IMPROVEMENTS IN APPARATUS AND IN THE ARRANGEMENT OF MECHANISM AND PARTS TO FACILITATE CONVERSATION BY TELEPHONE BETWEEN PERSONS AT DISTANT PLACES
Year: 1879

page_text: The decision of the Comptroller-General, of the 13th day of June 1893, allowed
under Section 18 of the latents, &c. Act, 1883, an Amendment of this
Specification.
LETTERS PATENT to Charles Ezra Scribner, of 53, Guildford Street, in the
County of Middlesex, for the Invention of IMPROVEMENTS IN APPARATUS
AND IN THE ARRANGEMENT OF MECHANISM AND PARTS TO FACILITATE
CONVERSATION BY TELEPHONE BETWEEN PERSONS AT DISTANT PLACES." Partly
a communication from abroad by George D. Clark and Milo G. Kellogg, both
of Chicago, United States of America, and George B. Scott, of New York,
also in the United States of America.
PROVISIONAL SPECIFICATION left by the said Charles Ezra Scribner at
the Office of the Commissioners of Patents on the 29th November 1879.
CHARLES EZRA SCRIBNER of 53 Guildford Street in the County of Middlesex.
"IMPROVEMENTS IN APPARATUS AND IN THE ARRANGEMENT OF MECHANISM AND
PARTS ΤΟ FACILITATE CONVERSATION BY TELEPHONE BETWEEN PERSONS AT
DISTANT PLACES." [Partly a communication from abroad by George D. Clark and
Milo G. Kellogg, both of Chicago, United States of America, and George B. Scott,
of New York, also in the United States of America.]
This Invention has for its object Improvements in Apparatus and in the
Arrangement of Mechanism and Parts to Facilitate Conversation by Telephone
between Persons at Distant Places.
The telephone is now being used extensively, more especially in America, on
what is known as the central office system.
On this system a large number of subscribers have each a wire leading to the
central office where there are attendants whose duty it is to connect the wire
belonging to any subscriber with that of any other subscriber with whom he may
Price So

page_text: desire to speak.
To facilitate this I make at the central office, the following
arrangements I cause each subscriber's wire to terminate in a metal block and
these blocks are arranged upon a board so that there are as many blocks upon
the board as there are subscribers.
Each block carries a blade similar to the folding blade of a pocket knife, and as
in such a knife the blade folds into a groove or recess in the block, the block corre-
sponding to the handle of the knife. A spring also tends to keep the blade closed
in its recess. When the blade is in this position it makes contact with an insulated
stud from which a wire passes through the electro magnet of an indicating appa-
ratus to an earth connection. In this state of affairs when the subscriber sends a
call current through the wire it excites the electro-maguet, the maguet attracts its
armature and allows an indicating shutter to fall; this shows to the attendant that
this subscriber calls for his attention. Each block (corresponding to the knife
handle) has two holes formed through it and into one of these holes the attendant
when called sticks a metal peg which displaces the knife blade partially opening
the knife. In this way the line wire is disconnected from the indicator. The peg
inserted into the hole in the block is attached by a flexible conductor to a telephone
by the aid of which the attendant receives the subscriber's order to couple his wire
with that of some other subscriber with whom he may desire to converse. Now
for making these connections a series of insulated bars are provided upon the lower
part of the board and the attendant selecting one that is out of use connects the
caller's line wire to it by a flexibla conductor terminating in pegs at its ends. Oue
peg he sticks into a hole in the subscriber's block and the other into a hole in the
coupling bar.
The attendant then calls, the subscriber with whom it is desired to converse and
this he does by means of one of the flexible conductors by which the connections
are made; he sticks the metal peg at one end thereof into one of the holes in this
subscriber's block and touches the peg at the other end of the flexible conductor
upon a band of metal which runs across the board. This band of metal is con-
nected with one extremity of a battery which at the other end is put to earth so
that when the band is touched in the manner described a current passes from the
battery along the subscriber's wire and this brings his call bell into operation. On
receiving an answer the attendant places the peg of the flexible connection into
one of the holes in the coupling bar and the two subscribers being thus coupled
they are left to their conversation which goes on without further care on the part
of the attendant.
In connection with each of the coupling bars there is an indicator to inform the
attendant when the conversation between the two subscribers' lines which the ban
serves to couple is complete.
Where there are a large number of subscribers several attendants are required
and the coupling bars are so long that an attendant cannot conveniently see
which of the coupling bars are disengaged and which are already in use: conse-
quently I so arrange the coupling bars that when brought into use they shall be
furned partly round or otherwise moved so that at a glance, it is apparent whether
a bar is or is not in use.
Also when the number of subscribers is large it becomes necessary to divide
them into sets so that one attendant may attend to the calls of one set, another to
those of another set, and so on. I then have a separate board for each set and on
the board are the call indicators of the set and those only; but the line wire of
each subscriber is brought to the board for a subscriber belonging to the set may
desire to speak with another subscriber out of the set and it is the duty then of
his attendants to make the necessary connections. But a difficulty arises when
the subscribers are thus divided into sets having different attendants for when a
subscriber is called for at one board the attendant does not know whether he may
not be already engaged and coupled for conversation at another board. To avoid
inconvenience arising from this cause I provide for each subscriber two blocks on
each board an upper and an under one, they are coupled in series, the upper block

