IMPROVEMENTS IN AND RELATING TO TELEPHONIC EXCHANGE SYSTEMS, AND IN APPARATUS EMPLOYED THEREIN.
Year: 1880

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, for an Invention of "IMPROVEMENTS IN
AND RELATING TO TELEPHONIC EXCHANGE SYSTEMS, AND IN APPARATUS
EMPLOYED THEREIN.". A communication from abroad by George Lee Anders,
of Boston, and Thomas Augustus Watson, of Everett, both in the State of
Massachusetts, United States of America.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at the
Office of the Commissioners of Patents on the 12th May 1880.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN AND RELATING TO TELEPHONIC EXCHANGE
SYSTEMS, AND IN APPARATUS EMPLOYED THEREIN." A communication from
abroad by George Lee Anders, of Boston, and Thomas Augustus Watson, of
Everett, both in the State of Massachusetts, United States of America.
This Invention relates to a telephonic exchange system consisting of the
combination of a central station, a series of circuits radiating from the said central
station, stations on each circuit, apparatus at each station controlled and operated
from the central station, which apparatus, when communication is desired at the
said station, will give an audible signal at that station only, switching dévices at
cach station for securing secrecy, means at each station for calling the central
station without signalling any other station on the same circuit, signalling apparatus
at the central station for sending currents of the proper number and character to
cause an audible signal at any desired station on the same circuit and a signal at
the other stations that the line is in use, and a switch board at the central station,
whereby any circuit can be connected with the signalling apparatus at the central
station, and any two circuits can be connected together.
The Invention comprises the following features, vist. :-
1st. In a telephone exchange system the use of means at a central station for
producing rapidly succeding currents of alternate polarity, and continuous currents
of either polarity, and individual signalling apparatus operated by the said currents
at the other stations of the system.
2nd. In a telephone exchange system a series of switches, each of which normally

page_text: short circuits the telephonic apparatus, and is adapted to establish an earth
connection on either side at each station without breaking the continuity of the
line.
3rd. In a telephone exchange system a switch placed at any station in a series,
which switch has the support for the telephone attached to it, and can be made to
establish a circuit from the earth in either direction, as may be desired, without
breaking the continuity of the line, and when the telephone is replaced upon its
support automatically establishes the main line circuit through the station to the
next station.
4th. A telephone switch, which in its normal position forms part of the main
line circuit, and is capable of being forced into a position to connect the telephone
to either "line in" or "line out," as may be desired, where it is held by means of
อ latch or its equivalent against a force tending to throw the switch back to its
normal position, and resisted by the latch when the telephone is off from its hook
or support and in circuit, and from which latch the said switch is automatically
released and returned to its normal position by replacing tho telephone on its
support.
5th. The combination with a telephone switch of a latching device for holding
the said switch in position when the latter is moved either to one side or the other
to establish a connection with the telephone of "line in" .or "line out," which
latching device, resists a force tending to throw the switch back to its normal
position, and is released by the weight of the telephone when the latter is replaced
on its support.
"
6th. In a telephone switch the combination with a pivoted lever of springs or
their equivalents connected respectively to "line in" and "line out," which springs,
when the lever is in the position which it has when the telephone is on its support,
are electrically connected, and according as the lever is moved to one side or the
other respectively bear upon the said lever, so as to connect the same to either
line in" or "line out," and when the telephone is replaced upon its support are
restored to their normal position.
7th. In a telephone switch the combination of the springs and lever before
mentioned, an insulating block, and a conducting plate, and projections on the said
lever, partially enclosing the said block and plate, and the telephone support
pivoted to the said lever, and a plate serving as à latch to hold the lever in
position.
Sth. The combination of the telephono. support and the plate before referred to,
each forming a terminal of the local battery circuit of a transmitting telephone.
9th. In a telephone exchange system a switch adapted for use at an intermediate
station, and forming a support for a telephone, thereby causing it to connect "line
in" with "line out" when the telephone is removed from its support, and acting
automatically when in its normal position to always connect the telephone to "line
in" and the central station.
10th. In a telephone exchange system a switch adapted for use at an inter-
mediate station, and normally connecting the telephones with "line in" when the
telephone is removed from its support, in combination with means for changing
the switch to such a position that "line out" will be connected to the telephone,
a latch which holds the switch in this position, and is released by the weight of
the telephone when the latter is replaced on its support, and means acting to return
the switch to its normal position when released.
11th. In a telephone switch the combination of U shaped springs or their
equivalents, the pivoted switch lever springs or their equivalents acting upon the
said lever and upon the lever supporting the telephone to draw the said switch
lever into the required position and to move the telephone supporting lever,
which is provided with a projection, into contact with spring points electrically
connected.
12th. The combination with a polarized armature oscillated by alternate positive
and negative currents of a ratchet wheel, which is rotated by the vibrations of a

page_text: neutral armature, and forms an obstacle to the full movement of the polarized
armature, except at any desired point in said rotation.
13th. An electro magnet and polarized armature for retaining a ratchet wheel
in position when said magnet is excited by currents of one polarity, and releasing
the said wheel when excited by currents of the opposite polarity, in combination
with a neutral armature for rotating the said ratchet wheel.
14th. A ratchet wheel which, except when in a predetermined position, forms or
operates an obstacle to the movement of a bell, hammer attached to a polarized
armature, in combination with a pawl operated by a neutral armature and rotating
the said ratchet wheel, and a pawl operated by a polarized armature and retaining
or releasing the said ratchet-wheel according to the direction of the current
operating the neutral armature.
15th. In a signalling apparatus the combination of a polarized armature arranged
to be operated by a rapid succession of alternate positive and negative currents,
and a neutral armature which is not affected thereby, but is operated only by
currents of longer duration, a pivoted pawl being provided arranged so as to work
between locking and releasing pins and propel a ratchet wheel, which controls the
movement of the hammer of the bell.
16th. The combination of a gravitating arm and an adjustable signal for indicating
"line in use" or "out of use."
17th. In an electric circuit two polarized electro magnets for operating signal
bells, and placed at different stations, each of which magnets has its armature held
by a spring or its equivalent against a different pole of the magnet, so that one
armature will be oscillated by a current of one polarity, and the other armature by
a current of the opposite polarity.
18th. In a telephone exchange system a series of individual signalling bells in
an open circuit each placed at a station, and capable of being operated from the
central station only, in a combination with a magneto induction apparatus at each
station for calling the central station.
19th. That improvement in the art or method of operating a telephone exchange
system which consists in adapting magneto electric machines to produce all the
varying currents needed for signalling purposes, and operating all the signals
entirely by magneto electric currents.
20th. In a magneto electric machine a permanent magnet and two armatures
provided with induction coils to be rotated to generate electric currents, the said
armatures being so placed relatively to one another that the current generated in
the coil of either one will be strongest when that in the other is weakest, and
suitable commutators in connection with the said coils, whereby all the currents
generated in both will be sent through a circuit in the same direction, thus giving
a steady current of nearly uniform intensity.
21st. In a magneto-electric machine an armature and coil therefor, in which
alternately positive and negative currents may be induced, and means to connect
the said coil with an exterior circuit, whereby only the intermediate currents of
one polarity are sent to the exterior circuit.
22nd. In a magneto-electric machine a permanent magnet and armature and
induction coil therein, and a commutator or circuit controlling device, by which
one end of the induction coil is connected to an exterior circuit during the whole,
and the other end thereof during a portion of each rotation of the armature to
cause only the alternate currents of one polarity to be transmitted to the exterior
circuit.
23rd. The combination with the induction coil of a magneto-electric machine, in
which alternating currents of opposite polarity are generated, of a commutating
device having contact pieces, which are in connection with one end of the coil
while the current therein is of one, and with the other end thereof when it is of
the other polarity, and contact pieces which are continuously in connection one
with one and the other with the other end of the said coil, and means to connect
any of the said contact pieces in circuit independently of the others, whereby

page_text: currents of alternating polarity, or separated or consecutive currents of the same
polarity, may be transmitted to an exterior circuit, as desired, by making the
proper connection.
24th. A magneto-electric machine with two armatures and induction coils there-
for, and means to connect the end of the said coils continuously or alternately
with an exterior circuit, whereby currents of various character, as steady or
fluctuating, or separated, may be transmittted to the exterior circuit as desired.
25th. In a magneto electric machine a magnet and two armatures, and a driving
mechanism to rotate them near the poles of the said magnet to generate electric
currents; combined with means to disengage one of the said annatures from the
driving mechanism, and hold it with its poles remote from those of the magnet.
26th. In a magneto machine two armatures, and a driving mechanism to rotate
them, in fixed relation to one another, combined with means to disengage one of
the said armatures from the driving mechanism, and then cause it to be re-engaged
in the required positive relation to the other.
27th. In a magneto electric machine the combination with the spindle of tho
rotary annatures, bored and lined with insulating material, of a metal pin split
longitudinally, and having its two parts thus divided, separated by a layer of
insulated material, and fitted within the said bored spindle so as to form a
commutator.
28th. A rotary commutator consisting of two metal pieces insulated from one-
another, and adapted to come alternately in contact with suitable contact springs
in their rotation, one of the said metal pièces being adapted to form contact with
an independent contact piece during its entire rotation.
29th. In a telephonic exchange system, two or more instruments, each placed at
a station on the same circuit, and having means to effect the production of au
audible signal at the said station by a determinate number, different at each station,
of decrements in the strength of the unbroken main line current, in combination
with means acting by the breaking of the main line current to unison said
instruments.
30th. In a telephone exchange system, the combination at each of the two or
more stations on the same circuit of two armatures, one retracted on decreasing the
strength of the main line circuit without breaking the same, and the other retracted
on breaking the main line circuit, but attracted while the circuit remains closed,
the first named armature acting by its vibrations to move a device having a
tendency to return to its starting point, and which after a determined number of
movements of its operating armature, different for each station, effects the pro-
duction of an audible signal at that station, and the other armature preventing the
backward movement of the said device while the main line circuit remains closed,
but releasing the said device when the main line circuit is broken.
31st. The combination of an armature lever retracted by decreasing the strength
of a line current, another armature lover 'vibrated by interruptions in the said
current, an electro-magnet or electro-maguets in the line circuit and operating the
said levers, a ratchet wheel, a propelling pawl on the armature lever, the means
for withdrawing the said pawl from the ratchet wheel when the armature lever is
retracted, circuit closing arm on the said ratchet wheel, conducting insulated plate
on one of the armature levers, a local circuit containing a magneto electric bell or.
its equivalent, and completed by the contact of the circuit closing arm and plate,
a holding pawl on the other armature, means acting to turn the ratchet wheel
backwards to a fixed point when the pawls are withdrawn from the said wheel,
an arm or an equivalent and a stop arresting the backward movement of the arm
and ratchet wheel, a resistence coil (at each station, and keys, one for breaking the
line circuit, and the other for connecting the resistence coil to the line circuit.
'

