IMPROVED MEANS AND APPARATUS FOR EFFECTING ELECTRICAL CONNECTIONS FOR TELEPHONIC COMMUNICATION
Year: 1880

page_text: LETTERS PATENT to George Westinghouse, junior, of 28, Southampton
Buildings, in the County of Middlesex, for an Invention of "IMPROVED
MEANS AND APPARATUS FOR EFFECTING ELECTRICAL CONNECTIONS FOR
TELEPHONIC COMMUNICATION."
PROVISIONAL SPECIFICATION left by the said George Westinghouse, junior,
at the Office of the Commissioners of Patents on the 29th January 1880.
GEORGE WESTINGHOUSE, junior, of No. 28, Southampton Buildings, in the County
of Middlesex. 'IMPROVED MEANS AND APPARATUS FOR EFFECTING ELECTRICAL
CONNECTIONS FOR TELEPHONIC COMMUNICATION."
When a number of persons situated at distances apart from each other have to
communicate by telephone a central station or "exchange" is usually provided, from
which electrical wires radiate to the houses or offices of the subscribers or persons
who desire to communicate with each other. The official at the exchange, at the
desire of one of the subscribers, puts his wire in connection with that of the sub-
scriber with whom he wishes to communicate, and thus any one of the total number
of subscribers can be put in communication with any other. According to this
arrangement each subscriber has to be provided with a separate wire from the
exchange, and notwithstanding that there may be a number of subscribers situated
near to one another in a district lying in one direction from the exchange, there
must be as many wires led in that direction, and no two of these neighbouring
subscribers can communicate except through the exchange. My Invention relates
to means and apparatus whereby such electrical connections can be greatly simplified,
by making one wire serve for connecting the exchange with a whole group of
subscribers, each of whom can nevertheless communicate with a member of another
group independently of the others of his own group, and can also communicate with
another of his own group directly without transmitting his communications through
the exchange. For this purpose, instead of leading the wire from each subscriber
of a group all the way to the exchange, I lead it to a switch apparatus in the
neighbourhood of the group, and I connect this switch apparatus by a single wire
with the central station or exchange, and I so arrange the switch apparatus, as I
will presently explain, that when one of the group of subscribers is communi-
cating through the exchange with some member of another group, or when he is

page_text: communicating with a member of his own group, all other members of his group are
excluded. According to one form of apparatus which I employ each member of a
group, in opening communication with the exchange, causes an electric-curent to
excite an electro magnet in the switch apparatus of his group, and this magnet, by
attracting its armature, releases a detent by the movement of which the branch wire
of the operating member is brought into connection with the main wire leading to
the exchange, and at the same time a locking bar or shaft is moved which locks the
detents belonging to all the other branch wires of the switch, so that no other
member of the group is able to put his branch wire in connection with the main
wire while the connection already established subsists. On the member having
finished his communication through the exchange an electric current transmitted
thence excites another electro-magnet at the switch apparatus, releasing a catch,
whereupon a clockwork movement takes place which unlocks all the detents that
bad been locked, and restores the switch apparatus to the condition in which it was
before the operation.
According to another form of the apparatus I provide at the switch station a
barrel that can be moved step by step round by a succession of electrical impulses
from the exchange, in a manner similar to the type wheel of a printing telegraph.
On the surface of this barrel I arrange a number of contact pins, and I provide a
number of contact springs, one connected to each branch wire of the group. In the
normal position of the barrel all the branch wires are through the contact pins in
connection with the main wire to the exchange, so that any member of the group
can communicate therewith. He may desire to communicate either with a member
of another group or with a member of his own group, and expresses his desire to
the official at the exchange. In the former case the official causes such a succession
of electrical impulses to actuate the barrel as will turn it to a position where only
the applicant's branch wire is in connection with the main wire, all the others being
excluded. In the latter case he causes the barrel to turn to such a position that
the applicant's branch wire is in connection with the branch wire of the member of
his group with whom he desires to communicate, and with none of the others.
