An Improvement in Telephone Systems.
Year: 1899

page_text: Date of Application, 23rd Mar., 1899-Accepted, 15th July,
1899
COMPLETE SPECIFICATION.
An Improvement in Telephone Systems.
I, JAMES C. SLATER, of 32, South Channing Avenue, in the City of St. Louis
and State of Missouri, United States of America, Electrician, 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 object is to construct a telephone system having an automatic exchange
and my invention consists of a switchboard having a switch for each telephone in
the system; an electro-magnet for each switch; mechanism for euch switch
whereby the electro-magnets operate the switches; a series of contact points for
each switch equal to the number of the other switches, each switch being numbered
and having a correspondingly numbered contact point upon each of the other
switches; telephones at outlying stations, one for each switch and correspondingly
numbered; a circuit breaker at each telephone; a battery at each telephone; a
set of electric conductors running one from each telephone receiver hook to the
electro-magnet of the corresponding switch, then back through the battery and
circuit breaker to the receiver hook, said circuit breakers being normally open
as required to keep the energy of the batteries from the telephones and wires when
not in use; a second conductor leading from each battery through the telephone
transmitter, and through the primary of the induction coils to the receiver hook;
means of operating said circuit breakers; and a third conductor connecting all the
telephones together; said third conductor having branches passing through the
secondaries of the induction coils and through the receivers and serving as a
return for the talking circuits established by the operations of the switches; and
my invention consists further of the details of construction herein shown, de-
scribed and claimed.
One of the great advantages of my system is due to the fact, that it is impossible
for a third party to hear a conversation going on between two other stations with-
out deliberately cutting in and thereby making his act known. The system is
simple and inexpensive in construction and positive in its action, and there may
be as many talking circuits in operation at one time as there are pairs of telephones.
Another great advantage lies in the fact that the wires are normally de-energized
by the open circuit breakers, thus preserving the batteries, protecting the tele-
phones and other mechanism and preventing short circuiting, etc., there being no
source of electrical energy at the central station the switchboard cannot become
disarranged by short circuiting during the time that the telephones are out of use.
Fig. I is a diagram illustrating my improved telephone system, and drawn for
the purpose of showing the line wires. Fig. II is a detail diagram of a telephone
and circuit breaker drawn for the purpose of showing the electrical connections.
Fig. III is a diagram of the switchboard, showing the electrical connections.
Figs. IV to VII show the details of the circuit breaker and mechanism for
operating the same. Fig. IV is a front elevation, taken looking in the direction
indicated by the arrow IV in Fig. V. Fig. V, is a side elevation taken looking
in the direction indicated by the arrow V in Fig. VI or in the same direction in
Fig. IV. Fig. VI is a view taken looking in the direction indicated by the arrow

page_text: on the line VI-VI in Fig. V. Fig. VII is a view in elevation of the circuit
breaker with the operating mechanism omitted. Fig. VIII is a front elevation of a
switch. Fig. LX is a side elevation taken looking in the direction indicated by
the arrow IX in Fig. VIII, showing the electro-magnets and the mechanism for
operating the switch. Fig. X is a rear elevation taken looking in the direction
indicated by the arrow X in Fig. IX. Fig. XI is a detail perspective of the
escapement lever and Fig. XII is a perspective of the escapement wheel.
