Improvements in Automatic Telephone Exchange Systems
Year: 1895

page_text: Date of Application, 20th Nov., 1895
Complete Specification Left, 20th Aug., 1896-Accepted, 17th Oct., 1898
Improvements in Automatic Telephone Exchange Systems,
I, WILLIAM FREDRICK LOUNSBURY, of 370 Main Street, Owego, Tioga
County, New York, United States of America, Inventor, do hereby declare the
nature of this invention to be as follows:-
:-
My invention relates to means for obtaining immediate telephonic communication
between subscribers' stations in pairs.
A brief of the description and operation as preparatory to the detailed speci-
fication is given as follows:-I provide a central exchange apparatus, which is
connected with any number of sub-stations by respective out-going and in-coming
main lines. I dispense with all step by step movements, both at the central and at
the sub-stations. Although there is but one line from the central station to each
sub-station and back yet the connections at the central station are such that any
sub-station whatever is electrically connected normally in closed circuits with each
remaining sub-station. In this normal condition, the system would not be appro-
priate for the conversation to be held between more than two sub-stations at a
time, while all the others would have to wait, because if more than two sub-stations
should talk simultaneously with one another, there would be a babel of tongues.
I provide at the central station a circuit closer in a normally closed circuit with
each pair of sub-stations. There is a magnet at each one of these circuit closers,
which is caused to be energized or neutralized, according as to whether the circuit
closers are to be opened or closed. If any two sub-stations are connected
telephonically together by means of my apparatus, they are each excluded by
means of the said circuit closers from each of the remaining sub-stations; and,
further, the latter cannot interrupt either of the communicated sub-stations, but
they can in pairs communicate with each other, all in view of the proper operation
of the said circuit closers. These circuit closers are controlled, as before stated,
by magnets, which in turn are magnetized when necessary by means of a local
battery at the central station. The maguets have to be shifted from one circuit to
another, according to predetermined conditions. Normally they are in respective
conductors closed upon themselves without a battery. The object of this kind of a
connection is to permit the cutting in of the local battery, and also to permit the
shifting of the magnets from one conductor closed upon itself without a battery to
another conductor closed upon itself without a battery. These are the three
conditions in which more or less of the magnets are placed before, during and after
operation of the whole system, or any part of it. When the magnet is shifted, as
to its connections, by the connecting up of two sub-stations, the shifting is of such
a nature, that all the circuit closers, which are to be opened belong to those
magnets which are thrown into active circuit with the local battery, and all the
remaining magnets remain neutral because they are simply thrown from one
conductor, closed upon itself without a battery to another conductor, closed upon
itself without a battery, excepting those magnets belonging to circuit closers that
have no electrical connection with the two sub-stations which are calling each
other.
The means for shifting the magnet from the circuit of the one conductor closed
upon itself, to the circuit of another conductor, closed upon itself, is effected by
means of a nole changer provided for the circuite of each meenat

page_text: A modification of my invention consists of a simplified sub-station apparatus.
It is found in practice that a certain maximum percentage of the total number
of subscribers are communicated in pairs simultaneously at the busiest part of the
day. The system is of such a nature that there need be but a small proportion
depending upon what this maximum number is of the number of central exchange
devices. If it were at all probable that all the subscribers in a large exchange
should hold simultaneous telephonic communication in pairs, then it would not be
possible to do away with any multiplicity of a similar electro-magnetic circuit
controllers at the central station.
In order to set forth the detailed construction and operation, drawings are
annexed and described.
Figure 1 is a diagram of a complete system, in its simplest form, for the accom-
modation of four subscribers.
The invention could not be well illustrated by a figure showing a less number of
subscribers, because it could not be seen easily how two pairs of the subscribers
could be holding communication without interfering with each other.
Figure 2 is a diagram of a modified sub-station apparatus.
The organization of the system comprises three general features.
First, the apparatus, located at the sub-stations, which are indicated in the
drawings by the numerals 1, 2, and 4, and, consequently, the system represented
in Figure 1 accommodates the telephonic intercommunication of four subscribers.
The apparatus at each sub-station may be distinguished from that at the central
station as slightly set apart at the lower part of the drawing, and each sub-station
is connected by two conductors to the central station.
The second general feature comprises the electro-magnetic circuit controllers
at the central station, numbered 1-2, 1-3, 1-4, 2-4, 3-4. As will appear
hereafter, this style of numbering the controllers will conveniently represent to the
eye the nature of their electrical connections with other elements of the system as
a whole.
The third feature involves the circuits classified as follows:-
One set of circuits is made up of the subscribers' main lines. Thus station 1 is
connected to certain parts of certain electro-magnetic circuit controllers by the
main line conductors 11 111; sub-station 2 to similar parts of similar devices by
main line conductors 21 211; sub-station 3 by main line conductors 31 311; and
sub-station 4 by main line conductors 41 41. The connections between these
subscribers' circuits and certain portions of certain electro-magnetic circuit
controllers are made in various, but predetermined, ways by various connecting
wires arranged in multiple arc, and more fully hereinafter numbered and
explained.
There is a second set of electric circuits, easily distinguished from the first
because they are what may be termed local circuits at the central exchange. The
main line conductors of the local battery 5 are numbered 6 and 6'. Certain
connecting conductors between the local main and certain parts of certain
electro-magnetic circuit controllers are arranged and numbered as hereinafter
described.
All of that part of the system above the sub-stations 1, 2, 3 and 4 is the central
station.
In the normal condition of the subscribers' circuits, the sub-station apparatus, of
any given sub-station is electrically in circuit with the apparatus of each other
sub-station.
To aid in the understanding, it should be stated here that the generators for
these subscribers' circuits in normal condition is the hand magneto generator 7.
Now the electric circuits from each sub-station to each other sub-station will be set
forth-The conductor, 8, connects the main line 1', with the main line 2. The
return circuit is 8¹. A conductor 9, connects the main line 1', with the main
line 31, and the return conductor is 9. The conductor 10, connects the main
line 1 with the main line 4" and the return conductor is 10', and in this way the

