IMPROVEMENTS IN APPARATUS FOR USE UPON TELEPHONE LINES
Year: 1881

page_text: LETTERS PATENT to George Pitt, of Sutton, in the County of Surrey, for an
Invention of "IMPROVEMENTS IN APPARATUS FOR USE UPON TELEPHONE
LINES." A communication from abroad by Charles E. Buell, of New Haven,
in the County of New Haven and State of Connecticut, United States of
Americe
COMPLETE SPECIFICATION filed by the said George Pitt at the Office of the
Commissioners of Patents on the 11th October 1881.
GEORGE PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN
APPARATUS FOR USE UPON TELEPHONE LINES." A communication from abroad
by Charles E. Buell, of New Haven, in the County of New Haven, and State
of Connecticut, United States of America.
The Invention relates,-
First. To means for signalling to one of several stations upon the same telephone
line without producing a signal at the others. The apparatus that I use for this
purpose I denominate an "individual signalling apparatus."
The second part of the Invention relates to an arrangement of the lines
connecting several stations with one another, or with the apparatus at the central
station of a telephone exchange system, the object being to increase the facilities
for telephone communication in locations where the telephones are in frequent use.
The third part of the Invention relates to the apparatus used at the central
station, and constitutes an improvement upon that class of central station switches
in which the operations of connecting and disconnecting the various lines are
automatically performed from the outlying stations, without the assistance of
attendants at the central station.
The object of this part of the Invention is to provide means, whereby in the
event of derangement or damage of the automatic switch, the operations of
connecting and disconnecting the various lines for oral communication may be
carried on without interruption, and whereby also oral communication may be
had at any time between the central office attendants and parties at the outlying
stations.

page_text: The fourth part of the Invention relates to an improved method of charging
the telephone lines during oral communication, for the purpose of increasing the
volume and distinctness of the sounds, and for the further purpose of enabling
speech to be transmitted to greater distances, and to also, if desirable, make it
possible to dispense with the use of induction coils.
Figure 1 shews an end view of an electro magnet and a local circuit, arranged as
hereinafter described for use in the individual signalling apparatus.
Figure 2 is a side view of another form of differential electro magnet for the
same purpose with a bell and vibrating bell hammer carried by the armature.
Figure 3 is a diagram of the circuits and apparatus upon a line provided with
three stations, whose bells may be rung independently of one another by currents
of the same polarity, but of different strength, showing also the apparatus at a
central station for changing the polarity as well as the tension when oppositely
polarized bell ringing devices are used at the various stations.
Figure 4 is a diagram of the circuits and apparatus upon a line with six stations,
whose bells are rung independently of one another, half by currents of one, and
half by currents of the opposite polarity, as indicated by the signs X, and,
Figures 5 and 6 show diagrams of line circuits and apparatus at a telephone
station designed to afford extra facilities for oral communication and signalling to
a subscriber of a telephone exchange during busy seasons.
Figure 7 shows in diagram a view of central office switch apparatus that may be
used when each subscriber is connected with the central office, and with other
subscribers by several lines, as indicated in Figures 5 and 6.
Figure 8 is a view of a telephone switch for suspending the telephone, and
automatically connecting and disconnecting the transmitter battery.
Figures 9 and 10 shew automatic and manually operated telephone central office
switches, combined in accordance with the third part of the Invention, in the
manner and for the purposes to be hereinafter described.
Figures 11 and 12 illustrate two ways of arranging batteries upon a telephone
line during oral communication, so as to give increased volume and distinctness to
the sounds.
Figure 13 illustrates diagramatically an arrangement of apparatus at a central
office switch, and at outlying stations upon the various lines that may be employed
when opposed or neutralizing batteries are made use of in the manner indicated in
Figures 11 and 12.
Figure 14 shews a modified arrangement of the batteries at a central station.
Figure 15 shews another modification in which the opposing batteries are placed
at the outlying stations, and the battery transmitter acts to short circuit the
battery to a greater or less extent at each vibration of the diaphragm.
Figure 16 shows two distant central stations connected by a trunk line with an
arrangement of opposing batteries, and means for placing then in the circuit
between the two stations.
In carrying out the first part of the Invention I employ at each station a
differential electro magnet of any of the well known forms, one of whose coils is in
a local and the other in the main line circuit, each station being also provided with a
local battery and suitable devices, whereby the amount of current circulating
through the local coils at the various stations may be adjusted to a different and
definite amount for each station.
The armature of the electro magnet is of the well known form, and may be used
to perform any of the well known offices of such a device when used for signalling
purposes.
These devices and the manner in which I employ them, as also the apparatus
used for transmitting the signals, are shown in Figures 1, 2, 3, and 4.
In the Drawings, Figure 1 is an end view of an electro magnet and local circuit,
arranged as hereinafter described; Figure 2 is a side view of a differential electro
magnet with a bell and vibrating bell hammer carried by the armature.
Figure 1 is an end view of an ordinary horse shoe electro magnet, one of whose

page_text: arms A has a coil in a main line circuit. The other arm B is provided with &
similar coil in a local circuit with a battery, but so wound, or with the poles of the
battery so placed, that the current flowing through it will exert an opposite
magnetizing effect upon the magnet from that exerted by helix.
If now equal currents circulate through both coils their magnetizing effects will
be neutralized, and the armature of the magnet will be retracted.
