IMPROVEMENTS IN CALL APPARATUS FOR TELEPHONE LINES
Year: 1882

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LETTERS PATENT to Martin Benson of N° 52 Chancery Lane London for an
Invention of IMPROVEMENTS IN CALL APPARATUS FOR TELEPHONE LINES
Communicated to him from Abroad by James Pleasants Stabler of Sandy
Spring in the County of Montgomery in the State of Maryland United States
of North America.
COMPLETE SPECIFICATION filed by the said Martin Benson at the Office of
the Commissioners of Patents on the 5th October 1882.
"
MARTIN BENSON of N° 52 Chancery Lane London. "IMPROVEMENTS IN CALL
APPARATUS FOR TELEPHONE LINES." Communicated to me from Abroad by James.
Pleasants Stabler of Sandy Spring in the County of Montgomery in the State of
Maryland United States of North America
"
In those systems of telephone service where there is a "Central Office or
Exchange "from which service wires radiate to the several subscriber's stations,
there are necessarily attendants or "operators" at said central office, whose duties
are to answer the signals made by persons at said stations, and to place any two of
them so desiring in communication. In order to accomplish this it is necessary
that the operator shall be able to send as well as receive signals. The signal to
the exchange is usually the dropping of an annunciator; that to the subscriber is
the sounding of a bell. One service wire may extend to a single subscribers station
or to a number of such stations. In the latter case there are two systems or
modes of calling the subscriber with whom it is desired to communicate. The first
and most generally employed is that wherein each local station bell on that line is
caused to sound the number designating the subscriber's station with which commu-
nication is desired. The other system is designated the "individual call," because,
no bell is sounded except at the station which it is desired to call.
My invention relates to the latter system. In all instruments heretoforé devised.
for individual calls, wherein the mechanism of each local station instrument is
brought into position by successive electrical impulses, these impulses are controlled

page_text: by a manual key; that is to say the circuit is closed for each impulse by a key
actuated by the hand of the operator. It is evident that in this method the
manual dexterity of the operator is the limitation as to speed and that it is also
liable to inaccuracies in accordance with the operators personal equation of error
My invention substitutes an automatic electrical pole changer to control the currents
which move the mechanism into position, and thus greatly facilitates the operation
and eliminates the personal equation of error and substitutes an automatic stop for
the manual stop depending upon the observation of the operator to limit the
movement of the mechanism.
The motive mechanisms of such instruments have generally been operated by
Voltaic batteries but occasionally magneto generators have been employed. In all
cases however, where magneto generators have been used they have been supplied
with commutators.so as to give off currents of one polarity only. In my invention
I am enabled to employ a magneto generator and to and fro currents to actuate the
local call instruments automatically.
My invention comprises an entire system and the mechanism embraced con-
stitutes but one instrument, necessarily in detached portions, but each, or its
equivalent, necessary to the other. For convenience one part is designated the
"Central Office Instrument" and another part is designated the "Local Station
Instrument." In these detached portions parts are duplicated and other parts
are peculiar to each portion as will be hereinafter fully shown and described.
Each local station instrument is provided with a travelling switch which forms a
part of the line circuit and may be actunted by currents controlled by the operator.
at the "Central Office" or Exchange. This travelling switch may thus be caused to
move from its direct line connection to local station circuit shunts, at will of said
operator at the Central Office. But when several local stations are served by one wire
all the travelling switches must of course be simultaneously moved and in order to
divert the current to the desired local circuit shunt it will be necessary to arrange
said local shunts with reference to each other, so that of several simultaneously
travelling switches only one will be at any one moment rest upon a local station
circuit shunt all the others at that moment making direct line connection. It is thus
easy to direct the current to either local shunt circuit and the local station call bell
being in the said shunt circuit either station bell may be sounded without sounding
any other bell on that line.
The travelling switch is most convently and preferably made to rotate in
contact with a dial rim which is also a part of the line circuit, and the local circuit
shunts are arranged in or concentric with a circular track formed by said dial
This order may howover be reversed and the line rim and local, shunts may be.
arranged to revolve in contact with stationary springs. For convenience I will first
describe that part of my invention denominated the Central Office instrument and
afterwards that part denominated the Local Station Instrument having reference to
the accompanying drawings wherein.
Fig. 1. is a perspective view of the Central office instrument, partly in section,
liaving attached to said fig: a diagram of the line and Local Station
Connections.
