IMPROVEMENTS IN SIGNALLING APPARATUS, AND IN THE ARRANGEMENT OF CIRCUITS TO BE EMPLOYED IN CONNECTION WITH TELE- PHONES
Year: 1879

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for
the Invention of "IMPROVEMENTS IN SIGNALLING APPARATUS, AND IN THE
ARRANGEMENT OF CIRCUITS TO BE EMPLOYED IN CONNECTION WITH TELE-
PHONES." A communication from abroad by George Lee Anders, of Boston,
Massachusetts, United States of America.
.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office of
the Commissioners of Patents on the 2nd July 1879.
SYDNEY PITT, of Sutton, in the County of Surrey.
" IMPROVEMENTS IN
SIGNALLING APPARATUS, AND IN THE ARRANGEMENT OF CIRCUITS TO BE EMPLOYED
IN CONNECTION WITH TELEPHONES." [A communication from abroad by George
Lee Anders, of Boston, Massachusetts, United States of America.]
The first part of the Invention relates to a system of circuits for a telephonic
exchange, by which, 1st, the central office can call any one of a series of telephonic
apparatus connected in a circuit without calling any of the others in such series ;
2nd, the central office only can be called from any point in the series; 3rd, all the
apparatuses in the circuit can be short circuited, or cut out when not in use; 4th,
a ground can be established on either side of the apparatus, as may be desired, for
the direction of communication, and points outside of the points of communication
are enabled to be put in communication with each other. The object of this part
of the Invention is to avoid the objections heretofore existing to the use of the
telephone, owing to the absence of means for effecting the above named results.
This first part of the Invention consists, 1st, in providing the central office with
a reversing key, to which is connected a battery for transmitting any definito
number of impulses in either direction, as may be desired, for ringing a bell in any
one of a series of telephonic apparatuses in a circuit, the hammer of such bell being
obstructed to prevent a signal at all times, excepting when the requisite number of
impulses has been transmitted, as set forth hereinafter; 2nd, in providing each
telephonic apparatus in a circuit with a magneto generator and push knob for
signalling the central office on a bell or annunciator; and, 3rd, in an automatic
switch applied to each telephonic apparatus for establishing a "ground" on either
side of the telephonic apparatus, said switch being so constructed that the telephone

page_text: may be hung upon it when not in use, the weight of the telephone bringing the
switch to its normal position to remove the ground connection, and short circuit
the telephonic apparatus to which the switch belongs.
The first part of the Invention is fully illustrated in Sheets 1, 2, 3, 4, of the
accompanying Drawings forming a part of this Specification, in which Figure 1
represents a front view of a telephonic apparatus, excepting the telephone; Figure 2
represents a section on line X, X, Figure 1; Figures 3 and 4 represent views of a
portion of the front of the apparatus, showing the automatic switch in different
positions, its outer or hook portion being removed; Figure 5 represents a partial
view of the inner side of the cover of the apparatus, showing the automatic switch
and the sound transmitter; Figures 6, 7, and 8 are diagrams representing the system
of circuits; Figure 9 is a diagram representing the central office and a series of
telephonic apparatuses in a circuit. Similar letters of reference indicate like parts
in all the Figures.
A, Figure 6, represents the central office, which is provided with a reversing
key B, to which is connected a battery C. Said reversing key and battery are
suitably connected to a series of telephonic apparatuses, and are adapted to transmit
to such apparatuses any definite number of electrical impulsos in either direction,
such impulses sent in one direction operating the hammer H¹ of signal bells B¹
(Figure 2) on said apparatuses, while the impulses sent in the opposite direction
operate mechanism for obstructing such hammers excepting at predetermined times
when they are permitted to strike these bells. These features, viz., the means for
transmitting impulses in either direction, and mechanism for preventing and
permitting the operation of the hammers to give signals are fully illustrated in
Sheet 5, 6, 7, and 8 of the Drawings, and described as the second part of the
Invention.
Each telephonic apparatus in the circuit consists generally of, 1st, a device for
signalling the central office; 2ndly, telephonic receiving and transmitting devices;
and, 3rdly, an automatic switch, all being mechanically connected to a box or
casing J, and electrically connected, as described hereinafter. The device for
signalling the central office is a permanent magnet D, an electro magnet E attached
to the poles of the magnet D, an armature Fattached to a lever G pivoted at H,
and a push knob I adapted to be moved to separate the armature from the electro
magnet.