If however the current strength in helix A be greater or less than in helix B,
the armature will be retained in the one case by the preponderating effect of A,
and in the other by the preponderating effect of B.
If two such mgnets be arranged in the same circuit, the local coil of one
exercising a magnezizing of, say 2, and the local coil of the other an effect of 3,
then the armature of the first will cease to be attracted when a current of sufficient
strength to exercise a magnetizing effect of 2 is thrown upon the line, while the
armature of the other will continue to be attracted, because of the preponderating
effect of its local coil; conversely a line current of a strength 3 will allow the
armature of the second to fall back, while the armature of the first will be held up,
because of the preponderating effect in this instance of the line coil.
The armatures of both may obviously be held normally in contact with their
front stops by allowing a current of a strength, either of 1 or of 4, to circulate in
the line coils. This principle of action may theoretically be extended indefinitely.
Six electro magnets arranged on the same circuit would have their locals
graduated to produce a definite magnetizing effect upon each relay, the amount
being different for each. The armatures would be normally held against their
front contacts by means of a line current producing an effect smaller or greater than
any of the local coils. By placing to a line a battery current of such strength that
its effects will be equal or approximately equal so the local effect in any given
relay, the armature of that relay would fall upon its back stop, while the armatures
of all the other relays would be retained, because in some the main line coils would
have a greater, and in others a less power than the locals, and in none of them
would there be a balance of the magnetic forces so as to allow the retracting
springs of the armature to act.
In Figure 2 is shewn an arrangement of circuits, whereby the counter balancing
local battery may be used for producing a vibrating signal; A, B, is the electro
magnet having differential coils; L, B, is a local battery, whose circuit is through
the local coil.
R is an artificial resistance for adjusting the current strength in the local coil to
a definite and determinate amount; a is a bell, and b a bell hammer attached to
an armature pivoted at c, and provided with the ordinary retracting spring.
Shunt wires from the local battery pass to the back stop of the armature, and to
the armature at c.
The local coil is so wound or the poles of the battery so placed in the circuit
that it will tend to neutralize the effects of the main line coil upon the core of the
electro magnet. When the main line current is at its normal, or when it is varied
to the degree necessary to call other stations, the armature is held away from its
back stop by the overbalancing effect of either the main or the local current.
When the main line current is of such a strength that it balances the local, the
core ceases to exert an attractive effect and the armature is drawn against its
back stop, thereby shunting the battery from the local coil, where upon the main
line current acts without opposition, the armature is drawn up, breaking the shunt,
and the operation is repeated, thus producing a vibrating movement of the bell
hammer.
In Figure 3 I have shewn three independent electro magnets and batteries,
keys, and resistances for varying the main line currents, so that the armature of
either one may be operated without affecting the others.
A, B, are horse shoe electro magnets whose coils A are in a single circuit, as
shown. The coils B are in local circuits with batteries and resistances arranged as
in Figure 2. The local resistances are so adjusted that the local and counter-

page_text: balancing current at station 2 will be greater than at 1, and at 3 greater than at 2;
C and D are two main line batteries with opposite poles to line, and d is a switch
for throwing either battery into circuit with coils A. This should by preference
be a continuity preserving switch.
If the local coils at the stations are all arranged to produce magnetism of the
same sign but one of these main line batteries is used; E is a switch or key for
connecting the main line to battery or to earth. When the apparatus is used with
a telephone exchange switch, the switch E and the ground connection may be
dispensed with. The connecting wire, No. 6, would in this case be carried to the
telephone switch to which the various telephone lines run, and by which they are
connected, and switches of ordinary construction and design, such, for instance, as
those shown at Figure 13, would be employed for disconnecting any line from the
switch board and connecting it to the wire leading to the signalling apparatus ;
F, G, and H are keys or switches, and R¹, R³, and R³ are adjustable resistances so
arranged that either one can be thrown into the circuit with the battery, and each
adjusted to interpose a definite resistance, differing for each switch F, G, H. With
battery D the counter-balancing local currents do not prevent coils A from exerting
sufficient magnetic effect to hold all the armature drawn forward. If however
battery D be closed through R', H, which in the present case is adjusted to a higher
resistance than R' or R³, the current will be so weakened that the local at station 1
will sufficiently counter balance it to allow the armature to be retracted. The
local currents at 2 and at 3 will however be sufficient to over-balance the main
line current and to hold the armatures up. If the battery be closed through G, R³,
which interposes less resistance than R, the line current will at station 1 over-
balance the local sufficiently to hold the armature up. At 2 it will balance the
local so that the armature will be retracted and the bell sounded, while at station 3
it will not sufficiently oppose the effects of the local to prevent it from still holding
its armature against the front stop.
Relay at station 3 may be operated by closing the main line battery through F, R³,
which interposes still less resistance than R2 or R', and the current strength is then
sufficient to counterbalance the local of station 3, and allow the armature to be
retracted, while at station 2 and station 1 the armatures will be held up by the
overbalancing effects of line current in coils A.
The number of stations capable of being signalled by variations of current within
the same degree may be doubled by simply arranging a second set of electro
magnets whose local coils are arranged to produce magnetism of the opposite sign
from those of the first set. An arrangement of this kind is shown in Figure 4.