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Henry Johnson in the Great Seal Patent Office on the 12th
November 1880.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN AND RELATING TO TELEPHONIC EXCHANGE
SYSTEMS, AND IN APPARATUS EMPLOYED THEREIN." A communication from
abroad by George Lee Anders, of Boston, and Thomas. Augustus Watson,
Everett, both in the State of Massachusetts, United States of America.
1
1
20
In this system there are a series of telephonic circuits radiating from a central
station, and on each circuit any number of stations, each station being provided
with an apparatus, which, when communication is desired with a station, will give
an audible signal at that station only. At the central station there is a switch-
board for connecting one circuit with another, and for connecting the signalling
apparatus to any circuit, and there are signalling apparatus for controlling the
number and character of the electric impulses to determine an audible signal at any
desired station and signals at the other stations on the same circuit that the line
is in use, and at each station there are switching devices for securing secresy,
whereby when any two stations are communicating telephonically'no other station
on the same circuit can overhear what is being said, and means for signalling the
operator at the contral station without signalling any other station on the same
circuit.
'
The arrangement of the system is shewn in the diagram on Sheet 1 of the
accompanying Drawings in which the parts are indicated without being shown'in
detail. The particular construction of these several parts will be shewn in other
Drawings, and will be hereinafter fully described.
1
Referring to Sheet 1 the diagram is divided into two sections I. and II.
"
Section I. shewing the appliances at the central station, and section II. showing
3 circuits, radiating from the central station, each circuit having two or three
stations, which are cach provided with a secrecy switch" 8, telephones d, d,
signal bell at e, which gives an audible signal at its own station only, and which is
therefore entitled an "individual signal bell," and in this Specification will be so
designated, and means for signalling the central station.
$
"
The appliances at the central station consist of a switch board A, to which the
circuits are connected; electro magnetic annunciators for each circuit, shown at
B, B, B; an apparatus for sending rapidly succeeding currents' of alternate polarity,
which is preferably a magneto electric machine of any suitable.form, and is shown
at C, though the currents may be derived from a battery D, or a magneto
electric machine for sending a continuous current of lower electro-motive force.than
the rapidly succeeding currents of alternate polarity; a key E for reversing the
current from the battery or magneto-electric machine sending a continuous
current; an electric magnetic tap bell, though this may be dispensed with if desired;
a switch F connected to the switch board, and having 3 buttons, one a connected
to the magneto electric apparatus or battery for producing currents of alternate
polarity, another b to the magneto electric machine or battery sending continuous
currents, and the third c connected to the telephone and telephonic apparatus G,
which may be a single telephone, or, as shewn in the diagram, a receiving telephone
and a transmitter and local.battery.
When magneto electric currents are used exclusively, the same machine may be
used to produce currents of alternate polarity or continuous currents, and keys will
be then used with the connections, as shewn on Sheet 6 of the accompanying
Drawings, in which this machine is represented in detail:
I'm 11.
This machine and its connections will hereinafter be more fully described with
reference to said Drawing.
... 2
12.
有 74

page_text: .
Upon each of the three circuits shewn on section II. of the diagram, Sheet I., is
shewn a different form of individual signal bell, each of which will be hereinafter
more particularly and fully described, but in all of these bells there is one common
feature, which is, that the bell hammer is attached to an armature centrally pivoted
over the poles of an electro magnet, and oscillated by exciting the electro magnet
by currents of alternate polarity, thus causing the vibration of the bell hammer
attached to the armature.
The "individual" signal bell on circuit 1 is designated as the "step by step
individual bell"; that on circuit 2, as the "earth switch individual bell"; and that
on circuit 3, as the "bipolar individual bell."
The several circuits of a system may be provided with such forms of individual
bell as are best adapted to the peculiar requirements of that circuit, and it is
preferable that all the stations on the same circuit should have the same form
of bell.
t
The construction of these several forms of bell will be particularly described
hereinafter, but for the purpose of giving a clear explanation of the system and
the relation of these different forms of bells to the apparatus at the central
station, whereby the same apparatus may be used for operating any one of these
forms, the general principle of the operation of each class of these bells will now be
stated.
In the "bipolar individual bell" the bell hammer is attached to the centrally
pivoted polarized armature of an electro magnet, but the said armature at one
station vibrates only when its electro magnet is excited by currents of a certain
polarity, as for instance, positive, while the said armature at the second station.
moves only when its electro magnet is excited by currents of the opposite polarity,
this result being accomplished by normally maintaining one of the poles of the
polarized armature in cach bell, and an opposite pole in each bell near one of the
poles of its electro magnet by a force which is overcome when the electro magnet
is excited by currents of a certain polarity.
In case a third bell is placed on the circuit, its polarized arinature is free to
vibrate under currents of either polarity, but is so made as to respond to rapidly
succeeding currents of opposite polarity of so short duration as to have no effect on
the polarized armatures of the other bells.
'
+
In the earth switch individual boll the electro magnet in each bell is connected
to earth when a current of one polarity exciting the said magnet is broken and
disconnected, from earth, and connected to the line passing to the next station when
a current of opposite polarity exciting the magnet is broken, and the polarized
armature of each electro magnet is free to vibrate only when the said magnet is
connected to earth.
The electro magnets at the several stations on a circuit are normally disconnected
from earth except at the end station, and signals are given at any desired station
by first connecting all the electro magnets to earth by breaking the circuit, then
reversing the circuit and breaking it a sufficient number of times to disconnect the
electro magnets from earth at all the stations. before that one which it is desired to
call, and then sending a succession of currents of alternate polarity, which are of
such a character as to oscillate the polarized armature attached to the bell hammer,
but are of so short duration as to have no effect on the 'armaturo operating the
earth switch.
In the "step by step individual bell" a toothed wheel vibrated by a neutral
armature prevents the bell hammer from striking the bell except when the said
wheel is in a certain position, which is different at each station, and signals are
given at any desired station by sending a sufficient number of impulses to rotate
the toothed wheel to the position in which the bell hammer is free to strike the
bell, such number corresponding to the number of the station, and then sending
alternate currents whichi oscillate the polarized armature to which the bell
hammer is attached, but are of so short duration as not to move the neutral
armature.

page_text: On sending a prolonged current of a polarity opposite to that, used for rotating
the toothed wheel, the holding pawls are released and the wheel returns to its
normal position.
It will be thus seen that by providing the central station with an apparatus or
battery for sending rapidly succeeding currents of alternate polarity, an apparatus
or battery for sending a continuous current, with means for reversing said current,
and switches for making the connections, the individual bell at any station on the
system can be operated.
The switch board A at the central station is adapted for connecting each of the
several circuits with the telephones, keys, and signalling apparatus at the said
station, and for connecting any two or more of the several circuits together.
It consists of a suitable frame supporting a series of upright metallic bars I which
are insulated from each other, and are connected respectively to the several circuits,
with the exception of one at either end of the series, which one is connected to the
switch F and thus to the telephones and signalling apparatus at the central station.
Immediately behind the upright bars and at right angles to them is a series of
parallel horizontal metallic rods K, also insulated from each other, which serve to
electrically connect two or more of the upright bars together by means of metallic
connectors L, to be more particularly described hereinafter, which connectors can
be slid on the upright bars, and when released spring into contact with the
connecting rods K.
Each of these sliding connectors rests normally upon a short metallic bar M,
which is connected to the electro magnet of a suitable annunciator, which lets fall
a number plate T when the electro magnet of the annunciator, is excited or
otherwise gives a signal, and from said electro inagnet connection is made with
the earth.
In front of the annunciators inay be placed a metallic rod R¹ connected to earth,
and the number plate may be connected to metallic levers which make contact
with the rod when the plates drop, and are so connected that the line is thus
connected to earth. A telephone may be placed between the rod R¹ and the
earth.
When the sliding connectors are on the short rods each circuit is connected
to the electro magnet of the annunciator, and thus when a station desires to
communicate telephonically notice can be given at the central station by the
dropping of the annunciator plate T, caused by sending a current from the station
desiring to communicate.
The operator at the central station, by means of the sliding connectors and
horizontal connecting rods, then connects the circuit on which the signal has been
received with liis telephone, and after having ascertained with what station
telephonic communication is desired connects the circuit on which that station is
situated with his signalling apparatus. by means of the sliding connectors, and
then notifies the said station by sending currents of the proper number and
character to cause an audible signal from the individual bell at the said station.
The other station is called in the same manner, and the two circuits are connected
together in order to establish telephonic communication between the two stations
by placing on the same horizontal connecting rod the connectors sliding on the
upright bars connected respectively to these circuits.
The operator is then ready to receive a signal from any other station.
It is desirable in a telephone exchange system to provide means whereby when
persons at any two stations are communicating with one another telephonically a
person at any other station is prevented from overhearing the conversation without
notifying the stations talking with one another.
This result is accomplished by means of a secrecy switch, which in this system is
placed at each station, as shown in the diagram, Sheet 1, at 8.
When a telephone is used with a secrecy switch a circuit normally passes through
the signal bell at each station to the next station, and the telephone when not in
use is not in circuit; but when it is desired to communicate by telephone with a