page_text: apparatus of the sub-station 1 is shown to be in closed circuits respectively with
each of the other sub-stations. The conductor 11, connects the main line 21, with
the main line 31, and the return conductor is 11. The conductor 12 connects
the main line 2¹, with the main line 41, and the return conductor is 12¹. The
conductor 13 connects the main line 31, with the main line 4" and the return
conductor is 13¹.
Each of the connecting conductors, being six in number, is provided with an
electro-magnetic circuit closer, the same being numbered in order 81, 91, 101,
11, 12 and 1311. These circuit closers are conveniently the ends of rods,
projecting upward from the armatures of the electro magnets 1-2, 1-3, 1-4, etc.
When the said electro-magnets are energized, the circuits of the conductors 8",
91, 101, etc. are opened.
The local circuits will now be set forth. The battery, as before stated, is 5, and
the main line 6 and 6. The relay magnets for throwing this battery into circuit
with the electro magnetic circuit controllers are 14 in main line 1'; 15 in main
line 21; 16, in main line 31; aud 17, in main line 4'. The main local battery lines
respectively 6 and 6' are provided with supplementary main local lines, which are
adapted to be brought into circuit with the battery 5, by means of armature circuit
closers 181, 181, 18, 18, which, respectively, normally connect the said supple-
mentary local mains, which are numbered in pairs 19, 20, 21, 22.
It should be stated here, that the relay magnets 14, 15, 16 and 17 are normally
not energized, because the generators 7 are not in operation. The means for
energizing them consists of certain batteries, bereinafter described, located at the
sub-stations. The magnet 1-2 is connected to the lines 19, by conductors 23
and 23', and to the lines 20 by the conductors 24 and 24' through a pole changer,
hereinafter ect forth. The path or each of the circuits of the conductors 19, 20,
23, 231, 24 and 241, is such as to be a ircuit closed upon itself without a battery,
in view of the two circuit closers 18¹d 18", which, as before stated, electrically
connect, respectively, the main lines and 20. It should be noted that the
conductors 23 and 23' connect different ma p lines of 19, and that the conductors 24
and 24', connect correspondingly different main lines of 20. The circuit closers 18'
and 181, when attracted by the respective magnets 14 and 15, move to the right
to the local battery terminals 25 and 26. By this means one of the main lines
of 19 and 20 is connected to one pole of the local battery 5. The other one of the
main lines 19 and 20, are permanently connected by conductors 29 and 30 to the
other pole of the same battery.
Similar connections exist between the other magnets and the various supple-
mentary main lines. Thus, the magnet 1-3 is connected by conductors 33 and 33¹,
respectively, to the upper and lower main lines 19, and by conductors 34 and 34¹,
respectively to the upper and lower main lines 21, there being, as before, a pcle
changer, controlled by the magnet 1--3, included in metallic circuit, this time,
with the circuit closers 18' and 18. When these said circuit closers are attracted
by their magnets 14 and 16, the magnet 1-3 is shifted from one conductor closed
upon itself without a battery to the other conductor closed upon itself without a
battery. It should be remembered that as all the parts cannot be described
simultaneously, the statement of the operation is postponed until later, but it may
be stated here incidentally that when the above circuit closers 181 and 1811 are
simultaneously closed, the above result occurs.
Passing now on to the circuits of the magnet 1-4, it may be stated that the
same is connected respectively to the upper and lower main lines 19 by cou-
ductors 35 and 35', and to the respective upper and lower lines 22 by conductors 36
and 36', there being included, as before, a pole changer, controlled by the
magnet 1-4; and also circuit closers, as before 18¹ for the lines 19 and 181, for
the lines 22.
In order that the description may be complete in detail, it may be stated that
the magnet 2-3, is connected by conductors 37 and 371 respectively with the
upper and lower lines of 20 and by conductors 38 and 38¹ respectively with the

page_text: upper and lower conductor 21, the circuit being metallically completed through a
pole changer, controlled by magnet 2-3 and by the circuit closers 1811 and 18111
Similarly, the magnet 2-4 is connected by conductors 39 and 39' respectively
with the upper and lower lines 20, and by conductors 40 and 40', respectively, with
upper and lower lines 22, through a pole changer controlled by the magnet 2—4,
and through the circuit closers 18 and 181
the
Finally, the magnet 3-4, is connected by conductors 41 and 41' respectively,
to the upper and lower lines 21, and by conductors 42 and 421, respectively, with
the upper and lower lines 22 through a pole changer controlled by the magnet 3-4,
and through a circuit closer 18 and 18111.
The pole changers of the different magnets are all alike, and, therefore, the
description of one applies to all. Each pole changer has two movable circuit
closers 43 and 44, insulated from each other, and adapted, when attracted by the
controlling magnet, to both depress and close certain spring terminals. In the
first pole changer, measuring from the left of the first sheet, the circuit closer 43
connects and depresses the terminals of the conductors 23 and 24'; in the second
pole changer, the circuit closer 43 connects and depresses the conductors 33 and 341;
in the third, it connects and depresses the terminals of the conductors 35 and 36';
in the fourth the terminals of conductors 37 and 38¹; in the fifth, the terminals of
conductors 39 and 40'; and in the sixth, the terminals of the conductors 41
and 42. The above closing and depressing takes place when the several magnets
are energized, and at the same time, the circuit closers 44 connect together in pairs
the remaining conductors that connect the magnets 1-2; 1-3; 1-4, etc., to the
lines 19, 20, 21 etc.
Normally, the pole changers are so connected by conductors 45 and 46 that in
the first the spring terminal 47 of the conductor 23 is connected to the spring
terminal 481 of the conductor 24; and the spring terminal 48 of the conductor 23
is connected to the spring terminal 47' of the conductor 24'. In the second pole
changer, the conductor 45 connects the spring terminal 47 of the terminal 33 with
the spring terminal 48 of the conductor 34; and the conductor 46 connects the
spring terminal 48 of the conductor 33' with the spring terminal 471 of the
terminal 34. In the third pole changer, the conductor 45 connects the spring
terminal 47 of the conductor 35 with the spring terminal 48' of the conductor 36;
and the conductor 46 connects the spring terminal 48 of the conductor 35¹ to the
spring terminal 471 of the conductor 36¹. In the fourth pole changer, a
conductor 45 connects the spring terminal 47 of the conductor 37 to the spring
terminal 48 of the conductor 38; and the conductor 46 connects the spring
terminal 48 of the conductor 371 to the spring terminal 471 of the conductor 381.
In the fifth pole changer, a conductor 45 connects the spring terminal 47 of the
conductor 39 to the spring terminal 481 of the terminal 40; and the conductor 46
connects the spring terminal 48 of the conductor 391 to the spring terminal 471 of
the conductor 401. In the sixth pole changer, a conductor 45 connects the spring
terminal 47 of the conductor 41 to the spring terminal 481¹ of the conductor 42;
and the conductor 46 connects the spring terminal 48 of the conductor 41¹ to the
spring terminal 47¹ of the conductor 42'.
The different spring terminals 47 and 48 and 471 and 48¹ are so arranged that
when depressed by the circuit closers 43 and 44, they are entirely moved out of
contact with the conductors 45 and 46, thereby producing differences in the
manner of connecting up the circuits.
As a part of the construction and the normal condition of the system, it should
be stated that the magnets 1-2; 1-3; 1-4, etc. are so connected, that they are
in the circuit of conductors, closed upon themselves, exclusively of a battery, so
that although they are in the circuit of closed conductors, they are not magnetized.
In order to show this by reference to the drawings, it may be noticed in regard to
the magnet 1-2 that its terminal conductors 23 and 24 are connected to the
respective upper lines of 19 and 20, and that those upper lines are connected to a
common pole of the battery 5, respectively, through the circuit closers 18 and 18",

