Improvements in Automatic Telephone Exchanges.
Year: 1897

page_text: This Print is in accordance with the Original Specification as it stands after
Amendment (under Section 18 of the Patents, &c. Act, 1883), as allowed by
the decision of the Comptroller General of the 13th day of January 1899.
Date of Application, 9th Oct., 1897-Accepted, 4th Dec., 1897
Improvements in Automatic Telephone Exchanges.
A communication by the STROWGER AUTOMATIC TELEPHONE EXCHANGE, of 947-949,
Rookery, Chicago, County of Cook and State of Illinois, United States of
America.
1
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street,
Manchester, both in the County of Lancaster, 118, New Street, Birmingham, in
the County of Warwick, and 322, High Holborn, in the County of Middlesex, Civil
Engineer, do hereby declare the nature of this invention and in what manner the same
is to be perforined, to be particularly described and ascertained in and by the follow-
ing statement:-
The objects of this invention are to simplify a portion of the mechanism of
electrical exchanges and to add thereto mechanism in combination with means at the
telephone station whereby the operative parts of each exchange may be automatically
released from the position in which two telephones are connected to the normal or
initial position; and another object is to provide means whereby each exchange may
be made to more quickly connect any two of a great number of telephones than is
practical with the mechanism embodied in the invention herein before mentioned.
And still another object is to so combine the system of wires connecting the make
and break circuit mechanism at the telephone station with make and break circuit
mechanisin at the central exchange, that the number of such wires is reduced to the
minimum without the use of such objectionable expedient as polarised magnets,
reverse currents, etcetera all of which is fully described hereinafter, and is illustrated
in the accompanying drawings, in which,
Figure 1 is a side elevation of the principal parts of the operative mechanism in
the initial position.
Figure 2 is a side elevation of the opposite side from that shown in Figure 1 of
of the principal parts of the operating mechanism, also in initial position.
Figure 2 is a vertical section on broken line A B, Figure 2, looking in the
direction indicated by arrow C.
Figures 3, 4 and 5 are plan views of the frames of three different exchanges
attached to the inter connecting wire table, with Figure 4 having the operative
mechanism attached complete, and in the initial position, while Figure 3 shows but
a portion of the operative parts, which are in a changed position from what is shown
in Figure 4, and will be hereinafter fully described.
Figure 5 is a plan with the main shaft removed to show several minor parts which
o explained hereinafter in full view.

page_text: Figure 6 is a vertical section on broken line A B, Figure 2, looking in the
direction indicated by arrow D.
Figure 6 is a vertical section on broken line E F, Figure 2, looking in the
direction indicated by arrow C, and Figure 6c is a vertical section on broken
line GH, Figure 2, looking in the direction indicated by arrow C; Figures 7
and 7 are partial vertical sections of the top portion of the frame of the exchange on
broken line J, and show two positions of a cut out device; Figure 8 shows
respectively a plan and a side elevation of a bell crank cut out lever.
Figure 9 shows respectively a side and an end elevation of a portion of an
auxiliary switch; and Figure 9 is a vertical section thereof.
Figure 9 is a vertical section of a metal sleeve with wipers attached thereto
showing position in Figure 9.
Figure 9 is a vertical section of a bushing of some insulating material which is
shown in position in Figure 94.
Figure 10 shows respectively a side and end elevation of one of the ratchet wheels,
with a cut-out rod attached thereto.
Figure 11 shows respectively a plan and side elevation of a combined thrust and
coupling piece.
Figure 12 is a side elevation of a portion of the main shaft with ratchet wheel,
Figure 10, and thrust ratchet cylinder, Figure 13, mounted thereon.
Figure 14 shows respectively a side and front elevation of one of the ratchet levers
with pawl trip and stop attached thereto.
Figures 15 and 15" are vertical sections of a portion of the top of the exchange
frame on broken line K, Figure 2, looking in the direction indicated by arrow B, and
showing several positions of the cut-out device.
Figure 16 is an elevation of a modification of the auxiliary switch shown in Figures 1
and 9.
Figures 17 and 17ª are side elevations of an actuating lever and pawl which serve
to impart a longitudinal movement to the main shaft, the pawl and lever being shown
in three different positions.
Figure 18 shows, respectively, a side elevation and a plan of a detent which engages
the ratchet wheel shown in Figure 10, and holds main shaft, Figure 12, in the
operative position.
Figures 19, 19 and 19B show a vertical section of an upper portion of the frame
ou broken line G H, Figure 2, looking in the direction indicated by arrow C, with a
side elevation of lever and pawl shown in Figure 14, in two different positions, and
the detent shown in Figure 18 in three different positions.
Figure 20 is a plan of three signal keys which are secured to a piece of insulating
material.