page_text: station on either side, the line entering the station on that side must be connected
to earth through the telephone. If then while two stations thus each having their
respective telephones put to earth are communicating with one another the telephone
at an intermediate station is put to earth, notice will bo given at each of the other
two stations by the interruption of the communication.
The switch which is used with this system is attached to the hook or other
support upon which the telephone is placed when not in use, and is moved to one
side or the other to establish connection with "line in" or "line out," as may be
desired, and when the telephone is replaced upon its support automatically returns
'to its original position, but differs from and is an improvement upon the switches
of this kind heretofore used in that all the electrical contacts are effected by the
action of springs, or their equivalents, which act upon opposite sides of the switch
lever to restore the latter to its normal position, in which "line in " and "line out "
are connected, in that said lever is held in position by means of a latch when the
lever has been moved by hand to one sido or the other to establish an earth con-
nection through the telephone with "line in" or "line out," and in that the
replacement of the telephone upon its support effects the release of the switch from
the latch, so that it is returned to its normal position by the action of the springs
or their equivalents.
A switch constructed according to this principle is represented in the Drawings
on Sheet 2 of the accompanying Drawings, which shows the apparatus at a station,
viz., the individual signal bell, the magneto induction apparatus for signalling the
central station, and the secrecy switch, as arranged and combined together in a
compact form in a suitable box or case.
In these Drawings Figure 1 shows the switch in elevation; Figure 2 shows the
switch in section; Figure 3 shows the switch in clevation and moved to one side,
and Figure 4 is a diagram showing the electrical connections when one terminal of
the telephone helix is connected to earth and the other terminal is connected to
the annunciator.
In these several Figures the same letters refer to the same parts.
In these Drawings the switch is shown as attached to the cover of the wooden
box which contains the magneto indication signalling apparatus, but it may be
otherwise situated, as may be found convenient.
It consists of a T shaped metallic lever A', which is pivoted to the wooden
cover B' at a¹, and is provided with vertical projections or lugs b', b', on cach
side.
A block of some suitable insulating material C¹ is attached to the lever A'
between the projections, and to the upper surface of this block is attached a plate
of metal D', the surface of which rises above the projections b', 61, and which plate
is shorter than the space between these projections, and therefore does not touch
the same; E¹, E', are two U shaped horizontal springs placed opposite to each
other and having their bent portions turned in opposite directions, and F¹, F', are
two plates of metal suitably fixed to the wooden cover B' side by side, but insulated
from each other, and of these metal plates that upon the left hand, when the
cover B¹ is turned back, is connected to "line in," and that upon the right to
"line out," as shown in Figure 1. Each of the springs E, E¹, is secured by one
end to one of these metallic plates respectively, and the other and free ends of these
springs bear upon the face of the metal plate D¹, and consequently when the
lever A¹ is in its normal position, as shown in Figure 1, the circuit is completed
through these springs and the plate D¹, but when the lever is turned to either one
side or the other one of the projections b' makes contact with one of the springs
and lifts its end from the plate, as shewn in Figure 3, thereby breaking the electric
connection with the other spring and establishing an electrical connection with the
lever A¹:
This lever is either connected to one terminal of the telephone helix and the
other terminal of the telephone helix is connected to earth, as shown in Sheet 1,
on circuit 1, and in Figures 1 and 4 of Sheet 2, or to the earth, as shown in Sheet 1,

page_text: on circuit 2, and in Figure 7 of Sheet 5, the terminals of the telephone helix being
then connected respectively to "line in" and "line out."
As will be evident from the diagrams, Figure 4, Sheet 2, and Figure 7, Sheet 5,
when the lever A' is connected as shown in the first named diagram, and is turned
to the right so as to connect the telephone at any station with "line out," tho
signal bell at the said station cannot be operated froin the central station for tho
reason that the main line is broken at the switch, but if the lever A' is connected
as shewn at the last named diagram, connection with "line in" and "earth"
through the telephone is always maintained, whether the lever A¹ is turned to
right or left, so that in either position of the switch the station can be called from
the central station.
When the connections are arranged as shown in Figures 1 and 4; Sheet 2, it is
desirable to prevent the switch from being able to be held in a position where a
branch circuit can be made through the telephono without breaking the main line
circuit, or in other words without breaking the electrical connection between the
springs E¹, E¹.
The result will be accomplished by having the upper surface of the insulating
block C¹ above the upper surface of the projections b', b', so that when the
lever A is moved to either one side or the other the connection between the
springs E¹, E¹ will be broken before either of the projections 61, 6¹, strikes the
spring above tliem.
When the connections are arranged as shewn in Figure 7, Sheet 5, it is desirable
that when the lever is moved to either one side or the other that the projection on
that side should come into firm contact with the corresponding spring before the
electrical connection between these springs is broken. This result will be
accomplished if the upper surface of the insulating block C₁ is lower than the upper
surface of the projections b', bl.
G¹ is the hook on which the telephone is placed when not in
is pivoted to the lever A¹.
use,
and this hook
Attached to the cover. B' above this hook G¹ is a projection I, and when the
telephone is removed from the hook for use and the lever A' is turned to either
one side or the other, the said hook is placed against the projection I' and will be
held against the same by the action of that one of the springs E¹, E', which bears
upon the corresponding projecting b' on the lever A¹ when the said lever is turned
to one side or the other.
This projection I therefore acts as a latch to hold the lever Ai in position when
turned to one side or the other, but when the telephone is replaced upon the hook
the weight of the telephone disengages the hook from the plate I¹, the lever A' is
restored to its normal position by the action of the spring, and the connection
between "line in" and "line out" is reestablished.
In this switch all the electrical contacts are firmly made and with a rubbing
contact, owing to the pressure of the springs E¹, E', on each side of the lever A¹.
In these Drawings, a transmitter and local battery are shewn as used with the
telephone, and in this case the projection I' may be made of metal, and be made to
close the local battery circuit through the transmitter when the lever A' is latched
on either side by having one terminal of the local battery connected to the lever A¹
and the other to the projection I, as shewn in Sheet 1, in Figure 4, Sheet 2, and
in Figure 7, Sheet 5.
This Invention is not confined to the particular form of latching device described,
as this may be modified in many ways, and any form of latch may be used which
will hold the switch in position when it is turned to one side or the other, and from
which it will be released by the weight of the telephone.
The Invention is also not confined to springs of the form shown, nor to a switch
lever constructed in the manner described, as the principle of the Invention may
be carried into effect by other forms or arrangements of springs; or even by weighted
levers, and by a switch lever adapted to these springs, or weighted levers of another
construction from that shewn.

page_text: In the use of a telephone exchange system a station establishes connection with
the "line in" and the central station much oftener than with a station on the
"line out" and further from the central station, and consequently a secrecy switch
is desirable in which in its normal position the removal of the telephone from its
supporting hook or other support will automatically establish the desired connection
with the central station, but which, in case it may be desired to communicate with
a station on the line out, will admit of being changed in position so that the
removal of the telephone from its support will automatically establish connection
with the "line out."
A secrecy switch of this description is shewn in Sheet 1 of the accompanying
Drawings as used on circuit No. 3, and is also shewn more fully on Sheet 3 of the
accompanying Drawings, which switch is a modification of the secrecy switch
shewn in Sheet 2 of the accompanying Drawings, and herein before described, and
is constructed in such a manner that though the removal of the telephone in the
normal condition of the switch automatically connects the telephone to "line in'
and the central station, and the connection through the station with "line in
and the central station is always automatically restored by the replacement of the
telephone on its support, as in the switch shewn in Sheet 2, the telephone can be
connected at will with the "line out."
"
,,
In Sheet 3 of the accompanying Drawings the switch is shown as attached to
the inside face of the box or case which contains the individual signal bell and the
means for sending a signal to a central station, and on this Sheet,―
Figure 1 is a view in elevation of the switch and its electrical connections when
in its normal position, with the cover of the containing box closed and the telephone
on its support.
Figure 2 is a sectional view of the switch on the line x, x, Figure 1.
Figure 3 is a view in elevation of the switch in its normal position with tho
cover of the containing box turned back and the telephone on its support, and
Figure 4 is a view of switch in elevation when turned to a position to connect
the telephone to "line out," with the cover of the containing box turned back and
the telephone removed from its support.
In these several Figures the same letters refer to the same parts.
Referring to the Drawing a² is a T shaped lever pivoted to the cover B2 of the
case and having two upright lugs or projections 62, 62; on each side of the cross
pieco E2, E2, are two U shaped strings constructed and attached similarly to those
used with the switch shown in Sheet 2,'and connected respectively to "line in "
and "line out." S' is a spring attached to the lever A2 and acting to turn the
said lever into such a position that one of the projections b' is in contact with that
one of the springs which is connected to "line in," and means are provided, as
shewn at F, for turning the lever into the other position, in which one of the
projections be on the lever A2 is in contact with that one of the springs E2 which is
connected with "line out."
I is the hook which supports the telephone when the latter is not in use, and this
hook is attached to a bar G2 which is pivoted at one end of the cover B* and extends
under the lever A². On this bar and under the end of the lever A is a projection H³,
which when the telephone is removed from the hook, and the lever A is turned to
the position in which it is in contact with the spring connected to "line out," comes
against the end of said lever and bolds it in position, as shown in Figure 4, a
spring R² attached to the said bar acting to draw it up when releived from the
weight of the telephone; a², d², are two flat metallic springs above the bar, and
with which the said bar H2 comes in contact when drawn up by the spring after
the telephone is removed from the hook I', as shewn in Figure 4; and c² is a similar
flat metallic spring under the bar G2, with which the said bar comes in contact
when drawn by the weight of the telephone, as shown in Figures 1 and 3.
The electrical connections are as follows:-
The left hand u shaped spring is connected to "line in," and the right hand U
shaped spring is connected to "line out;" one terminal of the telephone helix is

