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Патент USA US2405211

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Aug. 6, 1946.
Filed J_u1y 16, 1942
Patented Aug. 6, 1946
Ralph V. L. Hartley, Summit, N. J ., assignor to
Bell Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New York
Application July 16, 1942, Serial No. 451,139
10 Claims. (01. 179—90)
This invention relates to communication sys
tems and particularly to a signaling means for
use therein.
An object of the invention is to provide a
novel signaling device for controlling the switch
ing equipment in a central of?ce.
Another object of the invention is to provide
an improved calling device for controlling the
central office switching mechanism at a higher
circuit for the next impulse of current to be trans
mitted by the subscriber. Duration of the sig
naling impulse is variable and is determined by
the amount of resistance connected across the
secondary coil 21 by the actuated digital key,
actuation of key I providing the shortest impulse
and actuation of key 0 providing the longest im
The invention can be more readily understood
rate of speed with consequent reduction in the 10
by reference to the following detailed description
in connection with the drawing which shows one
A further object is to provide a signaling de
subscriber's signaling time.
embodiment thereof.
vice in which a single impulse is transmitted for
There is shown diagrammatically a telephone
each digit.
subscriber’s station 9 of the usual type and a
With the above objects in view, an embodiment 15 signaling
device In connected by a pair of line
of the invention discloses a signaling device
a central of?ce switching mechanism.
which, when operated, transmits to the central
Signaling device I 0 comprises a U-shaped elec
o?lce a characteristic signal pulse of variable du
tromagnetic core 12 having a pair of projecting
ration dependent upon the desired digit instead
I3, I 4, an armature l5 of soft iron rotatably
of the customary series of equal impulses for 20
disposed between said poles by means of a shaft
each digit dialed.
H, and an arm l8, which is secured to armature
The signaling device contemplated for use in
IS in any suitable manner, having near its free
this invention is of the electromagnetic type and
extremity an insulated ?nger l9. Arm I8 is
comprises an electromagnetic core having a pri
biased to its normal position, as shown in solid,
mary coil connected to a telephone line in series
with a manual circuit breaking switch and a
secondary coil connected to any one of ten values
of resistance through a series of ten digital keys,
each operated key connecting a predetermined
resistance thereto, key I inserting the maximum
resistance and key 0 the minimum resistance
into the secondary coil circuit. A movable ele
ment or armature of the electromagnet is pro
vided for conditioning the circuit breaking
switch, which in its inoperative position is closed
because of the action of a biasing spring attached
to the armature. When a telephone subscriber
raises his handset from the mounting, the pri
mary coil thereof is energized and the arma
ture in turn is attracted to a position which al
lows freedom of movement for the circuit break
25 by a retractile spring 2| which is secured at one
end to arm [3 and at the other end to a stud 22.
Stop pin 23 restricts the biasing action of spring
2| upon arm l8. Armature I 6 provides a closed
magnetic circuit in conjunction with poles l3,
30 M of core l2 when arm [8 is in its operated posi
tion, as shown dash-dotted, under the in?uence
of the pull exerted by the magnetic ?ux in core
l2, which will be explained in greater detail
hereinafter. Around core I2 is wound a primary
35 coil or winding 24, one end of which is connected
to one side of line H and the other end of which
is connected through a back contact 25 of switch
26 to the other side of line ll. Switch 28 may
be of the customary spring type of manual circuit
40 breaker, which can be rapidly snapped from a
closed to an open circuit basis or from an open
The subscriber in proceeding with‘
ing switch.
to a closed circuit basis, and is so arranged that
his call'initiates an impulse of current by actu
it is closed when armature I6 is released by the
ating one of the digital keys, which opens the line
magnetic flux ceasing to overcome the pull of
circuit by means of the circuit breaking switch
biasing spring 2|, as will be described hereinafter.
and which connects a resistance, the value of
A secondary coil or winding 27 is also wound
which is dependent upon the key punched, to the
around core l2, one end of the coil being con
secondary coil of the electromagnet. Interrup
nected to a common base plate 28 of key-set 29
tion of the primary coil induces an electromotive
force in the secondary coil which sets up a mag 50 while the other end of coil 21 is connected to
one end of resistance 3|, which is subdivided seri
netic ?ux su?icient to hold the spring biased ar
ally into ten sectional resistances of variable val
mature attracted for a period corresponding to
ue, as described hereinafter, by connecting taps
the digital key operated. Retraction of the arma
32 thereof to corresponding key levers I, 2, 3, 4,
ture completes the impulse by closing the cir
'cuit breaking switch, which conditions the line 55 5, 6, 1, 8, 9, i! of key-set 29. The lowest re
sistance value is connected to key lever 0, the
next higher resistance value is connected to lever
5.3, and in this sequence the resistance sections are
connected until the entire resistance 3| is con
nected to lever I. Resistance 3I, as illustrated,
is intended to be merely representative and it is
of course understood that individual resistances
of proper value may be so used.