The telephonic receiving and transmitting device consists of a bell receiver l'and
a microphonic transmitter J, said parts being of well known construction, and
needing no particular description here. The automatic switch consists of two
contact plates K, K', attached to the casing, a lever L pivoted to swing between
and make contact with either of said plates, a hook M connected mechanically but
not electrically to the lever L, and adapted to swing therewith, so as to make
contact with the upper edges of either or both of the plates K, K. The lever L
and hook M are supported by a spring N, which tends to raise them and force the
lever Linto and the hook M out of contact with one or other of the contact plates.
The hook M is adapted to support a hand telephone at its outer end, and the
weight of such telephone depresses the hook and lever, causing the hook to make
contact with both of the plates K, K', and separating the lever L from either of
said plates, as shown in Figure 6. The lever L is connected electrically with the
earth at all times, and with the transmitter J by a secondary wire passing through
an induction coil J'. The primary wire of said coil connects the plate K, receiver I,
and plate K¹. O represents a contact arm, which is connected to a local battery P,
and makes contact with the hook M when the latter is raised, as shown in Figures
7 and 8. The electrical connections of the apparatus described are as follows:-
The line enters on a plate R', which is one of three lightning arrester plates R, R', R²,
R being connected with the earth, and R³ with the line out to distant stations.
From the plate R¹ the line passes to the electro magnet C¹ of the signal bell B¹,
then to the electro magnet E of the magneto generator, which magnet is short
circuited except when in use, then to contact plate K¹. When the hook M and

page_text: ever L are depressed by the weight of the telephone, the plates K, K¹, are connected
by the hook M, which acts as a plug, short circuiting the receiving and transmitting
devices I, J, J, and thus cutting out the telephone. The circuit will then be
through plug M and plate K to plate R, and then out to a distant station. When
the telephone is removed from the hook the latter rises from the plates K, K', and
the lever L is swung to make contact with either of the plates K', K, according
to the direction in which it is desired to communicate from the apparatus. When
the lever L is swung to plate K, as shown in Figure 7, the circuit will be from
earth through lever L, and plate K, secondary wire of induction coil J¹, transmitter J,
receiver I, plate K¹, electro magnet E of magneto generator, electro magnet C³ of
signal bell B', plate R' of lightning arrester, and through the line to the central
office. When the lever L is swung to plate K¹, as shown in Figure 8, the ground
contact is placed on the opposite side of the receiving and transmitting devices,
through which devices the circit is established to plate K of the switch and plate R'
; of lightning arrester and line out to distant station.
When it is desired to communicate with the central office the operator pushes in
the knob I, thereby disconnecting the armature of the magneto generator from the
electro magnet, and transmitting an impulse which is not of sufficient power to
operate the signal bells B' at the different stations, the coils of the electro magnets C¹
being of coarse wire and of low resistance; the central office however is provided
with signal bells or annunciator drops and coils of such resistance that said impulse
will give the desired signal at the central office and at that point only. After
calling the central office the operator removes the telephone from the hook M, and
swings the lever to plate K, thus connecting the transmitting and receiving devices
with the central office. In Figure 10, 1, 2, 3, 4, 5, 6 represent different stations in
the circuit connected with central office A. When it is desired to communicate
from a station, say 4, to an outward station, say 5, 4 first calls the central office,
makes known his want, and replaces his telephone on the hook, thus cutting out
the transmitting and receiving apparatus at 4, and establishing a circuit through 4
from central office to 5. The central office then calls 5, and when 5 is ready the
central office so informs station 4, who swings the lever L to plate K, and is ready
to communicate. The last named movement of lever L grounds the circuit between
the telephonic apparatus and signal bell of 4, and thus enables the central office to
call or be called from the stations 1, 2, 3, 4, and enables any two of the stations
1, 2, 3, to communicate with each other while 4 and 5 are communicating; hence
two or more sections of the line can be used simultaneously.