When the communication is ended the official causes the barrel to turn to its normal
position ready for the passage of a communication from any member of the group
to the exchange. It is in all cases of advantage to provide the apparatus with
repeating or indicating signals, either visible or audible, so that any member of a
group who tries to communicate when the main wire is engaged may receive a
signal indicating that he cannot open communication.
The two forms of apparatus above described being combined into one, having
according to the first arrangement contacts under the control of the respective
members of the group, and also having, according to the second arrangement,
contacts under the control of the official at the exchange, any member of a group
can be put in communication with any member of another group or with any other
member of his own group.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Westinghouse, junior, in the Great Seal Patent Office on the
27th July 1880.
GEORGE WESTINGHOUSE, junior, of No. 28, Southampton Buildings, in the County
of Middlesex. "IMPROVED MEANS AND APPARATUS FOR EFFECTING ELECTRICAL
CONNECTIONS FOR TELEPHONIC COMMUNICATION."
When a number of persons situated at distances apart from each other have to
communicate by telephone, a central station or "exchange" is usually provided,
from which electrical wires radiate to the houses or offices of the subscribers or
persons who desire to communicate with each other. The official at the exchange,
at the desire of one of the subscribers, puts his wire in connection with that of the
subscriber with whom he wishes to communicate, and thus any one of the total
number of subscribers can be put in communication with any other. According to
this arrangement each subscriber has to be provided with a separate wire from the
exchange, and notwithstanding that there may be a number of subscribers situated
near to one another in a district lying in one direction from the exchange, there
must be as many wires led in that direction, and no two of these neighbouring
subscribers can communicate except through the exchange. My Invention relates
to means and apparatus whereby such electrical connections can be greatly sim-
plified, by making one wire serve for connecting the exchange with a whole group
of subscribers, each of whom can nevertheless communicate with a member of
another group independently of the others of his own group, and can also com-
municate with another of his own group directly without transmitting his
communications through the exchange. For this purpose instead of leading the
wire from each subscriber of a group all the way to the exchange, I lead it to a
switch apparatus in the neighbourhood of the group, and I connect this switch
apparatus by a single wire with the central station or exchange; and I so arrange
the switch apparatus, as I will presently explain, that when one of the group of
subscribers is communicating through the exchange with some member of another
group, or when he is communicating with a member of his own group, all other
members of his group are excluded. According to one form of apparatus which I
employ each member of a group in opening communication with the exchange
causes an electric current to excite an electro-magnet in the switch apparatus of
his group, and this magnet by attracting its armature releases a detent, by the
movement of which the branch wire of the operating member is brought into
connection with the main wire leading to the exchange, and at the same time
a locking bar or shaft is moved which locks the detents belonging to all the other
branch wires of the switch, so that no other member of the group is able to put his
branch wire in connection with the main wire while the connection already
established subsists. On the member having finished his communication through
the exchange, an electric current transmitted thence excites another electro-magnet
at the switch apparatus, releasing a catch, whereupon a clockwork movement takes
place which unlocks all the detents that had been locked, and restores the switch
apparatus to the condition in which it was before the operation.