Referring in detail to the drawings, I have shown a telephone system in which
there are nine telephones numbered T¹, T³, T³, T4, T5, T6, T7, T8, and T. The
switchboard has nine switches numbered S1, S2, S³, 8, 85, 8, S7, S8, and S° to
correspond to the numbering of the telephones. There is an electro-magnet 10
for each switch; and clock works 11, controlled by the electro-magnets, operate
the switches. Each switch has a series of contact points numbered 1, 2, 3, 4, 5,
6, 7, 8, and 9, to correspond to the numbers of the telephones. The electric con-
ductors numbered C, C, C, 0, 0, 0, 07, C, and C, run from the respective
telephones to the respective binding posts P1, P2, P³, P², P³, 1º, P7, P8 and P,
and the wires numbered R, R2, R³, R, R5, R, R7, R and R, run from the
respective binding posts RP, RP, R P³, RP, R P³, R P, RP, R P8, and R P⁹
to the respective telephones. The line wire 12 has branches connecting it to each
of the telephones. The wire 12 is connected to the right hand binding post 13 of
each telephone. The conductors C', 0, 0, 0, 0, 0, 0, 0, and are con-
nected to the binding posts 15 of each telephone and the wires R, R³, R³ ³,
R³, R, R, Rs, and I are connected to the binding posts 14 of each telephone.
Each telephone is wired as shown in detail in Fig. II. The three cell
batteries 16 are connected in a series and the wire 17 runs from the positive pole
of the last cell to the pivot screw of the receiver hook 18 and then to the binding
post 14. The wire 19 runs from the negative pole of the first cell to the screw 20
of the circuit breaker, thus making a connection with the contact spring 21, and
the wire 22 runs from the binding post 15 to the toothed contact wheel 23. The
spring 21 is normally out of contact with the wheel 23.
The wiring of the switchboard is shown in detail in Fig. III. The binding
posts P¹, to 1 and R P to R P inclusive are attached to the board or wall 24.
The board wires B', B², 13³, B', 13³, B6, B7, B8, and B run from the respective
binding posts 1" to 1" inclusive to the binding posts 25 of the respective switch
mechanisms then through the magnets 10, and then to the binding posts 26. The
return board wires RB, RB, RB³, RB, RB, RB, RB, RB, and RB, run
from the respective binding posts RP to R1 respectively to the respective
binding posts 26 thus completing the calling circuits.
The contact point wires CP", CP, CP³, CP, CP³, CP, CP, CP³, and CP
make conductors from the respective switches through the binding posts 26 to
the correspondingly numbered contact points of each of the other switches. The
wires RB to RB respectively connect with the wires CB to CB39 respectively
at or near the binding posts 26. There is a contact point numbered 0 for each
switch and it is not in any circuit. The contact point of each switch correspond-
ing to its number is not in any circuit. These contact points serve as indicators and
to stop the switches at their regular intervals. The wire 12 does not, or need
not, run to the switchboard.
The details of the mechanism for operating the circuit breaker are shown in
Figs. IV to VII. The front wall 27 of the telephone box is used to support this
mechanism. The feet 28 are secured to the wall 27 and the back frame 29 is
secured to the feet. Posts 30 extend forwardly from the frame 29 and the front
frame 31 is secured to the forward ends of these posts. Posts 32 extend for-
wardly from the front frame and a disk 33 is attached to the forward ends of these
posts. Posts 34 extend forwardly from the disk 33 and the disk 35 is attached to
the forward ends of these posts.
A clock spring and casing 36 is mounted upon the shaft 37 between the frames 29
and 31, said shaft extending through the disk 33 and having a square head to

page_text: receive a clock key which is inserted through the key hole 38 in the disc 35. A
clock gear 39 is loosely mounted upon the shaft 37 and carries a pawl 40 which
engages the ratchet wheel 41 fixed upon the shaft, as required to allow the spring
to be wound up without rotating the gear and communicating the power of the
spring to the gear. A second shaft 42 is mounted in the frames and extends
forwardly through the disk 33 and a pointer 43 is fixed upon the forward end of
said shaft. A pinion 44 and a gear 45 are fixed upon the shaft 42, said pinion
meshing with the gear 39. A third shaft 46 is mounted in the frames and a
pinion 47 and a gear 48 are fixed upon this shaft, said pinion meshing with the
gear 45. The contact wheel 23 is also fixed upon the shaft 46. A fourth shaft 49
is mounted in the frames and a pinion 50 and a gear 51 are fixed upon this shaft,
said pinion meshing with the gear 48. A fifth shaft 52 is mounted in the frames.