Fig. 2. is a sectional elevation of the same showing the electrical connections
and the magneto generators in the circuit.
Fig. 3. is an onlarged elevation of one of the key levers detached.
Fig. 4, is a perspective view of the motor magnets and connected parts
Fig. 5, is a plan of one of the travelling switches and its dial
Fig. 6, is a plan of the ratchet whool, pawls and escapement.
Fig. 7. is a perspective of the Local Station Instrumont, open,
Fig. 8, is an olevation of the Telephone Hook Lever and double clectrical connec-
tions for the telephone.
Fig: 0. is an elevation of the Local Station instrument.
A is a generator of electricity. As before stated I prefer to employ a magneto
generator for this purpose because it has great advantage in respect to economy,

page_text: and constancy of current and in my system I am enabled to utilize the normal to-
and-fro currents from such a generator as will hereinafter be more fully explained
The electric currents from the generator.A are conducted to the magnets B, C,
the bobbins whereof, are so, wound that said magnets always present opposite
polarities to each other which affect a pivoted polarized armature D so that at each
reversal of the direction of the current said armature is caused to move on its
pivot, vibrating between said magnets. The magnets B, C, are termed the motor
magnets because the vibrations of the polarized armature actuate the travelling
switch. The polarized armature D has attached to it, so as to partake of its
vibrations one or more pawls which are arranged to engage the teeth of a ratchet
wheel G and cause it to revolve progressively on its axis.
The shaft of the ratchet wheel G carries the travelling switch H, which I prefer
to construct of such a form that in addition to its office as a switch it may serve as
an index or pointer to give visual notice of its position. It will be readily under-
stood that this is only a matter of preference, because, as before stated the switch
may be located in a place invisible from the outside and it would then be
expedient to employ a separate index or pointer to give notice of the vision of the
position of the parts.
The travelling switch H is mounted on the axis of shaft I of the ratchet wheel G
and is carried around with said shaft and wheel in contact with the rim J of the
insulating dial K which is supported on the frame. Said shaft and switch are
in electrical communication with one terminal of one of the motor magnets and
the rim J is in electrical connection with the line, so that said switch controls the
currents.
It will now be convenient to allude to the structure of the local station instru-
ments, each of which is provided with motor magnets, a polarized arinature, pawls a
ratchet wheel actuated thereby a travelling switch and a dial rim concentric there-
with; all in the line circuit and substantially like the corresponding parts of the
central office instrument. In addition however in each local station instrument a
local station circuit shunt is interposed in the path of the travelling switch and the
local call bell is placed in said shunt which joins the line again further on,
so that at a certain point of its revolution the travelling switch passes from the dial
rim to the local station shunt and the current is thereby diverted to the local call
bell magnets and conducted again to the line.
.
Supposing that upon one service or line wire there are twelve stations and each
station is provided with a local station instrument, the travelling switch whereof is
set and maintained in unison with all the others by the coincident movements of
their polarized armatures it may be readily seen that by a proper arrangement of
the several local station shunts there will never be more than one of the travelling
switches upon a local station shunt at any one moment and therefore it will not be
possible to cause the current to excite the bell magnet of more than one local
station instrument at one and the same time.
Considering all the central instruments as separate parts of one system, and the
travelling switch of the central office instrument as a representative of the travelling
switches of the local station instruments, collectively, as will suppose the central
office dial K and its rim J to be divided into imaginary sections as many as there
are stations and other stops to be provided for. This imaginary subdivision is
shown in Fig. 5. where the dotted segmental lines indicate the relative positions of
the several local shunts. To return now to the central office instrument it will be
easily understood that if the movements of the several travelling switches may be
all arrested at pleasure, that arrest may be made when any one of them is on its bell
shunt, and then the bell magnet of that station may be so excited as to sound the
call, while no other bell on that line is in circuit. Heretofore the travelling
switches have been actuated by currents controlled by a manual key and hence
they come to rest when the operator ceased to manipulate said key. In my inven-
ion I substitute an automatic movement of the travelling switches, operated by
o-and-fro currents from a revolving armature and reduce the manual service to the

page_text: act of moving a circuit closing key and stop, corresponding with the local circuit
shunt in its position with reference to the dial rim to effect the movement of the
mechanism and an arrest of said switch at the proper moment. The contact of the
travelling switch with said, arresting stop immediately cuts out the lino by short.
circuiting the current and the local travelling switches therefore come to rest at the
same instant.