According to another form of the apparatus I provide at the switch station a barrel
that can be moved step by step round by a succession of electrical impulses from
the exchange in a manner similar to the type wheel of a printing telegraph. On
the surface of this barrel I arrange a number of contact pins, and I provide a
number of contact springs, one connected to each branch wire of the group. In
the normal position of the barrel all the branch wires are, through the contact
pins, in connection with the main wire to the exchange, so that any member of the
group can communicate therewith. He may desire to communicate either with a
member of another group, or with a member of his own group, and expresses his

page_text: desire to the official at the exchange. In the former case the official causes such
a succession of electrical impulses to actuate the barrel as will turn it to a position
where only the applicant's branch wire is in connection with the main wire, all
the others being excluded. In the latter case he causes the barrel to turn to such
a position that the applicant's branch wire is in connection with the branch wire of
the member of his group with whom he desires to communicate, and with none of
the others. When the communication is ended the official causes the barrel to turn
to its normal position ready for the passage of a communication from any member
of the group to the exchange. It is in all cases of advantage to provide the
apparatus with repeating or indicating signals, either visible or audible, so that
any member of a group who tries to communicate when the main wire is engaged,
may receive a signal indicating that he cannot open communication. For this
purpose an electric bell or a galvanometer may be introduced into the circuit of
each member of the group, so that when he makes contact for the purpose of
opening communication with the central station he hears, by the sounding of the
bell, or sees, by the movement of the galvanometer index, that his wire is in
circuit. By the absence of such indication he is apprised that his wire is out
of circuit, and that he cannot at that time communicate. When a bell is used for
this purpose it is of advantage to work it by relay from a local battery, so that
a very weak electrical impulse suffices to bring it into action. The two forms of
apparatus above described being combined into one having, according to the first
arrangement, contacts under the control of the respective members of the group,
and also having, according to the second arrangement, contacts under the control
of the official at the exchange, any member of a group can be put in communi-
cation with any member of another group, or with any other member of his own
Fig. 1 is a diagram plan illustrating the position of and connections for apparatus
according to my Invention. Assuming S to represent the central station or exchange,
Ss the telephonic apparatus of a subscriber in direct connection with S, and S³, S,
and S telephonic apparatus of several subscribers all at a distance from S, but
more or less near to one another, as they might be, for example, in a suburb. For
communication between any of the subscribers S³, S., and So, with a subscriber S³,
according to the usual arrangement of telephonic apparatus, each would require to
have a separate wire connecting his apparatus with S. I dispense with a number
of these wires by introducing in some convenient situation near the group of
subscribers S3, S4, and S5, the switch apparatus S¹, to which the apparatus of each
of the subscribers S³, S4, S5, is connected by a comparatively short wire c, whilst the
switch apparatus S' is connected by a single wire with the exchange S. One part
of the switch apparatus S¹, which I will first describe in its normal condition,
enables any one of the group S³, S, S³, as, for example, S³, to communicate with
the exchange S, and through it with any subscriber S³ connected with the exchange,
and while this communication is going on it excludes the other members S' and S³
from communication with S; but when the communication is ended the attendant
at S can restore the switch apparatus S¹ to its normal condition, in which it
becomes again available for any member of the group S3, S4, S5, opening communi-
cation with S. Another part of the switch apparatus at S¹ enables the attendant
at S to put any one of the group S3, S4, S5, in communication with S, excluding the
others of the group, and thus a subscriber at S2 can through S communicate with
one of the group, such as S³, the others, S4, S5, being excluded. By means of
another part of the switch apparatus S' the attendant at S can put any two
members of the group S3, S4, S5, in communication with one another, excluding the
other membera. By means of these various parts combined into one complete
switch apparatus at S¹, any member of a group, such as S³, S₁, S³, can be put in
communication with another member of his own group or with the exchange S,

page_text: and through it with a subscriber S in connection with S, or with any member of
a group connected with S by a switch apparatus, such as S¹.