Each of levers
I to U, inclusive, is provided with a button 33, a
contact 34 for engagement with a contact 35 se
cured to common base-plate 28, and a turned
over portion 36 for actuating a movable insulated
29. The interval during which line II is opened,
following operation of a digital key, depends upon
the time constant of the circuit comprising wind
ing 21, the sectional value of resistance 3| con—
nected to winding 21, and on the fraction of its
initial value to which the magnetic flux must fall
in order for ?nger I9 to close switch 26. The ?ux
may be kept reasonably constant by designing
core I2 so that it is always saturated by the line
current. The time constant varies inversely as
the resistance value connected to winding 21.
Therefore by providing resistance values, which
correspond to the various digital keys, as submul
A cam 39, formed 0n plunger 38 near the free
tiples of the overall resistance value, the intervals
end thereof, is arranged for engagement with
15 can be made proportional to the digital numbers.
the free end of a pivotal bar 4|, which has an ‘
In other ‘words, digital key I, which inserts the
insulated projection 42 on the under side and
maximum resistance, produces the minimum open
intermediate the ends thereof for actuating
circuit condition in line II; key 2, which intro
switch 26. Bar All is biased to the upward posi~.
duces one-half of the resistance of key I, pro~
tion by spring-43, stop 44 limiting the extent of
duces twice the open circuit period of key I; key
the upward travel and stop 46 limiting the ex
3, which introduces one-third of the resistance
tent of the downward travel thereof. The lower
of key I, produces three times the open circuit
end of plunger 38 engages a leaf spring 41, which
period of key I; and in like manner continuing
is attached to an insulated support 48 in any
to key 0, which inserts one-tenth of the resistance
suitable manner and which is adapted to main
of key I and produces ten times the open circuit
tain plunger 38 in an upwardly biased condition.
period of key I.
The detailed construction of key-set 29 is not
Thus a novel and useful method of indicating a
further illustrated as switches of this type are of
number is provided whereby the subscriber con
trols the duration of an interval which is observ
known design.
For operation of key-set 29, pressure on any
able at a central office and which is convertible
plate 31, which has a plunger 38 attached thereto.
of the series of buttons 33 ?rst causes engage
ment between contacts 34 and 35 and then
through the cooperation of plunger cam 39, bar
M and projection 42, movable insulated spring
thereat through well-known means into a nu
merical indication. A practical advantage of this
method lies in the-fact that if the interval can
be made short, the appropriate signals can be
49 of switch 26 is snapped open to the position
transmitted very quickly, thereby reducing the
shown in dot-dash lines. Bar M is restricted in 35 subscriber’s signaling time.
The detailed operation of signaling device‘ I0
its downward movement by stop 46 so that cam
39 continues to a position underneath the free
will now be described. Let it be assumed that
end of bar 4|, which thereupon because of the
the subscriber wishes to initiate a call and that
tension of spring 43, is retracted to its normal
line circuit I I is open at handset switch contact
position, thus clearing the way for restoral of
I5 by virtue of the handset (not shown) being
spring 49, as will be hereinafter described. Re
on its mounting, switch 26 is closed, arm I8 is
lease of pressure on button 33 enables leaf spring
biased to its upper position by spring 2|, and
41 to restore plunger 38 to its normal position as
armature I6 being attached to arm I8 is likewise
biased from that of a magnetically closed circuit
For a better understanding of the invention,
in conjunction with poles I3, I4. The subscriber
the principles applicable to electromagnetic relay
in removing the handset from the mounting es‘x
operation will be compared with those applicable
tablishes, in the customary manner, a direct cur
to the device disclosed herein. It is well known
rent circuit including primary winding 24 in se
in telephone relay practice that relays may be
ries with contact 25 of switch 26, handset switch
made slow in operating and releasing by causing 50 contact I5, and the central o?ice'switching mech
a current to be induced which in turn produces a
anism over line II. The resultant current ?ow
magnetic ?eld in opposition to the original chang
through primary winding 24 sets up in core. I2
ing ?eld and prevents the resultant magnetic
a magnetic ?ux, which is su?icient to rotate ar
?eld of the relay from building up or dying down
mature I6 and arm I8 in opposition to spring 2I,
as rapidly as the current in the relay coil. This
is done by means of a short-circuit winding on the
so that the opposite faces of armature I6 are
relay in which currents are induced to prevent
the current in the regular winding from building
I3, I4, respectively, thereby closing the magnetic
approximately parallel with the faces of poles
path therethrough. Finger I9 is also rotated
up its ?eld or dropping off its ?eld as rapidly on
with arm I8, the operated positions of armature
opening the circuit. Thus in operating, the full 60 I6, arm I8, and ?nger I9 being shown in dot
strength of the ?eld, which is required to pull
dash lines. While in the operated position, ?nger
up the armature of the relay, is not obtained
I9 is thus clear of movable spring 49 of switch
until after a de?nite lapse of time.