The object of the second part of the Invention is to enable a bell to be rung at
one of the several stations on an electrical circuit at the will of the operator at the
station from which the signal is given without ringing the bell at any of the other
stations. Hitherto when there have been several stations in one circuit all the
alarm instruments on that circuit have been duplicates of every other, so that a
signal sounded on one of them has been given by every other; and so far as the
inventor is aware it is still necessary that all the alarm instruments on a circuit
perform substantially the same mechanical movements when all the alarm instru-
ments are of substantially the same construction. This part of the Invention
consists in a contrivance by which, although all the hammers in the circuit are
thrown forward towards their bells in precisely the same way at the same instant,
only one hammer in the circuit, as the operator at the central office or station wills,
can reach its bell. A practical embodiment of the Invention is fully shown in
Sheets 5, 6, 7, and 8 of the accompying Drawings, in which Figure 7, Sheet 5, is
a side elevation of a call bell and accompanying mechanism embodying the Inven-
tion; Figure 2, Sheet 5, is a front elevation of the same construction; Figure 3,
Sheet 6, is a section on line Z, Z', Figure 1, looking toward the bell; Figure 4,
Sheet 7, represents a section on line X, X, Figure 1, looking upwardly at the bottom

page_text: 8
of the main plate of the apparatus; Figure 5, Sheet 7, represents a section on line
Y, Y, Figure 1, looking down on the main plate; Figure 6 represents a section on
line Z, Z, Figure 1, looking downwardly; Figure 7 represents a section on line
Z³, Z³, Figure 2; Figure 8 represents a section on line Z, Z, Figure 1, looking down
on the main plate, and showing the mechanism under different conditions; Figures 9
and 10 represent plan views of the notched disc and bell hammer a. b is a metal
frame consisting of a plate b', suitably attached to a box or casing a', and pro-
jections 6 extending downwards therefrom, as shown. c is an electro magnet
secured to the frame, as shown. Its cores project a little in advance of the coils,
and for the purposes of this description the one marked u is to be considered as the
positive pole, and the one marked & the negative pole. d is a bar rigidly attached
to a shaft e, which rocks on two pins a¹, a¹, screwed into the frame, as shown. To
the bar d is secured the soft iron armature f, and also a polarized armature g¹, the
latter however vibrating on a pin 6³ in the lower end of the bar, the vibrations
being caused by two soft iron lateral poles u', s', respectively inserted in the poles
u and a of the electro magnet. The polarized armature carries at its upper extremity
a metallic strip for a purpose hereafter explained. The bar & carries also at
its upper end the bell hammer H'. B' represents the bell, which is supported upon
a post p¹, as shown. g represents an arbor, which is journalled in the plate b¹ and
in an arm p projecting from the post p¹. The arbor g is revolved by a ratchet k
and pawl, the latter being pivotted to the lever m, which in turn is pivotted to
the plate b at r. The pawl is made to press in towards the ratchet by a spring o.
A pin o¹ limits the throw of the pawl, and prevents it from slipping from the
ratchet, while a spring p attached to the lever m throws the lever m back to its
original position after each forward movement of the pawl. The arbor g above the
ratchet carries a lock bar c³, having ends shaped as shown, to be caught on a detent t
on the end of an elbow lever v, thus locking the arbor at each half revolution. The
elbow lever v is pivotted to the plate J at r. A spring q attached to one arm of
the elbow lever, and pressing against a pin h¹, tends to hold the other arm back
against a pin c³, and when the elbow lever is thus held the detent is in the position
to catch the lock bar o, as before described.
The pin also limits the backward movement of the lever m. The lever m has
a projection m³, and the elbow lever v has an arm or projection ; and the strip d'
before mentioned strikes against one or the other of these projections whenever the
soft iron armature is swung towards its magnet, accordingly as the polarized
armature is attracted towards the pin n¹ or the pin 8'. When the strip d³ strikes
the projection m', it feeds the ratchet forward and turns the arbor; when it strikes
the projection v', it releases the lock-bar from the detent t, and the arbor is free to
be moved forward. Thus the operator at the other end of the line, by sending the
current in the direction to cause the soft iron armature &' to attract the polarized
armature and then making and breaking the circuit, can unlock the arbor, and by
sending the current in the other direction and making and breaking the circuit, can
revolve the arbor.
p is a disc placed upon the arbor as shown. Upon opposite sides of its periphery
it has two notches i, i, and underneath it has a collar in which are a number of
holes equal to the number of teeth in the ratchet. Any two boles which are
opposite each other may be made to receive two pins, one near either end of the
lock bar c; and by this connection the disc is made to revolve with the arbor. A
check out holds the disc in place as shown. The ratchet, lock-bar, and disc are so
placed upon the arbor and adjusted relatively to each other, that once in each
revolution of the arbor, each notch i will come opposite the place occupied by the
strip, when the latter is under the influence of the arinature s'. The office of the
dise p is to prevent the ringing of the bell, excepting when the disc is in this last
named position, its periphery preventing the bell hammer from reaching the bell,
excepting when the strip d³ can enter one of the notches i.