page_text: on the first board makes contact for the upper block on the second board and this
for the upper block on the third board and so on. Then at the end of the set of
boards the connections are continued through the lower blocks each in succession
until last in the series the lower block upon the subscriber's own board is arrived at
where (as previously described) the connection is made with the call indicator and
so to earth. Now for the purpose of calling a subscriber the peg is inserted
into the hole in the lower block and so will not interfere with any connection
which may have been previously made at either of the upper blocks but when such
a connection exists the call will not pass, the connection with the subscriber's line
having been previously broken.
Or according to another arrangement a small finger key or contact maker may
be provided in connection with each subscriber's block and the attendant when
he desires to know if a subscriber is at liberty places his finger on this key or
contact maker if the subscriber be occupied the contact thus made completes a
circuit in which is a battery and a small bell or "buzzer" and the sounding of this
bell or buzzer indicates that another contact connection ought not to be made, this
circuit however only becomes complete when one of the knife like blades corre-
sponding to this line wire is pegged out on one or other of the boards; the blade
being by this movement brought against a contact point and so completing the
circuit but when by the removal of the peg the blade is permitted to spring back
this local test circuit is broken and although the finger key or contact maker may
be pressed down the "buzzer" will not sound.
The apparatus with which the subscriber works consists of the following
combination of parts; namely, 1 a telephone transmitter of the carbon type and
hereinafter more fully described, 2 an induction coil with the primary of which
the telephone is connected when transmitting, the secondary being to line so that
the pulsations induced in it flow to the correspondent's receiving telephone. 3 a
call bell. 4 a local battery. 5 a relay to complete the bell circuit. 6 a key to
transmit a call current from the battery into the line wire to gain the attention of
the attendant at the central office 7 a switch to put the transmitting telephone
in and out of circuit. 8 a receiving telephone. These parts are coupled in such
a manner that the battery serves three purposes; 1 when the relay is brought into
action by an incoming current it puts the battery into circuit with the call bell
which then sounds. 2. when the key is depressed it as already stated sends a
current to line, calling, or answering the call, of the central station. 3. when the
transmitting telephone is switched in, the battery is put into local circuit with this
telephone and the primary of the induction coil. In working on the central office
system this set of instruments is used on open circuit, the battery being only
applied to the line when a call signal has to be given or answered, but provision is
made in the combined instrument admitting of its being also worked on private
lines on the closed circuit system. The battery being then always in the line circuit
when the apparatus is not in use.
The transmitting telephone which I employ consists of a metal cup closed at the
top by a thin metal diaphragmn immediately facing which there is a mouth pieco
so that the diaphragm can be thrown into vibration by the voice of a speaker. In
the centre of the diaphragm on the under side there is a rounded projection and
this bears upon a button of hard carbon. This button which is slightly roughened
on its under side, rests upon a button of soft carbon and this upon a thin plate of
platinum forming the face of an adjustable support within the cup.
This support has a screw stem passing through the bottom of the metal cup and
by turning the stem the height of the support and consequently the pressure
exerted by the diaphragm upon the carbon buttons can be adjusted. The upper
face of the hard carbon button is coated with copper by electro-deposition and one
of the circuit wires is soldered to it. The other is attached to the metal cup in any
convenient position. The local battery and the primary of the induction coil being
coupled in circuit with this transmitting telephone the flow of the current remains
uniform so long as there is no variation in the pressure of the carbon buttons the

page_text: one on the other, but when the pressure is caused to vary by the vibrations
imparted to the diaphragm by the voice a corresponding variation takes place in
the conduction of the current through the carbon buttons and a pulsation is set up
in the secondary or line circuit to which the receiving telephone at the other end
responds.
In some cases I substitute for the rounded projection on the diaphragm three
contact points ranged around the centre and these press on the upper or hard
carbon button. I form the stem of the support which carries the carbon buttons
with a globular end which is received into a corresponding socket upon a lever
where it is held by a spring. This arrangement permits the carbon buttons to
adjust themselves to the pressure of the points on the diaphragm so that the
pressure may be transmitted equally by all of them. The socket which receives
the globular end of the stem is formed upon a lever and this is adjustable by a
screw. Thus the button support can be set up to the diaphragm and the pressure
upon the carbon buttons varied at pleasure.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles Ezra Scribner in the Great Seal Patent Office on tho
28th May 1880.
AT
CHARLES EZRA SCRIBNER of 53 Guildford Street in the County of Middlesex.
"IMPROVEMENTS IN APPARATUS AND IN THE ARRANGEMENT OF MECHANISM AND
PARTS TO FACILITATE CONVERSATION BY TELEPHONE BETWEEN PERSONS
DISTANT PLACES." The result parily of communication from abroad made to me by
George D. Clark and Milo G. Kellogg both of Chicago United States of America
and George B. Scott of New York also in the United States of America and partly
of invention and discovery made by myself.
This Invention has for its object Improvements in Apparatus and in the
Arrangement of Mechanism and Parts to Facilitate Conversation by Telephone
between Persons at Distant Places.
The telephone is now being used extensively, more especially in America, on
what is known as the central office system. On this system a large number of
subscribers have each a wire leading to the central office where there are attendants
whose duty it is to connect the wire belonging to any subscriber with that of any
other subscriber with whom he may desire to speak. To facilitate this I make at
the central office the following arrangements. I cause each subscriber's wire to
terminate in a metal block and these blocks are arranged upon a board, so that
there are as many blocks upon the board as there are subscribers. Each block
carries a blade similar to the folding blade of a pocket knife, and as in such a knife
the blade folds into a groove or recess in the block, the block corresponding to the
handle of the knife. A spring also tends to keep the blade closed in its recess.
When the blade is in this position it makes contact with an insulated stud from
which a wire passes through the electro-magnet of an indicating apparatus to an
earth connection. In this state of affairs, when the subscriber sends a call current
through the wire it excites the electro-magnet, the magnet attracts its armature
and allows an indicating shutter to fall; this shows to the attendant that this
subscriber calls for his attention. Each block (corresponding to the knife handle)
has two holes formed through it and into one of these holes the attendant when
called sticks a metal peg which displaces the knife blade partially opening the
knife. In this way the line wire is disconnected from the indicator.
The peg
inserted into the hole in the block is attached by a flexible conductor to a
telephone by the aid of which the attendant receives the subscriber's order to
couple his wire with that of some other subscriber with whom he may desire to
converse. Now for making these connections a series of insulated bars are pro-
vided upon the lower part of the board and the attendant selecting one that is out
of use, connects the caller's line wire to it by a flexible conductor terminating in
pegs at its ends. One peg he sticks into a hole in the subscriber's block and the
other into a hole in the coupling bar.
The attendant then calls the subscriber with whom it is desired to converse and
this he does by means of one of the flexible conductors by which the connections
are made: he sticks the metal peg at one end thereof into one of the holes in this
subscriber's block and touches the peg at the other end of the flexible conductor
upon a band of metal which runs across the board. This band of metal is connected
with one extremity of a battery which at the other end is put to earth so that
when the band is touched in the manner described a current passes from the bat-
tery along the subscriber's wire and this brings his call bell into operation. On
receiving an answer the attendant places the peg of the flexible connection into one
of the holes in the coupling bar and the two subscribers being thus coupled they
are left to their conversation which goes on without further care on the part of the
nitendant.
In connection with each of the coupling bars there is an indicator to inform the