page_text: "
earth, and the other
The lever G' is also
is connected to the
connected through the induction coil of the transmitter to the
terminal of the telephone helix is connected to the spring a².
connected to the switch lever A, and the lower spring
"line out." The local circuit of the transmitter is completed through the switch
lever A and the spring contact a².
The normal position of the lever A² being in contact with the left hand spring E2,
it is obvious that when the telephone is removed from its supporting hook and
the lever Gmakes contact with the spring a that "line in" is connected to earth
through the telephone, and that in case it may be desired to connect the telephono
to "line out," this will be accomplished by turning the switch lever A to the right
and removing the telephone from the hook, when the projection on the lever will
hold the switch lever in that position until the telephone is replaced upon the
hook, when the lever being released will at once return to its normal position in
connection with the left hand spring.
The device which has been described is a convenient method of carrying the
principle of the Invention into effect, but the Invention is not confined to this
particular manner of embodying it in practice.
33
Its essential features are a switching device which normally connects "line in
with "line out" by the weight of the telephone when the latter is on its support,
and when the telephone is removed from its support automatically connects
line in" to earth through the telephone, and is capable of being moved to a
position so that "line out" will be connected to carth through the telephone when
the latter is removed from its support; a device which holds the switching device
in its position when the telephone is not on its support, but releases the switching
device by the action of the weight of the telephone when the latter is placed on its
support, and a. device which acts to return the switching device to its normal
position when released.
It is obvious that these devices may be constructed and arranged in many
different ways from that described, and still accomplish the desired result.
For the purpose of calling the station each station on a circuit is provided with
a magneto induction apparatus for sending a current to operate the annunciator at
the central station, but of such a character as not to produce any effect on the
individual signal apparatus at the several stations on the circuit.
A convenient form of this apparatus is shewn on Sheets 2 and 3; Figure 1,
Sheet 2, showing the apparatus in elevation.
Figure 2, Sheet 2, showing the apparatus in section on the line x, x; Figure 1
and Figure 2, Sheet 3, also showing the apparatus in vertical section.
It consists of a permanent horse shoe magnet L² fixed to the inside face of the
back of the box, to the cover B2 of which the secrecy switch is attached; a pair of
coils M³, M, fixed on the poles of this magnet with their axis at right angles to the
plane of the magnet, and an armature O for these coils attached to a lever P¹
which is pivoted on a suitable support attached to the magnet, so that by
depressing one end of the lever by a suitable sliding push bar R¹ projecting
through the cover of the case or box the armature O' will be removed from the
poles of the magnet L². This lever is insulated from the magnet L, and when this
armature is in contact with the poles of the magnet a circuit is completed from
"line in" to the magnet L², and thence through the lever P', the coils M³, M', being
short circuited; but when the armature is removed from contact with the magnet
by depressing the other end of the lever P¹ the coils are put in circuit and an
induced current is sent to the central station.
Other forms of magneto induction apparatus from that described can be used,
but this form is found convenient for the reason that a current is produced by the
depression of a push bar.
An apparatus embodying the principle of the "step by step" individual bell
woad with this awstem is represented on Sheet & on which Sheet.

page_text: enclosing case removed.
Figure 2 is an end view of the same.
Figure 3 is a front view of the apparatus, showing the indicator.
Figure 4 is a view shewing the position of the ratchet wheel when the bell can
be ring, and
Figure 5 is a view showing the position of the armature when the ratchet wheel
can return to unison.
In these several Figures the same letters refer to the same parts.
A³ is a suitable case which encloses the working parts of the apparatus and
affords a support for the same, and B³ is a bell attached to this case.
C3 is an ordinary polarized electro magnet suitably attached to the front plate
of the case A³, and D³ is its polarized armature pivoted at its centro to the per-
manont magnet W³. To this armature the bell hammer E³ is attached; F³ is a
bar, of soft iron, opposite the poles of the magnet, which bar is pivoted at one end
to the front plate of the case and has pivoted to its other extremity a propelling
pawl H. This bar forms the mutual armature of the electro magnet D³, or if made
of other metal than soft iron has a soft iron armature for the said magnet attached
to it; a spring S³ attached to the bar acts to draw it away from the magnet. 1³ is a
ratchet wheel attached to a suitable shaft K³, supported in the case A³, and with
the teeth of this wheel the pawl H³ engages. This pawl is formed to operate
between the pins 63 and c³ in such a manner that when the armature is attracted
towards the magnet the pawl will be lifted away from the teeth of the ratchet
wheel by its contact with the pin 63, and when the armature is drawn away from
the magnet the pawl will be acted upon by the pin ea to lock the ratchet wheel,
so that the other pawl 03 can be vibrated without changing the position of the
ratchet wheel. The shaft K³ projects through the case and carries an arm L³ on
the outside of the caso.
Arranged on an are described by the end of this arm are a series of perforations
a³, a³, a³, in the case corresponding to the teeth of the wheel, and MS is a moveable
pin which can be inserted in any one of these perforations, so as to limit the
movement of the arm for the purpose that will be hereinafter explained..
Attached to this pin is a small disc N³, to which the end of the arm is opposite,
when the latter is against the pin and the line is not in use.
To the upper end of the vibrating polarized armature D³ is attached a pawl 0³,
which engages with the teeth of the ratchet wheel, and acts to prevent the return
movement of the said wheel when it is rotated by the action of the pawl H³.
The ratchet wheel 13 is situated at such a distance from the magnet, and most of
its teeth are of such a depth that the contact of the pawl 03 with the said teeth
prevents the bell hammer from striking the bell when the polarized armature to
which the bell hammer is attached is vibrated; but by providing the ratchet wheel
with a tooth which is deeper than the others, the bell hammer is able to move far
enough to strike the bell when the pawl o falls into this deep tooth.
This deep tooth is situated at a different distance from the starting point of the
ratchet wheel in each of the apparatus of the series on the same circuit, and
consequently a different number of impulses for each instrument will be required to
bring this deep tooth opposite the pawl O³, so as to admit of the bell being rung,
thus enabling any bell in the series to be sounded without sounding any of the
other bells.
This deep tooth is situated so as to come opposite the pawl Os when the ratchet
wheel is rotated to such an extent as to bring the arm L³ to the highest point
against a suitable arresting pin, and consequently the number of impulses required
to effect this result will depend upon the number of teeth between the pawl O³ and
the deep tooth when the wheel is at rest, and the number is different in every
instrument, and depends upon the position of the pin M³.
When the arm L³ is brought to its highest point the ratchet wheel is held fixed,

page_text: and the pawl H³ in its movements works over the teeth of the ratchet wheel
without rotating the said wheel.
: The currents which are used for moving the neutral armature are preferably of
lower electro motive force than the alternating positive and negative currents
which are used for vibrating the polarized armature, the former currents being
perfectly derived from a battery, and the latter being preferably. the alternate
current produced by a magneto machine, which latter currents must be each of
such short duration as to have no effect on the neutral armature, as shewn in
Figure 4.
Battery currents rappidly reversed can be used instead of magneto induction
currents. The polarized armature must be lighter than the neutral armature, in
order that it may respond to quick impulses that will not move the neutral
armature.
The polarity of the currents which are used for moving the neutral armature to
effect the rotation of the ratchet wheel must be such as to repel the upper end of
the polarized armature; but a current of opposite polarity will attract this end of
the polarized armature, and withdraw both pawls from the ratchet wheel, thus
permitting the arm L³ to drop down against the pin M³, and returning the ratchet
wheel to its starting point.
The apparatus is operated by transmitting a sufficient number of currents of the
same polarity to bring the deep tooth on the ratchet wheel under the pawl 0³, and
then giving a signal by vibrating the polarized armature by alternate positive and
negative currents, of such a character as not to effect the neutral armature,
and finally after the signal has been given releasing the pawls and permitting the
ratchet wheel to come to the unison point by sending a current of such a character
as to affect both armatures, but of a polarity reverse to that used for rotating the
ratchet wheel.
Any suitable transmitting apparatus may be used for sending and reversing these
currents.
When a series of these individual signalling instruments are placed in an electric
circuit, and it is desired that any two of them shall have the facility of calling one
another, this can be accomplished by providing each of these instruments with a
generator of magneto induction currents, and providing on the ratchet wheels of
each of the two instruments a deep tooth at that point on the said wheel which is
presented to the pawl on the polarized armature when the indicating arm is
opposite to the signal disc M³, which is its position when the line is not in uso.
The stations having instruments with this provision can call one another by
sending magnetic currents for ringing the bells of the respective instruments, and
as the other instruments on the circuit are each unprovided with a deep tooth their
bells will not be rung.
In practice it is preferable to use the apparatus constructed as described, in
which both the armatures are operated by the same magnet, but it is obvious that
each of these armatures may be operated by a separate magnet, and that each of
the magnets may be in an independent circuit.
An apparatus embodying the principle of the earth switch individual bell used
with this system is shown on Sheet 5, on which Sheet,-
Figure 1 is a perspective view of the said apparatus in its normal position.
Figure 2 is a detached view of the switch.
Figure 3 is a detached view of the neutral and polarized armatures.
Figure 4 is a plan view of the apparatus shewing the switch disconnected from
the ground contact, and the polarized armature locked.
Figure 4 is a sectional view of the polarized armature and switch lever when in
this position, the section being taken through the line x, x, Figure 4.
Figure 4b is a sectional view of the polarized armature and switch lever when in
the same position, the section being taken through the line x', x', Figure 4.
Figure 4c is a view of the apparatus in elevation.