The operation of the signal mechanism above described at the receiving end of
the line is as follows:-Let the arbor at first be locked by the detent t, and lock-

page_text: bar c', and the disc p so set upon the arbor as to bring one of the notches i opposite
the strip d' at the instant the polarized armature is attracted toward the armature
8, the bell may now be rung at pleasure by making and breaking the circuit at
the key end of the line.
If now the current is reversed, the polarized armature is attracted to the soft
iron armature n', and the strip d takes a position opposite the projection m¹, when,
by making and breaking the circuit, the bell cannot be rung, but the ratchet is fed
forward by one notch at each pulsation of the circuit. There are twenty teeth on
the ratchet, ten on either side between the two ends of the lock-bar o'; and since
the two notches i, i, on the disc are opposite each other, it follows that when ten
pulsations have been made in the reverse current, the second notch i will be at the
starting point opposite the original position of the strip d, and the bell may again
be rung, by shifting the current and making and breaking the current. Thus far
the disc p has been supposed to be so placed on the arbor, that the notch i, the
projection, and the strip d, are all in line; but since there are twenty holes in
the collar of the disc, which like the teeth of the ratchet, are equally spaced; it
follows that the disc may be set upon the arbor in nine different positions back of
the end of the lock-bar which catches upon the detent t when the ratchet revolves.
And it is evident that when the disc is so set back of the locking end of the lock-
bar, the bell cannot be rung by the beat of the strip & which unlocks the ratchet.
But after unlocking the ratchet, it will be necessary to reverse the current, thus
sending the strip d³ to the position opposite the projection m², and then by making
and breaking the circuit necessary to feed the ratchet forward the requisite number
of steps to bring the notch i in line with the original position of the strip d³, when,
by reversing the circuit and sending the strip to that original position, the bell
may be rung by making and breaking the circuit.
Accordingly the operator, at the key end of the line, knowing the position of the
slots in the disc, relatively to the lock-bar will, after unlocking the ratchet, reverse
the current and give the requisite number of pulsations to carry the disc a sufficient
number of steps to bring the notch i, which is in advance, to the proper position,
when by shifting the current, he may ring the bell as before. It follows, that if
two notches are used in the disc as shown, there may be as many instruments in
the circuit as there are notches in half the ratchet, and that each instrument may
have its disca so set as to require its own, and a separate number of pulsations
before its bell can be rung.
With slight modification of the lock-bar, a disc with a single notch may be used,
and the number of instruments on the circuit doubled.
Where several instruments are used on one circuit, they must all be adjusted to
unlock their ratchets simultaneously, this gives an initial point from which the
operator at the key station may count the pulsations, to know the conditions of the
different instruments on the circuit; and in practice it will be found convenient to
bring all the instruments on the circuit to an initial point after the bell of one has
been rung. The ratchets unlocking simultaneously, it follows that they are fed
forward simultaneously, that is, when the strip d strikes the projection m¹ in one
instrument, it strikes it in every instrument, and in like manner, when the strip d³
strikes the projection in one instrument, it strikes that projection in all the
instruments. But although the notch i, in the disc p, and the projection v' are in
line when the bell is rung, they have no immediate connection with each other.
The bell may be rung in one instrument when the lock-bars of the several instru-
ments are not in a position to be caught by the detent t. When this happens, the
elbow-levers will vibrate to no purpose.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sydney Pitt in the Great Seal Patent Office on the 2nd January
1880.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN
SIGNALLING APPARATUS, AND IN THE ARRANGEMENT OF CIRCUITS TO BE EMPLOYED
IN CONNECTION WITH TELEPHONES." A communication from abroad by George
Lee Anders, of Boston, Massachusetts, United States of America.
In the present district telephone system when a series of stations are connected
in a circuit, and telephonic communication is established between any two points,
say the fifth and seventh stations, all the stations between the said fifth and seventh
stations and the central office are cut off from communication with each other and
with the central office. This is a defect in the system now used, for the reason
that it is desirable that the central office should at all times be able to hold com-
munication with the stations in the circuit.
The object of the first part of this Invention is to avoid this defect, and to this
end this part of the Invention consists in the use of a switch at each station con-
structed and connected as described so that an "earth" connection can be established
on either side of the telephonic apparatus, according to the direction in which it is
desired to communicate without breaking the continuity of the circuit, thus enabling
the central office to still maintain communication on the circuit for any desired
purpose, the signalling apparatus being placed between the earth connection and the
central office.
The object of the second part of this Invention is to enable a bell to be rung at
one of the several stations on an electrical circuit at the will of the operator at the
station from which the signal is given without ringing the bell at any of the other
stations.