and carries a pinion 53 meshing with the gear 51. A fan 54 is fixed upon the
shaft 52, to serve as a speed regulator for the clock work. A bar 55 of insulating
material is secured to the back frame with one of its ends near to the contact
wheel 23. The contact spring 21 is secured to the bar 55 by means of the screw 20
inserted into the opposite end of the bar from the contact wheel. The free end of
the spring is in position to yieldingly engage the teeth of the contact wheel, when
the wheel rotates and when the wheel is at rest the contact is broken. The wire 22
is attached to one of the feet 28 and the circuit passes through the frame work to
the contact wheel. The wire 19 is connected to the spring 21 by the screw 20 and
is insulated from the clock work by the bar 55.
The disks 33 and 35 have a series of perforations 56 arranged in a circle con-
centric to the shaft 42, said perforations being numbered 0, 1, 2, 3, etc., to corre-
spond to the numbers of the telephones, the switches, etc., and the perforations of
the rear disk being in alinement with the corresponding perforations of the front
disk. There are more numbers upon the circuit breaker than there are telephones,
as required by the addition of more telephones to the system, until the system is
full.
The stop pin 57 operates in the holes marked 0 in position to arrest the move-
ment of the pointer 43. When it is desired to call a certain telephone a removable
pin 58 is inserted into the hole corresponding to the number of that telephone, and
the pin 57 is partially withdrawn until the pointer is released, and then the clock
work moves the pointer until it is arrested by the removable pin, and the movement
of the clock work makes and breaks the circuit by the operation of the contact
wheel 23 against the spring 21. A spring pawl 59 is attached to one of the posts 30
and its free end engages the teeth of the gear 48 as required to prevent any back-
ward motion of said gear.
The details of a switch operating mechanism are shown in Figs. VIII to XII.
Each switch is mounted upon a square flat block 60 of insulating material. I will
assume that the switch shown is for telephone No. 1. The binding posts
numbered 0, 1, 2, 3, etc., corresponding to the numbers of the telephones are
arranged in a circle and project forwardly from the block 60. The posts 61 project
backwardly from the block 60 and the front frame 62 and the rear frame 63 are
supported by said posts in positions parallel with the block 60. The clock spring 64
has its outer end attached to one of the posts 61, and its inner end attached to the
shaft 65 which is mounted in the frames 62 and 63. The gear 66 is mounted
loosely upon the shaft 65, and the pawl 67 carried by the gear engages the
ratchet wheel 68 fixed upon the shaft. as required to communicate the power of
the spring to the gear. A second shaft 69 is mounted parallel with the shaft 65,
and the pinion 70 and gear 71 are. fixed upon this shaft, said pinion meshing with
the gear 66. A third shaft 72 is mounted in the frames and extends through the
block and carries the switch S' on its forward end, said shaft being located at the
center of the circle described by the binding posts 72, forming the contact
points 0, 1, 2, 3, etc. A gear 73 is fixed upon the shaft 72 and a pinion 74 is
fixed upon the shaft and meshes with the gear 71. A fourth shaft 75 carries

page_text: the escapement wheel 77, said escapement wheel consisting of a disk 78 and arms 79
projecting from the periphery of said disk in line parallel with the shaft.
The switch S¹ consists of a bar 80 fixed upon the shaft and a contacting spring 81
projecting outwardly from the outer end of said bar and yieldingly engaging the
contact points 0, 1, 2, 3, etc., and said contact points are also binding posts. A
screw threaded post 82 projects upwardly from the cross bar 83 of the electro-
magnet 10, between the pair of pins 84 extending horizontally from one frame
to the other. A nut 85 is placed upon the post 82 below the pins 84 and a similar
nut 86 is placed upon the post above the pins, thus holding the magnet adjust-
ably in position. The escapement lever 87 is connected at one end to the shaft 88
which serves as a pivot, said lever occupying a horizontal position below the
magnet, and its free end operating in conjunction with the escapement wheel.