page_text: attendant when the conversation between the two subscribers' lines which the bar
serves to couple is complete.
Figure 1 of the annexed Drawings is a front view of a coupling board arranged
according to this Invention. a, a, a, are the knife like terminal blocks; a front
view of one of these is shown at Figure 2 and an underside view at Figure 3, in
this latter Figure the board is seen in section b is a screw serving to attach the
metal block to the board and the nut upon it serves also to clamp and connect an
insulated wire which leads directly to the line wire of the subscriber. There are
as many blocks on the board as there are subscribers, who in this arrangement may
be supposed not to be so numerous as to require to be divided into different sets as
herein after explained. The block as will be seen is in each case slotted to
receive a blade like piece a¹ which-is pin jointed to the block and a spring all tends
to hold the blade in contact with the insulated screw a carried upon the block.
A wire passes from the screw to the coils of an electro-magnet through which
the screw has an earth connection. The electro-magnet forms part of an indicator
of well known construction: the armature when attracted withdraws a catch and
permits a shutter to fall. This it will be observed takes place whenever the
Eubscriber connects his line wire to a battery; the shutter on falling exposes a
number corresponding to that by which the subscriber is known in the office and
announces that this subscriber desires to speak. In Figure 1 these indicators are
represented at ecc. Each block a has it will be seen two holes aa in it and
a peg inserted into either of these holes has the effect of breaking contact at all.
To ascertain what it is that the subscriber desires the attendant inserts into either
of these holes a peg in connection with a flexible conductor leading to a receiving
telephone and through this instrument the circuit is then complete by the
permanent earth connection of the telephone.
On learning from a subscriber that he desires to speak with another the first
operation is to connect the subscriber's line to one of the coupling bars seen at
ddd in Figure 1, this the attendant does by means of a flexible conductor, of
which a number are kept ready to hand, he inserts a metal peg in which the con-
ductor ends into the vacant hole in the subscriber's block and a similar peg at the
other end of the conductor into a hole in any one of the coupling bars which he
sees to be at liberty. Next the attendant has to call the subscriber who is
wanted; he introduces the peg at one end of another of the flexible connectors
into one of the holes of this subscriber's block and he touches the other peg against
the metal band e which is fixed upon the board. The band e is connected with
one pole of a battery the other of which is put to earth. The current thus passed
into the subscribers' line rings a bell with which his instrument is provided and
thereby attracts his attention. The attendant then connecting his telephone as
already described gets into communication with the subscriber he has first called
and then proceeds to connect his line also with the coupling bar to which the line
of the subscriber who gave the original call has already been pegged.
The coupling bars d have separate carth connections each through an electro-
magnet to earth; this is done for the purpose of obtaining a notification of the
completion of the conversation between the two subscribers which the bar serves
to couple. The electro-magnet serves to liberate a shutter as in the indicators
previously described; either of the subscribers by passing a battery current
through his line wire to the bar coupling and so through the electro-magnet coils
is able to release the shutter and the attendant then removes the connections
which he had previously made as above described and replaces the shutter.
earth connection of the coupling bar being through the coils of a magnet in no
wav interferes with the telephonic conversation.
The
When this system of telephonic conversation is carried out on an extensive
scale some modifications in the arrangements above described become necessary.
Where there are a large number of subscribers several attendants are required
and the coupling bars are so long that an attendant cannot conveniently see which
of the coupling bars are disengaged and which are already in use; consequently I

page_text: so arrange the coupling bars that when brought into use they shall be turned partly
round or otherwise moved so that, at a glance, it is apparent whether a bar is or is
not in use.
A convenient arrangement is to substitute for the flat bars d fixed to the board,
round bars carried out in bracket bearings from the board. The holes for the pegs
are formed all on the same side of the bar and on the other side a broad stripe is
painted on the bar from end to end so that one side is readily distinguishable from
ihe other. The attendant when bringing a coupling bar into use turns it so as to
bring the holes to the upper side and similarly when he removes the connections
he turns the holes down or to the back and so at any time the position of the bar
which can be seen at a glance, shows whether it be in or out of use. The coupling
bars are also marked with numbers at convenient distances so that any required
bar can be found without difficulty.
Also when the number of subscribers is large it becomes necessary to divide
them into sets so that one attendant may attend to the calls of one set, another to
those of another set, and so on. I then have a separate board for each set and on
the board are the call indicators of the set and those only; but the line wire of
each subscriber is brought to the board for a subscriber belonging to the set may
desire to speak with another subscriber out of the set and it is the duty then of
his attendant to make the necessary connections But a difficulty arises when the
subscribers are thus divided into sets having different attendants for when a
subscriber is called for at one board the attendant does not know whether he may
not be already engaged and coupled for conversation at another board. To avoid
inconvenience arising from this cause I provide for each subscriber two blocks on
each board, an upper and an under one, they are coupled in series, the upper block
ou the first board makes contact for the upper block on the second board and this
for the upper block on the third board and so on. Then, at the end of the set of
boards the connections are continued through the lower blocks each in succession
until, last in the series, the lower block upon the subscriber's own board is arrived
at where (as previously described) the connection is made with the call indicator
and so to earth. Now for the purpose of calling a subscriber the peg is inserted
into the hole in the lower block and so will not interfere with any connection which
may have been previously made at either of the upper blocks: but when such a
connection exists the call will not pass, the connection with the subscriber's line
having been previously broken.
It is obvious that for upper and lower, right and left, may be substituted. The
arrangement of the connections as above described, to be used when multiple
boards are used is clearly shown by Figure 4 of the Drawings.
a, a bbc, dd are eight blocks all belonging to one subscriber, and each
subscriber has a similar series of blocks, that is to say, twice as many blocks as
there are coupling boards. The blocks a, a, are on one hoard, the blocks b, b', on
the next board and so on. These blocks are in all respects similar to those shown
at Figures 2 and 3 except that there is but one peg hole in each block. The
connections are carried from board to board in the manner shown; first the line
wire is brought to the body of one of the blocks, namely the right hand block of
the first board; from the contact screw of this block connection is made with the
borly of the right hand block on the next board and so on to the end of the set of
boards, from the contact screw of the right hand block of the end board connection
is made with the body of the left hand block on the same board and from this the
same method of connection is continued back, first to the left hand block of the
next board and so on to the end of the series; where the contact screw in connected
with the indicator and so to earth. The attendant then when calling a subscriber
inserts the peg of his flexible connector into the hole of the left hand block on his
board. By so doing he cannot interrupt any conversation but at the same time
if the subscriber be disengaged he gets into communication with him.
Or in place of this arrangement another requiring hut one block to each
subscriber on each board may be adopted; thus a small finger key or contact