In such a case it becomes necessary to use a second line battery of opposite
polarity, or a pole changing key with the single battery. With this arrangement
the armatures of the second set will be held against their front stops by the same
battery which is used in signaling to the first set, the locals in all of the second
set tending to reinforce the effects of the line battery. In sending signals to the
second set, however, the polarity of the line battery is changed, and the operation
of signaling is then the same as before described. During such operations the
armatures of the first set are all held against their front contacts, because in all
of them the line battery and the locals reinforce one another. Instead of closing
shunts to the local opposing batteries, the armature of the electro magnets may
close locals arranged to operate an ordinary vibrating bell in the well known
manner. Instead of resistances adjusted to different degrees in the local circuits of
the differential magnets.
I may use batteries of different strength, or the local coils may be of a different
number of convolutions or of different sized wire. So also I may vary the current
in the main line by varying the strength of battery. Any form of differential
magnet may be used in which the coils are so arranged as to tend to produce
magnetism of opposite name in the same core or cores.
This portion of the Invention is applicable to other purposes besides signalling
upon telegraph lines, and may be used whenever it is desirable to control or move

page_text: mechanism of any nature at different points upon the same circuit independently
of one another.
Heretofore the stations remote from the central station have had but one wire
for oral communication with the central station or other outlying stations of the
system, and by such limited facilities it often occurs that the subscriber is debarred
from the use of the system, when it is highly important that he should be able to
employ the system for communication either because the wire which includes one
or both of the stations is broken, or open by neglect, or is in use by others.
The object of the second part of the Invention is to increase the facilities for
communicating between the various stations of a system. This object I accomplish
by affording subscribers two or more wires and means adapted to place the
telephonic apparatus at each station in communication with the central station
through either of said wires, and through the central station with other like
subscribers' stations by either of the several wires thus afforded.
The arrangements whereby I accomplish this object are shown in Figures 5, 6,
and 7.
In Figure 6, the several lines passing through the station are designated 1, 2,
and 3; K, K, K, are call bells; and I, I, I, are ordinary circuit breaking keys, one
in each of the lines L, L, L, are switches adapted to break the lines to either side
of the station and connect in the telephone, which is done by operating one of the
switch levers shown, so as to connect it with the dotted line common to L, L, L,
and which passes through the wires 4, 4, and the secondary of the transmitter
induction coil to the receiving telephone T, and to earth at 5; M is the case of a
battery transmitter; L, B2, a local battery, and 6, 6, the wires connecting the
battery to the primary of the induction coil and the contacts in the transmitter.
telephone hook e is also shown, the operation of which will be hereinafter described.
Lightening arresters f. f. f, one for each line, are connected by a wire 8 to the
earth.
A
The operation of these devices can be readily seen from the Drawings. Let it
be supposed that wire 1 has been designated for ordinary use, and that a subscriber
at a station, upon depressing button I of that line fails to get a response. This
may happen either because a subscriber at a station between the station calling
and the central office is using the line, or because the outside line is broken or
crossed, or because of the neglect of some subscriber to replace the switch at his
station after using the line; or from other causes, under these circumstances it is
only necessary for the subscriber to depress the proper button of anotl er line 2 or 3,
and by turning the proper switch L; to place his telephone in communication with
the central office through that line, and afterwards, if communication is desired
with some subscriber on the same line with him, but further away from the central
office, to make the proper connection by a suitable manipulation of the switches L
Should he find that line 2 is not in condition for use, which may sometimes happen
n busy seasons, he can finally resort to line 3, and by a proper operation of the
witches can secure the desired communication.
In Figure 5 I have shewn spring jacks g, one in each line, and a switch plug h
o which are connected the terminals from the receiving telephone, and the
econdary of the induction coil as shown. By these means the telephone can be
nterposed in any line without breaking its continuity. In other respects the
pparatus is the same as in 6.
In Figure 8 I have shown a telephone hook e suspended from a spring i, which
when released from the weight of the telephone will make contact with a stud k
onnected by wire 9 to one pole of the local transmitter battery. The spring i is
onnected with one terminal of the primary of the induction coil, the other
erminal of which connects with the contact points of the transmitter, and so to
he other pole of the battery. It will be seen that when the telephone is taken
om its support for the purpose of oral communication, the circuit of the local
attery is automatically established, and when the telephone is restored to its
osition the circuit is broken.

page_text: This arrangement simplifies considerably the connections in the subscriber's
station apparatus, other forms of switch may be obviously substituted for that
shown without departing from the Invention. It is only necessary that the
switch when relieved from the presence of the telephone shall automatically
complete the local circuit, and that the restoration of the telephone to its place 5
shall automatically break the circuit by restoring the parts to their original
position. There are many well known and obvious ways of accomplishing this
result, other forms of switch besides those shown in Figures 5 and 6 may of course
be used for connecting the station telephone apparatus to either of the wires.
Any ordinary form of call bell may be used.
In Figure 7 is shewn the apparatus at a central station adapted to signalling
separately upon each of the wires 1, 2, 3, or 4, 5, 6, to the same station, or
connecting a station through which pass wires 1, 2, 3, in the manner shown in
Figures 5 and 6, with a like station included in like manner in several wires 4, 5, 6,
or vice versa.
Lines 1, 2, and 3, are supposed to pass through the same subscriber's stations,
and 4, 5, 6, are similarly connected to another set of stations.
N, N, N, are pivotted switch levers, each pivoted at the centre of a circular
range of studs, and adapted to connect with either of the studs. The studs are
numbered consecutively to correspond with the number of connected wires and as
shewn by dotted lines, the corresponding studs of the several ranges are connected.