page_text: Figure 5 is a plan view of the apparatus showing the switch connected to the
ground, and the polarized armature free to oscillate.
Figure 5a is a sectional view of the polarized armature and switch lever when in
this position, the section being taken through the line z, z, Figure 5.
Figure 5b is a sectional view of the polarized arinature and switch lever in the
same position, the section being taken through the line 2, 21, Figure 5.
Figure 6 is a diagram showing the ground connections open at two instruments,
and closed at the third and fourth, and
«
Figure 7 is a diagram showing the electrical connections with the secrecy switch
when one terminal of the telephone helix is connected to line in," and the other
terminal of the telephone helix is connected to "line out."
In these several Figures the same letters refer to the same parts.
In these several Figures A* is, an electro magnet attached to a plate B* which
supports the call bell, and D is a permanent magnet attached to the plate B, and
having one extremity bent at right angles so as to extend over and magnetize an
armature E which is pivoted above the poles of the electro-magnet A* upon a
lever F which is pivoted upon the plate B. In Figure 1 this bent extremity is
shown as broken away. Upon each of the poles of the electro magnet A* are
extension pieces G, G, of soft iron at right angles to the axis of the magnet, and
His a neutral arinature of soft iron which is attracted to the lever Ft. Both the
neutral armature and polarized armature therefore move with the lever F*, but the
polarized armature oscillates on the same. The bell hammer M' of the call bells is
attached to this polarized armature, and is vibrated by its oscillations. A retracting
spring is attached to the lever F, or the instruments may be so placed that the
armature will fall back from the poles of the magnet by its weight when the current
is broken. Attached to a standard on the plate B' is a metal plate I, and a block
H of some suitable insulating substance.
Above the armature H, and pivoted on the plate I', is a metallic lever L* having
two arms M5, M6, one on each side, and at right angles to the lever, which arms
extend over the polarized armature when the neutral armature is retracted, but
when the neutral armature is attracted the polarized armature in its oscillations
clears. the ends of the arms M5, M6.
In the block K is placed a plate of metal N*, which is connected to the earth,
with which plate the lever L4 which is connected to the line is caused to make and
break contact as it may be desired to connect the line to earth at the station or to
establish a circuit through the station. Upon the arm M5 is a projection a*
extending downward, and upon the arm M6 is also a projection a³, which differs
from the projection a' by being bevelled off on its under inner side.
When the lever L' is in the position shewn in the Figure 4, and its extremity rests
upon the insulating block K, so that the line circuit is completed through the
station, the arm M5 will be in such a position that if the end of the polarized
armature opposite the said arm is attracted, it will pass under the said arm when
the neutral armature makes its back stroke; but if the polarity of the current in
the electro-magnet is reversed, so that the end of the polarized armature opposite
the arm M is repelled, and the end of the polarized armature opposite the arm Mo
is attracted, as shown in Figure 5, the projection A* on the arm M³ will be struck
by the armature when the neutral armature makes its back stroke, and will move
the end of the lever L' into contact with the metallic piece N in contact with the
earth. The arm L' can be restored to its original position by changing the polarity
of the current in the electro-magnet A' and then breaking the current, when on the
back stroke of the neutral armature a projection as on the arm M will be struck
by a projection b on the polarized arinature. When the armatures are in the
position shown in Figure 4, the polarized armature is under the projection aº, as
shown in Figure 4b, and consequently the polarized armature is prevented from
oscillating; but when the armatures are in the position shown in Figure 5, the
polarized armature is not prevented from being oscillated, for the reason that the

page_text: projection as on the arm M and the projection b on the polarized armature are
bevilled off, as shown in Figure 5b.
The Invention is not confined to the particular form of apparatus described, as
this can be modified in many ways without departing from the principle of the
Invention.
.
The operation of this apparatus is as follows:-
A series of these instruments are arranged on the line, one at each station, and
the switch lever L on each instrument is in such a position that the earth
connection at each instrument is broken. The current is then put on the line, when
the neutral armatures will be attracted and the polarized armatures unlocked. The
current is then reversed so as to put the polarized armature into the position shown
in Figure 5, and then on breaking the circuit the neutral armature will be retracted,
and the polarized armature will strike the arm M6, and cause the lever or arm L* to
move into contact with the plate N, and thus establish an earth connection at each
station; when the line is in this connection, should it be desired to ring the signal
bell at any station, say, at station No. 3, a current in the reverse direction is closed
and broken as many times as there are stations on the line between the central
office and the station that it is desired to call, the first making and breaking of tho
current having the effect of removing the switch lever from the earth contact at
station 1, the second making and breaking of the current producing the same effect
at station No. 2, and so for each succeeding station. The earth contact at the
station which it is desired to call is not removed, and consequently, for the reason
that the polarized armatures at the succeeding stations are locked, as beforo
explained and as shown in Figure 4, while the polarized armatures at the other
stations are in the position shown in Figure 5, and free to oscillate, the bell at the
station which it is desired to call can be rung from the central office by vibrating
the polarized armature by alternate positive and negative currents of less force or
duration than required to affect the neutral armature; and as the current goes to
earth at that station, the armatures of the instruments at the stations beyond will
not be affected. After the station is called the switch levers at the preceding
stations are put on their respective earth contacts by the operation before explained.
An apparatus embodying this principle of the bipolar individual bell and with this
system is shown on the Sheet 3, and on this Sheet Figure 2 is a vertical sectional
view of the apparatus through the line x, x, Figure 1.
Figure 1 is a horizontal sectional view of the apparatus, and Figure 6 is a
diagram illustrating the Invention.
In these several Figures the same letters refer to the same parts.
Referring to the Drawing L2 is an electro-magnet, and M is its armature, which
is polarized by the permanent magnet N2 centrally pivoted above the poles of the
magnet L. To the centre of this armature the bell hammer 02 is attached, and P³
is a suitable bell which is struck by the hammer when the armature M² oscillates.
One end of this armature bears upon the end of a spring R² which acts to
maintain this end of the armature away from the pole of the electro-magnet
opposite to the said end, and to maintain the other end of the armature in contact
with the other pole of the electro magnet, and therefore the armature will not
oscillate except when the magnet is excited by currents strong enough to overcome
the said spring, and of the polarity which causes the attraction of the end of the
armature which is against the spring R³.
As shown in Sheet 1, and in the diagram Figure 6 of Sheet 3, opposite ends of
the armatures are acted upon by the springs in the two instruments on the circuit,
and consequently the armature of the apparatus at one station will be oscillated by
currents of one polarity, and the armature of the apparatus at the other station
will be operated by currents of the opposite polarity. The sliding connectors used
on the switch board at the central station are shown in Figures 1, 2, and 3,
Sheet 1, Figure 1 being a vertical sectional view through the switch board,

page_text: Figuro 2 an elevation of the same, and Figure 3 a view in perspective of one of the
sliding connectors.
It consists of a short rod of metal L provided with a notch on its lower
extremity, and having in it a slot N through which the bar J passes. This slot is
sufficiently longer than the bar is deep to permit of the extremity of the connector
being fully withdrawn from contact with the bar K. A spiral spring. G encircles
the rod L below the bar I, and bearing against the undersurface of this bar acts to
force the connectors L into contact with the bar K underneath it; but instead of a
spiral spring any other form of spring suitably placed may be used, or there may
be a cam on the rod L, so that a slight rotation of the connector L will bring its
end into contact with the bar K; O is a bent piece of metal which is fixed at its
centre in each connection above the bar on which the connector slides, and at each
extremity comes into close proximity to the upper surface of the bar I on each side
of the connector without touching the said bar. The object of this piece is to limit
the rocking movement of the connector. Attached to each connector is a handle of
some suitable insulating substance. A pointer R may also be attached to the
connector, which by its coincidenco with the medial line of the rod indicates that
the connector is correctly placed.
The notch in the extremity of the connector assures its more perfect contact with
the rod underneath it, and also permits the connector to be oscillated on the said
rod without being disconnected from it, thus enabling the contacts to be kept clean
by friction with one another.
The connectors instead of being made capable of sliding on the vertical bars I,
may be fixed to the same, and the bars be made capable of sliding in the frame, so
that the connector can be placed on any one of the cross bars K. A magneto-
electric machine capable of producing currents of the various character required for
operating the individual signal bells used with this system, and thus enabling a
battery at the central station to be dispensed with, is shown on Sheet 6 of the
accompanying Drawings.
The improvements embodied in this machine consist, first, in using two armatures
so placed that the currents produced by one is of minimum, while that of the other
is maximum intensity, and in providing suitable commutators therefor to send all
such pulsations in one direction, the current formed thereby being of an intensity
nearly the maximum of any pulsation, and of sufficient uniformity to produce the
effect of a battery current on an electro magnet and mechanism controlled thereby ;
in providing, in connection with a machine having a single armature in operation
or in circuit to give fluctuating currents of alternate polarity, a suitable device to
send only those of one polarity to line, the intermediate ones being omitted, thus
giving a series of waves or impulses of one polarity at short definite intervals; in
providing, in a machine having two armatures for producing nearly uniform
currents, means to throw one of said armatures out of gear when desired to use the
machine for fluctuating currents of alternative polarity, and then connecting it
again in the proper position relatively to the other arinature; in providing, in a
machine with a single armature in operation or in circuit, means to control the
currents therefrom, whereby either alternate impulses of opposite polarity or
the impulses of one polarity alone, the intermediate ones being omitted, or all
the pulsations made to pass in the same direction may be sent to line as desired,
and also in certain details of construction.
Referring to Sheet 6,-
Figure 1 is a plan view of this machine.
Figure 2, a horizontal soction thereof showing the relative position of the two
armatures when operating to give steady currents.
Figure 3, a section of the commutating device detached, such as used when one
of the armatures is to be thrown out of gear.
Figure 4, a plan thereof.
Figure 5a longitudinal sectional detail on line x, x. Figure 1.