page_text: maker may be provided in connection with each subscriber's block and the atten-
dant when he desires to know if a subscriber is at liberty places his finger on this
key or contact maker. If the subscriber be occupied the contact thus made com-
pletes a circuit in which is a battery and a small bell or "buzzer" and the sounding
of this bell or buzzer indicates that another connection ought not to be made.
This circuit however only becomes complete when one of the knife like blades corre-
sponding to this line wire is pegged out on one or other of the boards; the blade
being by this movement brought against a contact point and so completing the
circuit. But when by the removal of the peg the blade is permitted to spring back
this local test circuit is broken and although the finger key or contact maker may
be pressed down the "buzzer" will not sound.
The arrangements to be made, when this system of local circuits is applied to
ascertain when a subscriber is at liberty is illustrated by Figure 5. Here portions
of three boards are represented and two blocks, belonging to different subscribers
are indicated on each board. The blocks employed are similar to those shown at
Figures 2 and 3 except that in each case an insulated peg is provided upon tho
blade which, when the blade is lifted off its contact screw by the insertion of a
peg, raises a spring a into contact with a metal stud b. The three studs on the
different boards appertaining to each subscriber are connected by an insulated
wire c; two of these wires are seen in the Drawing.
"
The springs a of all the blocks on all the boards are connected to one common
wire d. Over each block there is a finger key e which when pressed down makes
contact with the corresponding stud b. Each board has its battery f and one polo
of the battery is connected with all the finger keys e on the board whilst the other
pole of the battery is connected through the electric bell or buzzer" (of which
also there is one to each board) to the common wire d. The attendant at either
board, when wishing to ascertain if a subscriber be disengaged, presses down the
finger key corresponding to this subscriber's block and thereby causes the bell
up buzzer"
y belonging to the board to sound if at either of the boards the
subscriber's wire is already coupled but otherwise the bell or "buzzer" does
not respond.
A modification of the arrangement above described is shown at Figure 6; here
the insertion of a pin into either of the blocks of a series completes a local circuit
and so operates an indicator at each of the boards. In the Figure a, b, and c are
three blocks on, as many different boards forming a series belonging to one
subscriber. Behind these blocks contact springs are placed in such positions that
the insertion of a peg into either block deflects the spring into contact with a stud d.
e is a battery, all the springs are connected with one pole of the battery and all
the studs with the other pole. The closing of the circuit by the insertion of a
peg may operate indicators at each board in any well known manner, a very
suitable way is to arrange an electro-magnet in the local circuit to operate on a
valve and so admit air under pressure to a pipe leading to small cylinder and
piston indicators of which one is provided in the vicinity of each block. When
air is admitted to the pipe the pistons are raised to the tops of the cylinders where
they remain until by another movement of the valve the air is allowed to escape
from the pipe; when the pistons fall by their own weight.
will-new-proceed t-de seribe-the-apparatus with which-each-subscriber-is
furnished-and-with-which-he-works.
The-apparatus with-which-the-subscriber works consiste-of-the-following-com-
bination of parts: namely 1-a-telephone-transmitter of the earbon-type-and
hereinafter-more-fully-described.-2-an-induction-coil--with-the-primary of which
the-telephone-is-connected when transmitting, the-secondary-being-to-line-so-that
the pulentions-induced in-it-How to the correspondent's-receiving-telephone. -n-en!!
bell: 4-a local battery: 5-a-relay to complete the bell-eireuit. -6-a-key-to-transmit
a-call current-from-the-battery into the line wire--to-gain-the-attention-of-the
attendunt-at-the-central office. 7-a-switch to put the transmitting telephone in
and ont-of-circuit. S-a-receiving telephone. These parts-are-coupled-in--snek-a

page_text: manner-that-the battery serves three-purposes: 1-when-the-relay-ic-brought into
nation-by-an-incoming current it puts the buttery-into-cirenit-with--the call bell
which-then-sounds. 2 when the key-is-depressed-it--ne-already-stated--sends-a
current-to-line, enlling or answering the enlly of the central station. 2-when-the
tranemitting telephone-is-ewitched in, the battery-is-put-inte leen! circuit-with-this
telephone-and-the-primary-of-the-induction-coil. In-working-on-the-central-office
system-this-set-of-instruments is used-on-open-eirenit, the battery being only applied
to the line-when-a-call signal has to be-given-or-answered, but provision is made
in-the-combined-instrument-admitting of its being alco-worked on private-lines--on
the closed-eirenit system, the battery being then-always-in-the-line circuit when the
apparatus-is-not-in-use.
A-diagramatie-view-of-this-instrument-is shown-ut Figure-The-several-parts
of which it is composed (with the exception already mentioned) are separately
of well-known-construction so that detailed description or Drawings of them is
unnecessary. The connecting wires (of which the arrangement is somewhat--com
pliented)-are--indiented by lines, these-wires-are-for-the-most-part-insulated the
one-from-the-other-except through the apparnius-which-they serve-to-conneet-und
combine. Where in the diagram one--line,--representing-n--wire-crosses another
similar line-n-double-bend-formed-in-one-of-the-lines-indientes-that-the-wires-de-not
come-into-electrient-contact-On-the-other-hand-where-the lines indienting-wires
meet-without-this-indication, netual-electrient-connection-is to-be-inferred. Tracing
these-connections it will be seen that when the finger-key-6-is-moved-from-the
position in which it is shown so us to change its contacts that one pole of the
battery 1 becomes connected-with-the-line wire-and-the-other-pole-is-put-to-earth.
The line circuit is then-complete-through-the corresponding indienter-c-ntthe
central-office-and-the-shutter-falls.
The battery has thus served to give the call-of-answer-as-the-ease may be
When the arm-of-the-switch--is-making contnet-with-the-two-studs to the left-of
it-(which-is-the-position in which-the-instrument-stands ready-to-receive-a-call)-the
line-circuit-is-complete through the key 6, the bobbin of the relay, the switch
arm-and-the-primmey wire of the induction coil 2. A local eirenit-also-stands
rendy-to-he-completed by the relays the tongue-of-the-relay 5-is-connected-through
the switch-arm-and the primary of the induction coil-with-one-pole-of-the
battery 1, whilst the other pole-of-this-battery-is-connected through-the-bobbin of
the-en-bell-3 and the bell-apparatus-with-the-contact point of the relay so that
immediately-n-current-from-the-central-office-ennses the tongue-of-the-relay-to-be
attracted the battery-4-acting-in-loent-eirenit-causes-the-hell to sound. When the
switch-arm-is-shifted-to-the-right-so-ne-to-make-contnet with the two-studs to the
right of it, the instrument-is-rendy for telephonie-conversation. The line-eircuit-is
complete-through-the-key--the-receiving telephone 2, the-secondary-wire--of-the
induction-coil-2, the switch and the primary-wire of the induction coil. At the
came-time-the-battery-4 is on short circuit through the primary of the induction
coil-2-as-is-required in order that--the--telephone--transmitter-+-may-be-operative.
The local circuit of the battery 1-passes through the primers wire-of the-induction
eeil 2,-the-switch-arm-7-and-the-telephone transmitter 1. Thus as-before-stated
the buttery-4-is-made-to-serve--three--distinct purposes: As-n loen! bell buttery;
as n-enll battery communienting through the line wire with--the central-office;
and-as-n-locul battery for the transmitting telephone.
By-a-clight-modification of the--connections-and--adjustments of the combined
instrument whore-described--it becomes applicable-for-use-on private-lines; each
terminal-being-supplied-with-sach-a-combined--instrument-und-the-working-being.
on the closed-eirenit system. Figure 3-is-a-diagramatic view of the instrument
with the connections and adjustments thus arranged. When the switch arm is
to-the-right--as it--is represented in the Drawing the instrument-is-arranged-for
elephonie correspondence the line eirenit is complete through the relay-3-the
key-6, the receiving tolephone S. the secondary wire of the induction coil-2, the
switch-arm 7-and-the-telephone-transmitter 1. The local eirenit of the battery