26. The subscriber next pushes a button 33 of
The above principle is applied to this invention
any one of the digital keys of key-set 29, say
wherein primary winding 24 corresponds‘to the 65 key lever B, which first engages contacts 34, 35
regular winding of a relay and secondary wind
connecting resistance element 53 of resistance 3I
ing 21 corresponds to the short-circuited winding
across secondary winding 21, and then actuates
of the relay. While variations in the operating
plunger 38. Movable spring 49 is snapped to its
and releasing periods of the relay are obtained
open circuit position by plunger 38in combina
mechanically by varying the gap between the ar 70 tion with cam 39, bar 4I, and projection 42, as
mature and core thereof, variations in the release
hereinbefore described, and as shown by the dot
of armature I6 of signaling device I0 are obtained
dash lines, whereby the above-traced line circuit
by connecting resistances of variable amounts
is opened. The line current stops abruptly‘but
to secondary winding 21 thereof through opera
75 it is to be noted that armature I6 does not im
tion of the corresponding digital keys of key-set
mediately retract to its biased position under the
tension of spring 2|. Instead, a value of current
substantially equivalent to the line current is set
up in Winding 21, through induction from pri
mary winding 24, which maintains the magnetic
inductance coil wound around said electromagnet
for controlling operation of said switch, and
means for establishing the time constants of said
control circuit at a plurality of ?xed values, said
means including a keyset operable to select any
one of said resistances and to concurrently open
flux in core I2 constant for the moment. This
prevents a surge of voltage across primary wind
ing 24. The current in secondary-winding 21 and
magnetic ?ux in core l2 then decrease exponen
said primary coil, whereby magnetic ?elds of
different de?nite durations for modifying the
the magnetic ?ux in core [2 falls to a value where
its pull on armature I6 is overcome by the pull
prising, in combination, an electromagnet having
tially at a rate determined by the above-described 10 time of operation of said switch are set up.
4. A signal transmitter for transmitting
time constant of the secondary circuit. When
variable length pulses over a line circuit com
a core, primary and secondary windings carried
of biasing spring 2|, armature I6 is retracted to
its biased position and while returning to this 15 by said core and an armature, pulsing contacts
serially including said primary winding in the
position causes ?nger l 9 to strike spring 49, which
line circuit to effect the operation of said arma
snaps back and closes the line circuit at contact
ture, manually operable means for operating said
25. The line current immediately rises to a value
contacts to disconnect said primary winding
determined by the resistance of primary winding
24, the magnetic flux in core l2 remaining un 20 from said line circuit, the operation of said con
tacts initiating the transmission of a pulse over
changed due to an equivalent current set up in
the line circuit and the deenergization of said
secondary winding 21, which then dies out and
electromagnet. means also responsive to the op~
permits the ?ux to- build up to the value corre
eration of said manually operable means for in
sponding to the line current. The subscriber then
releases button 33 which opens the circuit of sec 25 cluding a resistance in series with said secondary
winding concurrently with the operation of said
ondary winding 21 by separating contact 34 from
contacts whereby the deenergization of said elec
contact 35 and which permits plunger 38 to be
restored to its normal position by leaf spring 41,
tromagnet is delayed for an interval of time, the
as hereinbefore described. The signaling device
length of which is determined by the magnitude
I0 is now in condition for the next number or 30 of the said resistance, and means controlled by
the armature of said electromagnet when de
series of numbers that may be transmitted, as
required, in the above-described manner. It is to
energized for restoring said contacts, the restora
be noted that button 33 is kept in the operated
tion of said contacts terminating the transmis
sion of the pulse.
position during the impulse interval in order to
prevent the subscriber from prematurely opening
5. A signal transmitter for transmitting
secondary winding 21 before the entire pulse had
variable length pulses over a line circuit com
been transmitted.
While the features of this invention have been
disclosed with reference to a speci?c embodiment
only, it is, of course, understood that various mod
i?cations may be made in the details of construc
tion without departing from the scope of this
invention as de?ned in the appended claims.