page_text: Figure 6, a modified form of the two commutators as used when the two
armatures are to be always rotated, but one to be thrown out of circuit at
times.
Figure 7, another modification to be referred to, and
Figure 8 is a view of the operation table at a central station of a telephone
system, shewing the connections by which the individual signalling apparatus at
the other stations may be operated by magneto electric currents without the use of
galvanic batteries.
The Invention is shown embodied in what is known as the Siemens machine,
but it can readily be applied to others.
The usual permanent magnet A5 is provided with suitable pole pieces B³, C¹³,
between which the armatures D³, E³, of usual construction pivoted in suitable
bearings are rotated by the driving gear F³ engaging pinions G, H, on the armature
spindles I, J, in the usual manner.
The armatures are placed by causing the pinions G5, H³, to properly engage the
spur wheel F with the direction of their cores about at right angles with one
another, as shewn in Figure 2, such arrangement causing the current induced in
the coils of one to be of maximum while that in the other is of minimum strength.
The currents generated in the coils of the armatures will have their direction or
polarity reversed during each revolution thereof, but may be made to pass to line
all in one direction by the usual commutator employed for this purpose, such devices
being well known.
These commutators are shown in Figures 3 and 4 of an improved construction.
The spindles I, J, of the armatures are bored out at their lower ends and lined
with insulating material K³, into which pivots made of two pieces L, M, and L³
and Ms of metal separated by a strip of insulating material are driven.
One of these pieces L5 in the spindle Is of the armature D³ of which the currents
are always to be used is entirely insulated from the other and from the metal of
the armature and rest of the machine in electrical connection therewith, but is
extended down and properly shaped to form a pivot in electrical connection with
its step 5, which in this instance also forms the step of the pivot piece L³ of the
other armature.
.
The other metal M³ is connected as by screw 6 (see Figure 6) with the
armature spindle 15 and metallic parts in connection therewith.
In the other commutator shewn in Figure 3 the piece M8 is wholly insulated and
the one L connected by screw 7 with the spindle J³.
One end of the armature coil is connected with the piece L or L³ by screw 6
and the other with the piece M³ or M8 by the screw 7, and for the purpose of
sending the currents in one direction, as before described, these connections would
be sufficient if the said pieces were entirely insulated from everything else, but the
other connections, namely, with the step 5 and spindles 15, J³, will be needed to
give the other currents, as hereinafter described.
The currents are led away to the line by the usual spring contact pieces 1, 2, 3, 4,
which make connection with the pieces L5, M5, L³, M5, as they come around in the
rotation of the armature, one of the springs of each pair being thus always in con-
nection with the electrode of the coil of one polarity and the other with the electrode
of the other polarity.
The springs 1 and 3, for instance, may then always receive positive currents, and
may be connected in any suitable manner to one end of the circuit or line wire,
and the other or negative springs 2, 4, may be connected to the other end of said
circuit or ground.
The said springs should be properly insulated from the rest of the machine, and
the current generated by the rotation of the two armatures and conducted to the
line as described will be continuous and of nearly uniform strength, and may be
sent to line in either direction by a suitable key board or transmitting key,
When an independent machine is to be used to produce the steady currents the
binding screw 8 connected with springs 2, 4, as hereinafter described, may be also
B

page_text: connected to the binding screw 40 on the central station operator's table (see
Figure 8), and the screw 9 connected with the springs 1, 3, may also be connected
with the binding screw 41, the said screws 40, 41, being connected with the anvil U
and back strap V3 respectively of the reversing koys W³, Y³, one connected to
earth and the other to pivot S3 of the switch S, and by it to the switch board
and line.
The steady continuous currents thus produced will perform the work which has
usually been done by galvanic batteries.
When desired to use short fluctuating currents those generated in the coil of one
armature only will be needed, and those from the other coil may be removed by
breaking the current from one of the springs 3, 4, thereof, or by throwing the said
armature out of gear with the driving wheel F³.
In case the armature is to be thrown out of gear it would be stopped when its
poles or rounded ends of the core are most remote from the poles of the magnet,
that is, in the position of the one marked D5, Figure 2, and when again thrown into
gear it should be in the proper relation to the one which remains in gear, as herein-
before described and shewn in Figure 2.
This may be done quickly and without especial care on the part of the operator
by the gear shifting mechanism shown in Figures 1 and 5.
The driving gear F is pivoted in a bearing F8, which is itself pivoted to oscillate
about the shaft J of the armature D5 to cause the spur wheel F5 to engage and
disengage the pinion H5, the said spur wheel always remaining in engagement with
the pinion G.
A suitable holder P' is provided to engage the oscillating bearing arm of the spur
wheel F and hold it in either of its positions.
'
The pinion H³ and its armature E³ are stopped and held in the proper position
before described by the stop arm R5, pivoted at 20 and provided with a notch 21 to
engage one of the two teeth 22 projecting on each side of the armature spindle J³,
either above or below the pinion H³ as most convenient.
In order that the pinion H shall be re-engaged when in the proper position
relative to the pinion G5, a guide ring F provided with a series of notches 23 and
connected with the spur wheel F5 bears against the tooth 22 not engaged by the
arm Ro, until when one of the notches 23 comes opposite the said tooth 22 the spur
wheel F falls into the engagement with the pinion H³.
The notches 23 are so placed that the spur wheel F falls in when the pinion H³
is in the proper position, and while the said spur wheel is driving the said pinion
the teeth 22 successively fall into the notches 23 without interfering with the
proper action of the machine.
After the spur wheel F5 has come into engagement with the pinion H³ the latter
is released by throwing back the stop arm R³, which is retained in either of its
positions by the double notched spring arm S⁹.
When both the pinions are in gear and the machine in operation, one com-
mutator spring of each pair (for example those marked 2, 4,) will have to be
connected to one end of the line or ground, and in this case the holding arm R³ will
have to be back out of engagement with the teeth 22.
A convenient method of making the desired connection will be to connect the said
springs 2, 4, to a stop T against which the arm R is thrown when disengaged, the
said arm itself being connected with the binding screw S, and. in this case the
springs 1, 3, may be connected to the plates 1*, 3*, connected by a plug 5* with a
binding screw 9, the said screws 8, 9, being connected, as before described, to a
proper transmitting key to send the currents to line as desired.
When the pinion H5 is disconnected and armature E³ thrown out of action, as
just described, or if the circuit of the coil of the said armature is broken by a
suitable key or switch at any point in the circuit, the currents are derived from
the armature D alone, so that in either case the said currents and means of
controlling them may be the same as if derived from a machine having but one

page_text: armature (in fact it then has but one operative armature), and will be so
described.
1
When it is desired to use the currents just as generated in the coil, that is, of
alternate positive and negative polarity, as for example, to oscillate a light polarized
armature in a signal apparatus such as is used with the system herein described,
one end of the coil should be connected with one end of the circuit-or-line wire,
and the other end of the coil with the other end of the said circuit or ground during
the entire rotation of the armature.
as
The piece L' of the commutator connected with one end of the coil is, before.
described, always in connection with its step 5, and may consequently be connected
therefrom with one end of the main circuit, while the other end.of the coil is con-
nected with the metal piece M5 connected, as before described, with the armature
spindle J, and consequently through the gear F5 with the metal bearings and
framo work of the machine, which may be connected to the other end of the said
circuit.
As the ends of the coil must not be permanently connected either to line or
to ground when the machine is used with both armatures, as before described, to
produce steady currents the step 5 should be connected with a different binding
screw from, or its circuit controlled independently of, that of the springs 2, 4, then.
connected with the ground, and similarly the circuit from the metal of the machine.
to the line should be separate from that from the springs 1, 3.
When the armature E³ is to be thrown out of action, as before described, the
connection for the alternating currents may be as follows
=
The step 5 of the rotating armature may be connected with the pivot L³ of
the other armature, which may run in insulated bearings at both ends, and so be,
when out of gear, disconnected from the metal of the machine, but connected with
the arm R, itself in permanent connection with the binding screw 8, as before
described.
In this armature the piece L³ may be connected with the spindle J and the picce
M entirely insulated, such an arrangement not yitiating the operation of the said
armature when used in connection with the springs 3, 4.
The currents will thus find their way from one end of the coil connected with
the pivot piece L, through the step 5, spindle J of the motionless armature, and
arm R to the screw 8, while from the other end of the coil they pass through the
metal of the machine to the plate mx, which may now be connected by plug 5*
with the screw 8, the plates 1*, 3*, Being disconnected therefrom.
When it is desired to send to line only the intermittent currents of one polarity
generated in the coil, it may be done by connecting one end of the said coil to one
end of the circuit as to the ground, and allowing the other end to be connected only
during that part of the rotation of the armature in which the current generated is
of one polarity, that is to say, while one side of the commutator is connected with
one of the springs,
These currents,
S may also be sent by leaving the connections as last described, the
pivot L' connected to the binding screw S, and the machine or plate my to the coil,
and also connecting the plate 1 and spring 1 to line.
Then during a half rotation the pivot piece L³ will be connected to the screw S,
and the other piece M³ to the one 9 (both through the spring 1 and motal of the
machine), and the proper current will be sent from the said screws to an exterior
circuit connected therewith, but during the other half rotation of the pivot piece L³
will be connected to the screw 8 by the spring 1, and the other piece M5 also connected
to the same screw, so that the current will be shunted from the line, passing only
through the circuit connecting the said spring 1 and the,metal of the machine to
the screw S. 1
It is obvious that the intermittent currents would also be produced by connecting
the pivot Laid the spring 1 alone in circuit, the metal of the machine being
disconnected therefrom.
If it should be desired to send all the currents induced by the one armature D³ in