The lines 1, 2, 3, &c., are connected with the studs 1, 2, as shewn, and with the
pivots of the switch levers P, P, P. The circuit for each line in the normal
condition of the switch is through a lever P, and to the relays, O, O, and to a
battery M, B, and to the earth.
The back contacts of the relays connect as shewn with the annunciator R, and
one pole of a battery L, B³, whose other pole is connected to the armature levers.
Disconnecting switches M, M, are interposed in the connections from the back
contacts to the annunciator; S is a switch bar common to the levers P, P, either of
which may be swung so as to connect with said bar and through the same with a
magneto telephone T the secondary of an induction coil J and the earth. The
induction coil J2, local battery L, B³, connected to the primary and the circuit
breaking reed P, in the circuit of the local battery, constitute a call apparatus
operating after the manner shown in Patent of the United States granted to
T. A. Watson, No. 199,007, dated January 8th, 1878.
Other well known forms of call apparatus may be substituted. The pivots of
switches N, in lines 3 and 6, are connected to telephone T as shown.
The pivots of switches N in lines 2 and 5, and in 1 and 4, may be similarly
connected to telephones.
1
The operation of these devices is as follows:-A button on, say, line 1, having
been operated to break the circuit, the relay O of that line is demagnetized, and its
armature lever falls back, closing a local circuit of battery L, B³, thereby indicating
upon annunciator K a "call." The central office operator thereupon turns the
switch lever P into contact with S, thereby breaking the connection of the line
with the relay, and substituting the connection through the telephone Ts through
which he ascertains from subscriber on line 1 with whom communication is desired.
If with a subscriber upon another line, as 4, the appropriate switch lever P is con-
nected to S, lever P of line 1 having been first turned to an intermediate position,
as shown in dotted lines 1, thereby connecting the call apparatus J2, &c., to line 4,
the subscriber upon line 4 having been "called" by the predetermined signal,
switch lever N of line 1 is placed on button 1 and N of line, also upon its button 4,
thereby connecting lines 1 and 4 through telephone T. Telephone T is for the
purpose of enabling the central office operator to ascertain when the subscribers
have finished their communication. Should line 4 be in use and communication
be desired with some other subscriber on that line he may be called, and com-
munication established by line 5 or line 6 through either pair of switch levers N,
line 2, N line 5, or N line 3; N line 6, line 1, may be connected to line 5 through

page_text: levers N line 1 and N line 4 by turning lever N line 1 to the button numbered 5
upon its dial, which as before described forms one of a series of buttons in the
several dials, which buttons are connected together and to the line 5 as shown.
The circuit is then through line 1 to button 1 of the dial, to which N line 1 is
connected to switch lever N line 1 through telephone T° to switch lever N line 4,
to button 5 of its dial, thence through the series of buttons numbered 5 and their
connecting wires to the line 5. Lines 1 and 6 may be connected by placing
lever N line 1 upon button 1 and lever N line 4 upon button numbered 6 in its
dial, the circuit being to lever K line 4 as before, and thence to button 6 to the
connecting wire of the series of buttons 6 and to line wire 6. Lines 1 and 6
might be connected by placing N line 1 on buttons numbered 6, and N line 4 on
button numbered 1. Similarly any other two lines may be connected through the
telephone Tº.
Levers M, M, serve to disconnect the annunciator magnets, and are used when a
station is to be called, in which operation the circuit of the main line through its
relay is broken by turning one of the levers.
The latter operation would of course allow a corresponding relay armature to
drop back and close the local circuit, thereby ringing the annunciator bell, and to
prevent this the disconnecting levers M, M, are provided. The switch shown is
obviously of comparatively limited capacity. It is however only necessary to
multiply the parts in a well known manner, in order to extend its capabilities to
any desired degree.
Other forms of switches and connecting apparatus would be suitable for the
purpose, and other well known kinds of signalling devices may be substituted for
that described.
The third part of the Invention constitutes an improvement upon that class of
telephone exchange apparatus in which the connection and disconnection of the
subscribers' lines with one another is effected from the subscribers' stations, and
without the assistance of central office attendants.
This part of the Invention is applicable not only to automatic exchange apparatus
of the kind in which the connecting and disconnecting devices are controlled by
step by step mechanism, as in British Patent, No. 5114, of 1879, but also to any
other forms, as for instance those in which the operations are effected by varying
the tension of closed circuits, or by clockwork or other devices. I have shewn in
the accompanying Drawings one particular form of automatic switch for the
purpose of illustration only, and any other devices of an automatic character worked
by the subscribers themselves may take its place.
As hitherto constructed, automatic switch apparatus has been defective in that it
has been impossible for direct communication to be held telephonically or other-
wise between the central office and subscribers, over the wires used in operating
the switch, and in communicating between subscribers, while further, in case of
accident to the switch or derangement thereof, the business of the exchange would
for the time being come to a stand still.
The object of the Invention is to remedy these defects, and to provide means
whereby without disturbing the automatic switch, oral communication may be held
between the central office and any subscriber, and vice versa, while further in case
of derangement of any portion of or all of the automatic switch devices, communi-
cation may still be had between subscribers.
To this end the Invention consists in interposing between the automatic switch
and the subscribers' lines a manually operated telephone exchange switch of any
ordinary construction, the various subscribers' circuits passing through said switch
to the automatic switch, means being also provided for connecting the various lines
to ground before passing to the automatic switch, and for disconnecting or breaking
the connection to ground through the latter.