The first part of the apparatus above referred to, which may in some cases be
used alone without the other parts, is shewn at Figs. 1, 2, and 3, Fig. 1 being a
perspective view and Fig. 3 a plan of the apparatus for a group of three subscribers,
and Fig. 2 being a section on the line X, X, Fig. 3. M is the framing of wood,
ebonite, or other non-conducting material, or it might be of metal, the various con-
ducting parts being insulated. For each subscriber there is an electro-magnet B
with a spring armature B¹, having at its front end a hook b which engages with a
catch a at the upper end of a lever A. This lever, which is pivotted to the framing
at a¹, has an arm A¹ projecting transversely from it just above the upper edge of an
insulated bar D which is mounted on radius arms D₁ like the blade of a parallel
ruler, so that it can move to and fro in the direction of its length. In this bar
there are inclined notches d, one for each of the arms A¹. The bar is urged by a
light spring or by gravity towards the left against a stop, and in this position the
notches dare exactly under the arms A. Each of the levers A is held in its
normal position, shewn in Fig. 2, by the engagement of the hooks a, b, but when
the electro-magnet B is excited, attracting its armature, these hooks are released,
and the lever A by its weight or aided by a spring a falls back to the position
indicated by the dotted lines in Fig. 2. By this movement the arm A¹ descending
the inclined notch d causes the bar D to move towards the right. The other
arms A' of the apparatus, even if their hooks a were disengeged, could not descend,
but would simply rest on the upper edge of the bar D. Thus the movement of
any one of the levers A resulting from the excitement of its magnet B locks the
other levers, preventing their movement until it is itself raised again, withdrawing
its arm A¹ from the notch in D. Above the arms A¹ is fixed an insulated metal
bar G having pins g projecting from it towards insulated springs C which are pressed
back by contact points a projecting from the levers A. When one of these levers falls
forwards, as described, the spring C, which was beld back by the projection a³, advances
and makes contact with the pin g corresponding to it. The wires c from the different
members of the group are attached to the binding posts 1, 2, 3, each of which is
connected by a wire to one of the springs C. Each of the posts B2 which supports
the spring armature B' is connected by a wire e to the coil of the electro-magnet B,
which by a wire e¹ is connected by a post 4 and thence by a wire e² to earth. The
wire 8 from the central station or exchange is connected through the post 5 by a
wires to the coil of an electro-magnet H, which, by a wire 82, is connected to the
bar G. The armature of the magnet H is on a lever H³ which is pressed by a spring h²,
and has a booked end h³ engaging with teeth o¹ of a star wheel on a shaft O. This
shaft is connected by gearing p', p³, with a shaft P on which is wound a cord p
strained by a weight P³ that from time to time is wound up. On the shaft O are
fixed wheels, one for each lever A, having arms v, one of which when the shaft O is
permitted by the release of the catch h³ partly to revolve, acts on the tail a³ of the
lever A, moving it back to its normal position. The action of the apparatus is as
follows: A member of the group S³, S, S³, desiring to communicate with the
exchange S transmits a current through his wire c, as, for example, that connected
to the post 3. The circuit being completed through c¹, the spring C, the contact a³,
the lever A, the armature spring B', and post B³, the wire e, the coil of B, the
wire e', and post 4, to earth es, the magnet B attracts its armature, releasing the
catches a, b. The lever A thereupon falls forward, breaking contact with C at a³,
and allowing C to make contact with g, whence through G, S, the coil of H, 8',
post 5, and 8, there is electrical communication with the central station, the current
however being insufficient to move the armature lever H¹ of the electro-magnet H.
The member, in thus establishing communication with the central station, causes
the motion of one of the levers A, which, by its action on the bar D, prevents others
of the levers A being moved in like manner, and consequently, while the apparatus
remains in this condition, only the one member can communicate. When the
communication is ended the attendant at the central station sends a current

page_text: sufficiently strong to move the armature lever H'. The shaft O being thus released
moves one division round, one of the arms v upon it throwing back to its normal
position the lever A that had fallen forwards, and so breaking contact between g
and C and thereby excluding the central station. The lever A, in moving forward
from its normal position as above described, may pass a contact, whereby for the
moment of its passage a battery at S' is put in circuit with the wire c, an electrical
current being thus transmitted to give a visible or audible signal to the member to
shew that he has opened communication with the central station. If he should be
locked out by the existence of a communication from another member of the group,
then, as his lever A. cannot move, no such momentary current will be transmitted.
Although I have, for simplicity of description, shewn in Figs. 1, 2, and 3 apparatus
suited for a group of only three members, it is obvious that by mere multiplication
of the parts proper to one of them it could be extended to suit any number.
