thereof, now
closed, as well as the front contact I3 subse
quently closed, thence, over conductor I4, arma
ture and back contact of the relay I5, conductor
I6, back contact and armature of relay> I'l, con
ductor I8, winding of the allotter start relay I9,
to negative battery.
The operation of the al
lotter start relay I9 applies ground at its upper
armature and front contact for completing a cir
4
mature and back contact, opens the energizing
circuit of the relay 23. This relay, it will be re
called, is also sluggish in releasing its armatures.
The purpose of this sluggishness is to provide a
delay sufficient for the ñnder switch to come to
rest definitely, after its primary hunting move
ment and before its secondary hunting movement
is started.
However, after a very brief time, the
slow-releasing relay Z3 does release and thereby
cuit through the armature and back Contact of 10 completes a self-interrupting circuit for the sec
the relay 2i), armature and back contact of the
relay 2|, conductor 22, winding of the relay 23 to
the negative side of battery. It should be pointed
out that the relay 23 is sluggish not only in at
ondary magnet ‘i5 extending from the negative
' side of battery, winding of this magnet, its arma
ture and back contact, allotter brush l'sï, back
contact and armature of relay 23, front contact
tracting its armatures but also in releasing them. 15 and armature of relay 2|, now energized, back
contact and armature cf relay 20, front contact
The purpose of having the relay 23 sluggish in
and armature of allotter start relay i3 to ground.
operating, is to hold open its armature 24 and
Under the control of this circuit, the secondary
front contact for a slight interval, to insure that
stepping magnet fit advances the nnder brushes
the circuit of the primary stepping magnet of the
3l, £5, 39 and
in their units or secondary
20
ñnder is not completed until the pre-impulse cir
hunting direction. This hunting operation con
cuit has an opportunity to function. The pre
tinues until the brush ¿lil encounters the hunt
impulse circuit is energized by ground, applied at
terminal Iû (Fig. l) of the calling line. It Will
the inner front contact and armature of the re»
be recalled that when the subscriber of this line
lay I9, conductor 25, allotter switch contact 23,
conductor 2l, current limiting resistor 23, sec 25 initiated a call, he set up a condition whereby
the condenser 9 was charged. Consequently,
tion 29 of the link conductor, lower winding of
when the ñnder brush riß encounters the hunt
the combined battery feed and impulse relay 353, to
terminal Iii, a circuit is completed from the nega
the negative side of battery. Relay 3i) is energized
tive side of battery, primary winding 48 of a
in this circuit and at its upper armature and
step-up transformer (Fig. 2), front contact and
30
front contact removes ground from release con
armature 4S of the allotter start relay, conductor
ductor 83 while completing an obvious circuit for
El), allotter contact 5I, ñnder brush t0, hunt ter
energizing the slow-releasing relay 3| of the
minal I0, through the condenser S, to negative
connector. Relay 3| thus operates and at its
side of battery. This circuit discharges condenser
armature 32 and front contact applies master
ground for the various circuits or the connector. 35 9 through the primary winding 48 of the trans
former. This discharge induces a voltage in the
It will be recalled that the relay 23 is slow to op
secondary winding 52 of the transformer which
erate and that during the time that it is attract
voltage is applied ,through the condenser 53 t'o
ing its armature 2li, the pre-impulse circuit, as
the starter anode 54 of the finder stopping arc
described, has an opportunity to be completed.
When, however, the armature 2li and front con
tact of relay 23 is closed, a self-interrupting cir
cuit is completed for the primary magnet ‘ät of
the finder switch. This circuit extends from the
40 >discharge device 58.
The arc discharge device is
gas-ñlled and preferably of the cold cathode type,
sold under the code 1G21. This device comprises
the cold cathode 55, the starter anode 54 and the
anode proper 55. The mentioned induced volt
negative side of battery, winding of primary step
ping magnet 34, its armature and back contact, 45 age, when applied to the starter anode 54, causes
the ñnder stopping device 58 to conduct. As a
through the normally closed olif-normal contacts
result of this, the allotter control relay is ener
35, contacts 36 of the allotter switch, front con
gized from the positive side of battery through
tact and armature 2Q of relay 23, back contact
the capacitive network 59 and 6G, winding of
and armature ofrelay 2 I, back contact and arma
ture of allotter relay 2i), front contact and arma 50 the relay 25, across the space between the anode
55 and cathode 55 of the discharge device 58,
ture of relay I9, to ground. Under the control of
conductor 7|, lower front contact and armature
this circuit, the primary stepping magnet ad
of relay |9 to ground. The relay 2€) is thus ener
vances the tip brush 3l, ring brush 38, sleeve
gized and at its inner upper armature and back
brush 39 (at left of Fig. 3) and hunt brush liu
contact, it interrupts the stepping circuit for the
(at right of Fig. 2) in their primary or group se
secondary stepping magnet 45 so that the brushes
lecting movement. Also, the stepping magnet
of the ñnder come to rest. The arrangement,
advances the group selecting brushes 4| (at the
just described, for stopping the secondary move
right of Fig. 2) and ¿52 (at the left of Fig. 3) in
ment of the iinder switch is shown in simplified
their primary direction. The primary stepping
magnet 34 continues to self-interrupt its operat 60 form in Fig. 4.
It now becomes necessary to test the calling
ing circuit and thereby advances the mentioned
line to make sure that it has not been seized as
ñnder brushes until the rlnder brush 4I encoun
a called line by a connector, which condition may
ters the level contact |I (upper left Fig. 1) of
have arisen during the time that the finder switch
the group of lines in which the calling line is lo
cated. As soon as the brush lll encounters the 65 in question was hunting for the calling line. As
soon as the allotter control relay 2€) operates, it
contact |I, this completes a circuit from ground
also completes the necessary circuit for testing
at the armature and contact i2 of relay 5, group
the busy or idle condition of the calling line, for
contact II, finder brush 4I, allotter brush 43,
the purpose just mentioned. The busy test is
conductor 44, winding of allotter transfer relay
2 I, to the negative side ci battery. This energizes 70 accomplished by the cold cathode arc discharge
device 5I, preferably similar in construction to
the relay 2| and at its uppermost armature and
the device 58, in cooperation with the busy test
front contact it opens the self-interrupting cir
circuit. When the starter anode
causes the
cuit of the stepping magnet 34, thereby stopping
gas in the device to ionize the busy test circuit
the primary movements of the nnder switch.