page_text: In
the conductors 29 and 30, and finally to the positive pole of the battery 5.
order to illustrate thus further, and to show that there is no confusion in the
system, it may be noticed that the terminal conductors 33 and 34 of the
magnet 1-3, are connected to the respective upper lines of 19 and 21, and that
these, by apparent connections, are connected to but one pole of the battery,
namely, the positive pole. In regard to magnet 1-4, its terminal conductors 35
and 36, are connected also to the respective upper lines of 19 and 22, which are
connected to the positive pole of the battery. Similarly, the magnet 2-3 is
connected to the positive pole of the battery, as may be seen by noticing the
conductors 37 and 38, the upper lines of 20 and 21 and the electrical connections
between the positive pole of the battery and said upper lines. The circuit of the
conductor which includes the magnet 2-4 is as follows:-Begin at the positive
pole of the battery; go to the line 6, then to the conductor 30, to the circuit
closer 18, to the conductor 39, through the pole changer to the conductor 40, to
the upper line of 22, to the circuit closer 181, to the conductor 32, and back again
to the conductor 6 and to the opposite pole. The connections of the magnet 3-4
are of exactly the same nature.
Without taking into account at present the nature of the sub-stations, it may be
stated generally that when, for example, the subscribers of the stations one and
three are actually holding communication, the relay magnets 14 and 16 are
energized, the action taking place simultaneously so that the circuit closers 18'
and 18 are thrown to the right hand terminals 25 and 27 respectively. In this
manner, the magnet 1-3 will exist in a conductor closed upon itself, but in a
different one from formerly. This may be traced out as follows:-The terminal
conductors 33 and 34 become connected through the conductors 25 and 27 both to
the negative pole or line 6. In this manner stations 1 and 3 are kept in circuit
through the circuit closer 911 At the same time, the circuit closers 8", 10", 1111
and 13, become opened for the following reasons:-Take first circuit closer 811.
As circuit closer 1811 remains in its normal condition while the circuit closer 18¹ is
moved to the right, it follows that the terminal conductor 23 becomes connected to
the negative pole while the terminal conductor 24 remains connected to the positive
pole; consequently, there is a current from the local battery passing through the
magnet 1-2, causing it to operate its armature and open the circuit at the circuit
closer 8. No attention need now be paid to the pole changer, because the
function of this comes into play when two other subscribers wish to hold
communication without waiting for subscribers 1 and 3 to stop talking, and, at the
The circuit
same time, without interrupting or being interrupted by them.
closer 10" becomes opened for the following reasons: The terminal conductor 35
becomes connected to the negative pole, because the circuit closer 18¹ has been
put into connection with the conductor 25, while the terminal conductor 36 remains
connected to the positive pole of the battery because the circuit closer 181111
remains in its normal position.
The circuit closer 11" becomes opened because the terminal conductor 37.
remaius in connection with the positive pole of the battery because the circuit
closer 18 is in its normal position while the terminal conductor 38 becomes
connected with the negative terminal of the local battery 5. The circuit closer 1311
becomes open because the terminal conductor 41 is connected to the negative pole
of the battery because of the abnormal condition of the circuit closer 1811; while
the terminal conductor 42 remains connected with the positive pole.
The first thing that becomes necessary to understand about the sub-station
apparatus is the mechanical construction without regard to its relation to the
central station apparatus. As before stated, 7 represents the hand magneto
machine; 49 represents a magnet; 50 a wheel, prevented from rotating in the
direction of the arrow by being, provided with a projection 51, pressing against the
end of an armature spring 52 belonging to the magnet 49. The wheel carries a
rotary circuit closer 53, adapted to maintain the circuit closed during a part of its
rotation, and to keep the circuit open during the remainder of the rotation.
The

page_text: wheel 50 is supposed to be wound up against the action of a spring 54, which
serves also as an electric connector to the circuit closer 53. The wheel 50 when
released by the spring armature is caused to rotate slowly and practically
uniformly, by means of the resistance or fan wheel 55. There is a spring lever 56
held down by the weight of the telephone 57. The spring 56 carries three
insulated contacts 58, 59 and 60. The circuits at the sub-stations are connected up
as follows-Passing from the main line 1', the circuit is normally closed through
the generator 7; and electric bell 61, contact 59, magnet 49, circuit closer 53,
spring 54, and then to the main line 11. There is a branch circuit to the circuit
just described and normally open, and passing through a battery 62 to the
contact 58, where it is normally open, to the magnet 49, to the circuit closer 53, to
the spring 54, and then to the main line 11. There is another normally open
branch circuit, the same being from the main line 11, through the battery 62; the
contact 58 adapted to be closed with the contact 60 when the telephone is removed;
then through the telephone 57; and then to the main line 11.
Having now set forth the construction of the system, I will state the operation by
assuming, first, that station 1 is to call and hold communication with station 3, and
that while their telephones are in circuit, I will give the second step by showing how
two other stations may hold telephonic communication without interfering or being
interfered with that between stations 1 and 3. The other two stations, of course,
will be 2 and 4, but what holds true with reference to the four sub-stations will
hold true for a system built for any number of sub-stations.
Say that station 1 wishes to call and hold conversation with station 3. 1 operates
the generator 7, by a certain number of turns agreed upon by stations 1 and 3.
The same signal will be received at sub-stations 2 and 4, but they have agreed not
to pay any attention to that signal. The current generated by the generator 7 at
sub-station 1 energizes all the magnets 49 which move all the wheels 50. As it
takes a little time for the signal to be given, the circuit is maintained during a
portion of the revolution of the circuit closers 53 until the parts thereof, marked
in black move in contact with the terminals of the magnets 49. Simultaneously
with the operation of the generator 7, the bells 61, ring, in fact, these are call bells,
and they ring for a certain interval of time, and until the right parties are
summoned or called and perhaps until the circuits are interrupted at the circuit
closers 53. The instructions given to the subscribers are such that when any one
of them hears his call, he must, during the time that the circuit closers 53 are open,
take off his particular telephone 57. So must also the calling subscriber.
He may
take off his telephone as soon as the circuit closers 53 are open. By the operation
of removing the telephones at sub-stations 1 and 3, and while the circuit is broken
at the circuit closers 53, the batteries 62 at these two sub-stations only are thrown
into circuit with the lines 1, 1, 3¹, and 3", thereby energizing the relay
magnets 14 and 16. This closed battery circuit may be traced as follows:-
Beginning at the positive pole of the battery 62 at the sub-station 1, pass through
the generator 7, which is now quiet, to the main line 11, to relay magnet 14, to
conductor 9, through circuit closer 91, to line 3", to both the telephone by way
of contact 60 and to contact 58, both of the contacts being closed against the
arrows, to the negative pole of the battery 62, of sub-station 3 to the positive pole,
to the generator 7, now at rest, to the line 3', to the relay magnet 16, to the
connecting line 91, to the main line 11, and, finally, through the following elements
of sub-station 1, namely, the telephone 57, the contact 60, the contact 58, by way
of the two arrows just above them which are now closed, to the negative pole of
the battery 62, and, finally, to the starting point the positive pole of the same
battery.
It will be noticed, therefore, that if a subscriber at sub-station 3 as well as the
subscriber at sub-station 1 takes off his telephone while the circuits closers 53 at
all the stations are open, a battery circuit will send a current for energizing the
relay magnets 14 and 16.
If the subscriber at sub-station 3 does not take off his telephone 57, before his