The magnet armature 89 is fixed upon the lever 87 in position to be operated by
the magnet. The free end of the escapement lever is split horizontally thus form-
ing the arms 90 and 91, said arms being turned backwardly and the upper one of
said arms being nearer to the pivot than the other, and said arms engaging the
arms of the escapement wheel. There are stops to limit the up and down move-
ment of the armature lever, and the spring 92 withdraws the aimature from the
magnet. When the armature is elevated one of the arms of the escapement wheel
passes under the upper one of the lever arms and strikes the lower one of said
lever arms and when the armature is again lowered this escapement arm passes
upwardly over the lever arm and is released thus producing a step-by-step motion,
the clock work operating the escapement wheel and the magnet operating the
escapement lever. The switch is operated by the clock work and the magnet is
operated by the circuit breaker.
The block 60 is secured in position upon the base 92 by means of the brackets 93
and 94. The shaft 65 has a square head to receive a clock key to wind the spring.
Referring again to the wiring shown in Fig. II, the induction coil is indicated
by 95, the primary being marked P and the secondary being marked S. The
generator is indicated by 96, the transmitter by 97, the bell by 98, the receiver
by 99, and the push button of the generator by 100. Supposing that the receiver
is on the hook, the desired telephones have been connected and it is desired to ring
the bell. The push button 100 is pressed inwardly and the generator operated.
The electrical impulses pass from the generator through the push button rod 101,
over the wire 102 and the spring 103. through the receiver hook 18, then over
the wire 17 to the post 14, then over the wire R and its connections to the bell
of the called telephone, then over the wire 12 back to the post 13 of the calling
telephone, then to the bell of the calling telephone over the wires 104 and 105, and
then from the bell to the generator over the wire 106, thus completing the bell
circuit. The bell circuit of the called telephone passes around its generator over
the wire 107. The circuit over the wire 107 in the calling telephone is broken
by the operation of the push button pressing the spring 108 away from the contact
point 109 to which the wire 107 is attached.
After the bells have been rung and the push button is released, the talking circuit
is ready for use. The transmitter is in a circuit running from one pole of the
third battery cell over the wire 110 to the transmitter, then over the wire 111 to
and through the primary of the induction coil, then over the wire 112 to the
spring 113, to and through the receiver hook and then over the wire 17 back to the
opposite pole of the battery cell from which it started.
The receiver is in a circuit running from the post 13 over the wire 114 through
the receiver, then over the wire 115 to the spring 116, then through the hook to
the wire 17 and then to the post 14.
The operation of my telephone system is as follows:
A person goes to telephone No. 4 and desires to communicate with a person at
telephone No. 8. He places the pin 58 in the perforation No. 3 in the disk 35
and then partially withdraws the pin 57 and releases the pointer 43. The clock
work moves the pointer until it strikes the pin 58, and while the pointer is thus

page_text: moving, the teeth of the wheel 23 engage the free end of the spring 21, thus
making and breaking the circuit through the magnet 10 of the switch mechanism
belonging to the telephone No. 4. The operation of the magnet 10 operates the
escapement mechanism thereby releasing the clock work connected to the switch
and moving the switch to the contact point, 3. The caller then presses the push
button 100 and operates his generator, thereby ringing the bell of the telephone on
which he wishes to communicate, which in this instance is No. 3. The person
hearing the bell goes to telephone No. 3, the push button 100 is released and
communication is established between the two telephones; in this instance No. 4
is the calling telephone and No. 3 is the called telephone. In the first place, the
calling circuit of telephone No. 4 runs from its batteries through the wire 17 to
the post 26 of switch mechanism No. 4, then through the magnet 10 to the post 25,
then over the wire B to the post P', then over the wire C to the post 15, then
over the wire 22 to the contact wheel 23, then to the spring 21 and over the
wire 19 to the battery. As soon as the call is completed by the pointer 43 engag-
ing the pin 58, the caller presses the push button 100 and operates his generator,
thus ringing the bell of the called telephone. The bell circuit passes through
the telephones as heretofore described and from the post 14 passes over the wire R
to the post RP, then over the wire RB, to the post 20 of switch mechanism No. 4,
then to the switch St, then to contact point 3, then over the wire CP³ to the post 26
of switch mechanism No. 3, then over the wire RB3 to the post R P³, then over the
wire R to the post 14 of telephone No. 3, then through the telephone as hereto-
fore described to the post 13 of said telephone No. 3, then over the wire 12 to the
post 13 of the calling telephone No. 4, and then through the calling telephone.