page_text: one and the same direction, the spring 1 should be connected to one and the
spring 2 to the other end of the circuit, the metal of the machine and step 5 being
disconnected, such an arrangement requiring some alterations in the connection
of the arm R³, or step 5, and other parts which need not be described as they could
be readily made, and in practice this sort of current will rarely be used.
In practice the machine will generally be used with both armatures in operation,
without disengaging either of the pinions G, H, and the currents therefrom will
be controlled by suitable keys, such keys and their connections with the instruments
of the operator's table at a central station of a telephone system being shewn in
Figure 8.
When intended to be used in this manner, with both armatures in operation, the
holder and the arms R³, S³, and contact point will be omitted; the comutators
will be constructed and their pieces connected with their coils as before,
except that the step 5 of the armature D³ will not be connected with the other
armature E³.
In other words the metal pieces L³, M³, of the commutator of the armature E³,
the currents of which are to be used only when steady currents are desired, may be
entirely insulated from everything except the ends of the coil' and the spring
3, 4. The connections of the commutator of the armature D³ will be as before
described.
A series of binding screws are shown on the right hand of Figure 1, which are
connected as follows:-The one marked 11 with the spring 1; 12 with 3; 13 with
the petal of the machine, in connection, as before described, with the piece m³×;
'with springs 2 and 4, and 15 with step 5.
:
14
The machine may be kept at any desired place, and the said screw cups 11, 12,
13, 14, 15, connected with a series of normally open keys, 31, 32, 33, 34, 35
respectively, at a suitable point on the operator's table (see Figure 8), those
31, 32, 33, being adapted to form connection when closed with the back contact
strap V of the reversing keys W5, Y³, whilst the keys 34, 35, are adapted to form
connection with the anvil Ub.
!
By depressing keys 31, 32, and 34 the steady currents are sent to the reversing
keys W, Ys, and may be sent thereby to a line in either direction, as desired, in
usual manner.
1.
It will be seen that by this operation the springs 1, 3, screws 11, 12, and keys
31, 32, are connected to the back strap V5, and the springs 2, 4, screws 14, and
key 34 to the anvil. U³ of the said key.
x
By depressing keys 33 and 35, the screw 13 and metal of the machine and piece
m are connected to the back strap V, and the screw 15, step 5, and pivot
piece L to the anvil Us, and the short alternately reversing currents are sent, the
coil of armature E5 being in open circuit.
As these (namely, the steady and the short reversing currents) will be most
commonly used, and are the only ones needed to operate the individual signal
bell before referred to, it will be advantageous to so locate and connect the keys
that those 31, 32, and 34, and those 33 and 35 may be simultaneously operated by
depressing a suitable key or lever connected therewith.
By depressing keys 31 and 35 the spring 1 and step 5 are brought into circuit
and the intermittent currents of one polarity may be sent, and by depressing
keys 31, 34, the springs 1 and 2 are brought into circuit and all the currents of
the one armature D³ are sent in the same direction..
1
When desired to produce only the short intermittent currents of the same
polarity a convenient form of commutator which may be employed is that shewn
in Figure 7, one end of the coil being connected to the metal of the machine or
otherwise adapted to be in permanent connection with one end of the circuit, and
the other end of the coil with an eccentric pin L' adapted to come into contact with
a spring during a portion of the rotation of the armature when the strongest
currents of one polarity are produced.
By using two such springs, one on each side of the axis of the armature, the
5

page_text: currents of one. polarity may be sent by connecting one of the said springs in
circuit, and those of the other polarity by connecting the other spring, or by
connecting both to one end of the circuit the usual alternate reversing currents will
be sent.
It will be readily understood that while the direction of the currents in the main
circuit has been herein described as controlled by a reversing key it may be
controlled by reversing the direction of rotation of the machine.
In a telephone exchange system it is sometimes desirable that the several stations
on a circuit should be able to call or signal one another directly without the
necessity of first signalling the central station, as in the system hereinbefore
described, and without producing an audible signal at any other station than that
with which it is désired to communicate.
This result may be accomplished by providing each of the several stations on the
same circuit with an apparatus in which there are two armatures, one of which has
its retracting force so adjusted that the armature will be drawn from its magnet
when the strength of the main line current is decreased below a certain point,
though the circuit remains closed, and the other armature has its retracting force
so adjusted that the armature will not be withdrawn from its magnet until the
main line circuit is broken, a certain number of movements of the first named
armature, different for each station, effecting the production of an audible signal at
that station, and the retraction of the other armature effecting the unisoning of
the several apparatus.
An apparatus embodying this principle of construction is represented on Sheet 7
of the accompanying Drawings.
In this Sheet,--
Figure 1 is a view of the apparatus in elevation, showing the armatures retracted
from the polar pieces of the electro magnet.
Figure 2 is another view of the apparatus in elevation shewing the armatures
attracted to the pole pieces and the local circuit closed.
Figure 3 is a plan view of the apparatus, and
Figure 4 is a diagram shewing its mode of operation.
In these several Figures the same letters refer to the same parts.
Referring to the Drawing A is an electro magnet suitably supported, the poles
of which project through the plate B°; C6 is an armature attached to or forming
part of a lever Dº pivotted at one end on the plate Be below the poles of the
magnet on one side, and carrying a propelling pawl E which is pivotted on the end
of the lever D and acts on a ratchet wheel G. One end of this pawl is bevelled
off above and curved below, and plays between two pins aº, 6º, one above the other;
but the upper one a slightly in advance of the lower one 66, and the other end
of the pawl is provided with a projection c6 to which a spring He is attached, which
spring acts to withdraw the armature and keep the pawl E in engagement with
the ratchet wheel. When the pawl is moved forward it is forced into the teeth of
the ratchet wheel by the upper pin a³, and when drawn back it is raised from said
teeth by the lower pin be. The ratchet wheel Go is fixed on an arbor 16, shewn in
Figure 3, on which arbor is a spiral spring K6 which, after the ratchet wheel has
been rotated by the pawl E, acts on the release of the pawl to turn the ratchet
wheel backwards until its further backward rotation is arrested by the contact of
the arm LB on the arbor with a projection or stop Me on the inside of the plate Bº.
This arm L is in the same position on the arbor in all the apparatus, so that all
the ratchet wheels start from the same point.
No is a metallic arm on the face of the ratchet wheel at right angles to its arbor,
and O is a metallic plate which is attached to the armature Do, but is insulated
therefrom, and with which plate the arm makes contact on the rotation of said
wheel..
One terminal of a local circuit is connected to the arm, and the other terminal of
the said local circuit is connected to the plate. In this circuit is placed the electro
magnet of an ordinary electro magnetic vibrating bell Po

page_text: In each instrument the arm N° is turned to a different point on the face of the
ratchet wheel, and consequently the number of movements of the armature C
necessary to effect the closing of the local circuits as described, and the consequent
ringing of the bell, is different for each station.
The force acting to retract the armature B is so adjusted that on introducing a
resistance in the circuit the said armature will be drawn back from the said
magnet.
Re is another armature, also attached to or forming part of a lever S6, which is
pivotted at its lower end below the electro magnet A on the other side of its
projecting pole pieces. This lever has attached to its upper end a holding pawl Vo
which, by bearing against the teeth of the ratchet wheel Gº, prevents it from
turning backwards.
The force retracting this armature is so adjusted that the armature will remain
against the poles of the magnet as long as the main line circuit is closed, and
consequently the pawl Vo will remain against the teeth of the ratchet wheel during
the rotations of the other armatures.
A resistance coil do, which preferably represents two thirds or three fourths of the
total resistance of the circuit, is placed at each station, and keys e, f, are provided
at each station, one of which (f) when depressed puts the resistance into the
circuit, and the other (e) when depressed breaks the lino circuit, as shewn in the
diagram, Figure 4, and a signal or call is given at any station from any other
station on the circuit by increasing the resistance of the line by depressing the
key fa sufficient number of times to cause the vibrations thus produced in the
armature Do to close the local circuit on the other station in the manner before
explained, and which local circuit remains closed until the line circuit is broken by
the depression of the key e, when both armatures fall back and the ratchet wheel
being released returns to unison.
Instead of one magnet for both armatures each armature may have its own
magnet, and the apparatus may be otherwise modified in its construction without
departing from the principle of the Invention.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and original,
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is,
First. In a telephone exchange system, the use of means at a central station for
producing rapidly succeeding currents of alternate polarity and continuous currents
of either polarity and individual signalling apparatus operated by the said currents
at the other stations of the system, substantially as and for the purpose herein before
described.
Second. In a telephonic exchange system a series of switches, each of which
normally short circuits the telephonic apparatus, and is adapted to establish an
earth connection on either side at each station without breaking the continuity of
the line, substantially as and for the purpose herein before described.
Third. In a telephonic exchange system a switch placed at any station in a
series, which switch has the support for the telephone attached to it, and can be
made to establish a circuit from the earth in either direction as may be desired
without breaking the continuity of the line, and when the telephone is replaced
upon its support automatically establishes the main line circuit through the
station to the next station, substantially as and for the purpose herein before
described.
Fourth. A telephone switch which in its normal position forms part of the main
line circuit, and is capable of being forced into a position to connect the telephone
to either "line in" or "line out" as may be desired, where it is held by means of a
latch or its equivalent against a force tending to throw the switch back to its
normal position, and resisted by the latch when the telephone is off from its hook
or support and in circuit, and from which latch the said switch is automatically