I have shewn in the Drawings, Figures 9 and 10, two forms of manually operated
switch and two ways of carrying out the Invention. Other switch boards and
other means or devices for making the various electrical connections contemplated

page_text: by me may however be substituted for those shown without departing from the
spirit of the Invention.
Referring to Figure 9 of the Drawings, Bº represents a section of an automatic
switch constructed after the manner set forth in British Letters Patent, No. 5114,
of 1879, before referred to, wire 1 of the subscribers' wires being shown as con-
nected thereto.
The various subscribers' circuits are numbered from 1 to 6 consecutively, and
each passes to the automatic switch and its earth connections through a manually
operated telephone switch board C interposed between the automatic switch and
the various lines.
Entering the central office each circuit is through an annunciator and call bell H
of any preferred construction to a key or switch K adapted to disconnect the line
from the switch board, and connect it to a calling battery or generator M, B°, to a
spring jack t of any approved construction, to be used in connection with divided
insulated metallic tips P connected to telephone communicating apparatus M³, to a
vertical strip w of the switch board, to a switch X, and to the controlling devices of
the automatic switch and to earth. Line 1 is shown connected to a subscriber's
station at D, at which point the apparatus is of substantially the construction
indicated in the Patent referred to above, 10 representing the switch adapted to
connect the line either to a rheotome 11 and pole changer 12, for battery L, Bº, to
a call bell 13 or to a telephone 14, said switch also closes the circuit of
battery L, Bº, through the electrodes, and the primary of the induction coil in
transmitter T, Mº, at the same time that it connects the line to the telephone
receiver.
The switches X in switch apparatus Care each adapted to break the circuit of
a subscriber's line with the automatic switch apparatus and its ground, and connect
the line to earth through a wire 15.
The normal operation of the system when the various subscribers' circuits pass
to the switch apparatus B' is the same as described in the Patent above referred
to and need not be rehearsed.
Should however oral communication be desired between the central office and a
subscriber's station, or vice versa, the switch board apparatus may be instantly
brought into use, the predetermined signal necessary in order to make such a
desire on the subscriber's part known being given on the bell HP by the opening
and closing of the battery L, B, by means of switch 10 or other device, while,
vice versa, the central office attendant depresses key K°, thus placing battery or
generator M, B³, to line and simultaneously disconnecting the line from the auto-
matic and the manual switch devices, so as to prevent the battery from affecting
the electro magnetic devices of switch B⁹.
Telephone apparatus M may be inserted into the line by means of the spring
jackstand tips P. The necessity for such communication may arise from a failure
of the automatic switch device to operate properly so as to place a subscriber in
communication with the party desired, in which case he can communicate to the
central office the fact that he fails to get a response, and the attendant thereupon
makes the desired connection in the switch board C³, before closing which he
disconnects the switches X of the lines to be connected from the points to which
are connected the wires leading to the automatic switch.
Should the automatic switch become so far deranged as to require repair and
make its further use for the time being impossible, it and its earth connections
may be entirely disconnected from subscribers' wires by means of the switches ✗
and the ground connection 15 substituted. The lines may then be connected and
the business of the exchange continued without interruption by means of the
switch C alone, its operation in this duty being well understood. Other con-
tingencies may arise under which it may be brought either wholly or partially
into use, in conjunction with or wholly independent of switch B°; but I do not
deem it necessary to specify them all.
In Figure 10 of Drawings I have shewn a somewhat different form of manual

page_text: switch board, although the general operation of the apparatus is substantially
the same as that of Figure 9.
Instead of the switches X normally interposed in the circuit, and adapted to be
turned so as to substitute a ground connection.
I employ an upper row of switches y, whose pivots are connected to ground
wire 16 and a series of connecting plugs z, one in each circuit.
Switches y may be turned so as to connect with line strips r, thus connecting
the lines to ground while the connection of the various circuits with the automatic
switch B10 is controlled by the plug switches z.
Instead of connecting strips 18, as shewn in Figure 9, switch levers 17 are used
for_connecting the lines. The operation of these devices is well understood.
In Figure 10 line 1 is shown connected to the subscriber's station D10 and to
the automatic switch B10. Another form of pole changer 19 is here shown.
The effect of turning its arms 20, 21, so as to occupy the position shown in full
and dotted lines, and connect with the segments 22 can be readily followed by
tracing the circuits. The switch 23 connects the line to rheotome R¹º bell and
telephone in the manner indicated (also shown in Figure 9), but the circuit of the
battery through the transmitter is controlled by a gravity switch 24 in a well
known manner.
Other forms of manual central office switch may be substituted for those shown
by interposing them in the circuits in substantially the same manner.
The fourth part of the Invention relates to a mode of charging telephonic
circuits, and has for its object to give to the telephonic vibrations representing
articulate speech, an increased amplitude or variation of electrical force, and as a
consequence increased variations of current strength in the receiving instrument
and therefore louder articulation. As a further result of the Invention I am enabled
to dispense with the use of induction coils, and yet make the telephone available
as a means of communication over very long circuits.
The Invention consists in placing upon a circuit over which telephonic com-
munication is to be had, opposed or neutralizing batteries, and in carrying out the
Invention I have adopted various methods of arranging such opposed batteries,
which are set forth in detail herein after and are shown in the Drawings.
In Figure 11 I have shown two opposed batteries 24 and 25 placed at the
opposite ends of a line, and telephones T and T3, which may be of the ordinary
form known as "bell
«
or magneto telephones" that may be used either as
transmitters or receivers.