As soon as the bell has been rung and answered, talking communication is
established over the same line wires as the bell circuit and through
the telephones as heretofore described. Thus it will be seen that the
wires R, R, R, etc., are in constant use when the telephones are in operation,
whereas the wires C¹, C, C³, etc., are only in use when the circuit breaker is in
operation, thereby operating the magnets and controlling the switches. All of
the circuits are all metallic.
Suppose that while telephone No. 4 is in communication with telephone No. 3,
a person goes to telephone No. 7 and desires to communicate with the tele-
phone No. 2. The operation is exactly the same as that already described, and, in
the same manner, communication may be established between telephone No. 9 and
telephone No. 5, or between any other two telephones not already in use, there
being no possibility of the circuits being crossed, unless a person deliberately
cuts his telephone into the circuit already in use, as would be the case if a person
called either No. 4 or No. 3 while communication was going on between No. 4
and No. 3.
Having now particularly described and ascertained the nature of this said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. A telephone system consisting of a switchboard having a switch for each
telephone in the system; electrically controlled mechanism for each switch for
operating the switch, said mechanism being controlled from the telephone to which
the switch belongs; telephones at outlying stations, one to a switch, said switches
and said telephones being correspondingly numbered; an electric conductor run-
ning from the frame of each telephone to its switch operating mechanism and
back to the frame; a series of contact points for each switch and in position to be
engaged by the switch, there being one contact point for each of the other
switches in the system; a second set of conductors running one from each switch
to each of the correspondingly numbered contact points of the other switches;
a set of circuit breakers, one at each telephone for each of said first mentioned
conductors; means located at the telephones of supplying electrical energy to the
circuits; mechanical means of operating and controlling the circuit breakers;

page_text: and a conductor connecting the telephones together and serving as a return wire
for talking circuits established by the operation of the switches, substantially as
specified.
a
2. A telephone system consisting of a switchboard having a switch for each
telephone in the system; and electro-magnet for each switch; mechanism
for each switch whereby the electro-magnets operate the switches;
series of contact points for each switch equal to the number of the
other switches each switch being numbered and having a correspondingly
numbered contact point upon each of the other switches: telephones
at outlying stations, one to a switch and correspondingly numbered; a set
of electric conductors running one from the frame of each telephone to the electro-
magnet of the switch, then back to the frame; a second set of conductors running
one from each switch to each of the correspondingly numbered contact points of
the other switches; a set of circuit breakers one at each telephone for said first
mentioned conductors; batteries at each telephone in the lines with the circuit
breakers and said circuit breakers being normally open as required to keep, the
nergy of the batteries from the telephones and wires when not in use; means of
operating said circuit breakers; and a conductor connecting all the telephones
together, and serving as a return for the talking circuits established by the opera-
tion of the switches.
3. A telephone system consisting of a switch-board having a switch for each
telephone in the system: a set of electro-magnets one for each switch; mechanism
for each switch whereby the electro-magucts operate the switches; a series of
contact points for each switch equal to the number of the other switches; tele-
phones at outlying stations; a set of electric conductors running one from the frame
of each telephone to the electro-maguet of its switch and then back to the frame;
a second set of conductors running one from each switch to each of the correspond-
ing contact points of the other switches; a set of normally open circuit breakers
one at each telephone for each of the first mentioned conductors; a source of
electrical energy for each telephone in the line of the circuit breakers and a third
conductor connecting all the telephones together and serving as a return wire
for the talking circuits; said third conductor having branches passing through
the secondaries of the induction coils and through the receivers substantially as
specified.