page_text: released and returned to its normal position by replacing the telephone on its
support, substantially as and for the purpose hereinbefore described.
Fifth. The combination with a telephone switch of a latching device for holding
the said switch in position when the latter is moved either to one side or the other
to establish a connection with the telephone of "line in" or "line out," which
latching device resists a force tending to throw the switch back to its normal
position, and is released by the weight of the telephone when the latter is replaced
on its support, substantially as and for the purpose herein before described.
*
Sixth. In combination with the pivotted lever A', the springs E¹, E¹, or their
equivalents connected respectively to "line in" and "line out," which springs when
the lever is in the position which it has when the telephone is on its support are
electrically connected, and according as the lever is moved to one side or the other
respectively bear upon the said lever, so as to connect the same to either "line in "
or line out," and when the telephone is replaced upon its support are restored to
their normal position, substantially as and for the purpose herein before described.
Seventh. The combination of the springs E¹, E¹, the lever A', the insulating
block C, the conducting plate D¹, and the projections 6', 61, on the said lever, the
telephone support G₁ pivoted to the said lever, and the plate I, substantially as
and for the purpose herein before described.
Eighth. The combination of the telephone support G¹ and plate I¹, each forming
a terminal of the local battery circuit of a transmitting telephone, substantially as
and for the purpose herein before described.
"
Ninth. In a telephone exchange system a switch adapted for use at an inter-
mediate station and forming a support for a telephone, thereby causing it to
connect line in" with "line out" when the telephone is removed from its support,
and acting automatically when in its normal position to always connect the
telephone to "line in" and the central,station, substantially as and for the purpose
herein before described.
Tentbly. In a telephonic exchange system a switch adapted for use at an
intermediate station, and normally connecting the telephones with "line in" when
the telephone is removed from its support, in combination with means for changing
the switch to such a position that "line out" will be connected to the telephone,
a latch which holds the switch in this position, and is released by the weight of the
telephone when the latter is replaced on its support, and means acting to return the
switch to its normal position when released, substantially as and for the purpose
herein before described.
Eleventh. The combination of the U shaped springs E², E², or their equivalents,
the pivoted switch lever A2, the springs S2, R2, or their equivalents, the lever G²
supporting the telephone, the projection H2, and the spring contacts u², d², c², all
arranged, operating, and electrically connected, substantially as and for the purpose
herein before described.
',
Twelfth. The combination with a polarized armature oscillated by alternate
positive and negative currents of a ratchet wheel, which is rotated by the vibrations
of a neutral armature, and forms an obstacle to the full movement of the polarized
armature, except at any desired point in the said rotation, substantially as and for
the purpose herein before described.
Thirteenth. An electro magnet and polarized armature for retaining a ratchet
wheel in position when the said magnet is excited by currents of one polarity, and
releasing the said wheel when excited by currents of the opposite polarity, in
combination with a neutral armature for rotating the said ratchet wheel, sub-
stantially as and for the purpose hereinbefore described.
Fourteenth. A ratchet wheel which, except when in a predetermined position,
forms or operates an obstacle to the movement of a bell hammer attached to a
polarized armature, in combination with a pawl operated by a neutral armature
and rotating the said ratchet wheel, and a pawl operated by a polarized armature
and retaining or releasing the said ratchet wheel according to the direction of the.

page_text: current operating the neutral armature, substantially as and for the purpose
herein before described.
Fifteenth. In a signalling apparatus the combination of a polarized armature
arranged to be operated by a rapid succession of alternate positive and negative
currents, and a neutral armature which is not affected thereby, but is operated only
by currents of longer duration, substantially as and for the purpose hereinbefore
described.
Sixteenth. The combination of the pivoted pawl H³, the locking and releasing
pins 63, 3, and 3, and the ratchet wheel, substantially as and for the purpose
herein before described.
"
Seventeenth. The combination of the gravitating arm and the adjustible signal
for indicating line "in use or "out of use," substantially as and for the purpose
herein before described.
1
Eighteenth. In an electric circuit two polarized electro magnets for operating
signal bells and placed at different stations, cach of which magnets has its armature
held by a spring or its equivalent against a different pole of the magnet, so that
one armature will be oscillated by a current of one polarity, and the other armature
by a current of the opposite polarity, substantially as and for the purpose herein-
before described.
Nineteenth. In a telephone exchange system a series of individual signalling
bells in an open circuit, each placed at a station and capable of being operated
from the central station only, in combination with a magneto induction apparatus
at each station for calling the central station, substantially as and for the purpose
hereinbefore described.
Twentieth. That improvement in the art or method of operating a telephonic
exchange system which consists in adapting magneto electric machines to produce
all the varying currents needed for signalling purposes, and operating all the signals
entirely by magneto electric, currents, substantially as and for the purpose herein-
before described.
Twenty first. In a magneto electric machine a permanent magnet and two
armatures provided with induction coils to be rotated to generate electric currents,
the said armatures being so placed relatively to one another that the current
generated in the coil of either one will be strongest when that in the other is
weakest, and suitable commutators in connection with the said coils whereby all the
currents generated in both will be sent through a circuit in the same direction, thus
giving a steady current of nearly uniform intensity, substantially as and for the
purpose herein before described.
Twenty second. In a magneto electric machine an armature and coil therefor in
which alternately positive and negative currents may be induced, and means to
connect the said coil with an exterior circuit whereby only the intermediate currents
of one polarity are sent to the exterior circuit, substantially as and for the purpose
herein before described.
Twenty third. In a magneto electric machine a permanent magnet and armature
and induction coil therein, and a commutator or circuit controlling device by which
one end of the induction coil is connected to an exterior circuit during the whole,
and the other end thereof during a portion of each rotation of the armature, to
cause only the alternate currents of one polarity to be transmitted to the exterior
circuit, substantially as and for the purpose herein before described.
Twenty fourth. The combination with the induction coil of a magneto electric
machine in which alternating currents of opposite polarity are generated of a
commutating device, having contact pieces which are in connection with one end of
the coil while the current therein is of one polarity, and with the other end thereof
when it is of the other polarity, and contact pieces which are continuously in
connection, one with one end and the other with the other end of the said coil, and
means to connect any of the said contact pieces in circuit independently of the
others, whereby currents of alternating polarity, or separated or consecutive currents

page_text: of the same polarity may be transmitted to an exterior circuit, as desired, by making
the proper connection, substantially as and for the purpose herein before described.
Twenty fifth. A magneto electric machine with two armatures and induction
coils therefor, and means to connect the end of the said coil continuously or
alternately with an exterior circuit, whereby currents of various character, as steady
or fluctuating or separated, may be transmitted to the exterior circuit, as desired,
substantially as and for the purpose herein before described.
Twenty sixth. In a magneto electric machine a magnet and two armatures, and
a driving nechanism to rotate them near the poles of the said magnet, to generate
electric currents, combined with means to disengage one of the said armatures from
the driving mechanism and hold it with its poles remote from those of the magnet,
substantially as and for the purpose bereinbefore described.
Twenty seventh. In a magneto machine two armatures and a driving mechanism
to rotate them in fixed relation to one another, combined with means to disengage
one of the said armatures from the driving mechanism, and then cause it to be
re-engaged in the required positive relation to the other, substantially as and for
the purpose hereinbefore described.
Twenty eighth. In a magneto electric machine the combination with the spindle
of the rotary armatures, bored and lined with insulating material as described, of a
metal pin split longitudinally and having its two parts thus divided separated by a
layer of insulated material and fitted within the said bored spindle, substantially as
and for the purpose hereinbefore described.
Twenty ninth. A rotary commutator consisting of two metal pieces insulated
from one another and adapted to come alternately in contact with suitable contact
springs in their rotation, one of the said metal pieces being adapted to form contact
with an independent contact piece during its entire rotation, substantially as and
for the purpose hereinbefore described.
Thirtieth. In a telephonic exchange system two or moro instruments, each placed
at a station on the same circuit, and having means to effect the production of an
audible signal at the said station by a determinate number, different at each station,
of decrements in the strength of the unbroken main line current, in combination
with means acting by the breaking of the main line current to unison the said
instruments, substantially as and for the purpose hereinbefore described.
Thirty first. In a telephone exchange system the combination at each of the two
or more stations on the same circuit of two armatures, one retracted on decreasing
the strength of the main line circuit, without breaking the same, and the other
retracted on breaking the main line circuit, but attracted while the circuit remains
closed, the first named armature acting by its vibrations to move a devise having a
tendency to return to its starting point, and which after a determined number of
movements of its operating armature, different for each station, effects the production
of an audible signal at that station, and the other armature preventing the
backward movement of the said device while the main line circuit remains closed,
but releasing the said device when the main line circuit is broken, substantially as
and for the purpose hereinbefore described.
Thirty second. The combination of the armature lever D° retracted by decreasing
the strength of a line current, the armature lever R° vibrated by interruptions in
the said current, an electro magnet or electro magnets in the line circuit and
operating the said levers, the ratchet wheel G, the propelling pawl E on the
armature lever Do, means for withdrawing the said pawl from the ratchet wheel
when the armature lever is retracted, the circuit closing arm No on the said ratchet
wheel, the conducting insulated plate of on the armature lever D6, a local circuit
containing a magneto electric bell or its equivalent and completed by the contact
of the arm N° and plate O° holding pawl Ve on the armature R6, means acting to
turn the ratchet wheel backwards to a fixed point when the pawls E and V are
withdrawn from the said wheel, the arm L or its equivalent and a stop arresting
the backward movement of the arm L° and ratchet wheel G, a resistance coil at

page_text: each station, and keys e, f, one for breaking the line circuit, and the other for
connecting the resistance coil to the line circuit, substantially as and for the purpose
herein before described.
In witness whereof, I, the said John Henry Johnson, have to this my
Specification set my hand and seal, this Twelfth day of November, One
thousand eight hundred and eighty.
J. HENRY JOHNSON. (L.S.)