Figs. 4, 5, and 6 shew the part of the switch apparatus whereby the attendant at
the central station can open communication with any member of a group, as S³, S4,
So, Fig. 4, being a perspective view, Fig. 5, a transverse section, and Fig. 6, a part
transverse section to an enlarged scale. A weight Ps strains a cord p wound on a
barrel P so as to cause rotation of a spindle O connected to P by multiplying gear
P1, P2
The spindle O has on one end of it an escapement wheel x with which
engages an anchor x¹ connected to the arinature lever of an electro-magnet K,
the armature being kept off the magnet by a spring adjustable by a nut *. At
the other end of the spindle O is fixed a metal disc w against which bears a spring
n from a binding post n fixed on a bar N¹ of non-conducting material. On this
bar are fixed a number of similar posts 83, 84, etc., each with its spring n², and from
the spindle O project a number of metal pins q arranged helically round it, one in
the plane of each spring n², and one q¹ next to the escapement wheel & for working
a lever y¹ for a purpose to which I will refer hereafter. The first binding post n is
connected by the wire 8 (see Fig. 1a) to the central exchange, and as the first
spring n always bears against the disc w, the spindle O and its pins q are always
in electrical connection with the exchange. To each of the other posts S³, S*, etc.,
is attached a wire connected to one of the group of subscribers S³, S*, etc., any one
of which, such as S³, is brought into electrical connection with the exchange only
when one of the pins q is caused by the rotation of the spindle O to bear against
the spring n connected to his wire. The coil of the electro-magnet K is connected
to earth by a wire 812, and through binding post 811 and wire 810 it is connected to a
battery Re and a key and dial d at the central station. The dial d is marked
with division numbers corresponding to the pins on the spindle O, so that an index
on the dial revolves synchronously with the spindle O, both being caused to move
round step by step by successive impulses transmitted to the magnet K. When the
attendant at the exchange desires to open communication with one member of the
distant group, such as S³, he transmits a succession of impulses until the index on
the dial points to the proper number, as, for example, 3, and he thus knows that
the spindle O by the action of the armature escapement bas so far revolved as to
bring one of its pins against the spring connected to S³, and in like manner by
another number of impulses he can complete communication with some other
member of the group. Instead of arranging the contact pins 9 on the spindle O at
uniform intervals around it they might be arranged in groups so as to suit the
various combinations of pairs of the springs n2, as diagrammatically illustrated at
Fig. 4ª, in which it will be seen that the two first springs on the right are in
contact at the same time with their respective pins q. Thus by suitable grouping
of the pins q, according as the spindle O is turned more or less round, any two of
the springs n² may be simultaneously in contact, and in this manner any two
members of the group connected with the apparatus may be put in communication.
For a like purpose the apparatus described with reference to Figs. 4, 5, and 6 may
be provided in duplicate, and the electro-magnets K which work their respective
spindles may be actuated by polarised relay, so that the one is actuated by
positive electrical impulses and the other by negative impulses.
Thus the one

page_text: spindle O may be turned to bring one of its pins q in contact with its spring n²,
and the other spindle O may be turned so as to make contact for another of its
pins q, and in this way the two members of the group having connection respectively
with the two springs n³ may be put in communication.
This apparatus may be arranged to act in conjunction with the apparatus
previously described with reference to Figs. 1, 2, and 3, in the manner shewn by
the part transverse section Fig. 7. In this Figure H and H¹ represent the electro-
magnet and armature lever marked by the same letters in Fig. 2, and o¹ the teeth
of the star wheel so marked in that Figure, whilst O is the spindle with one of its
pin q, and y the lever marked by corresponding letters in Fig. 5. The armature
lever H¹ has an arm H2 connected by a cord or wire y to the lever y¹, which is
pivotted at y³ to the bar N', and is pressed by a spring y³. It will be seen that
independently of the action of the electro-magnet H (which may in this com-
bination be dispensed with), when by the pin q¹ the lever y' is pushed aside, one of
the star wheel teeth o¹ is released, and thus the spindle O of Fig. 2 is permitted to
make a partial revolution, restoring to its normal condition such of the levers A. as
had moved forwards as already described. Instead of providing two separate sets
of apparatus, such as the one set shewn by Figs. 1, 2, and 3, and the other set
shewn by Figs. 4, 5, and 6, and arranging them to act in conjunction, as shewn by
Fig. 7, both sets of apparatus may be combined into one, as I will now describe,
referring to the front view Fig. 8, the transverse section Fig. 9, and the plan
Fig. 10. The parts shewn in these Figures are, so far as the modifications of
construction and arrangement permit, marked by reference letters corresponding
with those which mark corresponding parts in the Figures previously referred to.