The armature of the bell magnet is provided with a retracting spring the tension
of which can be so adjusted that the ordinary operative or motive current will not
be sufficient to cause a movement of said armature. Otherwise cach local bell
would be sounded at ench passage of the local travelling switch over the bell shunt.
It has therefore been found proper to control the movements of the mechanisms by
an electrical current inadequate to sound the local bells and to sound them when
desired by a stronger current sent over the line at will and produced by an
nugmenting current from a reinforce battery or generator, or by one derived from
an independent source of electricity. I prefer the latter because of employing
magneto generators it is preferable for mechanical reasons to employ independent.
generators for currents of different strength. Therefore in the drawings A represents
the generator of less and L represents the generator of greater power. When the
travelling switches have been arrested as above stated the circuit is opened by the
release of the station key T, and thereafter the stronger current is sent over the line
by means of an independent manual key circuit closer and the local station bell is
sounded.
It is possible that from mechanical causes the travelling switch of some one
instrument shall fail to move, so that the same will fall behind its proper position
and thus cause one bell on the line to be improperly sounded. To afford a constant
corrective for such accidents I provide a detent stop M for each instrument and
locate all of said stops relatively in the same place on the dial, and normally always
in the path of the travelling switches so that as they revolvo they will all be
arrested by said dotents and when so arrested they will all be in unison or proper
initial position.
The dial K is also provided with a detent circuit shunt P directly in front of
said detent, so that when the travelling switch is arrested by said detent it will be
resting upon said shunt.
The detent M is attached to the armature of an electro magnet and said
arinature is provided with a retracting spring of adjustable tension, similar to that
of the bell magnet armature so that it will be actuated only by the stronger current,
and the arrangement is such that when so actuated the detent will be withdrawn
and the travelling switch liberated.
When the pawl or pawls have been actuated a number of times sufficient to
bring any lagging travelling switch to its detent and therefore to the place of
unison, the stronger current may be sent over the line and the detents thereby all
simultaneously withdrawn and all the travelling switches liberated in the normal
position of unison
Ench local station instrument includes a small magneto generator, whereby
currents may be sent over the line from any station, to notify the Central Offico
that communication is desired or is endod. This generator is connected with the
line through the local bell and detent circuits so that when the switches are
on the dial rim said generators are cut out Consequently when subscribers
on difforent lines are in communication; the mingneto generators at all other
stations are not in circuit..
The several radiating service wires from a telephone exchange or central office,
may be coupled as desired by a proper system of switches, and the central oflice
instrument may by similar means be put in electrical communication with any one
of said wires.
The above indicates in general terms the principles and mode of operation of
ny invention and I will now more particularly describe some of the details of
construction which I prefer to employ ¨

page_text: opening there is a ring R upon which the posts S are located to support the pivots
of the radial station stop and circuit closing keys T. Exterior to, and concentric
with the ring R there is a ring U against which the keys T severally make contact
when their out ends are depressed. Springs V under each of said keys keep them
normally out of contact with ring U.
The ring R is in electrical communication with the ground and the ring U is in
electrical connection with one terminal of the generator A, forming a part of its
ground circuit so that when the keys T are in normal position the circuit is open
but may be closed by the depression of any one of said keys. In radial position
each of said keys corresponds with one of the local station shunts before described
and is numbered in correspondence with said station.
Each key T is provided with an elastic metallic drooping stop W which depends
into the annular space around the dial, and is so shaped at its lower end that it is
out of the path of the travelling switch except when the key is moved to close the
circuit whereby said stop will be raised so as to arrest said switch when it has
travelled that far. By the contact of this arrest the line current is short circuited
from said travelling switch to the stop and by way of the key and ring R to the
ground. The line is thereby cut out and all the locall station travelling switches
are brought to rest The stop has sufficient depth and movement vertically to
ensure the breaking of contact with the ring U, when the key T is released,
before the travelling switch will part from said stop. This is to prevent the
current from passing again to the line at the moment of breaking contact with
said ring.