Figure 20 is a side elevation of the signal keys and base shown in Figure 20, with
one side post removed.
Figure 20 shows, respectively, a plan and side elevation of one of the keys.
Figure 20 is a vertical section of the keys and base thereof on broken KL,
Figure 20, and Figure 20° is the same as Figure 20" with the keys removed.
Figure 20 shows, respectively, a side elevation and a bottom plan of the top cross
piece seen in Figure 20.
Figure 20 is the same section as Figure 20B but with one of the keys shown in
the depressed position.
Figure 21 is a front elevation of a system of make and break circuit mechanism,
which is operated by the telephone receiver, the telephone receiver being shown in
the initial position.
Figure 21 is the same elevation as the portion shown in Figure 21, but with the
telephone lever in the position to serve as a cut-out.
Figure 21 shows, respectively, two different elevations of the sides of the spring
contact connections shown also in Figure. 21 in one position.
Figures 21%, 21, 21 and 21, show side elevations of a contact arm of the

page_text: telephone lever in several different positions in relation to the spring contact con-
nections, as will be hereinafter explained.
Figure 22 is a plan view of the telephone lever with the contact arm secured to
the side thereof; and Figure 22 shows respectively a plan and an end and side
elevation of this contact arın.
Figures 23 and 23 show, respectively, a side and an end elevation of the conductor
shaft with wipers thereon arranged spirally.
Figure 24 is a diagrammnatical view of the whole system to show method of wiring,
and the course of the electric current.
Similar numerals indicate like parts throughout the several views.
The main operating shaft 2 in this system is mounted in the frame of the
exchange and projects at both ends and is normally free to both revolve and slide
longitudinally.
To the end of this shaft, Figure 24, is attached by an insulating coupling 3, a
series of conducting shafts 4, each coupled to the others by an insulating coupling 5,
Figures 23 and 24, and each shaft is mounted in a bearing 6, which serves as a means
of communicating electrically with each shaft independently.
Each shaft is provided with a series of wipers 7, which usually comprise 10 in
number, but may be more or less than ten, and are arrranged around the shaft in
spiral order, each revolving in a different plane as shown, and are in electrical
communication with the shaft.
In Figures 1 and 2, and on Sheet 2 of the drawing, in connection with Figures 3,
4 and 5, are shown several groups of wires 12, which are arranged in the same plane
as the revolving wipers are capable of describing, whereby each of these wires may
be contacted thereby, as is hereinafter explained.
Secured to shaft 2 is an elongated ratchet wheel 8 having the teeth so arranged on
the main portion thereof, that by virtue of magnet 9, lever 10 and pawl 11, the shaft
may be revolved in one direction, step by step, eleven steps without completing a
revolution against the torque of helical spring 21. At one end of ratchet wheel 8 is
a reduced portion which is provided with but one tooth 111, against which pawl 11
initially strikes to rotate shaft 2 one step when beginning the cycle of movements to
connect the two telephones.
There is a detent. 81 which serves to retain the ratchet wheel in position after each
successive thrust of pawl 11 and this detent 81 also serves as an important factor in
a train of release mechanism which is hereinafter explained.
Attached to ratchet 8 is a pin 13 which serves as a cut-out by being thrown into
and out of contact with a spring 14, which has an insulated attachment to the frame
of the exchange. Ratchet cylinder 15 is secured to shaft 2 and is provided witli
circumferential teeth raked in one direction, which may be engaged at any point of
nearly a revolution of the cylinder by pawl 16 when impelled by virtue of magnet 17,
through lever 18, this being the means of imparting a longitudinal step by step
movement to shaft 2.
There is a post 16111, Figures 1, 2 and 174, which serves the double purpose of a
stop, against which the free end of pawl 16 contacts to limit the forward movement
of the pawl so that it cannot slide the ratchet cylinder with shaft 2 more at each
thrust than the distance between the teeth of the ratchet cylinder; this contact of
the pawl with the post also preventing the pawl from sliding out of engagement with
the ratchet cylinder at the termination of its thrust, and locks the ratchet cylinder
and shaft from moving by the momentum acquired in the thrust of the pawl,
farther than the distance between the teeth of the ratchet cylinder. The head on
the top of the post 16 serves to hold the pawl out of engagement with the ratchet
cylinder 15 when the parts have assumed the position shown in Figure 174, which
will again be referred to. There is a detent 19 for retaining the ratchet cylinder 15
with shaft 2 in the desired position after the thrust of pawl 16 against the resiliency
of helical spring 21. Figures 2, 6 and 13, show a groove 37 cut longitudinally at
one side of ratchet cylinder 15, so that when the cylinder is in the position shown in
Figures 2 and 6, the stop pawl 19 is out of engagement with the notches of

page_text: ratchet 15, which permits of a free, longitudinal movement of shaft 2 in either
direction.