Also, the operation of the relay 2| at its inner ar 75 extendsl from the source of high positive voltage
2,409, 145
5
6
of the order of 150 volts, anode B2, cathode 6A,
lay 2li, conductor 56, allotter brush El, conductor
58, upper winding of the connector cut-through
relay $3, ñnder sleeve brush 39, finder sleeve con
tact Se', which is individual to the calling line,
winding ci the cut-off relay 6 to the negative side
If the finder busy test device 5l indicatesa busy
condition on the calling line, brought about by a
connector seizing this line during the hunting
interval, this device will not become conductive
and the connector cut-through relay 69 (Fig. 3)
in series with it, will not be energized. The talk
ing connection will thus not be cut through and
of battery.
when the allotter advance relay il’ operates, as
conductor 55, armature and front contact of re
Current ñows in this circuit and
cnergizes the cut-off relay 6 to disconnect the
will be described, and the allotter delay relay 23
group line relay l? from the control of the calling 10 releases, the pre-impulsing ground will be re
line and also energizes the cut-through relay B9.
moved, the connector battery feed and impulsing
lît should be mentioned that the electron discharge
relay gli and the connector delay relay 3l Will also
device 6| is adjusted by means of a potentiometer
release and the release signal will be returned to
the line finder -release magnet 8l (at right of
conductive when sufficient voltage appears be 15
2). This will release the link seized by the
tween its cathode Gd and starter anode E53. When
calling party and he will be able to talk through
the busy test lead, including the conductors S6 and
the connection established by the connector which
S8 and iinder sleeve brush 39. is extended through
had seized his line during the hunting interval.
the sleeve terminal of the calling line in the mul
Before describing the operation of the con
tiple bank, the circuit is completed in such a way 20 nector in seizing the called line in response to
that the sum of 15G volts plus 48 volts appears
the dial impulses, it will be set forth how the
P across its ~cathode and anode so that it will be
across the device Si, if the line is in an idle condi
tion. The potentiometer P is adjusted so that the
allotter is released from this call in the course
of the completion of the line ñnding operation
and how the allotter preselects an idle link for
a succeeding call. This is brought about when
the allotter control relay 2D (Fig. 2) is operated,
thereby completing a circuit from ground, upper
iront contact and armature of relay I9, inner
armature and front contact of relay 20, conductor
this circuit, a voltage drop appears across the
22, winding of the slow operating relay 23 to the
cut-off relay E s0 that the voltage on the sleeve
negative side of battery. This relay is slow to
terminal of the calling line in the multiple bank
operate for the purpose of giving a suflicient in
no longer appears to be 4S volts negative, as
terval of time for the iinder busy test circuit
schematically indicated in Fig. _5. Thus, any
including the device 6| to operate. As soon as
other busy test lead of another link circuit will f the relay 23 does operate, it closes a circuit from
not encounter sufficient voltage on its busy test
ground on the lowermost front contact and arma
brush, to ionize the gas in its busy testing device
ture of relay 2B, lower front contact and arma
similar to El. rEhe time required for the busy
ture of relay 23, upper winding of the relay l1,
test to be completed and the line to be made per
to the negative side of battery. LThe relay l1 is
manently buey to any other link, is thus reduced 40 thus energized and at its upper, inner armature
to the ionization time of the discharge device, a
and back contact it opens the allotter start cir
matter of microseconds, as compared with oper
cuit which it will be recalled included the wind
ing of the allotter start relay I9, thereby caus
ating time or” a relay which may be several milli
seconds. This shortening of the unguarded inter
ing this relay to deenergize. Relay Il, at its
val reduces the possibility of double connections. 45 lower armature and iront contact, closes a lock
The cut~thrcugh relay ES
its upper airma
ing circuit for itself through its upper winding
tures and front contacts, extends the calling line
and through its lower armature and front con
through the länder brushes 3l and 3B, through
tact, to ground applied to conductor 18, through
both windings in series of the impulse relay 3s,
the armature and back contact of the allotter
to ground and grounded battery respectively. 50 busy relay ‘19. It should be mentioned that
discharge device (il will become conductive when
these voltage conditions are present. When the
device becomes conductive, the circuit is then
completed and the cut-off relay o and cut-through
relay @il become energized in series in the manner
above described. When current begins to ñow in
Also, the operation of the cut-through relay 69
this allotter busy relay 19 is normally operated
at its armature 'lil and front contact, closes a
locking circuit for itself from the master ground,
through its lower winding, resistor "il to the nega
is taken for use, relay ‘I9 deenergizes. The ener
tive side of battery. Also, the cut-through relay
at
armature "i90: and front contact applies
master ground _through the Finder sleeve brush
39 and to the terminal Sil' of the calling line (Fig.
1) thereby rendering the calling line busy and
also locking up the cut-oil relay â. Master ground
is also supplied through the armature lâ) and
front contact of the cut-through relay 63, con
ductor l2, normally closed fed-normal contact
i3 o_f the connector, lower winding of the primary
motion delay relay l?l of the connector, to the
negative side of battery. Relay lll is of the slow
releasing type. .es soon as relay 'li is operated,
it applies a dial tone over conductor l5, armature
and back contact of relay lili?, front Contact and
armature of relay ld, conductor l5, condenser 'l‘l
and thence over the ring side of the link and the
as long as the link is idle but as soon as the link
gizing circuit for the allotter busy relay 'I9 which
55 is closed as long as the link associated with this
relay is idle, extends from the negative side of
battery, upper winding of the relay i9, the allotter
brush Se (at right of Fig. 2), armature and back
contact of the ñnder release magnet 8l, armature
60 and back contact 82 of the connector release
magnet, to be described, conductor 83, back con
tacts and armatures of relays 3l and 3i) (Fig. 3)
to ground. It will be noted that when the link
is taken for use, this energizing circuit for the
65 allotter busy relay 'I9 is interrupted at the arma
tures and back contacts of both relays 3G and
5 i . Vfhen allotter busy relay 19 releases, it places
a ground on the conductor lß, this ground being
applied over conductor Sli, back contact andA
70 armature of the allotter start transfer relay l5,
to ground.
As soon as'the relay l1 was ener
calling line to the calling subscriber’s substation.
gized, it interrupted the operating circuit of the
This tone, of course, signals the calling subscriber
allotter start relay I9. This relay deenergizes
that the dial-controlled apparatus is in condition
and at its uppermost armature and front con
75 tact interrupts the circuit which has been hold
to receive dialling impulses.
2,409,145
7
ing the slow operating relay 23 (Fig. 2) in its
operated condition. When the relay 23 releases,
it completes a circuit for advancing the allotter to
seize an idle link. This operating circuit effects
the energization of the relay 85 from the nega
tive side of battery, winding of this relay, back
contact and armature of the allotter motor mag
net 85, conductor 81, back contact and armature
of relay 23, armature 88 and front contact of relay
8
mal, it opens its oñ normal contact 13 (top center
Fig. 3). This interrupts the initial operating cir
cuit of the relay 14, insuring that this relay will
not reoperate until the connector switch has been
fully restored to normal. However the relay 14
is maintained operated through its upper Wind
ing during the reception of the remainder of the
tens impulses.