4. In a telephone system, a series of switches mounted independently of each
other; a series of contact points for each switch; electrical connections between
each switch and the corresponding contact points of each of the other switches;
electrically controlled mechanism operated from the telephones for moving the
switches, as required to move the switch of the calling telephones until it engages
the contact point of the called telephone: wires making a conductor from the
calling telephone, through its switch to the switch of the called telephone, and
then to the called telephone, all the other telephones being out of said line; said
wires leading through the primaries of the induction coils and to the receiver
hooks; and a wire connecting all the telephones and serving as a return wire for
said circuit; said last mentioned wire having branches passing through the
secondaries of the induction coils and through the receivers; substantially as
specified.
5. A telephone consisting of a switch-board having a switch for each telephone
in the system electrically controlled mechanism for each switch for operating the
switch: telephones at outlying stations: a set of electric conductors running one
from the frame of each telephone to its switchboard-operating mechanism and
back to the frame; a series of contact points for each switch and in position to be
engaged by the switch; a second set of conductors running one from each switch
to each of the corresponding contact points of the other switches; a set of circuit
breakers, one at each telephone, for each of said first mentioned conductors: means
located at the telephones of supplying electrical energy to the circuits; mechanical
means of operating and controlling the circuit breakers; and a conductor connect-

page_text: ing the telephones together and serving as a return wire for the talking circuits
established by the operation of the switches, substantially as specified.
6. In a telephone system, a switch-board consisting of a series of switches;
each of said switches comprising a shaft, a bar fixed upon the front end of the
shaft and a contact spring projecting outwardly from the outer end of said bar;
a series of contact points for each switch and in position to be engaged con-
secutively by the switch; a set of conductors connecting each switch with corre-
sponding contact points of the other switches; each of said conductors being
electricall independent of each other and of all the contact points except its own;
electrically controlled mechanism connected to and operating each of said switches
independently of each other; telephones at outlying stations, one to a switch; a
circuit breaker at each telephone; a battery at each telephone; a metallic circuit
connecting the battery, the circuit breaker, the telephone receiver hook and the
mechanism for operating the corresponding switch together; a conductor leading
from the battery through the telephone transmitter, through the primary of the
induction coil and then to the receiver hook; and a conductor connecting all the
telephones together and having branches passing through the secondaries of the
induction coils, and through the receiver, substantially as specified.
7. In a telephone system, a switch-board consisting of a series of switches;
electrically controlled mechanism for operating the switches; telephones
at outlying stations; a set of electric conductors running one from
each telephone receiver hook to the electrically controlled switch-operating
mechanism, then back to the receiver hook; a second set of conductors leading
through the telephone transmitter and through the primary of the induction coils
to the receiver hooks; and a third conductor having branches passing through
the secondaries of the induction coils and through the receivers, substantially as
specified.
8. In a telephone system, switches at a central station; electrical mechanism
for controlling each switch independently of the other; contact points in position
to be engaged by the switch; conductors connecting each switch with the corre-
sponding contact points of the other switches; telephones at outlying stations
one to a switch; a circuit breaker at each telephone; a battery at each telephone;
a metallic circuit connecting the battery, the circuit breaker, the telephone receiver
hook and the mechanism for operating the corresponding switch together; a
conductor leading from the battery through the primary of the induction coils and
then to the receiver hook; and a conductor connecting all the telephones together
and having branches passing through the secondaries of the induction coils, and
through the receiver, substantially as specified.