The momentary effect of cutting out the line and all the resistance of the same
is to increase the tension of the electric current in the central office instrument, and
correspondingly increase the strain upon its parts. To obviate the danger of
damage from this cause, I have provided the ring Z with projecting points a, which
are placed behind the elastic stops, and almost but not quite, touching them. The
ring Z has an electric connection with the line conductor between the generator
and motor magnets. Therefore when the line it cut out by the arrest of the
travelling switch the elastic stop will yield under the increased tension mentioned
above and will make contact with the point a, and the motor magnets will thereby
be cut out because the current will thus be short circuited by way of the relief
ring Z, stop, key, and ground ring R.
The key to be depressed is that numerically corresponding with the local station
which it is desired to call, and by the arrest of the travelling switches that
particular local station switch is brought to rest upon its bell shunt while all the
other travelling switches remain upon the line rim J. The proper travelling switch
having thus been brought to rest upon its station shunt, the key is released and the
circuit opened. The stronger current may then be sent over the line and the bell
sounded. This is effected by a secondary and independent circuit closer and switch
key Y, located at a convenient place and preferably upon the same base board and
close contiguous to the keys T.
The independent or secondary circuit closer or intensity key Y controls contacts
normally in the line circuit of the weaker generator, and is employed to switch the
current of the weaker generator off the line and immediately afterwards to connect
the line terminal of the stronger generator with the line and close the ground
circuit of the same. The key is pivotally mounted upon a post, b, with a suitable.
spring for retaining it in normal position and for convenience the contacts affected
by it are located at either side of said post toward the end of said key. At one
end there is an adjustable pin, c. which rests upon a contact spring, d, one end
whereof is permanently in contact with one terminal of the generator through the
post d. For convenience this terminal is the conductor, e, It extends from the

page_text: generator frame and is common to both the weaker and stronger generators.
From said contact with the spring d, the conductor, e, extends to the outer ring
and the conductor el extends from the inner ring to the ground post g and
thence to the ground. Thus the conductors e, and e¹, constitute an open ground
circuit subject to be closed by depression of the key T or by the release of the
spring d. The spring & is adjusted so that when released from pressure under
the pin, c, it will make contact with the post g, and form a shunt circuit to the
ground, avoiding the rings and the keys T. Therefore this is a secondary circuit
closer.
The opposite terminal of the weaker generator is by means of the conductor h
connected with the post i near the key Y towards its other end and thence by the
switch spring k to the post, l, which the line conductor m, extends to the motor
magnets, and the relief conductor m extends to the relief ring Z. Immediately,
over said spring & there is an adjustable insulated button p, attached to the key Y'
the function of which is to cause said spring to break contact with the post, i, when
the key Y is depressed, and make connection with the pin q which is in electrical
communication with the corresponding terminal of the stronger generator by the
conductor thereby switching the weaker current off and the stronger one on the
line at will. But as, in depressing the button end of the key Y its opposite end is
raised, and the secondary circuit closing spring, d, makes contact with the ground
post g, it is necessary that the pin c, and button p, should be so adjusted that
the contact at i, is broken before ground is made at post' g, otherwise the
current of the generator A will be momentarily thrown on the line and the
travelling switches moved forward so as to throw out of circuit the bell on which
the call is to be sounded.
The contact spring, k, may, be made sufficiently strong to elevate the key Y
and retain it in normal position. No other spring will then be required for that
purpose and it will not be necessary to make the insulating button p adjustable..
As the weaker generator A delivers to and fro currents and the polarized
armature is always moved in the same direction by a current of given polarity, it'
is easy so to adjust the positions of the elastic stops that when called into action
they shall always arrest the travelling switch at or near the close of a current of
the same polarity And the stronger generator L which gives off currents of
one polarity only, can be so adjusted that the currents given off by it shall always
be of the same polarity as the current which was being given off by the weaker
generator at the moment when the travelling switch was arrested. Therefore said
stronger current will not move the polarized armature of the motor magnets,
and the sounding of the local station bell may be prolonged or repeated at will.
The detent consists of an elastic stop, u, mounted on an arm extending from the
counterpoised armature of an electro magnet in the detent shunt circuit. The
stop, u, is normally in the path of the travelling switch, so as to arrest the same.