At the conclusion of the tens se
ries of impulses, the relay 14 will deenergize be~
| 1, to ground potential that is now present on 10 cause its locking circuit is interrupted at the back
contact and armature of the impulse relay 30.
the conductor 18, as described above. Relay 85 is
thus energized and at its front contact and arma
As soon as the connector switch moved off nor
mal in its primary direction, it closed a circuit
ture, closes in multiple with its energizing cir
through its normally open primary oiî normal
cuit, an operating circuit for the motor magnet
86. This circuit extends from the negative side 15 contacts 91 and through its normally closed sec
ondary oi'f normal contacts 98, high resistance,
of battery, winding of this magnet, front contact
lower winding of the slow releasing secondary
and armature of relay 85 and thence over the
delay relay 99, to the negative side of battery.
conductor 81 and the remainder of the circuit,
This relay is thus energized preparatory to re
previously described, to ground potential present
on the conductor 18. This operates the magnet 20 ceiving the units series of impulses. Thus, when
the impulse relay 30 responds to the units series
85 to advance the allotter. Also, the armature
of impulses, the secondary motor magnet |00
of the motor magnet 86 interrupts the circuit
will be operated in a circuit extending from the
of the relay 85. Thus, the relay 85 and 86 operate
negative side of battery, conductor | 0|, low re
together in a pulse assuring arrangement, some
times referred to as flip-nop operation. Under 25 sistance winding of relay 99, its front contact and
armature, back contact and armature of relay
the control of this arrangement, the allotter
14, now released, front contact and armature of
advances until the brush 80 of the allotter en
counters the terminal associated with an idle
relay 3| , back contact and armature of the im
pulse relay 30 to ground. Thus, in response to
link, which terminal will be characterized by the
presence of ground potential thereon. This 30 each unit impulse, the mentioned circuit will be
completed to operate the secondary motor mag
ground potential is applied over the conductor
similar to conductor 83 and thence over back con
tacts and armtures of relays corresponding to
3| and 30 to ground. When an idle link is lo
net which advances the brushes of the connector
switch in their secondary direction. As soon as
the secondary _delay magnet 99 operated, it closed
cated, the mentioned ground potential is applied 35 a circuit from ground through its armature |0|
through the allotter brush 80, lowermost arma
ture and front contact of relay |1, low resistance
and front contact, lower winding of the slow re
leasing connector busy delay relay |02 to the
negative side of battery. The operation of the
Winding of the allotter busy relay 19 and the
relay |02 disconnects the dial tone and closes
negative side of battery. Also, ground is applied
through the upper high resistance winding of this 40 a break point in the test circuit. Consequently,
when the secondary delay magnet 99 releases at
relay to the negative side of battery. The com
pletion of the circuit through the lower winding of
the conclusion of the series of units impulses,
thereby closing a second break point in the tes
this relay, which is of low resistance, insures
that the relay will receive a surge of current,
circuit, and when the connector brush 93 is rest
causing it to operate promptly. The operation of 45 ing on the test terminal of the called line, the
the relay-19, at its upper armature and back con
testing of that line can be effected. If the called
tact removes ground potential from the conductor
line is idle, the starter anode |05 of arc dis
18 and thus insures that the relay 85 and the
charge device |03 will become conducting in the
allotter motor magnet 85 cease to operate.
same manner as the arc discharge device 6|, as
50
It will be recalled that at the point where the
described above. When discharge device |83 be
dial tone had been applied to the calling line to
comes conducting, a circuit from the positive
indicate that the connector was in readiness to
source of battery, anode |04, cathode |06 of the
receive dial impulses, the description was inter
device, lower winding of the busy test relay |01,
rupted to explain how the allotter operated to
lower armature and front contact of relay |02,
assign an idle link for use. It will be understood, 55 armature |08 and back contact of relay 99, con
however, that in normal operation these opera
ductor |09, connector brush 93, sleeve terminal
tions take place simultaneously. On receiving the
||0 (Fig. 1), winding of cut-off .relay ||| of the
dial tone, the calling subscriber operates his d'al
called line to the negative source of battery.
sender to transmit impulses corresponding to the
The relay |01 is operated in this circuit and at
tens digit of the wanted number. In response to
its upper front contact and armature locks itself
each of these tens digit, the impulse relay 30
operated to master ground. The relay |31 at its
releases its armature to complete a circuit for
uppermost armature and front contact applies
operating the primary stepping magnet 89 of the
ground over conductor H2, back contact and ar
connector. This circuit extends from the nega
tive side of battery, winding of this magnet, con 65 mature |08, conductor |09, connector brush S3,
sleeve terminal ||0, thereby locking up the cut
ductor 90, through the very 10W resistance wind
off relay |||. This application of ground to the
ing (3 ohms) of the relay 14, its upper front
sleeve terminal ||0 of the called line makes this
contact and armature, front contact and arma
line permanently busy to any other link. Relay
ture of relay 3|, back Contact and armature of
the impulse relay v3|) to ground. In response to 70 |01, when it operates, prevents the application
of busy tone at its armature ||3 and back con
each of the tens impulses, the stepping magnet
tact. At the armatures ||4 and ||5 and iront
advances the tip, ring and sleeve brushes 9|, 92
contacts of relay |01, the link is extended through
and 93 and connector hunt brush 94 and also
the tip and ring brushes 9| and 92 of the con
the group brush 95 of the connector. As soon as
the connector switch takes its ñrst step oiî nor 75 nector to the terminals of the called line, in readi
d
:2,409,145
iiess for applying the ringing current to this line.
and front contacts, it v'closes break points in a
circuit extending the battery through the Wind
ings of the battery feed relay |33 to the called
If the connector arc discharge device |03 indi
cates a busy condition of the called line, this dis
charge device will not become conductive and
the connector busy test relay lill in series there
with will not become energized. When the con
nector b
d ` y relay |92 then releases, busy
tone will be extended through the armature i i3
and back contact or the connector busy test re
lay lill, armature and back contact of the con~ 10
nector busy delay relay H82, conductor §26, ar
mature and back contact of the connector pri
mary motion delay relay M, conductor lâ, and
through condenser l? to the ring side of the link
and or" the calling line.