Hitherto when there have been several stations in one circuit all the alarm
instruments on that circuit have been duplicates of every other, so that a signal
sounded on one of them has been given by every other, and so far as I am aware it
is still necessary that all the alarm instruments on a circuit perform substantially
the same mechanical movements when all the alarm instruments are of substantially
the same construction.
This part of the Invention consists in a contrivance by which although all the
hammers in the circuit are thrown forward towards their bells in precisely the same
way at the same instant only one hammer in the circuit, as the operator at the
central office or station wills, can reach its bell.
And the third part of the Invention consists in the combination with the
telephonic apparatus at each station of a magneto induction apparatus, operated by
the depression of a push knob, for generating the current which operates the
annunciator or signalling apparatus at the central office.
In Sheet 1 of the accompanying Drawings I have shewn the above named devices
as used with a microphonic transmitter known as the Blake transmitter, a Bell
receiving telephone, and as combined and arranged together in a convenient manner
in a suitable case.
But any form of transmitting or receiving apparatus may be used, and the devices
may be separately arranged in any manner found convenient.
In Sheet 1 Figure 1 is a front view of this case showing the telephone hook and
switch, the mouth piece of the transmitter and the binding screws for making the
electrical connections; Figure 2, Sheet 1, is a longitudinal section through the case
on the line x, x, Figure 1, and shews the signal bell, switch transmitter, induction
coil, and magneto induction apparatus in section; Figures 3 and 4, Sheet I are
front views of a portion of the case shewing portions of the switch in different
positions; Figure 5, Sheet 1, is a back view of the transmitter and switch.
Figures 6, 7, and 8, Sheet 1, are diagrams shewing the connections in different

page_text: positions of the switch; and Figure 9, Sheet 1, is a diagram showing the manner
of establishing communication between two stations, but in order to avoid com-,
plexity in this diagram the earth connection is represented as made opposite to the
side on which it is desired to communicate, instead of on the same side as in the actual
switch as shewn in Figures 6, 7, and 8. In these several Figures the same letters
refer to the same parts. Sheet 2 shews a practical embodiment of the second part
of this Invention alone. Figure 1, Sheet 2, is a side elevation of a call bell and
accompanying mechanism; Figure 2, Sheet 2, is a front elevation of the same;
Figure 3, Sheet 2, is a vertical section on line 2, 2, Figure 1; Fignre 4, Sheet 2, is
a section on line x, x, Figure 1, looking upwardly; Figure 5, Sheet 2, is a section
on line y, y, Figure 1, looking downwardly; Figure 6, Sheet 2, is a section on line
2,2, Figure 1, looking downwardly, the mechanism being represented in condition
to prevent a signal being given in all of said Figures; Figure 7, Sheet 2, is a
vertical section on line, Figure 2, shewing the mechanism in condition to give
a signal; Figure 8, Shect 2, is a section on line 2, s, Figure 1, looking downwardly,
shewing the mechanism in the same condition as in Figure 7; Figures 9 and 10 are
respectively top views of the bell hammer and device for arresting or allowing the
same to operate.
The receiving telephone and microphonic transmitter are shown at I and J
respectively, and being well known need not be more fully described. Jis the case
enclosing and supporting the several devices. The switch consists of two plates of
metal K, K, attached to the front of the case and separated from each other by a
short space and a lever L pivoted to a standard on the case, so as to swing from side
to side under the plates K, K, and a metallic hook M, used for supporting the
telephone when it is not in use, which hook is attached to the lever Lso as to move
with it, but is electrically insulated therefrom. The end N of the lever L is a
spring, and consequently acts to force the other end of the lever against the under
side of the plate K or K³, according as the lever is turned to one side or the other,
as shewn in Figures 3, 7, and 8, Sheet 1, except when the telephone is suspended to
the hook, when the weight of the telephone depresses the lever L and hook so that
the lever is not in contact with either of the plates, and the hook is brought between
the two plates K, K', and in contact with the upper edge of the plates K, K¹, being
curved downward towards each other, for the purpose of guiding the hook as shewn
in Figures 4 and 6, Sheet 1. O is a metallic spring arm, which is attached to one
side of the case and extends above the hook M, and is curved at its extremity, and
is at such a distance from the upper edges of the plates K, K¹, that when the hook
rises on the detachment of the telephone it makes contact with the spring arm O
and one of the plates K, K', according to the side that is turned, as shewn in
Figures 3, 7, and 8, Sheet 1. This spring arm O is only used when a microphonic
transmitter is used as its object is to complete the local battery current when the
telephone is in use, and the lever L is in contact with either of the plates K, K'.