page_text: is-complete--through-the primary wire-of-the-induction-coil-2-the-switch-arm--and
the telephone transmitter 1, when the switch-arm-7-is to the left the battery-is-to
line-and-earth-through the relay coil. The enrrent may be traced-from-line
through the relay bobbin 5, the ker G-the-switch arm 7, the primary wire-of-the
induction coil-2-and-the battery 1 to earth. When this line cirenit is broken-by
the movement of the finger-key-at-either station the tongue of the relay 8-is-drawn
bock-by-its spring and the local bell-eirenit is completed; it passes from the
battery-4-through the hell call the tongue of the relay 5 and the switch
Arm-to-the-primary of the induction coil 2 and so back to the battery-henee
as before the battery-4 serves three-purposes it is n loen! bell battery +-also-a-en!!
battery-and-alse-a-leen!-battery for the-telephone-transmitter.
The transmitting telephone which I empley consists of a metal-cup-closed-at-the
top by a thin-metal diaphragm immediately facing which there is a month-piece
co-that-the-diaphragm can be thrown into vibration by the voice of a speaker. In
the-centre of the diaphragm-on-the-underside-there is a rounded projection und
this bears-upon-a-button-af-hard-carbon. This button which is slightly renghened
on its under side, rests-upon-a-button of soft carbon and this upon a thin-plate of
platinum-forming the face-of-an-adjustable support within the cup. This support
has a serew-stem-passing-through-the bottom of the metal-eup-and-by turning the
stem-the--height-of-the-support-and--ronsequently the pressure-exerted by the
diaphragm-upon-the-carbon-buttons-can be adjusted. The upper-face of the hard
earbon-button-1-coated with copper-by-electro-deposition-and-one-of-the-eirenit
wires-is-soldered to it. The other is attached to the metal eup in any convement
position. The loent battery and the primary of the induction coil-being-coupled-in
eircuit with this transmitting telephone the dow of the current remains uniform
co-long us there is no variation in the pressure of the carbon-buttons-the-one-on
the other. But when the pressure-is-enused-to-vary by the vibrations imparted te
the diaphragm-by-the-voice-a-corresponding variation takes place in the conduction
of-the-current-through-the-carbon-buttons-and-a-pulention is-set-up in the secondary
er-line-eireuit-to-which-the-receiving telephone-nt-the-other-end responds. In some
enses 1-substitute for the rounded-projection-on-the-diaphragm three contact points
ranged-around-the-centre, and these press on the upper or hard carbon button.
1 sometimes form-the-stem-of the-support-which-carries the carbon buttons-with-n
globular-end-which-is-received-into-a-corresponding socket upon a lever where it is
held-br-a-spring. This arrangement-permite-the-earken buttons-to-adjust them
selves to the pressure of the points on the diaphragm-so that the-
e-pressure-my-he
transmitted-equally by all of them. The cocket which receives the globular end
of the stem is formed upon-a-lever-and-this in-adjustable-by-n-screw. Thue the
button-support-can-be-set-up-to the diaphragm-end-the-pressure upon the carbon
buttons-varied-at-pleasure.
Figures -show-n-transverse-section-and-a-back-view-of n-hard and soft earbon
telephone-transmitter-of-the-form-just-referred to a-is the month-piece-and
immediately-in-front-of-it-is-the-ordinary telephone-diaphragm b. To the centre
of the diaphragm--there-is--cemented--n-piece-c-having-three projecting points.
Figure-10-shows-the-diaphragm b-in-plan-together with the triple-horned-bearing
pieee-c-which-it-entries. The piece-c-is-not-in-electrient-connection-with-the-metal
of the diaphragm, the japan and the cement by which-it-is-attached-being of an
insulating nature. The horns of the piece-c-bear-upon-a-coin-like-dise-d-made-of
hard-carbon-of-such quality as is eemmonly-employed-in microphones-and-for
earbon-electrodes for-the-display-of-the-electric-are: One-side-of-the-dice-d-namely
that upon which-the--horne-of-the-piece-c-bear- is thickly conted with-copper-be
electro-deposition. cis n-metal-bution-conted-with-platinum-on-the-side-next-the
diaphragm and it has a ring of vulcanite-fixed-around it us-a-rim-and so it is
converted-into-n-shallow-box-into-which-soft-carbon-or-lamp-black is firmly.com-
pressed-in-ench-mammer-us-to-form-#-soft-enrhen-dise. The hard-carbon-dise-d-ties
upon the soft-carbon dise-and-it-is-connected (br-a-thin strip of platinum-soldered
to its back)-to-the-insulated-binding-serew-inserted into the vulcanite-ring--which