The selector will now be described loosely mounted on shaft 2 to revolve only, is
a ratchet wheel 22, and metal sleeve 23, having a pulley 24, the ratchet wheel and
sleeve being held to revolve in unison and insulated from each other, and from shaft 2,
and the frame of the exchange by means of a bushing 25, Figure 90, of insulating
material.
There is a series of wipers 26 arranged spirally around the sleeve 23, each adapted
to revolve in a different plane from the other, and each capable of contacting, one at
a time, some one of the metal strips 27, which are held in position, each independent
o the other by means of insulating material, and forming an auxiliary switch. A
helical spring 28, which has the lower end attached to a block of insulating
material 281, and the upper end to a metal cord which is attached to the pulley .24,"
serves to rotate the sleeve 23 and ratchet 22 backwardly until arrested by the pro-
jection 29, Figure 6ª, contacting a piece from the frame of the exchange, the spring
and cord serving to establish electrical communication between sleeve 23, wipers 26,
and block 28¹.
The means by which the wipers 26 are revolved to contact the metal strips. 27,
consists of a long shaft 30 mounted to partially rotate and to slide longitudinally in
bearings in the frame of the exchange.
Near the centre of length of shaft 30 is an arm 31, Figures 1 and 6°, to the top
end of which is pivotally attached one end of the thrust and coupling piece. 32,
Figures 4, 60 and 11, which is bifurcated, the arms thereof passing, one above, and
the other below shaft 2, in a groove 33, Figure 12, found between the end of ratchet
wheel 8 and ratchet cylinder 15, this arrangement permitting the thrust and coupling
piece 32 to slide longitudinally to vibrate the arm 31, and at the same time.couple
shaft 2 to shaft 30 so that, although both may revolve independently, they must slide
longitudinally in unison.
The free end of the thrust and coupling piece 32 is in contact with lever 10 near the
top thereof, Figure 60, and is held normally in such contact by spring 30' on shaft 30
so that any inward movement of lever 10 also causes arm 31 to vibrate, and shaft 30
to turn a partial revolution. Secured to the inner end of shaft 30 is an arm 34,
Figures 1 and 64, which has a pawl 35 with one end pivotally attached to the top
thereof, which pawl engages with the notches of ratchet wheel 22, the hook of
pawl 35 being normally always out of engagement with the ratchet wheel, as shown in
Figure 6ª, there also being a detent 36 which is normally out of contact with ratchet
wheel 22, but which will change position to hold the same in its forward step by
step movements at the proper time as hereinafter shown.
In the modification of the selector shown in Figure 16, which has been used in
some form in several auxiliary switches, the ratchet wheel 22" is insulatingly mounted
upon shaft 2 to revolve loosely thereon, same as ratchet 22, Figure 9, and ratchet
wheel 22 may be operated by the same form of pawl as 35, and held by the same
form of detent as 36, and held against the detent and pawl, and revolved backwards
in release by a spring 28ª, attached to cord 28°, same as 28, and 281, Figures 1 and 2,
but instead of the wipers 26, and the contact strips 27, herein before described, there
is attached to one end of the ratchet wheel 22", a switch arm 26, and upon the
opposite end of the ratchet wheel winds the metal cord 28b, which is connected to
release spring 28", whose electrical connection with the other parts of the exchange is
the same as berein before described for spring 28 and cord 28¹.
Again referring to the modification, Figure 16, a piece of insulating material is
attached to the frame of the exchange, and is provided with a series of contact
points 27, arranged in circular form, and adapted to be successively contacted by the
end of switch arm 26, as it is revolved step by step by the action of the ratchet pawl
on ratchet wheel 22", and the wire connections with the contact 27' are the same in
their electrical connections as the wires which communicate electrical current
from the strips 27, hereinbefore described.

page_text: In Figure 18 are two views of detent 81, together with an attached arm 811 whose
free end 38 is bent at a right angle, so that when the detent is in position, the
portion 38 has a position outside of lever 10, as shown in Figures 2, 6, 19, 19*
and 19B, there being a short pin 40 projecting from lever 10, which serves at the
proper time to hold up the arm 8 and 38, and release detent 8¹ from ratchet
wheel 8.
Lever 10 has an arm 39 which projects inwardly and is contacted at the proper
time by a crooked wire 161; Figures 17, 17^ 19, 19, which forms a tail piece of
pawl 16, and serves to release the pawl from engagement with ratchet cylinder 15.
Pawl 11 of lever 10 is normally held out of contact with ratchet 8 by means of an
arm 41 which contacts a wire 42, Figures 2, 3, 4 and 19, when lever 10 is in initial
position.