Jis the induction coil used with the microphonic transmitter, the function of
which in this connection is well known. The magneto induction apparatus for
sending currents from each station to operate the signal bell or annunciator at the
central office consists of a permanent magnet D, a coil E upon the poles of this
magnet, and an armature Fattached to one end of a lever G, which is operated by
a rod attached to the push button L. The coil E is connected to the circuit, and is
short circuited by a suitable spring and contact attached to the lever G, when the
lever is in its normal position, but on depressing the button I the coil is included in
the circuit, and by the separation of the armature from the coil an electric current
is induced, which is sufficient to operate the electro magnet of the signal bell or
annunciator at the central office. The electro magnet of the signal bells at the
different stations on the circuit are not affected by this induced current, owing to
being of low resistance.
The electrical connections are as follows:-The line enters at the plate R¹ of the
lightning arrester, and the current passes from said plate to the coil of the signal
bell, thence to the magneto induction apparatus, the coil E of which is short

page_text: circuited except when the armature F is removed, and thence to the plate K'.
When the telephone is on the hook M, and the said hook and lover L are depressed
by the weight of the telephone, so that the plates K, K', are connected metallically
by the hook, the current will be through the hook M and plate K to the plate R³
of the lightning arrester, and thence to the line and the distant station, and the
telephone will be short circuited, but when the telephone is removed from the hook
and the latter rises from contact with the plates K, K', and the lever L is swung to
make contact with either of the plates K, K, according to the direction in which it
is desired to communicate, one terminal of the telephonic apparatus will be connected
to the line on one side or the other of the station, and the other pole to earth, so
that the station can communicate by telephone with any station on that side which
is connected to the telephonic apparatus. The signal bell will always be maintained
in connection with the central office. In Figures 6 and 7 the lever is shewn upon
the left hand, and the circuit is shewn as from the central office to the plate R³ of
the lightning arrester; thence to the signal bell C, thence to the magneto electric
signalling apparatus, thence to the plate K', and through the telephone and the
secondary coils of the induction coils to the plato K, and from thence by the lever
L to earth, while the local circuit of the transmitter is completed through the arm
O, book M, plate K, and the primary coil of the induction coil. In Figure 8, Sheet 1,
the lover L is moved to the right hand, and the circuit from the central office passes
through the magnet of the signal bell to earth, but the circuit from the plate R³ of
the lightning arrester is to the plate K, the secondary coils of the induction coil,
the telephone, the plate K¹, and lever L to earth, and the local circuit is completed
through the transmitter, the primary coils of the induction coil, the arm O, hook M,
and plate K.
The operation is as follows:-When it is desired to communicate with the central
office from any station the push knob I is depressed, thereby separating the
armature F from the coils E and causing a current to be induced, which, though
not of sufficient power to operate the electro magnetic signal bells at the different
stations, owing to the low resistance of the their magnets, is able to operate the
signal bell or annunciator magnet at the central office, owing to their comparatively
high resistance. The telephone at the station communicating is then removed from
its hook and the lever Ĺ swung to the plate K, whereby the transmitting and
receiving instruments are connected on one side to the earth, and on the other side
to the line and the central office. Should it be desired to talk outward from a
station, say, from station No. 4 to another station, say, No. 6, the central office is
first called by No. 4 and the station made known with which it is desired to com-
municate; the telephone is then replaced upon its hook, thus cutting it out and
establishing a circuit from the central office through the signalling apparatus at
stations Nos. 4 and 5 to the signalling apparatus at station No. 6. The central
office then calls station No. 6 and informs him that station No. 4 desires to com-
municate, when by swinging the levers at stations 4 and 6 to establish an earth
connection and place the telephonic apparatus at these stations between the two
earth connections, conversation can be carried on, while at the same time station 4
having its carth connection between the telephonic apparatus and signal bell the
central office can call this station and any other between it and the central office.
The object of the second part of the Invention is to enable a bell to be rung at
one of the several stations on an electrical circuit at the will of the operator at the
station from which the signal is given without ringing the bell at any of the other
stations.
Hitherto when there have been several stations in one circuit all the alarm
instruments on that circuit have been duplicates of overy other, so that a signal
sounded on one of them has been given by every other, and so far as the inventor
is aware it is still necessary that all the alarm instruments on a circuit perform sub-
stantially the same mechanical movements when all the alarm instruments are of ;
substantially the same construction.