"
The batteries 24 and 25 as represented have the same pole to line, so that they
oppose one another's action, and if they are of the same strength they will
neutralize one another.
It is not to be understood that the batteries are necessarily of precisely the same
electro motive force. One may be of less strength than the other, but if it is
arranged with the same pole to line, so as to oppose the action of the battery at
the other end, good results may be obtained. The telephonic currents from either
of the telephones transmitted over a circuit "charged" as described with either
opposed batteries of the same or different strength, are received at the other end
in the ordinary manner, but are found to produce in the receiving instrument
articulate sounds of greater volume than if transmitted through a simple circuit
unprovided with the opposed batteries.
The telephones may obviously be battery or contact transmitters, in which case
the transmitter itself would be in local circuit with a battery, and the primary of
an induction coil, the secondary of which would be placed in the line circuit after
the well known manner.
The opposed batteries are found to add to the volume or amplitude of the
received communication on a circuit equipped in this manner as well. Another
arrangement of opposed batteries and communicating instruments is shown in
Figure 15 and will be described further on.
In Figure 12 the opposed batteries a* and * are at the same end of the line,

page_text: but their relation electrically to one another and the circuit of which they form a
part is, as will be observed, virtually the same as in Figure 11.
In Figure 13 I have shown a portion of a central office switch board, and one
of the subscriber's stations upon a line connected to the central office with an
arrangement of opposed batteries that may be used in operating a telephone
exchange.
The switch board B is of ordinary construction, consisting of a number of parallel,
vertical, and horizontal bars perforated, as shown, for the reception of connecting
plugs. Each of the vertical bars is connected to a subscriber's line through drop
annunciators A*, and is also provided at its lower end with plug sockets, as shown,
to make connection with a horizontal bar B extending beneath the vertical strips
and connected through opposed batteries c and d with a telephone T and the
earth.
The horizontal switch bars are arranged in pairs, each pair m³, n³, being con-
nected, as shown, to opposed batteries.
Each line in entering the annunciator passes through the back or upper contacts
of keys or buttons k*, whose lower or front stops are connected to a common
battery M, B³, and to earth; M, B³, is a signalling battery to be used in " calling
subscribers.
"
The subscriber's station apparatus is shown on line 2, and consists of the following
devices shown for the sake of perspicuity in their simplest form :-
T7 is a telephone, and M7 an ordinary contact transmitter, the primary of whose
induction coil is in circuit with the local battery L, B', and whose secondary is in
the earth connection 26, leading from one of the points of switch 27 through the
telephone T' to earth.
The branch 29 connected to the other point of switch 27 contains an ordinary
magneto electric call bell and generator B12 (whose button d¹ serves to throw the
generator into the circuit), and a carbon resistance c12. Each of the several lines
connected to the central office switch and telephone T is equipped with the same
apparatus.
The operation of the devices is briefly thus:-In all the subscriber's lines the
switch levers should be connected to branch 29, so that the bell in any subscribers
wire may be operated by manipulating the appropriate key to throw in the
signalling battery or generator at the central office.
Should any subscriber desire to call the central office he does so by putting his
line to earth through line 26, and communicating orally with the central office
operator, who is constantly listening at telephone T. The carbon resistances c
in the various lines prevent the diversion of the transmitted currents from the
central office receiving telephone, and these currents pass to earth through the
opposed batteries c', d*.
The listening telephone operator having learned the name or number of the
subscriber with whom communication is desired, directs that subscriber to be called,
which is done by simply operating the proper key k².
The operation of the key it will be observed, puts the signalling battery M, B³, to
line, but it also breaks the connection of that line with the annunciator and switch,
thereby preventing battery M, B from dropping the annunciator card.
The switch plugs at the bottom of the line strips having been withdrawn to
break the connection of the lines with the receiving telephone, the subscribers may
then be connected through either pair of bars m³, no, by simply inserting the same
or other plugs into the proper line strip, one over bar m³, and the other over
barn. The lines are thus connected through opposed batteries e at the same time.
To indicate that disconnection is to be made at the central office, either subscriber
connects his line to earth through branch 29, depresses button d, and operates the
generator, thereby causing the annunciator drops in the connected lines at the
central office to fall.
It is obvious that as many pairs of connecting bars m³, ns, and opposed batteries
may be used as circumstances may render necessary, and that other means besides

page_text: those shown might be employed for connecting subscribers' lines through opposed
batteries at a central office. It is plainly within the scope of the Invention to use
simple magneto telephones instead of battery telephones and induction coils at the
subscribers' stations, and it is also obvious that the opposed batteries may be used
only between connected lines and communication be held between subscribers and
the central office by means heretofore used.
In Figure 14 is shown a modified arrangement of opposed batteries at a central
station. Each line according to this plan passes through its appropriate line strip
of the switch D, through switch lever h, opposed batteries 1, and telephone 17
to earth. The batteries will prevent in large degree the diversion of the
telephonic vibrations received from any line from the telephone T7, and the use of
carbon resistances c¹ would not then be absolutely necessary.
The switch levers serve to disconnect the line strips of any two lines that are to
be joined from the opposed batteries and the listening or receiving telephone. I
5 contemplate the employment of the opposed battery in other telephone systems
besides that above described, and it may obviously be applied in conjunction with
any receiving or transmitting telephone.