page_text: rigid
embraces-the-button-e-and-from this screw a fine wire-passes-to-the-insulated
binding post-f-by which the instrument is coupled in circuit. The-stem-of the
button e-is-received-into-a-enp-like-hollow-at-the-end of the-metal-arm-g-which-is
serewed-to-the-bar-/-se-that-the--two-together-form-n-stiff-but-not-absolutely
lever-and-this-is-connected at one end-to the frame of the instrument for the
spring striphAt the other end-of-the-lever-n-spring-i-is-interposed between it
and-the-frame-and-it-is-clamped-down to the frame by a screw-k. By means of
this serew-k-the-pressure upon the carbon-dises is adjusted by experiment until the
best effect is obtained. The-electrical-connection-of-the-soft-enrben-dise is through
the-button-e-the-lever-g-h-and-the-metallic-frame of the instrument. As alrendy
stated--the--construction-of-the-instrument may be simplified by substituting-n
rounded-projection-for the triple-horned piece-c-on the diaphragm-also-by-adjusting
-pressure simply-by-a-serew-stem-passing through-the bottom of a cup-like-frume
und bearing-directly upon the button c. The screw-stem-then takes the place of
the-lever-g-h:
the-
Sometimes it is advisable to arrange telephonic circuits with two line wires in
place of completing the circuit by means of earth connections. Figure 11 shows
the modification which it is then necessary to make in the knife like blocks a of
Figure 1 and in the flexible connectors by which these are coupled together. Each
knife block has a piece of vulcanite a fixed on its face and one of the line wires is
brought to it and there connected with a small curved spring, the other line
wire is brought to the body of the bolt as before. The indicator c is connected
between the spring a* and the insulated screw all of the block as the Drawing
indicates thus when the blade like piece bears on the screw the indicator c is
in the circuit of the two line wires. The pegs at the ends of the flexible connectors
are now constructed in the following manner; Each is composed of a metal conc
having a stem surrounded with an insulating collar of vulcanite and over the
collar there is a metal ring. A handle screwed on the stem clamps the whole
together. There are two insulated wires running through the Hexible connector
connecting together the cones and the rings respectively. When the pegs are
inserted into the holes in the blocks the springs come against the rings and so
the circuit of one line wire is closed whilst that of the other is complete through
the cones.
Having thus described the nature of the said Invention and the manner of
performing the same I would have it understood that I claim :-
First. The knife like block with its blade completing the connection of the
subscriber's line through the indicator to earth and breaking this connection
when the blade part is displaced by the application of the flexible connector.
Second. The combination upon a connecting board of the knife like blocks, the
subscriber's call, the'indicators, the connecting bars and the metal band coupled
with the call battery.
Third. The combination with each connecting bar of an indicator having an
earth connection and serving to show when the flexible couplers may be removed
from the bar.
Fourth. The combination with the connecting board of coupling bars which are
moveable in their bearings and which are so arranged that the position of the bar
serves to indicate if it be in or out of use.
Fifth. The arrangement for use when the subscribers are so numerous that more
than one connecting board is required consisting in providing for each subscriber
two connecting blocks on each board one for use in coupling one subscriber's line
with another and the other for connecting the apparatus used in calling and com-
municating from the central office the whole so combined and arranged as
described in respect to Figure 4 that calls from the office cannot interrupt iba
conversation of subscribers.
Sixth. The arrangement in combination with duplicate or multiple connecting
boards of local circuits at the central office substantially as described in respect

page_text: to Figures 5 and 6 by which either of the attendants can ascertain whether a
subscriber's line wire is at liberty or has already been coupled at another board.
Seventh. The-arrangement-of-the-combined instrument described-in-respect--to
Figures 7 and 9-by which the same battery is made-to-serve-three uses: namely
as-a-local battery to werk the bell; as the call battery-to-open-communication
with-the distant station and as the local battery for-the telephone-transmitter.
Eighth. The construction of telephone-transmitters-in-such--manner that the
vibrations-imparted by the voice to the diaphragm-are-communicated--to-two-dises,
one-of-hard-and-the-other-of soft carbon and are made-to-influence an-electrie
current passing in a cirenit of which-the-hard-and-soft-carbon-dises form part:
Ninth. The construction of a telephone transmitter substantially as described-and
indicated-in-the-Drawing-annexed.
Tenth Seventh. The knife like blocks and the coupling pegs in the modified form
represented in Figure 11 for use when two line wires are in each case employed in
substitution for earth connections..
In witness whereof I the said Charles Ezra Scribner have hereunto set my
hand and seal this Tenth day of May in the year of our Lord One thousand
eight hundred and eighty.
C. E. SCRIBNER. (L.S.)

page_text: LETTERS PATENT to Charles Ezra Scribner, of 53, Guildford Street, in the
County of Middlesex, for the Invention of "IMPROVEMENTS IN APPARATUS
AND IN THE ARRANGEMENT OF MECHANISM AND PARTS TO FACILITATE
CONVERSATION BY TELEPHONE BETWEEN PERSONS AT DISTANT PLACES." Partly
a communication from abroad by George D. Clark and Milo G. Kellogg, both
of Chicago, United States of America, and George B. Scott, of New York,
also in the United States of America.
Sealed the 14th May 1880, and dated the 29th November 1879.
PROVISIONAL SPECIFICATION left by the said Charles Ezra Scribner at
the Office of the Commissioners of Patents on the 29th November 1879.
.
CHARLES EZRA SCRIBNER, of 53, Guildford Street, in the County of Middlesex.
*IMPROVEMENTS IN APPARATUS AND IN THE ARRANGEMENT OF MECHANISM AND
PARTS TO FACILITATE CONVERSATION BY TELEPHONE BETWEEN PERSONS AT
DISTANT PLACES." [Partly a communication from abroad by George D. Clark and
Milo G. Kellogg, both of Chicago, United States of America, and George B. Scott,
of New York, also in the United States of America.]
This Invention has for its object Improvements in Apparatus and in the
Arrangement of Mechanism and Parts to Facilitate Conversation by Telephone
between Persons at Distant Places.
The telephone is now being used extensively, more especially in America, on
what is known as the central office system.
On this system a large number of subscribers have each a wire leading to the
central office where there are attendants whose duty it is to connect the wire
belonging to any subscriber with that of any other subscriber with whom he may
desire to speak. To facilitate this I make at the central office the following
arrangements:-I cause each subscriber's wire to terminate in a metal block, and
these blocks are arranged upon a board, so that there are as many blocks upon
the board as there are subscribers.
Each block carries a blade similar to the folding blade of a pocket knife, and as