page_text: circuit closer 53 has become again closed, the instructions are that the subscriber
at station 1 should call sub-station 3 again just as soon as the former's circuit
closer 53 has become closed. By showing the reason of the necessity of ringing
subscriber 3 up again, the invention and its operation will be more positively
understood. If the subscriber at sub-station 3 does not take off his telephone
while the circuit closer 53 is open, then will not his battery 62 be in circuit, but
battery 62 at sub-station 1 will be in circuit. The consequences of this is that the
only relay magnet which becomes energized is 14, and it becomes energized only
intermittently for the following reason:-It operates upon the circuit closers 811, 911
and 10 like an ordinary vibrating electric bell. When the magnet 14 attracts
the circuit closer 18', a circuit is formed through the magnet 1-2, 1-3 and 1-4,
causing them to open the circuit closers 8, 9 and 10", and, therefore, the circuit
of the relay magnet 14 becomes open, and then closed again, and so on. Therefore,
all the subscriber at sub-station 1 can do if he gets no answer from the subscriber
at sub-station 3 before the complete rotation of the wheel 50, is to ring up again.
On the other hand, just as soon as the subscriber at sub-station 3 removes his
telephone, he is in instantaneous communication with the subscriber at sub-station 1,
provided only that he and subscriber at sub-station 1 remove their telephones
before the closing of the circuit closers 53. The system is, therefore, what may
appropriately be termed a system of instantaneous intercommunication.
The system is, further, of such a nature that it is not necessary for the circuit
closers 53 to be accurately synchronous in their operation. They are so pro-
portioned that they require a little time, say about a minute or two, or any other
period desired, for making a complete rotation. It is evident that they will all
start off at the same time, and it is true that whether they are synchronous or not
it is only necessary for the called subscriber to remove his telephone before the
circuit closers 53, at sub-station 1, 2 and 4 become closed. It is evident that if the
circuit closers 53 start to rotate at the same time they may be sufficiently
accurately constructed to stop roughly at about the same time.
The subscriber at sub-station 1 may now hold communication with the subscriber
at sub-station 3 and they may continue to do so as long as they please, and without
interruption, in view of the pole changers.
It will now be shown how sub-stations 2 and 4 may be telephonically connected
without interfering with the communication between sub-stations 1 and 3, and
without being interfered with by them. The subscribers at sub-stations 2 and 4
go through the same operation as related regarding the other two subscribers.
Consequently, the relay magnets 15 and 17 become energized, and the circuit
closers 18 and 18 become attracted and connect the upper lines of 20 and 22
to the negative pole of the battery 5, while the lower lines of 20 and 22 remain
connected with the positive pole. The connections of the lines 19 and 21 have
been changed so as to become the same as just described in reference to the
lines 20 and 22. The circuits may now be traced in order to show that
magnet 1-3 remains neutral, and, therefore, that the circuit closer 911 remains
closed.
The manner in which the magnet 1-3 is electrically connected up is as follows:
Start at the negative pole of the battery 5 and go to the conductor 27, to the
circuit closer 18, to the upper line of 21, to the conductor 34, to the spring
terminal 48', to the spring terminal 47, to the magnet 1-3, to the upper line of 19,
to the circuit closer 18', and back to the negative pole of the battery 5. There-
fore, the magnet 1-3 is included in a conductor closed upon itself without a
battery, and consequently the circuit closer 911 remains closed, and the subscribers
at sub-stations 1 and 3 may continue their conversation.
To show that the subscribers at sub-stations 2 and 4 are properly electrically
and telephonically connected when the relay magnets 15 and 17 are energized, the
circuit closer 12 should be found closed-that is, the magnet 2-4 should be
found neutral. Its circuit may be traced as follows:-Start from the negative
pole of the battery 5, then go to the lower line 6', then to the conductor 26, to the

page_text: circuit closer 18" to the upper line of 20, to the line 39, to the magnet 2-4, to the
spring terminal 47, to the conductor 45, to the spring terminal 48', to the con-
ductor 40, to the upper line of 22, to the circuit closer 181111, to the conductor 28,
and back to the negative pole of the battery 5. Consequently, the magnet 2-4 is
in a conductor closed upon itself without a battery, and the circuit closer 12"
continues to connect electrically the telephones at sub-stations 2 and 4.
It should now be shown how sub-stations 2 and 4 are not connected electrically
to sub-stations 1 and 3. To this end, it will be found that the circuit closers 8¹¹,
10, 11 and 13" are open. It has already been shown that when 1 and 3 are
connected, the magnet 1-2 was energized. It remains energized although the
circuit closer 18" has been connected to the conductor 26. The magnet 1-2
having been energized connects the spring terminal 47 to spring terminal 47', and
spring terminal 48 to spring terminal 48', while the conductors 45 and 46 have
been cut out. The circuit, therefore, is from the positive pole of the battery 5 to
the upper line 6, to the conductor 29, to the conductor 23¹, to the spring
terminal 48, directly across to the spring terminal 48¹, to the conductor 24, to the
upper conductor of lines 20, to the circuit closer 18", to the conductor 26, to the
negative pole of the battery. This circuit just traced does not include the magnet.
The one which includes the magnet is as follows:-From the positive pole of the
battery 5, to the upper line 6 as before, to the conductor 30, to the conductor 24',
to the spring terminal 471 directly across to the spring terminal 47, to the
magnet 1-2, to the conductor 23, to the upper line of 19, to the circuit closer 18¹,
to the conductor 25, to the negative terminal of the same battery 5, and back to
the starting or positive pole of the said battery 5. It will be found that the
magnet 1-4 is in an electric circuit as follows, it being remembered that the
circuit closers 181, 181, 18111 etc. are all moved to the right. Start at the positive
pole of the battery 5 to the upper line 6, to the conductor 32, to the conductor 36¹,
to the spring terminal 47' across to the spring terminal 47 to the magnet 1-4, to
the conductor 35, to the upper line of 19, to the circuit closer 18¹, to the con-
ductor 25, to the lower line 61, and, finally, to the negative pole of the same
battery.
In a similar manner, those versed in the art may find that magnets 2-3
and 3-4 are also energized.
When the parties have finished their conversation they may replace their
telephones 57, either simultaneously, or in any order whatever of time, and yet the
Fystem will become restored to its normal condition exactly as soon as all the
telephones are suspended upon the springs 56.
A modification of the sub-station apparatus is shown in Fig. 2, the purpose
Leing to dispense with the circuit closer 53 and accompanying mechanism and
magnet 49. The exact construction is thus. One sub-station apparatus only is
shown in Fig. 2, but they would all be alike. The generator 7 is in circuit with
the lines 1, 1, and with the bell 61, as before, and to these are added the equal
electric resistances, 76 and 77, between which is a portion of a lever, acting as a
circuit closer 56', normally closed, and held closed against a spring 78 by the
telephone 57. The telephone as before, is in open circuit with the battery 62,
connected across lines 11" above the generator 7 and said resistances. When the
telephone is removed the resistances 76 and 77 are cut out and the battery 62 and
telephone 57 are cut in. If sub-station 1 has rung up sub-station 3, then both parties
remove their telephones, and a battery circuit is closed through magnets 14 and 16
with full strength, accomplishing the same result as by the sub-station apparatus
in Fig. 1; but in view of the resistances 76 and 77, at the other sub-stations, the
magnets 15 and 17 are not energized, because the batteries and resistances are
properly proportioned for this purpose. If it were not for the resistances,
magnets 15 and 17 would also be energized, which is exactly what is not wanted,
as may be known from description of Fig. 1. The same operation occurs if sub-
stations 2 and 4 were connected, and also, if after 1 and 3 are connected, 2 and 4
are to be connected, then will the ringing and cutting in of the telephones occur

page_text: without interfering with or being interfered with by sub-station apparatus at 1
and 3, or with or by any other sub-stations if more than four are in the system.
Signed at New York City, in the County and State of New York, this
Seventh day of November, One thousand eight hundred and ninety-five.
WILLIAM FREDRICK LOUNSBURY.
R. J. Urquhart,
57, Barton Arcade, Manchester, and 5, Clayton Square, Liverpool,
Consulting Engineer and Patent Agent.
Improvements in Automatic Telepon PACH
I, WILLIAM FREDRICK LOUNSBURY of 370 Main Street, Owego, Tioga
County, New York, United States of America, Inventor, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
My invention relates to means for obtaining immediate telephonic communication
between subscribers' stations in pairs.
A brief of the description and operation as preparatory to the detailed specifi-
cation is given as follows:-I provide a central exchange apparatus, which is
connected with any number of sub-stations by respective outgoing and in-coming
main lines. I dispense with all step by step movements, both at the central and at
the sub-stations. Although there is but one line from the central station to each
sub-station and back, yet the connections at the central station are such that any
sub-station whatever is electrically connected normally in closed circuits with each
remaining sub-station. In this normal condition, the system would not be
appropriate for the conversation to be held between more than two sub-stations at
a time, while all the others would have to wait, because if more than two sub-
stations should talk simultaneously with one another, there would be a babel of
tongues. I provide at the central station a circuit closer in a normally closed
circuit with each pair of sub-stations. There is a magnet at each one of these
circuit closers, which is caused to be energized or neutralized, according as to
whether the circuit closers are to be opened or closed. If any two sub-stations are
connected telephonically together by means of my apparatus, they are each
excluded by means of the said circuit closers from each of the remaining sub-
stations; and, further, the latter cannot interrupt either of the communicated
sub-stations, but they can in pairs communicate with each other, all in view of the
proper operation of the said circuit closers. These circuit closers are controlled as
before stated, by magnets, which in turn are magnetized when necessary by means
of a local battery at the central station. The magnets have to be shifted from one
circuit to another, according to predetermined conditions. Normally they are in
respective conductors closed upon themselves without a battery. The object of
this kind of a connection is to permit the cutting in of the local battery and also
to permit the shifting of the magnets from one conductor closed upon itself
without a battery to another conductor closed upon itself without a battery.
These are the three conditions in which more or less of the magnets are placed
When
before, during and after operation of the whole system, or any part of it.
the magnet is shifted, as to its connections, by the connecting up of the two sub-
stations, the shifting is of such a nature, that all the circuit closers which are to be
opened belong to those magnets which are thrown into active circuit with the local.
battery, and all the remaining magnets remain neutral because they are simply
thrown from one conductor, closed upon itself without a battery to another
conductor, closed upon itself without a battery, excepting those magnets belonging
B