Wire 42 is attached to a post 43, and a portion of the free end of the wire is bent
outwardly at a right angle, Figures 3, 4 and 5, which portion is contacted by an arm 1611
of pawl 16 to hold the pawl out of engagement with ratchet cylinder 15 for
another purpose, and at another time, than what has been described in regard to the
tail piece wire 161, acting upon projection 39 of lever 10.
At 44, Figures 3, 4 and 5, is a spring which bears downwardly upon the arm of 811
of detent 8 to hold the detent in contact with the ratchet wheel 8.
Detent 36 which engages ratchet wheel 22 is secured to the end of a short shaft 45,
and this detent is held in contact with the ratchet wheel by means of a spring 46,
and at 47 is an arm, Figure 5, which has its free end bent at a right angle and rests
upon arm 8 of detent 8¹, so that whenever arm 811 is lifted, detent 36 is released
from engagement with ratchet wheel 22.
Figures 2, 7 and 7^ show a pendent arm 48 which is attached to and electrically
insulated from the frame of the exchange, but the lower end thereof is normally in
contact with a spring arm 49, which arm is attached at one end to a screw 50, which
electrically. connects it with the frame of the exchange. At 51 is a U shaped wire
having the free end flattened, the other end being attached to a screw 52, which also
holds, spring contact 14, and forms electrical cominunication between these two parts,
Figures 1, 2 and 15.
Figure 8 is a bell crank cut-out lever 53, which is shown in position in Figures 2
and 6, pivotally mounted upon screw 50, one arm of this lever being bent down-
wardly, Figure 2, and in contact with spring wire 49, while the remaining arm,
Figure 6, is in contact with the front edge of magnet lever. 18, so that when the
armature, of lever 18 is drawn to magnet 17, the bell crank lever moves wire 49
inwardly, out of contact with pendent arm 48, and into contact with the flattened
portion of the bent wire 51.
At 101, Figures 1, 2 and 6, C is an arm secured at one end to the base of lever 10,
which is actuated by electro-magnet 9, so that whenever pawl 11 is actuated to
revolve shaft 2 by virtue of electro magnet 9, the arm 10¹ presses inwardly and serves
to also move wire 49 inwardly, out of contact with pendent arm 48, and into contact
with the flattened portion of bent wire 51, which action is the saine as above
described for one arm of the cut-out lever 53, which is operated by lever 18, and
serves for a similar purpose.
The signal key system particularly adapted to this exchange, comprises a base
plate 57, Figures 20 and 20%, of insulating, material, having keys of spring
metal 54, 55 and 56, each secured at one end to this base.
Secured to, and insulated from these keys, is a bent strip of metal 58, and crossing
above the series of keys is a bar 59 of insulating material, to which is secured a series
of short strips of metal 60, each insulated from the other, and when the keys are in
proper position, the bent strips 58 normally contact and connect the several strips 60,
as is shown in Figure 20³, but should one of the keys be depressed, as shown.in
Figure 20, the strips 60 will be disconnected.
At the underside of the base plate 57, is a strip of metal 61, to which is electrically
connected the three contact plates 62, 63 and 64, plate 61 being connected to one
pole of battery 65, by wire 65¹.

page_text: In practice, these signal keys are designated as hundreds, tens, and units keys, and
are usually marked as shown in Figure 20, respectively, H, T and U.
Wire 66 connects the hundreds and units keys, and wire 67 connects the units key
with magnet 9 in the exchange, Figures 1 and 2, and with the telephone by con--
nected wire 671, and wire 68 connects the tens key with magnet 17 through the frame
of the exchange.
Wire 69 connects one end of a series of strips 60 with the telephone,
and wire 70 connects the other end of a series of strips 60 with electro magnet 17, also
through the frame of the exchange. Wires 68 and 70 are connected usually at the
same place on the exchange frame. Wire 71 connects magnets 9 and 17 with the
opposite pole of the battery 65 from that connected with wire 65¹.
On Sheet 5 of the drawings is shown in detail a system of mechanism which serves
in combination with the electro inagnets of the exchange, and with the peculiar
combination of trips for the pawls and detents, to cut out the telephone and
automatically release the mechanism of each exchange, so the operative parts are
returned to the initial position after two telephones have been connected, as herein-
after explained.
Figure 21 shows a lever 72 which is pivoted at one end to vibrate vertically, and
at the other end is shown suspended therefrom, an ordinary telephone receiver, whose
weight is sufficient to hold the lever in the initial position shown against the resiliency
of spring 73.