This will take place once in each complete revolution of said switch, so that if
unison is momentarily lost it will be again restored before another revolution has
been commenced. As the detent u, is normally in position to arrest the travelling
switch the key T₁, which corresponds with said detent, is not provided with an
elastic stop: When the travelling switches have all been brought to unison, they.
are liberated from the detent by use of the key Y which sends the stronger
current to the line. The stop u is made elastic so that it will yield to the contact
pressure of the travelling switch, and is provided with a rigid arm w¹, to limit such
motion. When said stop is withdrawn below the dial rim by the action of the
detent magnet, it is released from engagement with the switch and by its elasticity
is returned to its normal position, and is therefore incapable of engaging said
switch again until the completion of its revolution.

page_text: To operate a system of instruments simultaneously by an electric current which
may be switched off or on the line at will, it is necessary that the initial current
shall affect all of the motor magnets equally; otherwise one or more of the
instruments may fail to move, and thereby be thrown out of unison, On the other
hand it is highly desirable to avoid so far as possible all complexities of the
apparatus especially those of the nature of commutators. It is therefore a question
whether it be more advisable to simplify the apparatus at the risk of possible lack
of unison and apply correctives for that condition, or to prevent such lack of unison
by complexity of structure. Experience has led me to prefer the former. In, my.
early experiments I applied to the generator A a commutator and supplemental
circuit closer, actuated by the station stop keys but so adjusted that notwithstanding.
the key might be depressed and contact made with the circuit ring U, still the
supplemental circuit closer could not close on the commutator until the revolving
armature had assumed a certain position. Thereby the initial current was caused to
be of full strength and duration, or to bo inoperative because of the same polarity
as the last preceding operative current.
Inter experience has convinced me that in taking to and fro currents from the
gonerator A just as they come the proportion of failures will be insignificant becauso
the arrest of the travelling switch always takes place during the current of one given
polarity, and the probabilities are that in a given number of contacts one half tho
nuinber of initial currents will be inoperative because of the same polarity as the
last preceding operative current and the succeeding current will always be operativo
because of full strength and duration. Of the remaining half there is but small
probability that the initial operative current will be so fraginental that one or
inore motor magnets will be efficiently excited and others not. I therefore prefer to
dispense with the commutator on the generator A., and correct the errors if any
our in the following way
Supposing the line rim J of each dial to be divided into imaginary sections as many
as there are station and other stops provided for on the single line each station bell
shunt will be located within one of these imaginary sections, but no two of said
station shunts will be located in the same section.
Said shunts all have the same relative position in their several sections" but each
shunt is shorter than the section in which it is located:, So that each of said station
sections may be regarded as including a shunt and a space on the dial rim and
the whole dial as being divided into alternato shunts and intervening spaces.
In figure. 5. the dotted lines on the dial represent the different positions of fourteen
shunts with their intervening spaces belonging to twelve stations supposed to be on
the line and two other shunts having a location common to all the instruments
Therefore to give a clear idea of the operation, the travelling switch may be
described as moving over alternate shunts and spaces though in fact the station
dial has but one bell shunt and the movements so described are distributed over
the whole number of instruments comprising the system for one line.
Supposing it to be possible that a travelling switch may fall out of unison as
above described it is evident that it cannot fall behind more than one, movement
because the error will always occur on a insufficient initial current, "I therefore
provide, the ratcliet wheel with teeth not less than one and one balf times as
numerous as the stops of the central office instrument and as each movement of the
vibrating polarized armature carries the ratchet wheel forward half a tooth length,
it therefore requires not less than three movements and pauses to carry the
travelling switch over the space devoted to one station and the length of the shunt
is so graduated as to these movements of the travelling switch, that said switeh

page_text: will not make less than two of said pauses in contact with its shunt. Therefore
if the switch of the bell to be sounded shall have lagged one movement behind, it
will nevertheless at the time of arrest have reached its shunt so that the current
will be properly diverted to the bell magnets; or if the switch of the bell®
immediately preceding it in the series shall have lagged one point it will still, have
moved forward one point, thus carrying it off its shunt to the intervening space, so
that the bell will be out of circuit. And, as previously stated, before commencing
another revolution, said switch will be brought to unisou by the detent.
The movements of the travelling switches being derived from reverse currents
from the generator, will be very rapid, and the momentum of the revolving parts:
may be sufficient to cause a continuance of said movements after the motive force
has ceased to act
For this reason the travelling switch may possibly be caused to move off its
shunt after its motor armature has ceased to move, and to prevent this contingency
I have placed upon the vibrating armature an escapement which will cause the
positive arrest of the ratchet wheel when the armature ceases to act. This arrest
is.only important when the travelling switch is about to move onto or off from,
its bell shunt and the escapement is therefore arranged to act only at those
moments.