page_text: to circuit closers that have no electrical connection with the two sub-stations which
are calling each other.
The means for shifting the magnet from the circuit of the one conductor closed
upon itself, to the circuit of another conductor, closed upon itself, is effected by
means of a pole changer, provided for the circuits of each magnet.
A modification of my invention consists of a simplified sub-station apparatus.
It is found in practice that a certain maximum percentage of the total number
of subscribers are communicated in pairs simultaneously at the busiest part of the
day. The system is of such a nature that there need be but a small proportion
depending upon what this maximum number is of the number of central exchange
devices. If it were at all probable that all the subscribers in a large exchange
should hold simultaneous telephonic communication in pairs, then it would not be
possible to do away with any multiplicity of similar electro-magnetic circuit
controllers at the central station.
On the drawings sent in with the Provisional Specification, to which reference
is made hereinafter,
Figure 1 is a diagram of a complete system, in its simplest form, for the
accommodation of four subscribers.
The invention could not be well illustrated by a figure showing a less number of
subscribers, because it could not be seen easily how two pairs of the subscribers
could be holding communication without interfering with each other.
Figure 2 is a diagram of a modified sub-station apparatus.
The organization of the system comprises three general features.
First, the apparatus, located at the sub-stations, which are indicated in the
drawings by the numerals 1, 2, 3, and 4, and, consequently, the system represented
in Figure accommodates the telephonic intercommunication of four subscribers.
The apparatus at each sub-station may be distinguished from that at the central
station as slightly set apart at the lower part of the drawing, and each sub-station
is connected by two conductors to the central station.
The second general feature comprises the electro-magnetic circuit controllers at
the central station, numbered 1-2, 1-3, 1-4, 2-3, 2-4, 3-4.
As will appear
hereafter, this style of numbering the controllers will conveniently represent to the
eye the nature of their electrical connections with other elements of the system as
a whole.
The third feature involves the circuits classified as follows:-
One set of circuits is made up of the subscribers' main lines. Thus station 1 is
connected to certain parts of certain electro magnetic circuit controllers by the
main line conductors 11 111; sub-station 2 to similar parts of similar devices by
main line conductors 2' 2"; sub-station 3 by main line conductors 31 311; and
sub-station 4 by main line conductors 41 4 The connections between these
subscribers' circuits and certain portions of certain electro-magnetic circuit
controllers are made in various, but pre-determined ways by various connecting
wires arranged in multiple arc, and more fully hereinafter numbered and
explained.
Certain
There is a second set of electric circuits, easily distinguished from the first
because they are what may be termed local circuits at the central exchange. The
main line conductors of the local battery 5 are numbered 6 and 6¹.
connecting conductors between the local main and certain parts of certain
electro-magnetic circuit controllers are arranged and numbered as hereinafter
described.
All that part of the system shewn above the sub-stations 1, 2, 3 and 4 is the
central station.
In the normal condition of the subscribers' circuits, the sub-station apparatus, of
any given sub-station is electrically in circuit with the apparatus of each other
sub-station.
To aid in the understanding, it should be stated here that the generators for
these subscribers' circuits in pormal condition is the hand magneto generator 7.
11

page_text: Now the electric circuits from each sub-station to each other sub-station will be set
forth: The conductor, 8, connects the main line 1', with the main line 2". The
return circuit is 81. A conductor 9, connects the main line 1', with the main
line 3, and the return conductor is 91. The conductor 10, connects the main
line 1 with the main line 4", and the return conductor is 10', and in this way the
apparatus of the sub-station 1 is shown to be in closed circuits respectively with
each of the other sub-stations. The conductor 11, connects the main lines 21, with
the main line 3", and the return conductor is 11. The conductor 12 connects the
main line 21 with the main line 4, and the return conductor is 12. The
conductor 13 connects the main line 31, with the main line 41, and the return
conductor is 13¹.
Each of the connecting conductors, being six in number, is provided with an
electro-magnetic circuit closer, the same being numbered in order 81, 91, 10", 11",
12, and 13. These circuit closers are conveniently the ends of rods, projecting
upwards from the armatures of the electro magnets 1-2, 1-3, 1-4, etc. When
the said electro-magnets are energized, the circuits of the conductors 8, 9", 10", etc.
are opened.
The local circuits will now be set forth. The battery, as before stated, is 5, and
the main line 6 and 6. The relay magnets for throwing this battery into circuit
with the electro magnetic circuit controllers are 14 in main line 11; 15 in main
line 21; 16, in main line 31; and 17, iu main line 41. The main local battery lines
respectively 6 and 6' are provided with supplementary main local lines, which are
adapted to be brought into circuit with the battery 5, by means of armature circuit
closers 18', 18, 18, 18, which, respectively, normally connect the said
supplementary local mains, which are numbered in pairs 19, 20, 21, 22.
It should be stated here, that the relay magnets 14, 15, 16 and 17 are normally
not energized, because the generators 7 are not in operation. The means for
energizing them consists of certain batteries, hereinafter described, located at the
sub-stations. The magnet 1-2, is connected to the lines 19, by conductors 23
and 23', and to the lines 20 by the conductors 24 and 24' through a pole changer,
hereinafter set forth. The path of each of the circuits of the conductors 19, 20.
23, 23, 24 and 24', is such as to be a circuit closed upon itself without a battery,
in view of the two circuit closers 181 and 18", which, as before stated, electrically
connect respectively, the main lines 19 and 20. It should be noted that the
conductors 23 aud 23¹ connect different main lines of 19, and that the conductors 24
and 24', connect correspondingly different main lines of 20. The circuit closers 181
and 1811, when attracted by the respective magnets 14 and 15, move to the right to
the local battery terminals 25 and 26. By this means one of the main lines of 19
and 20 is connected to one pole of the local battery 5. The other one of the mait
lines 19 and 20, are permanently connected by conductors 29 and 30 to the other
pole of the same battery.
Similar connections exist between the other magnets and the various
supplementary main lines. Thus, the magnet 1-3 is connected by conductors 33
and 331, respectively, to the upper and lower main lines 19, and by conductors 34
and 34, respectively to the upper and lower main lines 21, there being, as before.
a pole changer, controlled by the magnet 1-3, included in metallic circuit this
time, with the circuit closers 181 and 1811. When these said circuit closers are
attracted by their magnets 14 and 16, the magnet 1-3 is shifted from one
conductor closed upon itself without a battery to the other conductor closed upon
itself without a battery. It should be remembered that as all the parts cannot be
described simultaneously, the statement of the operation is postponed until later,
but it may be stated here incidentally that when the above circuit closers 18¹
and 18 are simultaneously closed, the above result occurs.
Passing now on to the circuits of the magnet 1-4, it may be stated that the
same is connected respectively to the upper and lower main lines 19 by
conductors 35 and 35, and to the respective upper and lower lines 22 by
conductors 36 and 36', there being included as before, a pole changer, controlled