15
Ringing current is now applied 'to the called
subscriber’s line from the ringing generator,
through the ringing delay device H8, which ai'
fords suiñcient time for the ringing trip heater
type gas tetrode iig to become available for 0D 20
eration. The ringing circuit extends from the
device llt, over conductor |29, upper armature
and back contact or" the ringing trip relay lì’i,
conductor i222, armature i iii and iront contact,
through the tip brush 9| of the connector and 25
thence over the calling subscriber’s line and sta
tion B, thence through the ring brush Q2 of the
connector, front contact and armature H5, con
duc-tor its, armature and back contact of trip
relay |25, resistor läd to ground. Interrupted 30
superimposed ringing current is applied over the
circuit just described to signal the called sub
scriber at'B. During the time that the ringing
current is being applied, a ringing tone is trans
mitted back to the calling subscriber, this tone 35
being applied over conductors |22 and £25, ar
mature and front contact or" relay itl, back con
tact and armature of relay |522, conductor |26,
back contact and armature or" relay lil, conductor
le, condenser ll' and to the ring side of the call 40
ing end of the link to the calling subscriber’s
substation.
When the called party answers by removing
subscriber’s line. VAt the armatures
back
contacts of relay i12 l, break points are introduced
into the ringing circuit. The connection has
thereby been established between the calling and
the called subscriber’s line in readiness for tele
phone conversation.
.
t the conclusion of the conversation when
the calling subscriber replaces his receiver on its
switch»hook, the impulse relay Se deenergizes.
At its armature and iront Contact, it interrupts
the circuit of the slow-releasing relay 3| which
on releasing disconnects master ground from the
various circuits. This relay at its upper inner
armature. and back contact, applies a release
ground to release conductors |54 and 83 which
energize the connector release magnet |35 and
nnder release magnet 5|. These magnets, on
operating, release the connector and the finder
switches respectively, allowing them to return
to their normal idle positions.
In systems or this type it is frequently desir
able that a called subscriber be provided with
two or more lines so that in the event that the
iirst one oi these lines is busy, a second or third
will be available so that the subscriber can always
be reached. This arrangement is commonly
known as consecutive number hunting, since in
originating a call, the calling subscriber will dial
the number assigned to the called subscriber
and in the event that that line is busy, the con
nector will hunt over the remaining lines of a
group assigned to the given subscriber until a
line is found that is idle. To achieve this end,
a vpermanern; ground is placed on the connector
hunt multiple iâ-lä oi all numbers in the consecu
tive group except the last. When the connector
switch rests on the iirst number of the consecu
tive group, ground is red from the multiple bank
contact §35 through connector hunt brush S4,
conductor §35, back contact and armature of re
his receiver from its switch-hook, a direct cur
lay 9d, conductor iS’i, baci; Contact and armature
rent circuit is extended through the called sub 45 oi relay itil, to conductor |38. This ground is ex
station B. This sets into operation the ringing
tended to the busy delay relay m2 so that the
trip circuit which may be described as follows:
test may be made over the regular busy test
An electron discharge device lle has been main
circuit. In the event that the ñrst line in the
tained in its non-conducting condition by means
consecutive group is busy, the electron discharge
of the negative bias supplied over potentiometer 50 device iíiâiwill not become conductive and thus
£28 through resistor |29 to the control grid of
relay le? will not be energized. rî‘he ground po
this device. The alternating current voltage
tential is applied from conductors |36 and |39
which exists across resistance |25 during the
through the back contact and armature of the
ringing period does not affect the bias of this
connector secondary motor magnet lûíl through
tube since the cathode ilgb and grid liga are 55 the winding oi the connector pulse assuring relay
maintained at the same potential being coupled
í?liì to negative battery. The operation of this re
on an alternating current basis by condenser |39.
lay lilo completes a circuit through its front con
Thus, alternating voltage will not fire the tube.
tact and armature, extending ground to the sec
However, when direct current continuity is es
ondary motor magnet
,thus advancing the
tablished in the ringine circuit, as a result of 60 switch to the second line in the group. The con
the subscriber answering as just described, a
nector sleeve brush sli then rests on the second
constant drop occurs across resistance |2li which
line in the consecutive group and the busy test is
is negative as it is applied to the cathode oi the
again applied in the same manner as described
ringing trip device H9. This in effect reduces
previously. il" the second line in the group is also
the bias on the ringing trip device and the de 65 busy, the relays illíl and Eile will operate to
vice becomes conductive. The conducting cir
gether in the pulse` assuring arrangement to ad
cuit then extends from the grounded side of re
vance the connector switch in its secondary mo
sistance 52e through ringing trip device H9, con
tion until either an idle line is found and out
ductor itl, armature and front contact of relay
through by the conventional busy test operation
l, conductor 232, armature and back contact of 70 or if all the lines in the group are busy, ground
relay S33, lower winding of ring trip relay |2I,
no longer appears on connector hunt brush 94
to a positive source of voltage of the order of 150
and relay H32 will be deenergized to allow busy
volts. When the ringing trip relay operates, it
tone to be applied to the calling subscriber’s line.
locks up to master ground at its uppermost arma
Relay |37 operates to interrupt the operating
ture and iront contact. At its inner armatures
circuit of magnet ltdwhen an idle line is found.
12
_.
11
Frequently in systems of this type, the con
nector is provided with a series of trunks lead
_
.
,
,
cold cathode arc discharged device 53 which lsl
also used to stop the line finder in its secondary
hunt motion. It will be recalled that as soon
ing to a distant exchange. In such a system,
as the master start ground is applied to the cir
when a calling subscriber of the local exchange
cuit by means of the group line relay 5, the al
Ul
wishes to reach a distant exchange he will dial a
lotter stop relay I9 (Fig. 2) is energized. The
single digit. In response to this single digit, the
operation of this relay closes through a circuit
connector will operate to effect its group selection
extending from a positive source of voltage
after which this connector will operate to hunt
through variable resistance |10, front contact and
for an idle trunk in the group selected. This is
armature |1| of relay I9, conductor |12, to con
accomplished in this system by extending a lead 10 denser
|13, thence over conductor 1|, front con
from one of the group multiples into all con
tact and armature of relay |9, to ground. Re
nectors in this office. In the connector circuit
sistance |10 is adjusted so as to permit condenser
under discussion, this is lead number |4| (Fig.
|13 to charge slowly and so that the rise in po
3). Upon the completion of the series of tens
tential appearing across this condenser will not
impulse, ground is extended from master ground
be sufficient to ñre arc discharge device 58, this
in the connector through normally opened pri
voltage being applied to starter anode 54 through
mary off normal contacts 91, and the normally
protective resistance |16 until sufficient time has
closed secondary off normal contacts S3 through
elapsed for the normal operation of the allotter
back contact and armature of relay 14, conductor
and the line finder. If this time is exceeded,
|42 'to the connector brush 95. If the number 20 the ñring of the device 58 will cause the opera
dialed brings the connector brush 95 into con
tion of relay 20 as if the device had been ñred
tact with lead |4|, the group is thus identified
through current flowing in winding 48 in a nor
as a trunk group and the hunting circuit is ener
mal manner and the allotter will thus release.