Secured to one side of lever 72 is a metal contact arm 74, Figures 22 and 224, which
is bent outwardly at its free end, and which has attached thereto a piece of insulating
material 75 to form the whole of one side near the end of the arm, and a part also of
the opposite side, both ends of the insulating piece being formed into a wedged shape
as shown.
At 721 is a wire which electrically connects lever 72 and the contact arm 74 with
wire 651 from battery 65, Figure 24.
At 76 and 77, Figure 21", are shown two strips of metal which are secured at one
end to a piece of material which insulates one from the other at this end, which at
the opposite ends are formed projections which are normally in contact and electrical
communication. At 78 and 79 are shown two other strips similarly secured and
similar in shape to strips 76 and 77, but are placed in a reversed position relative
to strips 76 and 77. Strips 76 and 77 are adapted to make and break electrical
communication, through wire 671, which has an end thereof attached to strip 76, and
another end attached to strip 77.
Strips 78 and 79 are adapted to make and break electrical communication through
wire 70, which has an end attached to strip 78, and another end attached to strip 79, the
strips having sufficient resiliency to permit the wedged shaped piece of insulating
material with the end of arm 74 to pass down between the free inwardly projecting
ends of the strips and first, successively operate each pair of strips, and then
successively communicate electric current from wire 721 to one strip 76 of the
first pair, and then to one strip 78 of the second pair, and then respectively and
successively cut out communication from strips 76 and 78 with wire 721, strips 77
and 79 being always cut out from electrical connection with wire 72, so that no
current from battery 75¹ ever reaches the telephone, and this mechanism, in
connection with the release of the exchange, so that the several parts will
automatically move back to the normal or initial position, is hereinafter referred to
and more fully explained.
In Figure 24 are diagrammatically represented six banks of interconnecting
wires 12, the first and last wires only of each bank being shown, but it must be
understood that between these first and last wires, many others may be placed in
groups of ten in the same plane and parallel therewith, similar to what is shown in
Figure 1, and in combination with Figures 3, 4 and 5, banks No. 1, 2, 3, 4, 5 and 6 are
represented respectively by the space between the wires 12.
Each telephone exchange is provided with a series of rotary and longitudinal
movable connectors 4, each insulated from the other, though connected together to
above simultaneously, and each of these connectors is provided with wipers 7,

page_text: Figure 23, in electrical connection therewith, there being one connector for each
bank of one hundred wires for each exchange, and electrical communication may be
made from each connector, journal bearings 6, to the telephone line, through
wires 80, 81, 82, 83, 84 and 85 to the metal strips 27, thence to the wipers 26 to
spring 28, and then through wire 401 to pendent wire 48 on the frame of the
exchange, which is normally connected with the telephone line.. Through the frame
of the exchange, each of the bank wires 12 is connected to an insulated arm 87 of
soine particular exchange by a wire 871, Figures 3, 4 and 5, this arm being initially
in contact with an arm 88 which projects from the shaft to; and is in electrical
connection with the frame of the exchange.
Shaft 2 is always rotated one step at the beginning of its cycle of movements
before any of the wipers 7 or 26 contact respectively either of the wires 6 of metal
strips 27.
This exchange may be operated a variety of ways, although but one way is herein
shown and described, which comprises in the train of mechanism therefor the peculiarly
constructed keyboard shown in detail in the drawing on Sheet 4, the keys and connections
therewith being so constructed and placed relatively to each other, and so wired that
but three keys are necessary to accomplish the results intended. To illustrate the
manner of operating the exchange through the action of these signal keys; suppose
the subscriber desires to call telephone 399, he first presses the key H, which
indicates hundreds, three times, which causes a flow of three different currents of
electricity from battery 65 through wire 651, key H, and wire 66, and then wire 67
to inagnet 9, which operates pawl 11, and then through the shaft 2 which turns one
step of ratchet wheel 8, because it can engage at first only one tooth, which is
represented by the pin 111, Figures 1, 19, 19%, and 19B but since the thrust teeth 32,
Figures 11, 3, 4 and 6 is in line of the movement of lever 10, the ratchet pawl 35,
Figure 6 is operated to turn ratchet wheel 22 three steps successively, when the
third wiper 26 thereof will be in contact with the third metal strip 27, which is
electrically connected by a wire 82, Figure 24, with the third wiper shaft 4, and héld
in this position against the pull of the spring 28, by detent 36.