page_text: by the magnet 1-4, and also circuit closers, as before 18¹ for the lines 19
and 18, for the lines 22.
In order that the description may be complete in detail, it may be stated that
the magnet 2-3, is connected by conductors 37 and 37¹ respectively with the
upper and lower lines of 20 and by conductors 38 and 38¹ respectively with the
upper and lower conductor 21, the circuit being metallically completed through
a pole changer, controlled by magnet 2-3 and by the circuit closers 1811
and 18111.
Similarly, the magnet 2-4 is connected by conductors 39 and 39' respectively
with the upper and lower lines 20, and by conductors 40 and 40', respectively,
with the upper and lower lines 22, through a pole changer controlled by the
magnet 2-4, and through the circuit closers 18 and 18.
Finally the magnet 3-4, is connected by conductors 41 and 41', respectively,
to the upper and lower lines 21, and by conductors 42 and 42', respectively, with
the upper and lower lines 22 through a pole changer controlled by the magnet 3-4,
and through a circuit closer 18111 and 181111
The pole changers of the different magnets are all alike, and, therefore, the
description of one applies to all. Each pole changer has two movable circuit
closers 43 and 44, insulated from each other, and adapted, when attracted by the
controlling magnet, to both depress and close certain spring terminals.
In the
first pole changer, measuring from the left of the first sheet, the circuit closer 43
connects and depresses the terminals of the conductors 23 and 24¹; in the second
pole changer the circuit closer 43 connects and depresses the conductors 33
and 34'; in the third, it connects and depresses the terminals of the conductors 35
and 36; in the fourth the terminals of conductors 37 and 38¹; in the fifth, the
terminals of conductors 39 and 401; and in the sixth, the terminals of the con-
ductors 41 and 42¹. The above closing and depressing takes place when the
several magnets are energized, and at the same time, the circuit closers 44 connect
together in pairs the remaining conductors that connect the magnets 1-2; 1-3,
1-4; etc. to the lines 19, 20, 21, etc.
Normally, the pole changers are so connected by conductors 45 and 46 that in
the first the spring terminal 47 of the conductor 23 is connected to the spring
terminal 481 of the conductor 24; and the spring terminal 48 of the conductor 23¹
is connected to the spring terminal 47¹ of the conductor 24¹. In the second pole
changer, the conductor 45 connects the spring terminal 47 of the terminal 33 with
the spring terminal 48' of the conductor 34; and the conductor 46 connects the
spring terminal 48 of the conductor 33' with the spring terminal 47¹ of the
terminal 34¹. In the third pole changer, the conductor 45 connects the spring
terminal 47 of the conductor 35 with the spring terminal 481 of the conductor 36;
and the conductor 46 connects the spring terminal 48 of the conductor 35 to the
spring terminal 47' of the conductor 36'. In the fourth pole changer, a con-
ductor 45 connects the spring terminal 47 of the conductor 37 to the spring
terminal 48 of the conductor 38; and the conductor 46 connects the spring
terminal 48 of the conductor 37' to the spring terminal 471 of the conductor 38.
In the fifth pole changer, a conductor 45 connects the spring terminal 47 of the
conductor 39 to the spring terminal 48¹ of the terminal 40; and the conductor 46
connects the spring terminal 48 of the conductor 39¹ to the spring terminal 471 of
the conductor 40'. In the sixth pole changer, a conductor 45 connects the spring
terminal 47 of the conductor 41 to the spring terminal 481 of the conductor 42;
and the conductor 46 connects the spring terminal 48 of the conductor 41¹ to the
spring terminal 47' of the conductor 421.
The different spring terminals 47 and 48 and 47¹ and 48¹ are so arranged that
when depressed by the circuit closers 43 and 44, they are entirely moved out of
contact with the conductors 45 and 46, thereby producing differences in the manner
of connecting up the circuits.
As a part of the construction and the normal condition of the system, it should
be stated that the magnets 1-2; 1—3; 1-4; etc. are so connected that they are

page_text: in the circuit of conductors, closed upon themselves, exclusively of a battery, so
that although they are in the circuit of closed conductors, they are not magnetized.
In order to show this by reference to the drawings, it may be noticed in regard to
the magnet 1-2 that its terminal conductors 23 and 24 are connected to the
respective upper lines of 19 and 20, and that those upper lines are connected to a
common pole of the battery 5, respectively, through the circuit closers 181 and 18",
the conductors 29 and 30, and finally to the positive pole of the battery 5. In
order to illustrate this further, and to show that there is no confusion in the system,
it may be noticed that the terminal conductors 33 and 34 of the magnet 1-3, are-
connected to the respective upper lines of 19 and 21, and that these, by apparent
connections, are connected to but one pole of the battery, namely, the positive pole.
In regard to magnet 1-4, its terminal conductors 35 and 36 are connected also to
the respective upper lines of 19 and 22, which are connected to the positive pole of
the battery. Similarly the magnet 2-3 is connected to the positive pole of the
battery, as may be seen by noticing the conductors 37 and 38, the upper lines
of 20 and 21 and the electrical connections between the positive pole of the battery
and said upper lines. The circuit of the conductor which includes the magnet 2-4
is as follows: Begin at the positive pole of the battery; go to the line 6, then to
the conductor 30, to the circuit closer 18", to the conductor 39, through the pole
changer to the conductor 40, to the upper line of 22, to the circuit closer 1811, to the
conductor 32, and back again to the conductor 6 and to the positive pole. The
connections of the magnet 3-4 are of exactly the same nature.
Without taking into account at present the nature of the sub-stations, it may be
stated generally that when, for example, the subscribers of the stations one and
three are actually holding communication, the relay magnets 14 and 16 are
energized, the action taking place simultaneously so that the circuit closers 18'
and 1811 are thrown to the right hand terminals 25 and 27 respectively. In this
manner, the magnet 1-3 will exist in a conductor closed upon itself, but in a
different one from formerly. This may be traced out as follows:-The terminal
conductors 33 and 34 become connected through the conductors 25 and 27 both to
the negative pole or line 61. In this manner stations 1 and 3 are kept in circuit
through the circuit closer 911. At the same time, the circuit closers 81, 10, 11,
and 131, become opened for the following reasons:-Take first circuit closer 811.
As circuit closer 1811 remains in its normal condition while the circuit closer 18¹ is
moved to the right, it follows that the terminal conductor 23 becomes connected
to the negative pole while the terminal conductor 24 remains connected to the
positive pole; consequently, there is a current from the local battery passing
through the magnet 1-2, causing it to operate its armature and open the circuit
at the circuit closer 81. No attention need now be paid to the pole changer,
because the function of this comes into play when two other subscribers wish to
hold communication without waiting for subscribers 1 and 3 to stop talking, and,
at the same time, without interrupting or being interrupted by them. The circuit
closer 101 becomes opened for the following reasons. The terminal conductor 35.
becomes connected to the negative pole, because the circuit closer 181 has been put
into connection with the conductor 25, while the terminal conductor 36 remains
connected to the positive pole of the battery because the circuit closer 181111 remains.
in its normal position.
The circuit closer 11" becomes opened because the terminal conductor 37
remaius in connection with the positive pole of the battery because the circuit
closer 18 is in its normal position while the terminal conductor 38 becomes
connected with the negative terminal of the local battery 5. The circuit
closer 13" becomes open because the terminal conductor 41 is connected to the
negative pole of the battery because of the abnormal condition of the circuit
closer 181; while the terminal conductor 42 remains connected with the positive
pole.
The first thing that becomes necessary to understand about the sub-station
apparatus is the mechanical construction without regard to its relation to the