gized. This circuit extends from negative bat
however, the allotter successfully completes its
tery through the winding of relay |40, armature 25 If,
operation, the charge of condenser |13 will be
and back contact of magnet |00, lead |39, arma
removed upon the release of relay I0, over the
ture and back contact of relay |01, lead |31,
path which can be traced from condenser |13
armature and front contact of relay 99, which
through conductor |12, back contact and arma
is in its operated condition, conductor |4|, con
ture of relay |9, through resistor |18 and back to
nector brush 95, conductor |42, armature and 30
condenser |13.
back contact of relay 14, through the off normal
In the event that the line finder goes to the
contacts 91 and 98 to master ground. This sets
overflow
position due to failure of the allotter
into operation the pulse assuring arrangement
transfer relay 2| or some failure in the second
of relay |40 and magnet |00 which act to ad
ary motion circuit, the arrival at the overfiow
vance the brushes in their secondary motion. As 35 position of the switch will close the overflow
soon as the trunk group is reached, a circuit is
contact |50 (Fig. 2) in the switch itself which
completed for energizing relay |43. This cir
will return a ground through allotter brush 5|
cuit extends from negative battery through wind
to the hunting lead 50 of the line finder. This
ing of relay |43, make before break contact of
pulse of ground will be transmitted through the
this relay, conductor |14, lead |4|, connector 40 armature 49 and front contact of relay I9 and
brush 95, lead |42, armature and hack Contact
through the primary winding 48 of the trans
-of relay 14, the off normal contacts 91 and 98, to
former. The voltage induced in the secondary
master ground. The operation of relay |43 acts
winding 52 of the transformer initiates conduc
to remove battery and ground respectively from _
tivity in the electron discharge device 58 which
-relay |33 and to interconnect the windings of
will again simulate the completion of the line
this relay so that it becomes merely an imped
finding operation. The allotter and line finder
ance across the called trunk. This interconnect
will be released as previously described and a
ing path extends from lead |44 to relay |33,
new link will be seized.
through lead |45, armature and front contact of ,
This system is particularly adapted for use in
relay 30, lead |46, armature and front contact of
remote and unattended branch exchanges.
relay |43, lead |41 to relay |33. The operation
Therefore, adequate protective devices must be
of relay |43 also extends ground through its
incorporated therein so that extensive tie-up of
armature and upper front contact, through lead
service will not occur. Since the relays in the
v|48 to energize the upper winding of relay |2|,
allotter are common to all the links in the
thus immediately tripping the ringing current 55 first
systems, it is necessary to provide a secondary
-and thereby preventing ringing current from go
allotter which will function in the event of fail
ure of the first. In order that this secondary
allotter will not stand idle during functioning of
the first allotter, the system is arranged so that
60
tion, contact 98 opens, thus interrupting the cir
each will serve one-half of the lines and one-half
cuit of relay 99. When this relay falls back,
of the links in the system. A transfer circuit is
ground is continued from multiple bank termi
incorporated which will allow the lines served by
nals opposite the connector hunt brush 94 and
the first allotter to start the secondary allotter
pulsing is completed in the same manner as in
in the event of the failure of the first. If all the
consecutive number hunting, the busy test be 65 links served by the first allotter are busy, a ground
ing applied at each step. When an idle trunk is
is extended through normally open off-normal
found, the busy test device |03 becomes conduc
ycontacts |5| (upper left in Fig. 2) in series of all
tive and the talking connections are cut through
links served by the first allotter, through the lower
to the trunk in the conventional manner.
winding
of allotter start transfer relay |5, to
70
Several safety features have been employed in
.negative side of battery. When this relay is ener
the design of this system to protect the mecha
gized, any master start ground which comes from
nism and circuits from extensive tie-ups due to
the group line relays, such as 5, which are ordi
Yfailure of parts or dirty contacts in relays which
Anarily served by the first allotter will be trans
hinder'the closing through of circuits. One of
ferred to the master start lead |52 (Fig. 1) of
these features involves the use of the gas filled 75
ing out on the trunk. The switch now hunts in
the secondary motion direction. As soon as the
switch moves off normal in its secondary direc
2,409, 145
i4'
the second allotter.
Thus, the second allotter
the line finding operation is also indicated by the
will respond to signals from all the lines in the
system. When any link served by iirst allotter
operation of the cut-01T relay 6 of the calling line
again becomes idle, allotter start transier relay
i5 will be deenergized and will again allow signal»
ling from the group line relays ordinarily 'served
by the ñrst allotter to be transmitted into this
allotter. if allotter start relay l5 is energized
group served by the first allotter are waiting to be
and. in the event that no other lines in that
found, allotter failure relay |55 is deenergized
and a discharging ground is returned to con
denser |55 through the armature and back con
tact of allotter failure relay |513.
and a signal from any group line relay, such as 5
A modiiìed form of ringing trip arrangement
ordinarily served by the first allotter, is tran-s 10 or trigger circuit which can be substituted for
mitted into the second allotter, the operation of
v that disclosed in Fig. 3, is shown in Fig. 6. in.
the allotter start relay ES in the second allotter,
this arrangement, the voltage on the starter an
will complete its cycle of operation. This is
ode |8| of the gas-filled arc discharge device
eifected by a circuit extending from ground
|35 is adjusted by means of the potentiometer
through the lowermost armature and »front con 15 P, to be within a few volts of the iiring poten
tacts of an allotter start relay similar to relay
tial of the device. superimposed, interrupted
i9 (at left of Fig. 2), conductor l d8, armature and
ringing current is applied vto the called line
front contact of the number one allotter start
transfer relay i5, the lower winding of this relay.
through resistor |2ê and condenser |86. During
the ringing and silent periods the voltage drop
to the negative side of the battery. This main 20 across condenser ißt is negligible and thus >the
tains allotter start transfer relay |5 in number
potential between the cathode |82 andstarter
one allotter in its operated position until the com»
anode its of the discharge device remains con
pletion of the line finding operation and thus pre'
vents this relay from being deenergized in case a
link. ordinarily served by this allotter becomes
idle during that hunting period of the iinder
started by the number two allotter.
stant. When, however, the hook-switch at the
called substation is closed and direct current ñows
in the line, a drop appears across resistor |24 and
condenser |86, such that the cathode |82 of the
discharge device becomes more negative. This
As soon as a group line relay similar to relay 5
brings the device to firing potential and it be
is energized, a circuit is closed which energizes
comes conductive. The ring trip relay l2 lo. oper
the allotter failure relay |55. The operation of 30 ates in series with the discharge device and acts
this relay opens a contact which removes ground
to disconnect the ringing current and to apply
from the allotter failure circuit. This allows
talking battery to the line in the manner simi
condenser |55 to start charging through resistors
lar to that shown in Fig. 3.
|55 and iig. The charging circuit extends from
a positive source of voltage, of the order of 150
volts, through the upper winding of the allotter
start transfer relay i5, through resistors |79 and
|56 to condenser |55, and ground. In the event
of mechanical failure of certain relays in the
allotter circuit or mechanical failure of the
A further modified form oi trigger circuit is
shown in Fig. 7 which differs from the trigger
or ringing trip circuit of Fig. 3 in the specific
manner in which the tripping Voltage is applied
to the cathode H95 of the gas discharge device
or Thyratron H9. In the arrangement of Fig.