The escapement consists of a pin v set rigidly in the ratchet wheel at the proper
point and two arms w, y, which are carried by the vibrating armature. The
extremities of said arms are properly fashioned and located to intercept the path
of the pin valternately and thereby arrest any movement of said ratchet wheel
and travelling switch due to momentum. The particular location of said arms is
such that one of them will be interposed to arrest a momentum movement which
would carry the travelling switch into contact with its shunt too soon and the
other to arrest the momentum movement which would correspondingly cairy said
switch off its shunt too soon. This escapement may be either constructed with one
pin and two arms as above described or with two pins and a single arm.
mode of construction will give the same result.
Either
If two parties desiring to speak with each other are on the same line, it is
necessary at the completion of the call to return all the switches to the unison shunt,
so that the instruments to be used shall both be in circuit. This, of course puts all
the other instruments on that line in circuit and the other subscribers have it in
their power to interrupt. To prevent an unintentional interruption I provide an
additional shunt a¹ connected with the telephone shunt circuit, to which the
springs may be moved so as to give notice visually, by the position of the switch
that the line is in use.
This shunt may be located anywhere on the dial but it is more convenient to
locate it adjoining the unison shunt, and I prefer not only to locate it adjacent to
said shunt but to make it an extension of the same, and connect it with the
telephone circuit by way of the detent magnet and thereby avoid a separate
conductor.
DOUBLE TELEPHONE CONNECTION
When two local station instruments on different lines are connected through the
central office their switches may rest on their respective local station or bell shunts,
and at that time all the other instruments on those lines are cut out becauses their
switches are on their dial rims. This secures to subscribers on different lines

page_text: therefore place over the whole a cover A¹ provided with holes through which the
finger knobs B¹ of the keys may protrude. The cover A¹ may be made of any
suitable material, and if opaque, a central section over the dial may be glazed so
that the operator can see the travelling switch or index as it moves. The knobs B
may be detached from the levers being kept in position by suitable guides.
Having now described the construction and operation of my invention to which
I have given the name of "The Stabler Individual Call," I disclaim all other
individual calls now in use. But what I do claim as my invention is.
-"
1 In a telephone line, a series of call instruments with travelling switches and
motor magnets all in the line and local shunt circuits, combined with a magneto
generator of electricity and a circuit closer for the operation of same.
2 A travelling switch actuating electro magnets for the same, and a circuit
closer all in the electric line, combined with a series of station stops provided with
ground connections to arrest the movements of said switch, short circuit the current
and cut out the line and means whereby said circuit closer may be controlled.
3 A travelling switch, actuating electro magnets, and a circuit closer all in the
electric line combined with a series of station keys and a corresponding series of
station stops having ground connections controlled severally by said keys to arrest
the movement of said switch and means whereby said keys severally control said
circuit closer so that when either station key is moved the circuit will be closed
and said switch will be caused to move until arrested by the corresponding station
stop, the current will be short circuited and the line be cut out.
4. The travelling switch H and its motor magnets in the electric line combined
with a key T, and stop W and ground connections for the same, and a circuit.
closer whereby, when said key is depressed, the line circuit is closed on the
generator the switch H automatically moved to and arrested by, the stop W and
the current then short circuited, as set forth.
5 A generator a circuit closer in the line conductor therefrom a travelling switch
which also forms part of the line a key having a ground connection a stop to
arrest said switch and short circuit the current to the ground, and means whereby
the motion of said key will also operate the circuit closer.
6 In a telephone local call central office instrument the combination essentially
as follows, a magneto generator motor magnets, a travelling switch all in the line
circuit, a series of radial station key levers, stops severally controlled by said keys
to arrest the switch a ring against which said keys severally make contact to close
the circuit and a ground connection for said ring
7. In a telephone local call central office instrument the combination of a magneto
generator without a commutator motor magnets actuated by to and fro currents
therefrom a travelling switch in the line circuit, a series of radial key levers
severally mounted on a ring having a ground connection and stops severally
attached to said keys to arrest said switch and a ring against which said keys
make contact to close circuit, whereby the circuit is closed by depressing one of
said key levers and contact of the travelling switch with the stop of said depressed
lever will short circuit the current to the ground and cut out the line.