page_text: central station apparatus. As before stated, 7 represents the hand magneto
machine; 49 represents a magnet; 50 a wheel, prevented from rotating in the
direction of the arrow by being provided with a projection 51, pressing against the
end of an armature spring 52 belonging to the magnet 49. The wheel carries a
rotary circuit closer 53, adapted to maintain the circuit closed during a part of its
rotation and to keep the circuit open during the remainder of the rotation. The
wheel 50 is supposed to be wound up against the action of a spring 54, which
serves also as an electric connector to the circuit closer 53. The wheel 50 when
released by the spring armature is caused to rotate slowly and practically uniformly,
by means of the resistance or fan wheel 55. There is a spring lever 56 held down
by the weight of the telephone 57. The spring 56 carries three insulated
contacts 58, 59 and 60. The circuits at the sub-stations are connected up as
follows: Passing from the main line 11, the circuit is normally closed through
the generator 7; and electric bell 61, contact 59, magnet 49, circuit closer 53,
spring 54, and then to the main line 11. There is a branch circuit to the circuit
just described and normally open, and passing through a battery 62 to the
contact 58, where it is normally open, to the magnet 49, to the circuit closer 53, to
the spring 54, and then to the main line 1". There is another normally open
branch circuit, the same being from the main line 11, through the battery 62; the
contact 58 adapted to be closed with the contact 60 when the telephone is removed;
then through the telephone 57 and then to the main line 111.
Having now set forth the construction of the system I will state the operation
by assuming, first, that station 1 is to call and hold communication with station 3,
and that while their telephones are in circuit, I will give the second step by
showing how two other stations may hold telephonic eommunication without
interfering or being interfered with that between stations 1 and 3. The other two
stations, of course, will be 2 and 4, but what holds true with reference to the four
sub-stations will hold true for a system built for any number of sub-stations.
Say that station 1 wishes to call and hold conversation with station 3. 1 operates
the generator 7, by a certain number of turns agreed upon by stations 1 and 3.
The same signal will be received at sub-stations 2 and 4, but they have agreed not
to pay any attention to that signal. The current generated by the generator 7 at
sub-station 1 energizes all the magnets 49 which move all the wheels 50. As it
takes a little time for the signal to be given the circuit is maintained during a
portion of the revolution of the circuit closers 53 until the parts thereof, marked in
black move in contact with the terminals of the magnets 49. Simultaneously with
the operation of the generator 7, the bells 61, ring, in fact, these are call bells, and
they ring for a certain interval of time, and until the right parties are summoned
or called and perhaps until the circuits are interrupted at the circuit closers 53.
The instructions given to the subscribers are such that when any one of them hears
his call, he must, during the time that the circuit closers 53 are open, take off his
particular telephone 57. So must also the calling subscriber. He may take off
his telephone as soon as the circuit closers 53 are open. By the operation of
removing the telephones at sub-stations 1 and 3, and while the circuit is broken at
the circuit closers 53, the batteries 62 at these two sub-stations only are thrown
into circuit with the lines 11, 11, 31, and 3", thereby energizing the relay magnets 14
and 16. This closed battery circuit may be traced as follows:-Beginning at the
positive pole of the battery 62 at the sub-station 1, pass through the generator 7,
which is now quiet, to the main line 11, to relay magnet 14, to conductor 9, through
circuit closer 9, to line 31, to both the telephones by way of contact 60 and to
contact 58, both of the contacts being closed against the arrows, to the negative
pole of the battery 62, of sub-station 3 to the positive pole, to the generator 7, now
at rest, to the line 3', to the relay magnet 16, to the connecting line 9¹, to the main
line 11, and, finally, through the following elements of sub-station 1, namely, the
telephone 57, the contact 60, the contact 58, by way of the two arrows just above
them which are now closed, to the negative pole of the battery 62, and, finally, to
the starting point, the positive pole of the same battery.

page_text: It will be noticed, therefore, that if a subscriber at sub-station 3 as well as the
subscriber at sub-station 1 takes off his telephone while the circuit closers 53 at all
the stations are open, a battery circuit will send a current for energizing the relay
magnets 14 and 16.
If the subscriber at sub-station 3 does not take off his telephone 57, before his
circuit closer 53 has become again closed, the instructions are that the subscriber
at station 1 should call sub-station 3 again just as soon as the former's circuit
closer 53 has become closed. By showing the reason of the necessity of ringing
subscriber 3 up again, the invention and its operation will be more positively under-
stood. If the subscriber at sub-station 3 does not take off his telephone while the
circuit closer 53 is open, then will not his battery 62 be in circuit, but battery 62
at sub-station I will be in circuit. The consequence of this is that the only relay
magnet which becomes energized is 14, and it becomes energized only intermittently
for the following reason:-It operates upon the circuit closers 811, 9 and 10, like
an ordinary vibrating electric bell. When the magnet 14 attracts the circuit
closer 18', a circuit is formed through the magnet 1-2, 1-3, and 1-4, causing
them to open the circuit closers 811, 911, and 101, and, therefore, the circuit of the
relay magnet 14 becomes open, and theu closed again, and so on. Therefore, all
the subscriber at sub-station 1 can do if he gets no answer from the subscriber
at sub-station 3 before the complete rotation of the wheel 50, is to ring up.
again.
On the other hand, just as soon as the subscriber at sub-station 3 removes his
telephone, he is in instantaneous communication with the subscriber at sub-station 1,
provided only that he and subscriber at sub-station 1 remove their telephones before
the closing of the circuit closers 53. The system is, therefore, what may appro-
priately be termed a system of instantaneous intercommunication.
The system is, further, of such a uature, that it is not necessary for the circuit
closers 53 to be accurately synchronous in their operation. They are so propor-
tioned that they require a little time, say about a minute or two, or any other
period desired, for making a complete rotation. It is evident that they will all
start off at the same time, and it is true that whether they are synchronous or
not it is only necessary for the called subscriber to remove his telephone before
the circuit closers 53, at sub-stations 1, 2 and 4 become closed. It is evident that
if the circuit closers 53 start to rotate at the same time they may be sufficiently
accurately constructed to stop roughly at about the same time.
The subscriber at sub-station 1 may now hold communication with the subscriber at
sub-station and they may continue to do so as long as they please, and without
interruption, in view of the pole changers.
It will now be shown how sub-stations 2 and 4 may be telephonically connected
without interfering with the communication between sub-stations 1 and 3, and
without being interfered with by then. The subscribers at sub-stations 2 and 4 go
through the same operation as related regarding the other two subscribers.
Consequently, the relay magnets 15 and 17 become energized, and the circuit
closers 18 and 1811 become attracted and connect the upper lines of 20 and 22 to
the negative pole of the battery 5, while the lower lines of 20 and 22 remain
connected with the positive pole. The connections of the lines 19 and 21 have been
changed so as to become the same as just described in reference to the lines 20
and 22. The circuits may now be traced in order to show that magnet 1-3
remains neutral, and, therefore, that the circuit closer 9" remains closed.
;
"
The manner in which the magnet 1-3 is electrically connected up is as follows:
Start at the negative pole of the battery 5 and go to the conductor 27, to the
circuit closer 18, to the upper line of 21, to the conductor 34, to the spring
terminal 481, to the spring terminal 47, to the magnet 1-3, to the upper line of 19,
to the circuit closer 181, and back to the negative pole of the battery 5. Therefore,
the magnet 1-3 is included in a conductor closed upon itself without a battery, and
consequently the circuit closer 911 remains closed, and the subscribers at sub-
stations 1 and 3 may continue their conversation.