In the methods herein before described of arranging the opposed batteries, they
have all been placed at the central station. A plan of arranging the opposing
batteries, one at the contral end the other at a subscriber's station, as also a method
of originating telephonic impulses or vibrations from the opposing battery by
means of a contact transmitter is shown in Figure 15.
In this Figure the central office switch board is shown at F, and each line is
represented as connected to earth through a section of battery, which has the
same pole to line as the battery r³ at a subscriber's station.
S³ represents a switch adapted to sever the continuity of the main line and
connect it to earth through a receiving telephone T¹, and a battery transmitter
M, B, is an ordinary electro magnetic call bell. The devices so far as described
are of well known construction, or are clearly shown in the Drawing. The battery
transmitter is constructed and its connections are arranged in the following
manner-
Two springs 30 and 31 are supported from a pivoted block 32 held in position
and capable of being adjusted by a set screw. Each spring at its lower end has a
conducting face, and between the two faces is supported a piece of carbon 33 or
other resistance contact hung from the block 32 by means of a spring or flexible
support 34 insulated, as shown from the block. The springs rest against the
diaphragm d, so that the vibrations of the same will act to vary the degree or
intimacy of contact between the carbon electrode and its embracing springs, and so
vary the resistance to the passage of the current in a manner well understood.
The battery is connected by a wire 35 to block 32 or to one of the attached
springs, and from the block a connection is carried to the switch S5 and line. The
other pole of the battery is connected by a wire 36 to the carbon, and also has a
ground connection. It will thus be seen that when the switch S3 is connected to
the line two paths are open to the current from 75, one through the line to earth
and back to the other pole of the battery; the other through 31 and 32, carbon 33,
and wire 36, the latter being a shunt or derived circuit to the former, the amount
of resistance in which is varied at the points of contact between 33 and 31 and 32.
As the resistance to the passage of the current increases and diminishes in
accordance with the movements, of the diaphragm the strength of current flowing
to line will fall and rise in accordance with well known laws, and the result is a
series of pulsations or vibrations corresponding to said movements. The batteries
and as will be observed have the same pole to line, and hence oppose one
another. All the batteries at the various subscribers' stations in the various lines
have the same poles to line, and hence, when any two stations, either upon the
same or different lines, are connected, their batteries are opposed.
Other forms of transmitter besides that described may be used for varying the

page_text: strength of the current flowing to line from the opposing or neutralizing battery
at the subscriber's station.
The battery
may be of such a size with relation to the opposed battery at
the central station that its current will be normally the same in strength, or greater
or less than that of r
In Figure 16 are shown two central offices A and B connected by a trunk
line 38 provided with opposed or neutralizing batteries 712, 713, and communicating
telephones T¹s
The central office switches may be of any desirable construction, the form shown
consisting of vertical and parallel "line strips" and horizontal parallel connecting
strips.
Referring to station A7 each line passes to ground through a switch lever S¹ and
a common receiving telephone T provided with opposed batteries. In conjunction
with switch levers S12 are a number of metallic studs, one for each line, connected
by means of wire 40 to a stud 41, with which trunk line switch lever 42 may be
connected. The switches are normally in the position shown in the Drawing, and
the trunk line telephones T18 are connected to line by the switches 42 and 43.
Should it be desired to connect a subscriber of office A" with a subscriber of
office B', notice of that fact is given by means of telephones T¹³, and the levers 42
and 43 are turned to disconnect the trunk line from the telephones and connect it
to studs 41 and 44. The appropriate switch levers S1 and S13 on the respective
boards having been placed upon the proper studs the two lines are thereby
connected through the trunk line 38 and the opposed or neutralizing batteries
18, 13, the circuit being as follows:-Subscriber's line office A7, switch lever S¹³,
stud 45, wire 40, stud 41, lever 42, battery 218, line 38, battery 18, lever 43,
stud 44, wire 46, stud 47, lever S¹s and to subscriber's line of office B'. The above
arrangement of opposed batteries and trunk lines may be used with advantage in
connection with other central office systems, and I contemplate the application of
it to the systems now in use for connecting the subscribers of distant central
offices.
I claim as the Invention and desire to secure by Letters Patent,―
First. The method of sending independent signals over a single circuit consisting
in varying the strength of current in the circuit to different and determinate amounts,
and opposing the magnetic effects of such currents by different and corresponding
amounts at the points at which the signals are to be received.
Second. In a single circuit a series of differential electro magnets, one of the coils
on each of which is arranged to exert an effect different in degree from the
corresponding coils in the other electro magnets, substantially as described.
Third. A series of differential electro magnets having coils in the main and local
circuits, substantially as described, batteries and resistances in the local circuits,
whereby the opposing effects of said local coils may be adjusted, as described, in
combination with batteries and resistances in the main circuit for correspondingly
varying the current strength in said main circuit.
Fourth. A differential electro-magnet, one of whose coils is in circuit with a
local battery, in combination with an armature which on falling away from the
electromagnet shunts said local battery, substantially as and for the purpose
described.
Fifth. A series of electro-magnets whose oppositely wound coils are in main
and local circuits, substantially as described, local batteries for the local circuits,
armatures arranged to shunt the local batteries on their back contacts, and devices
in the main circuit for varying the current strength, whereby the armature of any
electro-magnet may be released so as to fall upon its back contact.