What is claimed is:
prising, in combination, a normally closed contact
whose opening determines the start of a pulse and
whose reclosure determines the end of a pulse,
and means for controlling said contact compris
ing an electromagnet having two inductively re
lated windings mounted on the core thereof, one
of said windings being serially included in the
line circuit by said normally closed contact,
1. In combination, an electromechanical switch, 45 manually operable means for operating said con
tact to open circuit condition and for concurrent
ly closing said other winding through a resist
ance, the magnitude of which determines the
cuit including a plurality of impedance elements
length of the pulse transmitted over the line cir
properly proportioned with respect to each other 50 cuit, whereby the magnetic condition of said elec
tromagnet which prevailed prior to the opera
for varying correspondingly the ?ux ?owing in
said magnetic circuit, and means for selecting
tion of said contact is maintained through the
any one of said impedance elements and for con
inductive interaction of said windings for an in
currently rendering said ?ux producing means
terval of time commensurate with the value of
ineffective, whereby the time of operation of said 55 resistance connected to the said other winding
switch is predetermined for a ?xed interval.
incident to the operation of said manually oper
able means, and means including an armature
2. In combination, an electromechanical switch,
controlled by said electromagnet for reclosing said
a magnetic circuit in said switch, means for gen
a magnetic circuit in said switch, means for pro
ducing ?ux in said magnetic circuit, a control
circuit for said switch, means in said control cir
contact at the end of the said interval of time.
erating a flux in said magnetic circuit, a control
6. A time duration signaling device for a tele
circuit for said switch, means in said control 60
phone switching system comprising means for
circuit including a plurality of impedance ele
ments properly proportioned with respect to each
other for varying correspondingly the ?ux flow
ing in said magnetic circuit, and means for select
establishing a predetermined line signaling con
dition of selectable duration, said means com
prising, in combination, a line circuit, a local
ing any of said impedance elements and for con
selecting circuit inductively coupled to said line
currently rendering said flux generating means
ineffective, whereby the operating time of said
switch is predetermined for a plurality of ?xed
intervals of variable duration.
3. An electromechanical switch comprising an 70
electromagnet, an armature associated with said
electromagnet, a primary inductance coil for gen
circuit, a contact maintaning said line circuit in
closed condition, manually operable means for
operating said contact to open said line circuit,
and means controlled by said inductively coupled
circuits for operating said contact to close said
line circuit.
7. In an electromagnetic signal transmitter,
erating a magnetic ?eld of a ?xed value wound
around said electromagnet, a time control circuit
including a series of resistances and a secondary
the combination with a line circuit of an energy
storage element serially connected with said line
circuit, a switch for interrupting said line circuit,
?ux generating means inductively coupled with
said storage element for controlling said switch,
energizing circuit for said electromagnet includ
ing a primary winding and an impulse contact,
a series of resistances for varying the impedance
a control circuit for said electromagnet including
of said generating means, digital keys for opera
a secondary winding and a resistance adaptable
tively connecting said resistances to said flux gen
i or connection in series with said secondary wind
erating means and for operating said switch, and UL ing, said resistance being subdivided into pre
flux responsive means held actuated for a period
determined elements, and a key-set for connect
corresponding inversely to the value of said re
ing any of said resistance elements with said
sistance connected to the generating means cir
secondary Winding and for concurrently opening
cuit, said flux responsive means effective to re
said contact to initiate an impulse signal, whereby
tract said switch to its’original position at the
said armature is e?ective to close said contact to
end of said period.
8. A device for producing impulse signals in an
complete said impulse signal after a predeter
mined time, dependent upon the resistance ele
electrical circuit comprising a switch contact, an
ment selected.
electromagnet having an armature for closing
10. An impulse signaling device comprising an
said contact, an energizing circuit for said elec 15 impulse switch contact, manual means for open
tromagnet including a primary winding and said
ing said contact to initiate an impulse, electro
contact, a control circuit for said electromagnet
magnetic means for reclosing said contact, said
including a secondary winding and a resistance
‘electromagnetic means comprising a primary
adaptable for connection in series with said sec
winding in series with said contact, a spring biased
ondary winding, said resistance being subdivided 20 armature under control of said winding for clos
into predetermined elements, and separate means
ing said contact, and a time control circuit in
for connecting any of said resistance elements
cluding a secondary winding and a series of re
with said secondary winding and for concurrently
sistance elements for controlling the time of re
opening said contact to initiate an impulse sig
closure of said contact, said manual means also
nal, whereby said armature after a predetermined 25 operative for connecting a particular one of said
time, dependent upon the resistance element se
resistance elements in circuit with said secondary
lected, recloses said contact to complete said im
winding concurrently with the opening of the
pulse signal.
contact, whereby the length of said impulse is
9. A device for producing impulse signals of
predetermined for a ?xed interval.
variable duration in an electrical circuit compris
ing an electromagnet having an armature, an
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