After this the key T is pressed down nine times, each time making connection
whereby a current passes from battery 65 through wire 65¹, key T, and wire 68, to
magnet 17, through the frame of the exchange, when pawl 16 is operated to engage
the teeth of the ratchet cylinder 15 nine times, and is held in this operated position
by detent 19, after which key U is pressed down nine times, making connection each
time with battery 65, through wire 65¹ key U, and wire 67 to magnet 9, and cause
pawl 11 to operate shaft 2 through ratchet wheel 8, nine steps, which causes the ninth
switch arm of each of the different wiper shafts 4, to contact some wire 12, but since
only the third bank of wires is in electrical connection with the exchange through
journal bearings 6, wire 80, the third strip 27", the third wiper 26, of the auxiliary
switch, then cord 28¹, spring 28, and wire 48¹ to pendent arm 48 attached to the
frame of the exchange, the third wiper shaft 4*, Figure 24, serves as a switch, with
the wiper now in electrical connection with wire 399, whence if the telephone receiver
is lifted from its suspension lever 72, the lever assumes the upper position shown in
Figure 21, in the broken lines, or in Figure 24, when the strips 76 and 77 will spring
together and connect wire 671, and strips 78 and 79 spring together and connect
wire 70, which wires complete an electrical circuit from wire 69 and the telephone
through the wire 60¹, and springs 58 under the signal keys, see Figures 20B and 20°,
to wire 70, thence to the central station, into the frame of the exchange, which forms
a terininal for wire 70, see Figure 2, thence through bell crank lever, 53, and spring
arm 49, to pendent arm 48 and wire 481 to spring 28 and wire rope 281 to metal pulley 24,
and wiper 26 of the auxiliary switch, then to one of the contact bars 27, thence by a
wire 80, Figure 1 to one of bearing posts 6 of shaft 4, to one of the wipers 7 in contact
with an interconnecting arm 12, thence by wire 12 into one of the wires 871,
Figures 3, 4, 5 and 24, thence to the exchange of the station to be spoken to, the
wire 87' connecting with the pin 87; see Figures 1, 2, 3 and 4, then connecting arm 88

page_text: and shaft 2, and the frame of the exchange belonging to the telephone set to which
the spoken message is intended.
After the conversation is ended, the automatic release mechanism is operated as
follows: The telephone receiver is hung upon the hook at the free end of lever 72,
when gravity causes the lever to descend to the position shown in the solid lines in
Figure 21, but the attached contact arm 74 in passing down, first opens the upper
strips 76 and 77, and since the head at the free end of the contact arm is faced with
insulating material on the side next to the strip 77, no electric current will pass over
the attached wire 671 to the telephone set, but a current will pass from battery 65
through 72¹ and the lever 72, and arm 74 into strip 76 and thence over wire 67¹ to
magnet 9, which will be operated and cause the projection 39 of lever 10,
Figures 14 and 19, to contact the underside of the tail piece 16¹ of pawl 16 of lever 18,
and release pawl 16, when lever 10 is in the position shown in Figure 19, and while
lever. 10 is held in this position, the arm 74, Figure 21, passes still further down until
the lower strips 78 and 79 are first opened as shown in Figure 21°, then the strip 78
is contacted with the side of arm 74, while the opposite strip is in contact with the
insulation at the side of the arm 74, so that no current can pass through wire 70
from that side or direction, but electric current passes from arm 74, out through
strip 78, and thence to magnet 17, which causes lever 18 to assume the position shown
in Figure 17; the lower convex portion of tail piece 16¹ thereof riding upon projection
39 of lever 10, causing a still further movement of pawl 16, and the tail piece 16
contacting with a cross rod 811 connected with pawl 81 causes this pawl to release, and
shaft 2 being now free, first revolves around backwardly until pin 88 near the outer
end, Figures 1 and 2, strike against the insulated pin 87, and then slides longi-
tudinally to the initial position, similar to what has been before described in a
prior Patent No. 860704.
A special cut-out mechanism is shown in Figures 1, 2, 6B, 60 and 8, and consists
as has been already partially described, of bolt 52 insulated from the frame of the
exchange, Figures 1 and 2, to which bolt on the lower side is attached a U-shaped
wire 51, and above a spring 14, which spring is adapted to connect the pin 13, better
seen in Figures 3 and 4. Also in intimate connection therewith is the arm 88 at the
extreme end of shaft 2, which is adapted to contact, when in the initial position,
the pin or arm 87, which is insulated from the frame of the exchange to which it is
secured.
Near the bolt 52 is insulatingly secured to the frame of the exchange, the pendent
arm 48, and attached to the lower end of a pendent pin 50, is one end of a
horizontally disposed spring wire 49, whose front end is normally in contact with
pendent arm 48, so that normally, pendent arm 48 is in electrical communication
with the frame of the exchange, and therefore with the line wire 70, and is always in
communication with wire 48' as before stated.
The bars upon which lever 10 vibrates has an upwardly projecting arm 101, which
crosses spring wire 49, and an arm of elbow lever 53, a downward projection which
crosses spring wire 40, so that, when either of the levers 10 or 18 are operated, these
arms force spring wire 49 out of contact with pendent arm 48, and into contact with
the lower free flat end of the U-shaped wire 51.