Sixth. The combination in a single circuit of a series of differential electro-
magnets controlled in part by the main circuit, and in part by generators and
local circuits adapted to produce in the various electro-magnets magnetic effects

page_text: opposite in kind, and means upon the main circuit for changing the polarity of the
current upon the main circuit at will, substantially as described.
Seventh. The combination with a main electric circuit of a differentially wound
electro-magnet controlled in part by the main circuit and in part by a local circuit,
substantially as described.
Eighth. A series of differential electro-magnets having coils in independent
circuits, as described, a portion of the neutralizing coils being arranged to produce
magnetism of one sign in the cores of the electro magnets, and a portion to produce
magnetism of the opposite sign, substantially as described.
Ninth. The combination with a main electric circuit of a series of telephone
stations, each of which includes an electro-magnet for signalling purposes, which is
adapted to respond to variations of the tension of current and to currents of one
direction, and not to those of an opposite direction, in combination with means at a
signal sending station for manipulating the currents charging the circuit to reverse
and vary said currents, as shown and set forth.
Tenth. Two or more wires passing from a central office to the same subscriber's
stations, each wire containing at the subscriber's stations signalling apparatus
whereby calls may be sent and received separately upon each circuit, combined
with one branch circuit which includes a telephone and switch devices, whereby
said branch circuit can be switched to form a part of either of said circuits, as and
for the purpose described.
Eleventh. In a telephone station apparatus the combination with several main
circuits, each passing from a central office to the same subscriber's stations, of
devices included in each such circuit at the subscriber's stations, and independent
switch devices for putting a fragment of either of said circuits to a common ground
branch including a telephone.
Twelfth. In a telephone station apparatus the combination with several main
circuits, each passing from a central office to the same subscriber's stations, of
switch devices located at the subscriber's stations and common to all of said circuits,
and means for signalling upon each of such circuits separately.
Thirteenth. In a telephone exchange system a series of main circuits at each
subscriber's station, signalling apparatus for each circuit, and one telephone
common to all the said circuits, with devices at a central station for signalling
upon each circuit separately, and connecting devices whereby either of the main
circuits can be connected with any other of the circuits or to an earth connection
for oral communication.
Fourteenth. The combination with a telephone transmitter and its local battery
of devices for closing and opening the circuit of the local battery by the removal
and replacement of the telephone, substantially as described and shown, with
independent devices for switching the telephone into and out of circuit.
Fifteenth. The combination with an automatic telephone exchange switch of a
manual exchange switch interposed between the several lines and the automatic
switch, substantially as described.
Sixteenth. The combination of an automatic telephone switch, a manual exchange
switch interposed in the subscriber's circuits between the lines and the automatic
switch, and devices adapted to break the connection of the lines with the
automatic switch, and to substitute an independent ground connection for the
manual switch.
Seventeenth. The combination, substantially as described, of an automatic tele-
phone switch and a manual exchange switch interposed between the automatic
switch and the several lines, and signalling keys adapted to make connection with
a generator, and to simultaneously break connection with the automatic switch
devices, substantially as described.
Eighteenth. The combination, substantially as described, of an automatic tele-
phone exchange switch, a manual exchange switch, and a disconnecting switch
interposed between the two and adapted to close an independent connection to
earth.

page_text: Nineteenth. A main electric circuit charged by opposed or neutralizing batteries,
substantially as described, in combination with devices included in the same circuit
and adapted to set up electrical waves or pulsations therein corresponding to the
sound waves or pulsations representing articulate speech, and receiving apparatus
adapted to reconvert said electrical waves or pulsations into articulate sounds, as
and for the purpose described.
Twentieth. At a central office telephone station opposed or neutralizing batteries
in a circuit to earth, in combination with switch devices for breaking the connection
of the same with the subscriber's lines, substantially as described.
Twenty first. At a central office telephone station opposed or neutralizing
batteries, in combination with switch devices for connecting the same between any
two subscriber's lines.
Twenty second. In a telephone exchange system the combination of two or more
subscriber's lines switch devices for connecting any two lines and opposed batteries
in circuit between them.
Twenty third. The combination with two telephone exchange systems of two or
more trunk lines connecting said exchanges, devices for connecting either of said
lines to either of the series of lines constituting said exchange systems for oral
communication, and opposed or neutralizing batteries adapted to be included in the
trunk lines when the exchanges are thus connected, substantially as and for the
purpose described.
Twenty fourth. In a telephone trunk line connecting two distant exchanges
opposed or neutralizing batteries in connection with telephones placed in earth
connections from said lines, and switch devices located between the telephones and
the opposed batteries and serving to break the ground connection and establish a
connection with the switch apparatus of a telephone exchange system, substantially
as described.
Twenty fifth. The combination in the same electric circuit of opposed or neutra-
lizing batteries and a battery or contact transmitter in a shunt or derived circuit
around one of said batteries, substantially as described.
Twenty sixth. The herein described method of transmitting electrical waves or
pulsations representing articulate sounds by varying the amount of current flowing
to lines from one of two opposed or neutralizing batteries, as and for the purpose
described.
Twenty seventh. In a telephone exchange embodying two or more subscriber's
wires connected to a central connecting switch board, the combination at each
subscriber's station of a battery or generator having the same pole to line at all the
stations with a contact transmitter acting to vary the amount of current flowing to
line from said battery, substantially as described.
In witness whereof, I, the said George Pitt, have hereunto set my hand and
seal, this Tenth day of October, in the year of our Lord One thousand eight
hundred and eighty one.