page_text: .
in such a knife the blade folds into a groove or recess in the block, the block corre-
sponding to the handle of the knife. A spring also tends to keep the blade closed
in its recess.
When the blade is in this position it makes contact with an insulated
stud from which a wire passes through the electro magnet of an indicating appa-
ratus to an earth connection. In this state of affairs when the subscriber sends a
call current through the wire it excites the electro-magnet, the magnet attracts its
armature, and allows an indicating shutter to fall; this shows to the attendant that
this subscriber calls for his attention. Each block (corresponding to the knife
handle) has two holes formed through it, and into one of these holes the attendant
when called sticks a metal peg which displaces the knife blade, partially opening
the knife. In this way the line wire is disconnected from the indicator. The peg
inserted into the hole in the block is attached by a flexible conductor to a telephone,
by the aid of which the attendant receives the subscriber's order to couple his wire
with that of some other subscriber with whom he may desire to converse. Now
for making these connections a series of insulated bars are provided upon the lower
part of the board, and the attendant, selecting one that is out of use, connects the
caller's line wire to it by a flexible conductor terminating in pegs at its ends. One
peg he sticks into a hole in the subscriber's block and the other into a hole in the
coupling bar.
The attendant then calls the subscriber with whom it is desired to converse, and
this ho does by means of one of the flexible conductors by which the connections
are made; he sticks the metal peg at one end thereof into one of the holes in this
subscriber's block, and touches the peg at the other end of the flexible conductor
upon a band of metal which runs across the board. This band of metal is con-
nected with one extremity of a battery, which at the other end is put to earth, so
that when the band is touched in the manner described a current passes from the
battery along the subscriber's wire, and this brings his call bell into operation. On
receiving an answer the attendant places the peg of the flexible connection into
one of the holes in the coupling bar, and the two subscribers being thus coupled
they are left to their conversation, which goes on without further care on the part
of the attendant.
In connection with each of the coupling bars there is an indicator to inform the
attendant when the conversation between the two subscribers' lines which the bar
serves to couple is complete.
Where there are a large number of subscribers several attendants are required,
and the coupling bars are so long that an attendant cannot conveniently see
which of the coupling bars are disengaged and which are already in use, conse-
quently I so arrange the coupling bars that when brought into use they shall be
turned partly round or otherwise moved so that at a glance it is apparent whether
a bar is or is not in use.
Also when the number of subscribers is large it becomes necessary to divido
them into sets, so that one attendant may attend to the calls of one set, another to
those of another set, and so on. I then have a separate board for each set, and on
the board are the call indicators of the set and those only; but the line wire of
each subscriber is brought to the board, for a subscriber belonging to the set may
desire to speak with another subscriber out of the set, and it is the duty then of
his attendants to make the necessary connections. But a difficulty arises when
the subscribers are thus divided into sets having different attendants, for when a
subscriber is called for at one board the attendant does not know whether he may
not be already engaged and coupled for conversation at another board. To avoid
inconvenience arising from this cause I provide for each subscriber two blocks on
each board, an upper and an under one, they are coupled in series; the upper block
on the first board makes contact for the upper block on the second board, and this
for the upper block on the third board, and so on. Then at the end of the set of
boards the connections are continued through the lower blocks each in succession
until last in the series the lower block upon the subscriber's own board is arrived at,

page_text: where (as previously described) the connection is made with the call indicator, and
so to earth. Now for the purpose of calling a subscriber the peg is inserted
into the hole in the lower block, and so will not interfere with any connection
which may have been previously made at either of the upper blocks; but when such
a connection exists the call will not pass, the connection with the subscriber's line
having been previously broken.
Or according to another arrangement a small finger key or contact maker may
be provided in connection with each subscriber's block, and the attendant, when
he desires to know if a subscriber is at liberty, places his finger on this key or
contact maker. If the subscriber be occupied the contact thus made completes a
circuit in which is a battery and a small bell or "buzzer," and the sounding of this
bell or buzzer indicates that another contact connection ought not to be made; this
circuit however only becomes complete when one of the knife like blades corre-
sponding to this line wire is pegged out on one or other of the boards, the blade
being by this movement brought against a contact point, and so completing the
circuit, but when, by the removal of the peg, the blade is permitted to spring back
this local test circuit is broken, and although the finger key or contact maker may
be pressed down the "buzzer" will not sound.
The apparatus with which the subscriber works consists of the following
combination of parts, namely:-1, & telephone transmitter of the carbon type, and
hereinafter more fully described; 2, in induction coil, with the primary of which
the telephone is connected when transmitting, the secondary being to line, so that
the pulsations induced in it flow to the correspondent's receiving telephone; 3, a
call bell; 4, a local battery; 5, a relay to complete the bell circuit; 6, a key to
transmit a call current from the battery into the line wire to gain the attention of
the attendant at the central office; 7, a switch to put the transmitting telephone
in and out of circuit; 8, a receiving telephone. These parts are coupled in such a
manner that the battery serves three purposes; 1, when the relay is brought into
action by an incoming current it puts the battery into circuit with the call bell,
which then sounds; 2, when the key is depressed it, as already stated, sends a
current to line, calling, or, answering the call, of the central station; 3, when the
transmitting telephone is switched in the battery is put into local circuit with this
telephone and the primary of the induction coil. In working on the central office
system this set of instruments is used on open circuit, the battery being only
applied to the line when a call signal has to be given or answered, but provision is
made in the combined instrument admitting of its being also worked on private
lines on the closed circuit system; 'the battery being then always in the line circuit
when the apparatus is not in use.
The transmitting telephone which I employ consists of a metal cup, closed at the
top by a thin metal diaphragm, immediately facing which there is a mouth piece,
so that the diaphragm can be thrown into vibration by the voice of a speaker. In
the centre of the diaphragm on the under side there is a rounded projection, and
this bears upon a button of hard carbon. This button, which is slightly roughened
on its under side, rests upon a button of soft carbon, and this upon a thin plate of
platinum forming the face of an adjustable support within the cup.
This support has a screw stem passing through the bottom of the metal cup, and
by turning the stem the height of the support and consequently the pressure
exerted by the diaphragm upon the carbon buttons can be adjusted. The upper
face of the hard carbon button is coated with copper by electro-deposition, and one
of the circuit wires is soldered to it; the other is attached to the metal cup in any
convenient position. The local battery and the primary of the induction coil being
coupled in circuit with this transmitting telephone, the flow of the current remains
uniform so long as there is no variation in the pressure of the carbon buttons, the one
on the other, but when the pressure is caused to vary by the vibrations imparted
to the diaphragm by the voice a corresponding variation takes place in the
conduction of the current through the carbon buttons, and a pulsation is set up in