8 A local call key board, comprising a series of keys each one whereof has a
ground connection contact when depressed and elastic stops to arrest the travelling
switch and thereby short circuit the current and cut out the line combined with a
relief ring Z provided with its contact points, a, and temporary ground connections,
whereby the electrical tension in the switch instrument is relieved as set forth.
9 In a telephone local call instrument a source of electric energy, motor
magnets and a travelling switch in the line circuit actuated by said magnets a
unison detent shunt and a series of radial station stop key levers whereby said
switch may be arrested, combined with an indicator stop key T¹ whereby said.
.

page_text: switch may be moved to a position aside from its normal position of rest, as and
for the purpose set forth.
10 The secondary circuit closing and switch key Y, which does not form a part
of the circuit conductor e, e¹, combined with the contact switch spring and contact
closing spring, d, and the circuit connections substantially as set forth.
11 A series of call instruments and a magneto generator to operate the local
travelling switches of said instruments, combined with an intensity key Y contact
points and g and a magnetic generator L provided with a single current
commutator, whereby the current may be shifted from one generator to the other
for the purpose set forth.
12 In a telephone local call central office instrument a travelling switch in the
line circuit a dial rim in the line circuit for contact with the same a detent or
unison shunt interposed in said rim motor magnets to actuate said travelling
switch, detent magnets, the armature spring whereof will not yield to the current
which actuates the motor magnets, combined with two magneto generators of
different generative powers and a suitable switch key whereby the weaker or
stronger current may be passed to the line at will.
13 In a telephone local call central office instrument, motor magnets, a vibrating
armature a travelling switch actuated thereby combined with a series of radial key
levers provided with elastic stops said key levers and stops being arranged with
reference to the movements of said armature so as to arrest said switch at or near
the conclusion of a movement of said armature in the same direction whereby n
stronger current of the same polarity as the last operative current may be sent
over the line to operate the local bell or detent magnets without moving either the
vibrating armature or travelling switch from its position.
14 The travelling switch of a telephone local call with its operative motor
magnets vibrating polarized armature, push and pull pawls, and ratchet wheel,
combined with an escapement actuated by said armature, whereby the ratchet wheel
is arrested prior to the engagement of said switch with or disengagement from,
the station shunt for the purpose set forth.
15 The travelling switch H with its motor magnets and the vibrating armature
and push and pull pawls, combined with the ratchet wheel G, provided with the
pin V and the escapement arms w. y. projecting from said armature as set forth.
10 In a telephone local call a travelling switch, and dial rim in the line circuit
combined with an unison shunt twice as long as the local station shunts, or there-
abouts whereby the travelling switch may be moved forward out of its normal
position of rest without going off the unison shunt for the purpose set forth.
17 In a telephone local call a travelling switch in the line circuit with a local
station or bell shunt combined with a telephone receiver in the bell shunt circuit,
and an automatic switch whereby the current will be shunted to the bell magnets
and line when said receiver is hanging on its hook, or through said receiver to the
line when said receiver has been taken off the hook as set forth.
18 In a telephone local call a travelling switch, in the line circuit, a local station
or bell shunt and switch spring, in connection with said local shunt, combined
with a pivoted hook lover whereon the telephone may hang when not in use, and
contact springs c", m', one or the other whereof is in contact with said spring it, as
said lever is up or down, and the current correspondingly shunted to the bell or to
the telephone as set forth.
10 In a telephone local call a travelling switch in the line circuit a unison shunt
and a station bell shunt separated therefrom, suitable springs and hook, lever,
respectively in electrical connection with the bell shunt and detent shunt combined
with the switch springs g', m, whereby the current may be automatically sont to
the telephone from either the unison shunt or station bell shunt, by the act of
removing said telephone from its hook.
20 In a telephone local call a dial rim and a travelling switch in the line circuit,
combined with a local bell shunt on said dial, the length whereof is such that the
index in passing must make at least two pauses upon said shunt.

page_text: 21. In a telephone local call central office instrument, comprising motor magnets,
a dial travelling switch and a series of radial station keys combined with a
protecting cover. A provided with perforations to permit the protrusion of the
finger buttons B' and a transparent centre over the dial as set forth.
In witness whereof I the said Martin Benson have hereunto set my hand
and seal this third day of October in the year of our Lord 1882.