In this modified apparatus the barrel shaft P worked by the weight drives by
gearing P, P¹, the spindle 0%, which by gearing 03, 04, drives the spindle O¹, which
has on it the star wheel with its teeth o' subject to the action of the electro-
magnet H. The spindle O2 has on it a number of discs Q instead of the pins
described with reference to Figs. 4 and 5, each of these discs having a piece q
projecting at one part of its periphery, which comes to make contact with a
spring n². The conducting pieces q of the successive discs are arranged helically,
as described with reference to the pins q in Figs. 4 and 5; and the contact of
each of the projecting pieces q with its spring n² is made of such breadth that
when the spindle O2 is turned round, before one contact is broken the next in
order is made. Thus there is no position of the spindle O2 in which one or other
of the contacts does not subsist, completing the circuit for the main wire. Each
disc also carries a roller V, which as the disc revolves in the direction of the arrow
acts on the tail a³ of the lever A that may have fallen forward, as described with
reference to Figs. 1, 2, and 3, restoring it to its normal position, in which it is held
by the engagement of its hooked end a with the hook 6 of the armature lever B¹.
The hook 6 which makes electrical contact with a when engaged with it has
inserted in its sloping face a piece of non-conducting material 6'. The armature
lever B¹ is inverted in position, being pivotted so that the attraction of the
magnet B causes its hook 6 to be raised when it is disengaged from a.
electrical contact of the lever A is made by its shoulder a normally bearing
against the spring C which is in connection with n², this spring being at the same
time kept away from the contact g. When however the lever A falls forward, the
contact of a with C is broken, and C makes contact with g. It is of advantage
that there should be a connection from the coil of the electro-magnet H to earth, in
which connection there is introduced a resistance somewhat exceeding that of the
main wire itself. This is not essential to the working of the apparatus in its
proper condition, but it provides for a case that may happen by accident to some of
the conductors to the members of the group. If one of these conductors should be
accidentally severed so that the main circuit would be interrupted, the earth
connection above mentioned will complete the circuit, the resistance introduced in
it excluding this connection, while the other connectious remain entire. By means
of this combined apparatus the functions of both the sets of apparatus previously
The

page_text: described can be performed, that is to say, when a member of a group, such as
S³, S*, S³, desires to communicate with some one through the central station he
sends an impulse, which, as described with reference to Figs. 1, 2, and 3, causes the
lever A with which his wire is connected to fall forwards, placing him in com-
munication with the central station, and also by means of the locking bar D with
its inclined slots d preventing any other member of the group from communicating
until the lever A is restored to its normal position. It is so restored by the
action of the roller V when the spindle O³ is caused to revolve. The revolution of
this spindle is effected step by step, as already described, by the action of the escape-
ment lever H', in consequence of successive impulses from the central station
exciting the magnet H, either directly or by relay. The operator by means of
these impulses can cause the spindle O2 to turn a certain number of divisions, and
can thus by effecting the contact of one of the springs n² on the corresponding
disc put one member of the group in connection with another member, who has
already put his wire in connection with the main wire, or he can cause the spindle
O to turn so far round that the roller V on any disc raises the corresponding
lever A which had previously dropped forwards, and thus restores the apparatus
to its normal condition ready to be employed again for communication with or
from any member of the group. Besides the levers A, one for each member
of the group connected with the switch apparatus, there is a lever X, the lower
arm a of which extends somewhat farther down than the arms a³ of the other
levers. This lever is not worked by an electro-magnet B, as the levers A
are worked, but, like them, it has an arm a¹ acting in an inclined notch of
the locking bar D. Assuming that this locking bar has not been moved by
the action of any of the levers A, but that the attendant at the central
station has to put some member of the group into communication by causing
the spindle O to revolve step by step until the projection q from the disc Q
appropriated to that member makes contact with the spring n², then during
the first part of this revolution of the spindle 02, the lever X having its lower
end disengaged from the roller V2 on the disc Q below it falls forward, and its