It will be understood that when the magnets 9 and 17 are not energized, the free
end of spring wire 49 is always in contact with the pendent arm 48', in which
position there may pass an electric current from line wire 70 through the frame of
the exchange, to and through bolt 52, then spring wire 49, pendent arm 48, wire 48,
and thence, as explained, to the wipers of some electric shaft 4, and thence to some
one of the interconnecting wires 12, thence to the telephone exchange, and telephone
of the person spoken to, and this circuit is used for telephone purposes entirely, from
the pendent arm 48 to the telephone spoken to, and when in the normal condition
with the spring wire 49 in contact with pendent arm 48, wire 70 is in communication
with wire 481, so that two distant telephones through their respective exchanges, are
in communication with each other, and in the operation of the exchange the end of

page_text: spring wire 49 is always forced away from the pendent arm 48 to the U shaped
contact terminal 51.
Magnet 9 always operates lever 10 first, and causes arm 10¹ thereof to press spring
wire 49 in contact with U-shaped contact terminal 51, when a current may descend
over line wire 70 to the frame of the machine, thence by shaft 2, pin 13, spring 14,
U-shaped terminal 51, thence by wire 70 to magnet 17, or vice versa, as the current
may flow, all of which is for the purpose of preventing a heavy battery current from.
reaching the interconnecting wires 12, or any part of the telephone set of the party
speaking or of the party being spoken to, or any other telephone set in connection
with any of the wires 12.
It will be particularly observed that the purpose of the springs 58 on the signal
keys 54, 55 and 56, are for the purpose of connecting the several strips 60 so that,
wires 69 and 70 are in circuit when the keys are in the normal position, so that a
telephone circuit may be made over wires 69 and 70, but as soon as either of the
keys are operated, they first cut out connection between wires 69 and 70, and after-
wards connect wires 67 or 68 with the battery 65, but not with the telephone, and
which serves another purpose in reducing both the number of line wires and the.
number of signal keys necessary to operate an exchange.
There are various ways of arranging the spring arm 74, and substitutes for the
contact strips 76 and 77 and 78 and 79 to accomplish the result as herein before
described, and it must be understood that my correspondents do not confine them-
selves to this exact construction.
It will be observed that when the telephone lever 72 rises by virtue of spring 73.
after the removal of the telephone receiver that, the end of arm 74 does not succes->
sively pass through between the free ends of strips 78 and 79 and 76 and 77, but it:
passes up outside of strips 78 and 76 as shown in Figure 21" with the insulated:
piece 75 in contact with the strips so that no current of electricity is communicated
in any direction from wire 721
It can be seen in Figure 21" that the upper edges of the lips or projections at the
free end of the contact strips 76, 77, 78 and 79 are not only rounded, but flare.
outwardly so as to preserve a V-shaped space into which may easily enter the
V-shaped lever end of the head 75 of insulating material at the end of frame 74,
the springs on two sides clasping the head closely in the downward passage thereof.
when the telephone is hung upon its hook at the end of lever 72, but in the ascent
the upper end of the piece of insulating material 75, being beveled to one side, and
the lower pair of strips 78 and 79 being in close contact, and strips 78 having a
shorter head than strips 79, the arm. 74 is sprung outwardly to permit the back of
the head 75 to ride over the outside of the strips as before explained.
Arm 74 should be made of very thin material in order not to produce an undue
amount of friction when moving upwardly in order that a comparatively weak spring:
may be used at 73, and also to save wear upon the back of insulation at 75.
1
In case this automatic release device should become deranged, the release may:
be accomplished with the signal keys by first pressing upon the U or units key, and
holding it down until the T or tens key is pressed, when the units key. may be
released, and then the tens key released, the shaft 2 in the meantime successively
revolving and sliding back to the initial position.
Having now particularly described and ascertained the nature of the said in
vention and in what manner the same' is to be performed, as communicated to me.
by my foreign correspondents, I declare that what I claim is :-
1. The combination with a series of wires or contact of a series of rds or parts,
each insulated from the other, and each carrying angularly displaced contact arins or
wipers, and means for rotating the rods step by step to bring the arms thereof into
engagement with the wires, and a selector for connecting a line wire with either of
said rods, substantially as described.
:
2. The combination with a series of wires or contacts of a series of rods or parts,"
each insulated from the other and each carrying contact arms or wipers, means for
12

page_text: imparting to the rod a step by step longitudinal motion, and means for rotating the
rods step by step to bring the arms thereof into engagement with the wires and a
selector, for connecting a line wire with either of the said rods substantially as
described.