9. In a telephone system, a switch; spring actuated clock work attached to the
switch for operating the same, and an escapement mechanism for controlling the
clock work; said escapement mechanism consisting of an electro-magnet mounted
with its cores in a vertical position, an escapement lever mounted in a horizontal
portion below said magnet, an armature attached to the intermediate position of
said lever, arms projecting laterally from the free end of said lever one above the
other and one farther from the pivot than the other, an escapement wheel driven by
the clock work, and arms projecting laterally from said wheel in position to be
engaged alternately by the arms of the escapement lever, as required to give a step-
by-step movement to the switch when the escapement lever is operated by the action
of the magnet, substantially as specified.
10. In a telephone system, an automatic switchboard; telephones at outlying
stations; a set of electric conductors running one from each telephone to the
switchboard mechanism and back to the telephone a second set of conductors
running one through each telephone transmitter and through the primary of the
induction coils; and a third conductor having branches passing through the
secondaries of the induction coils through the receivers, substantially as specified.
11. A telephone system consisting of a switchboard having a switch for each
telephone in the system; an electro-magnet for each switch; mechanism for each

page_text: switch whereby the electro-magnets operate the switches; a series of contact
points for each switch equal to the number of the other switches, each switch
being numbered and having a correspondingly numbered contact point upon
each of the other switches; telephones at outlying stations, one for each switch
and correspondingly numbered; a circuit breaker at each telephone; a battery at
each telephone a set of electric conductors running one from each telephone
receiver hook to the electro-magnet of the corresponding switch, than back through
the battery and circuit breaker to the receiver hook, said circuit breakers being
normally open as required to keep the energy of the batteries from the telephones
and wires when not in use; means of operating said breakers; and a third con-
ductor having branches passing through the secondaries of the induction coil and
through the receivers, and connecting all the telephones together, and serving as
a return for the talking circuit established by the operation of the switches, sub-
stantially as specified.
12. A telephone system consisting of a switchboard having a switch for each
telephone in the system, electrically controlled mechanism for operating the
switches; a series of contact points for each of the switches, equal to the number
of the other switches; telephones at outlying stations; a circuit breaker at each
telephone; a battery at each telephone; a set of electric conductors running one
from each telephone receiver hook to the switch operating mechanism, then back
through the battery and circuit breaker to the receiver hook; a second conductor
leading from each battery through the telephone transmitter, and through the
primary of the induction coil; and a third conductor having branches passing
through the secondaries of the induction coil, and through the receivers, and
serving as a return for the talking circuits established by the operation of the
switches; substantially as above set forth and for the purposes specified.
13. An automatic telephone system, consisting of a switch at the central station
for each telephone in the system, and an electro-magnet for each switch; mechan-
ism for each switch whereby the electro-magnets operate the switches;
telephones at outlying stations, and an electric conductor running from each
telephone to the electro-magnet of, its switch controlling mechanism and then
back to the telephone; a second conductor running from each switch to each of the
corresponding contact points of the other switches; as required to allow of the
telephones being automatically connected in pairs; a normally open circuit breaker
at each telephone for each of the first mentioned conductors; a course of electrical
energy for each telephone, and a conductor connecting all, the telephones together
and serving as a return wire for the talking circuit, said conductor having
branches passing through the secondary of the induction coil; substantially as
above set forth, and for the purposes specified.
14. In a telephone system, an automatic switchboard, electro-magnets for
operating the switchboard, telephones at outlying stations, a set of electric con-
ductors running one from each telephone through one of the electro-magnets and
back to the telephone, a make and break mechanism at each telephone for each
of said conductors, a clock work operating said make and break mechanism, a
dial in front of said clock work, stops operating through said dial, a pointer carried
by said clock work behind said dial and engaging said stops, said stops being
withdrawable as required to release the pointer and allow the clock work to
operate the make and break mechanism, thus causing electrical impulses to pass
through said electro-magnets and operating the switch-board, a second set of con-
ductors running one through each telephone transmitter and through the primary
of the induction coil; and a third conductor having branches passing through the
secondaries of the induction coils and through the receivers, substantially as
specified.
T
QU