arm dropping into the inclined notch of the locking bar D moves that bar, and
so prevents any of the levers A from falling forward. When the attendant at the
central station restores the switch apparatus to its normal condition by causing the
spindle O to complete step by step its revolution, lever X is raised by the roller V³
on the disc Q below it, and the locking bar D being thus released returns to its
normal position ready to receive in its inclined notches the arm of X again, or
the arm of any of the other levers A. When the locking bar D is in this, which
may be termed its normal position, a contact is made by one of the radius bars D',
which support it with a pin connected to the main wire, so that impulses can be
transmitted to the electro-magnet H when none of the members of the group are
in communication with the apparatus. When, however, by the falling forward of
any one of the levers A or of the lever X the locking bar is moved aside, this
contact is broken, and another contact is made by the lever that has moved as
described above. When by the falling forward of X, or of any one of the levers A,
the locking bar D has been moved so as to prevent the falling forward of any
other of the levers A, it may happen that some member of the group desires to
open communication. In making contact for this purpose he excites his electro-
magnet B, which attracting its armature releases the hooked end a of his lever A
from the hook b. The lever A can then fall a little forward till its arm A' rests
on the edge of the locking bar D. When it is so resting its hooked end a bears
against the piece of non-conducting material 61 above referred to, and thus the
wire of the member who had tried to open communication is cut out of circuit,
and it remains so until by the completed revolution of the spindle O' all the levers A
as well as the lever X and the locking bar D are restored to their normal condition.
The magnet H, by the action of which the spindle 02 is turned, is preferably
worked by a polarised relay, such as is shewn at H³, Fig. 10. This relay is so
arranged that currents of one sign, such as positive, cause contact to be made,

page_text: whereby a local battery is brought into connection with the coil of H, thereby
exciting it and producing the step by step rotation of the spindle O'. When, on
the other hand, currents of the opposite sign, such as negative, are transmitted to
H³, contact is made excluding the coil of H, and forming connection for audible or
visible signals, which connection is excluded when H is excited. Thus, according
as positive or negative impulses are transmitted to H³, either the spindle O' will
be turned step by step while no signals are given, or signals will be given while
the spindle O² remains at rest. It is obvious that a battery, such as R6 and dial d*,
which have been stated above to be provided only at the central station for the
purpose of effecting the step by step movement of the spindle 0%, might be pro-
vided for each member of the group connected to the apparatus described with
reference to Figs. 8, 9, and 10. Each member could in this case cause the move-
ment of the spindle O, and could thereby put himself in communication with
another member of the group, directly without the intermediate action of the
attendant at the central station.
Having thus described the nature of my Invention, and in what manner the
same is to be performed, I claim in respect of electrical connections for telephonic
communication,―
First. Connecting a central telephonic station to a group of distant but neigh-
bouring telephones through a switch apparatus near the group, connected by one
conductor to the central station, and by separate conductors to the separate
members of the group, the switch apparatus being so arranged that when any
member of the group communicates with the central station, or when the central
station communicates with any member of the group, the other members of the
group are excluded, substantially as and for the purposes herein set forth.
Second. The use of apparatus, substantially as herein described with reference to
Figs. 1, 2, and 3, whereby any one of a group of telephones can open communi-
cation with a distant telephonic station to the exclusion of all others of the
group.
Third. The use of apparatus, substantially as herein described with reference to
Figs. 4, 5, 6, and 7, whereby a distant telephonic station can open communication
with any one of a group of telephones to the exclusion of all others of the
group.
Fourth. The use of a combined apparatus, substantially as herein described with
reference to Figs. 8, 9, and 10, whereby communication can be opened by or with a
distant telephonic station with or by any one of a group of telephones to the
exclusion of all others of the group.
In witness whereof, I, the said George Westinghouse, junior, have hereunto
set my hand and seal, this Twenty-second day of July, in the year of
our Lord One thousand eight hundred and eighty.