This part of the Invention consists in a contrivance by which, although all the

page_text: hammers in the circuit are thrown forward towards their bells in precisily the same
way at the same instant, only one hammer in the circuit, as the operator at the
central office or station wills, can reach its bell. A practical embodiment of the
Invention is fully shown in Sheet 2 of the accompanying Drawings. b is a metal
frame, consisting of a plate b', suitably attached to a box or casing, and projections 6ª
extending downward therefrom, as shown; c is an electro magnet secured to the
frame, as shewn. Its cores project a little in advance of the coils, and for the
purposes of this description the one marked n is to be considered as the positive
pole, and the one marked a the negative pole; d is a bar rigidly attached to
a shafts, which rocks on two pins a¹, a', screwed into the frame as shown.
To the bar d is secured the soft iron armature f and also a polarized armature g',
the latter however vibrating on a pin 6 in the lower end of the bar, the vibrations
being caused by two soft iron lateral poles n', s', respectively inserted in the poles
nands of the electro-magnet. The polarized armature carries at its upper
extremity a metallic strip dª for a purpose hereafter explained.
The bar d carries also at its upper end the bell hammer H'; B' represents the
bell, which is supported upon the post p' as shown.
9 represents an arbor, which is journalled in the plate b and in an arm p³ pro-
jecting from the post p¹. The arborg is revolved by a ratchet k and pawll, the
Intter being pivoted to the lever m, which in turn is pivoted to the plate b' at r.
The pawl is made to press in towards the ratchet by a spring o. A pin limits
the throw of the pawl and prevents it from slipping from the ratchet, while a
spring pattached to the lever m throws the lever m back to its original position
after each forward movement of the pawl. The arbor g above the ratchet carries
a lock bar c', having ends shaped as shewn, to be caught on a detent t on the end
of an elbow-lever v, thus locking the arbor at each half revolution. The elbow
lever vis pivoted to the plate b³ at r³. A spring g attached to one arm of the
elbow-lever and pressing against a pin h¹ tends to hold the other arm back
against a pine, and when the elbow-lever is thus held the detent t is in the
position to catch the lock-bar c', as before described.
The pin also limits the backward movement of the lever m. The lever m has
a projection m² and the elbow-lever v has an arm or projection v1, and the strip d
before mentioned strikes against one or the other of these projections whenever the
soft iron armature is swung towards its magnet, accordingly as the polarized
armature is attracted towards the pin n' or the pin 8'.
When the strip strikes the projection m' it feeds the ratchet forward and turns
the arbor, when it strikes the projection v² it releases the lock-bar from the detent t
and the arbor is free to be moved forward. Thus the operator at the other end of
the line, by sending the current in the direction to cause the soft iron armature s'
to attract the polarized armature, and then making and breaking the circuit, can
unlock the arbor, and by sending the current in the other direction and making
and breaking the circuit can revolve the arbor.
p is a disc placed upon the arbor as shewn; upon opposite sides of its periphory
it has two notches i, i, and underneath it has a collar in which are a number of
holes equal to the number of teeth in the ratchet. Any two holes which are
opposite each other may be made to receive two pins, one near either end of the
lock bar c', and by this connection the disc is made to revolve with the arbor. A
check nut holds the disc in place as shown. The ratchet, lock-bar, and disc are so
placed upon the arbor and adjusted relatively to each other that once in each revo-
fution of the arbor each notch i will come opposite the place occupied by the strip
when the latter is under the influence of the armature s'. The office of the disc p
is to prevent the ringing of the bell excepting when the disc is in this last named
position, its periphery preventing the bell-hammer from reaching the bell excepting
when the strip d can enter one of the notches &
The operation of the signal mechanism above described at the receiving end of
the line, is as follows:-Let the arbor at first be locked by the detent t and lock-bar
c', and the disc p so set upon the arbor as to bring one of the notches i opposite

page_text: the strip d at the instant the polarized armature is attracted toward the armature s'
the bell may now be rung at pleasure by making and breaking the circuit at the
key end of the line.