page_text: To show that the subscribers at sub-stations 2 and 4 are properly electrically and
telephonically connected when the relay magnets 15 and 17 are energized, the circuit
closer 12 should be found closed that is, the magnet 2-4 should be found neutral.
Its circuit may be traced as follows:-Start from the negative pole of the battery 5,
then go to the lower line 6', then to the conductor 26, to the circuit closer 18 to
the upper line of 20, to the line 39, to the magnet 2-4, to the spring terminal 47',
to the conductor 45, to the spring terminal 481, to the conductor 40, to the upper
line of 22, to the circuit closer 181111, to the conductor 28, and back to the negative
pole of the battery 5. Consequently, the magnet 2-4 is in a conductor closed
upon itself without a battery, and the circuit closer 12" continues to connect
electrically the telephones at sub-stations 2 and 4.
It should now be shown how sub-stations 2 and 4 are not connected electrically to
sub-stations 1 and 3. To this end, it will be found that the circuit closers 811, 10",
11 and 13 are open.
It bas already been shown that when 1 and 3 are connected, the magnet 1-2
was energized. It remains energized although the circuit closer 1811 has been
connected to the conductor 26. The magnet 1-2 having been energized connects
the spring terminal 47 to spring terminal 471, and spring terminal 48 to spring
terminal 48', while the conductors 45 and 46 have been cut out. The circuit, there-
fore, is from the positive pole of the battery 5 to the upper line 6, to the
conductor 29, to the conductor 231 to the spring terminal 48, directly across to
the spring terminal 48¹ to the conductor 24, to the upper conductor of lines 20,
to the circuit closer 18", to the conductor 26, to the negative pole of the battery.
This circuit just traced does not include the magnet. The one which includes the
magnet is as follows:-From the positive pole of the battery 5, to the upper line 6
as before, to the conductor 30, to the conductor 24 to the spring terminal 47'
directly across to the spring terminal 47, to the magnet 1-2, to the conductor 23,
to the upper line of 19, to the circuit closer 181, to the conductor 25, to the
negative terminal of the same battery 5, and back to the starting or positive pole
of the said battery 5. It will be found that the magnet 1-4 is in an electric
circuit as follows, it being remembered that the circuit closers 181, 181, 18111 etc.
are all moved to the right. Start at the positive pole of the battery 5 to the upper
line 6, to the conductor 32, to the conductor 36', to the spring terminal 47¹ across
to the spring terminal 47 to the magnet 1-4, to the conductor 35, to the upper line
of 19, to the circuit closer 181, to the conductor 25, to the lower line 6', and, finally,
to the negative pole of the same battery.
In a similar manner, those versed in the art may find that magnets 2-3 and 3-4
are also energized.
When the parties have finished their conversation they may replace their tele-
phones 57, either simultaneously, or in any order whatever of time, and yet the
system will become restored to its normal condition exactly as soon as all the
telephones are suspended upon the springs 56.
A modification of the sub-station apparatus is shown in Fig. 2, the purpose being
to dispense with the circuit closer 53 and accompanying mechanism and magnet 49.
The exact construction is thus. One sub-station apparatus only is shown in Fig. 2,
but they would all be alike. The generator 7 is in the circuit with the line 11, 1",
and with the bell 61, as before, and to these are added the equal electric
resistances, 76 and 77, between which is a portion of a lever, acting as a circuit
closer 56', normally closed, and held closed against a spring 78 by the telephone 57.
The telephone as before, is in open circuit with the battery 62, connected across
lines above the generator 7 and said resistances. When the telephone is
removed the resistances 76 and 77 are cut out and the battery 62 and telephone 57
are cut in. If sub-station 1 has rung up sub-station 3, then both parties remove
their telephones, and a battery circuit is closed through magnets 14 and 16 with
full strength, accomplishing the same result as by the sub-station apparatus in
Fig. 1; but in view of the resistances 76 and 77, at the other sub-stations, the
magnets 15 and 17 are not energized, because the batteries and resistances are

page_text: properly proportioned for this purpose. If it were not for the resistances,
magnets 15 and 17 would also be energized, which is exactly what is not wanted,
as may be known from description of Fig. 1. The same operation occurs if sub-
stations 2 and 4 were connected, and also, if after 1 and 3 are connected, 2 and 4
are to be connected, then will the ring and cutting in of the telephones occur
without interfering with or being interfered with by sub-station apparatus at 1
and 3, or with or by any other sub-stations if more than four are in the system.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim as the invention is,-
1. An automatic telephone exchange system, consisting of the combination of a
given number of telephones located at respective sub-stations, independent electric
conductors connecting each telephone with all the other telephones respectively, a
circuit closer in circuit with each of the said conductors, and means located at the
central station governed by devices located at the sub-stations for controlling said
circuit closers in a predetermined manner.
2. An automatic telephone exchange system, consisting of the combination of a
given number of telephones, located at respective sub-stations, independent electric
conductors connecting each telephone with all the other telephones, respectively, a
circuit closer in circuit with each of the said conductors, a magnet for each circuit
closer, a given electric generator, a pair of electric conductors closed upon itself
for each magnet, one of the conductors normally including the magnet in each case,
and means for changing for the purpose set forth, some of the magnets, each from
one conductor closed upon itself to the other conductor closed upon itself, and for
including in circuit with the said generator some of the said conductors in pairs and
in series with each other.
3. An automatic telephone exchange system, consisting of the combination of a
given number of telephones, located at respective sub-stations, independent electric
conductors connecting each telephone with all the other telephones, respectively, a
circuit closer in circuit with each of the said conductors, a magnet for each circuit
closer, a given electric generator, a pair of electric conductors closed each upon
itself for each magnet, one of the conductors normally including the magnet in
each case, and means for changing for the purpose set forth, some of the magnets
each from one conductor closed upon itself to the other conductor closed upon
itself, and for including in circuit with the said generator some of the said
conductors in pairs and in series circuit with each other, said means consisting of
electro-magnetic switches, whose magnets are in circuit with given sub-station
generators, and whose switches are normally included both in circuit with groups
of said pairs of conductors and in open circuit with said first named generator.
4. An automatic telephone exchange system, consisting of the combination of a
given number of telephones, located at respective sub-stations, independent electric
conductors, connecting each telephone with all the other telephones, respectively, a
circuit closer in circuit with each of the said conductors, a magnet for each circuit
closer, a given electric generator, 5, a pair of electric conductors for each magnet
closed respectively upon themselves, one of the conductors normally including one
of said magnets, electro-magnetic switches whose magnets 14, 15, 16, &c., are ia
circuit with given sub-station generators 7, and whose switches are normally
included both in circuit with groups of said pairs of conductors, and in open
circuit with generator, signals at the sub-stations in closed circuit with the
generators 7, generators 62 in open circuit with generators 7, and including
circuit closers for opening the circuits of the generators 7 for a predetermined
period, and means both for closing the circuits of the generators 62, through the
magnets 14, 15, 16, &c., and for opening the circuits of generators 7.
5. An automatic telephone exchange system, consisting of the combination of a
given number of telephones located at respective sub-stations, independent electric
conductors connecting each telephone with all the other telephones respectively, a

page_text: circuit closer in circuit with each of the said conductors, and means located at the
central station, governed by devices located at the sub-stations for controlling said
circuit closers in a predetermined manner, said devices consisting of resistances and
generators normally in closed circuits with said circuit closers, and batteries normally
in an open circuit with said circuit closers and said telephones, and a switch 56' for 5
cutting out the said generators and said resistances, and for cutting in the said
batteries and telephones.
Dated this 17th day of August 1906
R. J. URQUHART,
57, Barton Arcade, Manchester, 5, Clayton Square, Liverpool,
Consulting Engineer and Patent Agent.