40 7, the resistor 2% and the condenser I 31| con
allotter motor magnet 85 (Fig. 2), the allotter
stitutes a voltage divider.
would not move to seize a new link and any
rent flowing through resistor |24, the grid ||Sa
subsequent calls would not be completed. The
condenser |55 then charges through this circuit
until the voltage on the starting anode |59 or"
the electron discharge device itil (Fig. 1) becomes
high enough to initiate conduction between the
of the discharge device HS is biased by means
of a potentiometer |23 so that the discharge de
vice does not conduct. Alternating current may
electrodes |52 and |63. ' When the electron dis~
time constant of the resistor 2S@ and the con
With no direct cur
also be passed through the resistor i213 and the
discharge device still will not conduct, if the
charge device becomes conductive, it energizes
denser |3ß is greater than the period of the
the allotter start transfer relay l5 through a cir 50 alternating current. When direct current iiows
cuit which extends from a positive source of
through the resistor iâß at the time when the
voltage through the Lipper winding of this relay
called partly answers by removing his receiver
|5, key i6@ through the anode |62 and cathode
from its switchhook, a drop appears across re
itâ oi the electron discharge device ißt to ground.
sistor iìil as a result of which the condenser |39
This acts to transfer the master start ground 55 is charged so that a negative voltage appears on
which cornes from the group line relays ordi
the cathode M927 of the discharge tube. The
narily served
the ñrst allotter to the master
start lead |52 of the first allo‘tter. The allotter
start transfer relay l5 remains operated until
vacuum or gas rectifier 253|, as the case may be,
in the cathode circuit ci the discharge device I I9,
prevents the discharge of the condenser. Thev
the circuit through the electron discharge device 60 mentioned negative voltage present at the cath
|55 is broken at the manually operated key |54
ode ||9b efîectively reduces the bias on the dis
by a repair man who is also signalled by the oper
charge device ||9 causing it to conduct. The
ation oi this device. The completion of the line
rectifier tube âti now passes the plate current
finding operation is indicated to the allotter fail
of the discharge device HQ, in a circuit from
ure circuit by the operation of the allotter control
ground, through rectifier 2B |, cathode l I‘Bb, anode
relay 2?; and by the allotter advance relay il'
||9c of the arc discharge device H9, lower wind
which close a circuit from ground in series with
ing of relay |2|a through armature |3341 of re
the armatures and front contacts of these relays
lay |33, to the positive source of high voltage.
over the lead i‘l‘t through resistors |51 and |55
Ringing trip relay i2! becomes energized to dis
to condenser |55. Condenser |55 is thus dis 70 connect the ringing current and to cut through
charged through this path and prevents electron
the connection from the calling line to the called
discharge device |559 from operating, The time
line.
.
interval allowed the line finder and allotter to
Resistor |24 may be made quite low so that
complete their operations is determined by the
any circuit associated with this trigger circuit
magnitude of resistor H9; The completion of 75 will not be appreciably affected thereby. Re»v
:34,469,145
15
sistor 200 can be made quite high so thatV the
minaL‘an arc discharge device having an anode,
trigger circuit is of such impedance as to have
a negligible effect on any associated circuit.
If the present arrangement is used only to
detect the presence of direct current and no al
ternating current discrimination is desired, con
denser l3ll« can be omitted. Resistor 282 is in
serted to dampen any relaxation oscillation.
It should be understood that the present dis
closure is for the purpose of illustration only and 10
a cathode and a starter electrode enclosed in a
gaseous atmosphere, a unidirectional source of
electrical energy, a circuit including said source
as well as said cathode, said anode and the gas
eous atmosphere, whereby current ñows in said
circuit when an arc discharge is initiated in said
device, means for discharging said electrostatic
charge responsive to the engagement of said
switch with said terminal, and means responsive
to said discharge for applying a starting poten
» that this invention includes all modifications and
tial to said starter electrode to eiîect arc dis
equivalents which fall within the scope of the
charge in said device, and means for stopping said
appended claims.
switch operated in response to current ñowing in
What I claim is:
l. The method of initiating electrical conduc 15 said circuit.
6. In a telephone system, a line having a ter
tion through an arc discharge device having an
minal, means for associating an electrostatic
anode, a cathode and a starter electrode, said
charge with said terminal when said line is to be
cathode and said anode being connected in series
selected, a movable switch for selecting such line,
with a source of unidirectional electrical energy,
which method comprises accumulating an elec 20 means for moving said switch to engage said ter
minal, an arc discharge device having an anode,
trostatic charge from a relative low voltage
a cathode and a starter anode enclosed in a gas
source, discharging said charge, utilizing said
eous atmosphere, a unidirectional source of elec
discharge to develop a voltage of a higher order,
trical energy, a circuit including said source as
applying said higher voltage to the starter elec
well as said cathode, said anode and the gaseous
trode to cause a discharge in said device.
atmosphere, when an arc discharge is initiated
2. The method of initiating electrical conduc
in said device, means for discharging said elec
tion through an arc discharge device having an
trostatic charge responsive to the engagement of
anode, a cathode and a starter electrode, said
said switch with said terminal, and means includ
cathode and said anode being connected in series
with a source of unidirectional electrical energy 30 ing a step-up transformer responsive to said dis
charge for applying a starting voltage to said
which method comprises accumulating an elec
starter anode to effect arc discharge in said de
trostatic charge from a relative low voltage
vice, and means for stopping said switch oper
source, discharging said charge, inductively uti
ated in response to the arc discharge in said
lizing said discharge to develop a voltage of a
higher order, applying said higher voltage to the
starter electrode to cause a discharge in said de
device.
'
7. In a, telephone system, a telephone line com
prising tip, ring and huntconductors, contacts
in which said conductors respectively terminate,
a switch having tip, ring and hunting brushes
charge device responsive only to voltage of a 40 movable into engagement respectively with said
tip, ring and hunt contacts, operating means for
higher value, said arc discharge device compris
moving said switch brushes into engagement with
ing a cathode, an anode and a starter electrode
vice.