If now the current is reversed the polarized armature is attracted to the soft
iron armature n¹ and the strip d takes à position opposite the projection m³, when,
by making and breaking the circuit, the bell cannot be rung, but the ratchet is fed
forward by one notch at each pulsation of the circuit. There are twenty teeth on
the ratchet, ten on either side between the two ends of the lock bar c', and since the
two notchea i, i, on the disc are opposite each other, it follows that when ten
pulsations have been made in the reverse current the second notch i, will be at the
starting point opposite the original position of the strip d, and the bell may again
be rung, by shifting the current and making and breaking the current. Thus far the
disc p has been supposed to be so placed on the arbor that the notch i, the projection v³,
and the strip d' are all in line, but since there are twenty holes in the collar of the
disc, which, like the teeth of the ratchet are equally spaced, it follows that the disc
may be set upon the arbor in nine different positions back of the end of the lock bar
which catches upon the detent t when the ratchet revolves. And it is evident that
when the disc is so set back of the locking end of the lock bar the bell cannot be
rung by the beat of the strip d which unlocks the ratchet.
But after unlocking the ratchet it will be necessary to reverse the current, thus
sending the strip d³ to the position opposite the projection m³, and then by making
and breaking the circuit necessary to feed the ratchet forward the requisite number
of steps to bring the notch i in line with the original position of the strip d³, when
by reversing the circuit and sending the strip d² to that original position the bell
may be rung by making and breaking the circuit.
Accordingly the operator at the key end of the line knowing the position of the
slots in the disc relatively to the lock-bar, will, after unlocking the ratchet reverse
the current and give the requisite number of pulsations to carry the disc a sufficient
number of steps to bring the notch i, which is in advance, to the proper position,
when by shifting the current he may ring the bell as before. It follows that if two
notches are used in the disc, as shewn, there may be as many instruments in the
circuit as there are notches in half the ratchet, and that each instrument may have
its discs so set as to require its own and a separate number of pulsations before its
bell can be rung.
With slight modification of the lock-bar a disc with a single notch may be used
and the number of instruments on the circuit doubled.
Where several instruments are used on one circuit they must all be adjusted to
unlock their ratchets simultaneously; this gives an initial point from which the
operator at the key station may count the pulsations to know the conditions of the
different instruments on the circuit, and in practice it will be found convenient to
bring all the instruments on the circuit to an initial point after the bell of one has
been rung. The ratchets unlocking simultaneously it follows that they are fed forward
simultaneously, that is, when the strip a strikes the projection m³ in one instru-
ment it strikes it in every instrument, and in like manner when the strip d³strikes
the projection ¹ in one instrument it strikes that projection in all the instruments.
But although the notch i in the disc p and the projection v' are in line when the
bell is rung they have no immediate connection with each other. The bell may be
rung in one instrument when the lock bars of the several instruments are not in a
position to be caught by the detent t. When this happens the elbow-levers will
vibrate to no purpose.
I claim,―
First. In a district telephone system a series of switches, each of which normally
short circuits the telephonic apparatus and is adapted to establish an earth con-
nection at each station on either side, according to the direction of the communica-
tion without breaking the continuity of the line, substantially as and for the purpose
specified.
Second. A switch placed as any station in a series forming a support or receptacle

page_text: for a telephone, and acting when the the telephone is in place to form a circuit
through the station, and when the telephone is removed acting to establish a circuit
from earth through the telephone without breaking the continuity of the line in
either direction as may be desired, and also acting when the telephone is replaced
to automatically reestablish the circuit through the station, substantially as and for
the purpose specified.
Third. The combination, substantially as and for the purpose set forth, with a
telephonic apparatus of the plates K, KI, spring lever L, hook M, and the electrical
connections as described.
Fourth. An individual signalling bell provided with devices for preventing the
hammer from striking the bell except when a definite number of electric impulsos
in a certain direction are transmitted through it, substantially as and for the purpose
specified.
Fifth. In a district telephone system an individual signal bell at each station
capable of responding to its own signal only, in combination with a magneto induc-
tion apparatus at said station and a signal apparatus at the central office actuated
by said magneto induction apparatus.
Sixth. The combination, substantially as and for the purpose set forth, of the
individual signalling apparatus, the magneto induction apparatus, the telephonic
apparatus, the automatic switch, and the electrical connections, as described.
Seventh. The mechanism herein described for controlling the action of the bell
hammer, consisting of the electro-magnet c with its soft iron and polarized armature
and the notched disc p with the mechanism to revolve and lock and unlock said
disc, substantially as described.
Eighth. The bell and hammer provided with the rotating alotted disc, substantially
as described, for arresting the blow of the hammer when desired.
Ninth. A series of signal bells combined in an electric circuit, each bell being
provided with the herein described mechanism for arresting the blow of the bell
hammer, except at a predetermined point, all substantially as described for the
purpose specified.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand and
seal, this First day of January, in the year of our Lord One thousand
eight hundred and eighty.