3. The combination with a series of wires or contacts, connected respectively with
the telephone lines, of a series of rotating rods or parts, each insulated from the
other, and each carrying angularly displaced contact arms or wipers, connected with
one of the telephone lines, an electro-magnet controlled from the subscriber's station,
mechanism operated by the electro magnet, for rotating the rods step by step to
bring the arms thence into contact with the wires and a selector connecting a line
with either of the said rods substantially as described.
4. The combination with a series of wires or contacts, connected respectively with
the telephone lines, of a series of rotating rods or parts, each insulated from the
other, and each carrying contact arms, or wipers, connected with one of the telephone.
lines, an electro-magnet controlled from the subscriber's station, mechanism operated
thereby for moving the rods longitudinally step by step, a second electro-magnet
controlled from the subscriber's station, mechanism operated thereby for rotating the
rod step by step to bring the arm into contact with the wires and a selector connect-
ing a line wire with either of the said rods substantially as described.
5. The combination with a series of wires or contacts, of a series of rotating rods.
or parts each insulated from the other, and each carrying angularly displaced contact
arins or wipers adapted to make contact with the wires, a ratchet wheel mounted to
rotate with the rods, an electro-magnet, a pawl operated thereby and adapted to
engage the rack to move the rod longitudinally step by step, a ratchet wheel mounted
to rotate with the rods, an electro inagnet, a pawl operated thereby and adapted to
engage the ratchet wheel to rotate rods step by step and a selector connecting a line
wire and either of said parts, substantially as described.
7. The combination with a series of rods, each insulated from the other, and each
rod carrying contact arms, of an electro magnetic device for moving the rods
longitudinally step by step, an electro-magnetic device for rotating the rods step by
step, a selector connecting a line wire with either of said rods, and mechanism
controlled by the electro-magnetic devices for releasing the rods and returning the
same to their original position, substantially as described.
8. The combination with a series of rotating rods each insulated from the other, a
number of series of wires corresponding to said rods, a selector for connecting a line
wire with either of said rods, and each carrying contact points, of a ratchet wheel
mounted on the driving shaft thereof, an electro-magnet and a pawl controlled thereby
for rotating said ratchet wheel, a detent or dog engaging the ratchet wheel to prevent
backward rotation, a rack provided upon the driving shaft, an electro-magnet and a
pawl controlled thereby for moving the rack longitudinally, a detent or dog engaging
the rack to prevent backward movement of the same, and means controlled by
electro-magnet for removing the detent from engagement with the ratchet wheel
and rack, and returning the rod to their original position, substantially as
described.
9. The combination with contact spring 14, of the pin 13, rotating with shaft 2, and
adapted to engage spring 14, spring wire 49, electro-magnets 9 and 17, and means
substantially as described for operating spring wire 49, when either magnet 9 or 17 is
energized whereby spring wire 49 is made to contact alternately terminals 48 and 51
for the purpose herein before stated.
10. The combination with a shaft 2, and mounted thereon of the ratchet wheel 8
having longitudinal grooves with the rack 15, having circumferential grooves, pawls
for engaging the teeth of the ratchet wheel and the rack, means substantially as
described for operating the pawl whereby a longitudinal or a rotary step by step
motion may be imparted to the shaft, for the purpose stated.
11. The combination in an electrical telephone system having a mechanical central
exchange with motor electro-magnets operated from a sub-station, the herein before
described means for releasing the mechanism at the central station, whereby it ma

page_text: assume the initial position after having connected two distant telephones, comprising
mechanism at the sub-station operated by hanging up the telephone receiver, and
consists of a contact in communication with a battery, which is adapted in combination
with other contacts in communication on separate currents of electricity to the magnet
of an exchange at the central station in such manner that, one of said currents is
transmitted first to one magnet, and is continued until a second current is transmitted
to another magnet, the two currents being cut out in the order of the time of their
transmission, substantially as, and for the purpose described.
12. In a telephone exchange the hereinbefore described mechanism for operating
an auxiliary switch by the action of lever 10, before any longitudinal movement of
shaft 2, substantially as stated.
13. In a telephone exchange syster, substantially as described, three signal keys
at each sub-station for controlling the motor magnets at the central station for
operating the switch arms on the decimal system, the signal keys, designated,
hundreds, tens and units, the tens key having one line wire in communication with
the central station, and the hundreds and units key having one line wire in common
in communication with the central station, substantially as described, and shewn in
the drawings.
14. In a telephone exchange system, substantially as described, having a plurality
of signal keys at each sub-station for controlling the motor inagnets of the central
station, said keys operating to electrically connect the motor battery with the motor
magnets of the central station, but cutting out the motor battery from the telephone
set at the sub-station every time the motor magnets of the central exchange are
operated, substantially as described, and shewn in the drawings.