3. In a low voltage arrangement for initiat
ing electrical conduction through an arc dis
enclosed in a gaseous atmosphere, a load unit
and a source of unidirectionl current connected
said contacts, a condenser and a resistor con
ing varying current or“ relatively low voltage to
flow through said primary winding.
and a starter anode enclosed in a gaseous atmos
nected in multiple, a circuit closed responsive to
45 the initiation of a call on said line, said circuit
in series with said anode and said cathode, said
including a battery as well as said tip and ring
source having its positive and negative termi
conductors in series with the multiple-connected
nals respectively connected to said anode and
resistor and condenser whereby said condenser
said cathode, a step-up transformer having a
becomes charged, said hunt contact being con
primary winding and a secondary winding, said
secondary winding being connected in circuit 50 nected to one terminal of said condenser, an arc
discharge device including a cathode, an anode
with said starter electrode, and means for caus
phere, a stopping relay, a discharge circuit in
cluding a source of unidirectional electrical energy
4. In a low voltage arrangement for initiating
electrical conduction through an arc discharge 55 in series with said relay and also in series with
said cathode and said anode as well as the space
device responsive only to voltage of a higher value,
therebetween, a step-up transformer having a
said arc discharge device comprising a cathode.
primary winding and a secondary winding, a
_an anode and a starter electrode enclosed in a
circuit including said secondary winding and said
unidirectional current connected in series with 60 starter anode, a circuit including said primary
winding, said hunting brush and said hunt ter
said anode and said cathode, said source having
minal and also said condenser whereby said con
its positive and negative terminals respectively
denser discharges through said primary winding,
connected to said anode and said cathode, a step
up transformer having a primary winding and a 65 and means including said relay for stopping said
operating means.
secondary winding, said secondary winding being
8. In a telephone system, a telephone line com
connected in circuit with said starter electrode,
prising tip, ring and an associated hunt conduc
a condenser, means including a relatively- low
tor, contacts in which said conductors respec
voltage source of electrical energy for charging
tively terminate, a switch having tip, ring and
said condenser, and means for discharging said
70 hunting brushes movable into engagement re
condenser through said primary winding.
spectively with said tip, ring‘and hunt contacts,
5. In a telephone system, a line having a ter
operating means for moving said switch brushes
minal, means for associating an electrostatic
into engagement with said contacts, overflow con
charge with said terminal when said line is to be
tacts closed as a result of a predetermined move
selected, a movable switch for selecting such line,
means for moving said switch to engage said ter 75 ment of said switch, a condenser and a resistor
gaseous atmosphere, a load unit and a source of
42,409,145
17
18
>connected in multiple, a circuit closed responsive
ageof such low vvalue applied thereto that it
fails to render said device conducting when the
cathode is connected with the line characterized
Ato the initiation of a call on said line, said cir
cuit including battery as well as said tip and ring
conductors in series with the multiple-connected
-resistor and condenser whereby said condenser
becomes charged, said hunt contact being con
as busy, and means controlled vby the conducting
_condition of said device for indicating the idle
condition of said line.
11. Ina telephone system, a line having Va
terminal, means forv associating an electrostatic
charge with said terminal when said line is to be
selected, a movable switch for selecting such line,
nected to one terminal of said condenser, an arc
discharge device including a cathode, an anode
'and a starter anode enclosed in a gaseous atmos
phere, a stopping relay, a discharge circuit in
cluding a source of unidirectional electrical en
lmeans for moving said switch to engage said ter
ergy in series with said relayand also in series
minal, an arc discharge device having an anode,.a
with said cathode and said anode as well asv the
cathode and a starter anode enclosed in a Igas
eous atmosphere, a unidirectional source of elec
fspace therebetween, a step-up transformer hav
ing- a primary winding and a secondary winding, '
trical energy,l a >circuit including -said source i' as
_a circuit including said secondary Vwinding and
.said starter anode,ha circuit including said pri
jwellfas said 'cathodajsaidfanode and the gaseous
mary windingsaid hunting brush and said hunt
îterminal and `also said condenser whereby said
cuit vwhen an arc‘ discharge is initiated in said
device, means, for discharging said electrostatic
charge responsive to the engagement of ‘said
switch with said terminal, means responsive to
atmosphere, whereby current' ñows in saidcir
condenser discharges through said primary wind- ~«ing, means responsive- to the closure of said over
iiow contacts for transmitting current through
Vsaid discharge for applying a starting' potential
to said starter anode .to operate- said arc dis
said primary winding whereby the discharge cir
cuití isßclosed through said device, and means in
cluding said relay for stopping said operating
means.
` charge device„means including acondenser hav
ing a delayed charging rate for applying a start
ing potential to said starter anode after a pre
determined'interval to effect arc discharge in
said device, and means for rendering said con
‘
9. In a telephone system, a group of telephone
lines, each having a pair of talking conductors, a
group relay common to said group of lines, said
relay having one terminal of its winding con
nected to one pole of battery and having its other
terminal connectable in series with the talking
conductors of any one of said lines on theini
tiation of a call thereon, a hunt conductor for
each line terminating in a hunt contact and'nor
denser ineffective as aresultofthe normal oper
ation of said arc discharge device in response-to
the discharge of said electrostatic charge, and
means for stopping said switch operated in re->
sponse to current flowing in said circuit.
.. 12. In a ringing trio arrangement, a conductor
having a source of alternating current superim
mally connected to one of said talking conductors
posed on. direct vcurrentconnect'ed thereto, said
of its line, a condenser and a resistor each hav
conductor` during a ñrst period being connected
ing a pair of terminals, the first terminal of
ina circuit continuous-only to alternating cur
each pair being connected in common tov said
rent and being connected'during a second period
hunt conductor and the second terminal of each 40 ina second circuit continuous to direct current,
pair being connected in common to the other
a dischargedevice having a cathode, an anode
pole of battery, whereby said conductor becomes
and a control electrode, an anode circuit includ
charged, a cut-off relay individual to each line
ing said anode, Vsaidcatl'ioda-a ringing trip.re-.
and eliective on operation to disconnect said
group relay and to disconnect the hunt conduc
lay and >also,afsource of current, meansfor biasf
tor from said talking conductor, va switch for
device does not conduct`.during saidñrst period,
ing' said control electrode-tc a degree. that said
seizing a line characterized by a charged con
denser, said switch having brushes including a
hunt brush movable into successive engagement
with the hunt contacts of said lines, means for
and means responsivefto-the flow of direct, cure.
rent through said conductor duringlthe second
, period .for rendering said> cathode `negative` with.
moving said switch brushes, means responsive to
the engagement of the hunt brush with the hunt
contact connected to said charged condenser for
respect l’tofit'sîcondition during said fñrst 'period'
whereby .the bias. on ls'aidgde'vice is effectively re.-.¿.
duced sô'th'at thedevice becomes conducting'an'd.
thetrio rt-:la-y.-- operates.
'_l.' '1`..
’
‘
causing said switchv to seize said line, and means
" 13.' In @ringingtriparfaugement, a. conductor..
responsive to the seizure of said lineior operat-` CA' Ll having a source 'of alternating current superim-v
ing the cut-oîî relay thereof.
Y
l
10. In a telephone system, a, line, means for
characterizing said line as idle by a negative
voltage of a given value and for characterizing
,
said line as busy by a negative voltage of a lesser (i i)
value, a test circuit, an arc discharge device in
cluded in said- circuit, said arc discharge device
comprising a cathode, an anode and a starter
anode enclosed in a gaseous atmosphere, a source
of relative high positive voltage connected to
said anode, means for connecting said cathode to
said line, a voltage divider having its íiXed ter
minals connected respectively to said anode and
to said cathode and having its movable element
connected to said starter anode, said movable ele
ment being adjusted so that the starter anode
has a starting voltage of such value applied there
to that it renders said device conducting when
said cathode is connected to the line when char
acterized as idle but the starter anode has a volt
posed o`n 'direct current' connected thereto, .said
conductor duringT aiirst vperiod being connected
in a circuit continuousonly to alternating cur
rent and being _connected _during a second period
in a second'circuit continuousto direct current,
a resistor connected 'in' series with said conduc
tor, a discharge device having a cathode, an
anode and a control electrode, an anode circuit
including said anode, said cathode, a ringing trip
relay and also a relatively high voltage source of
current, a second resistor and a condenser con
nected in series and placed across the terminals of
said first resistor, one terminal of the condenser
being connected to the positive side of said direct
current source, and a rectifier tube having a
cathode and an anode, the anode of said rectifier
being connected to the cathode of said device
and the cathode of the rectiñer being connected
to the positive side of said direct current source.
14. In a ringing trip arrangement, a wanted
2,409,145
19
telephone line, a conductor, a source of ringing
current, a ringing trip relay for controlling the
connection of said source of ringing currentlto
said conductor, means for connecting said con
ductor to said wanted telephone line in the course
of extending a telephone call to said line whereby
said line is signalled, an electron discharge device
20
of alternating current through said second resis
tor.
17, In an arrangement for initiating electrical
conduction through a discharge path, a discharge
device including a cathode together with an anode
constituting said discharge path, said device also
including a control electrode, means normally
biasing said control electrode to a value whereby
having at least a cathode, and an anode, .an
said device does not discharge, a network com
anode circuit including said anode, said ringing
trip relay and a source of current, means respon 10 prising a capacitor and a resistor together having
a period or time constant of a given value, a
sive to the answering of the signal on the wanted
source of alternating current of shorter period
line for causing said discharge 4device to pass
than that of said network, a source of direct cur
suñîcient current to operate .said >relay whereby
the source of ringing current is disconnected from
rent, a second resistor through which either said
said wanted line.
alternating current or said direct current can be
,
15. In a ringing trip arrangement, .a wanted
_telephone line, a conductor, a >source of ringing
current, a ringing trip relay for controlling the
caused to ñow, ,means for applying to said net
work the drop across said second resistor due to
direct current flow therethrough whereby said
capacitor is charged, vmeans for connecting the
connection of said source of ringing current to
said conductor, means for _connecting said con zO negative terminal of said capacitor to said
cathode, a cathode circuit connected to said
ductor to said wanted telephone line in the course
cathode, anda rectiñer .connected in said cathode
of. extending a telephone call> to said line whereby
circuit to prevent unwanted discharge of said
said line is signalled, an electron discharge de
vice Vhaving a cathode, a control electrode and an Y
anode, an anode circuit including said cathode,
said anode, said ringing trip relay and a source
of current, means for applying a bias to said
control electrode whereby said device vdoes not
pass current, means responsive to the answering
of the signal on the wanted line for overcoming
said bias whereby said discharge device passes
suñicient current to operate said relay thereby
disconnecting the ringing current from said
wanted line.
,
,
16. In an arrangement for vdiscriminating be
tween the ñow of alternating current and direct
current in a given circuit, a discharge device in
cluding a cathode together `with an anode con
capacitor.
18. In an arrangement for initiating electrical
conduction through a discharge path, a discharge
device including a cathode together with an anode
constituting said discharge path, said device also
including a control electrode, means normally
biasing said control electrode to a value whereby
said device does not conduct, a cathode circuit
connected to said cathode, and means for apply
ing a negative potentia1 to said cathode whereby
the bias applied to said device is effectively re
duced and it becomes conducting.
19. In an arrangement for initiating electrical
conduction through a discharge path, a discharge
device including a cathode together with an anode
constituting said discharge path, said device also
stituting an electric discharge path, said device
also including a control electrode,> meansv nor 40 including a control electrode, means normally
biasing said control electrode to a value whereby
mally biasing said control electrode to a value
said device does not conduct, a cathode circuit
whereby said device does not discharge, a net
connected to said cathode, a rectiñer connected
work comprising a capacitor and a resistor to
in said cathode circuit, and means for applying
gether having a period or time constant ,of a given
value, asource of alternating current- of shorter ï a negative potential to said cathode whereby the
bias applied to said device is eiîectively reduced
period than that of said network and a source of
and it becomes conducting.
direct current to be discriminated, a second .re
20. In an arrangement for initiating electrical
sistor connected in saidcircuit through .which
conduction through a discharge path, a discharge
either said alternating current or said direct cur-f
rent can be caused to now, means for applying -
to said network the ydrop across said second resis
tor due to direct current flow.. therethrough
whereby said capacitor is charged, means for
device including a cathode together with an anode
constituting said discharge path, said device also
to said cathode, a rectiñer connected in said
cathode circuit ,to prevent unwanted discharge
of said capacitor, a relay connected in said dis
charge path to be `operated by the electric dis
charge therethrough, and means responsive to
including a control electrode, means normally
biasing said control electrode to a value whereby
said device does not conduct, a cathode circuit
connected to said cathode, an anode circuit con
nected to said anode, a rectiñer connected in said
cathode circuit and connected to said anode cir
cuit, and means for applying a negative potential
to said cathode whereby the Abias applied to said
device is effectively reduced and it becomes con
the operation of said relay for stopping the flow
ducting.
connecting the negative terminal of said capaci
tor to said cathode, a cathode _circuit connected
FRANK A. MORRIS.
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