page_text: the secondary or line circuit, to which the receiving telephone at the other end
responds.
In some cases I substitute for the rounded projection on the diaphragm three
contact points ranged around the centre, and these press on the upper or hard
carbon button. I form the stem of the support which carries the carbon buttons
with a globular end, which is received into a corresponding socket upon a lever,
where it is held by a spring. This arrangement permits the carbon buttons to
adjust themselves to the pressure of the points on the diaphragm, so that the
pressure may be transmitted equally by all of them. The socket which receives
the globular end of the stem is formed upon a lever, and this is adjustable by a
screw. Thus the button support can be set up to the diaphragm, and the pressure
upon the carbon buttons varied at pleasure.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles Ezra Scribner in the Great Seal Patent Office on the
28th May 1880.
.
CHARLES EZRA SCRIBNER, of 53, Guildford Street, in the County of Middlesex.
"IMPROVEMENTS IN APPARATUS AND IN THE ARRANGEMENT OF MECHANISM AND
PARTS TO FACILITATE CONVERSATION BY TELEPHONE BETWEEN PERSONS AT
DISTANT PLACES." Partly a communication from abroad by George D. Clark and
Milo G. Kellogg, both of Chicago, United States of America, and George B. Scott,
of New York, also in the United States of America.
This Invention has for its object Improvements in Apparatus and in the
Arrangement of Mechanism and Parts to Facilitate Conversation by Telephone
between Persons at Distant Places.
The telephone is now being used extensively, more especially in America, on
what is known as the central office system. On this system a large number of
subscribers have each a wire leading to the central office where there are attendants
whose duty it is to connect the wire belonging to any subscriber with that of any
other subscriber with whom he may desire to speak. To facilitate this I make at
the central office the following arrangements:-I cause each subscriber's wire to
terminate in a metal block, and these blocks are arranged upon a board, so that
there are as many blocks upon the board as there are subscribers. Each block
carries a blade similar to the folding blade of a pocket knife, and as in such a knife
the blade folds into a groove or recess in the block, the block corresponding to the
handle of the knife. A spring also tends to keep the blade closed in its recess.
When the blade is in this position it makes contact with an insulated stud, from
which a wire passes through the electro-magnet of an indicating apparatus to an
earth connection. In this state of affairs when the subscriber sends a call current
through the wire it excites the electro-magnet, the magnet attracts its armature,
and allows an indicating shutter to fall; this shows to the attendant that this
subscriber calls for his attention. Each block (corresponding to the knife handle)
has two holes formed through it, and into one of these holes the attendant when
called sticks a metal peg which displaces the knife blade, partially opening the
knife. In this way the line wire is disconnected from the indicator. The peg
inserted into the hole in the block is attached by a flexible conductor to a
telephone, by the aid of which the attendant receives the subscriber's order to
couple his wire with that of some other subscriber with whom he may desire to
converse. Now for making these connections a series of insulated bars are provided
upon the lower part of the board, and the attendant selecting one that is out of use
connects the caller's line wire to it by a flexible conductor terminating in pegs at
its ends. One peg he sticks into a hole in the subscriber's block, and the other into
a hole in the coupling bar.
The attendant then calls the subscriber with whom it is desired to converse, and
this he does by means of one of the flexible conductors by which the connections
are made; he sticks the metal peg at one end thereof into one of the holes in this
subscriber's block, and touches the peg at the other end of the flexible conductor
upon a band of metal which runs across the board. This band of metal is connected
with one extremity of a battery which at the other end is put to earth, so that
when the band is touched in the manner described a current passes from the battery
along the subscriber's wire, and this brings his call bell into operation. On
receiving an answer, the attendant places the peg of the flexible connection into one
of the holes in the coupling bar, and the two subscribers being thus coupled they
are left to their conversation, which goes on without further care on the part of the
attendant.
"
In connection with each of the coupling bars there is an indicator to inform the

page_text: attendant when the conversation between the two subscribers' lines, which the bar
serves to couple, is complete.
Figure 1 of the annexed Drawings is a front view of a coupling board arranged
according to this Invention. a, a, a, are the knife like terminal blocks; a front
view of one of these is shown at Figure 2, and an underside view at Figure 3; in
this latter Figure the board is seen in section; b is a screw serving to attach the
metal block to the board, and the nut upon it serves also to clamp and connect an
insulated wire which leads directly to the line wire of the subscriber. There are as
many blocks on the board as there are subscribers, who in this arrangement may
be supposed not to be so numerous as to require to be divided into different sets, as
herein after explained. The block a, as will be seen, is in each case slotted to
receive a blade like piece a' which is pin jointed to the block, and a spring all tends
to bold the blade in contact with the insulated screw a¹¹¹ carried upon the block.
A wire passes from the screw all to the coils of an electro-magnet through which
the screw has an earth connection. The electro-magnet forms part of an indicator
of well known construction; the armature when attracted withdraws a catch and
permits a shutter to fall. This, it will be observed, takes place whenever the
subscriber connects his line wire to a battery; the shutter on falling exposes a
number corresponding to that by which the subscriber is known in the office, and
announces that this subscriber desires to speak. In Figure 1 these indicators are
represented at c, c, c. Each block a has, it will be seen, two holes a*, ax, in it, and
a peg inserted into either of these holes has the effect of breaking contact at a To
asce ain what it is that the subscriber desires, the attendant inserts into either of
these holes a peg in connection with a flexible conductor leading to a receiving
telephone, and through this instrument the circuit is then complete by the
permanent earth connection of the telephone.
On learning from a subscriber that he desires to speak with another the first
operation is to connect this subscriber's line to one of the coupling bars, seen at
d, d, d, in Figure 1; this the attendant does by means of a flexible conductor, of
which a number are kept ready to hand. He inserts a metal peg in which the con-
ductor ends into the vacant hole in the subscriber's block, and a similar peg at the
other end of the conductor into a hole in any one of the coupling bars & which be
sees to be at liberty. Next the attendant has to call the subscriber who is
wanted; he introduces the peg at one end of another of the flexible connectors
into one of the holes of this subscriber's block, and he touches the other peg against
the metal band e, which is fixed upon the board. The band e is connected with
one pole of a battery, the other of which is put to earth. The current thus passed
into the subscribers' line rings, a bell, with which his instrument is provided, and
thereby attracts his attention. The attendant then connecting his telephone, as
already described, gets into communication with the subscriber he has first called, and
then proceeds to connect his line also with the coupling bar to which the line of
the subscriber who gave the original call has already been pegged.
The coupling bars d have separate earth connections each through an electro-
magnet to earth; this is done for the purpose of obtaining a notification of the
completion of the conversation between the two subscribers which the bar serves
to couple. The electro-magnet serves to liberate a shutter, as in the indicators
previously described; either of the subscribers, by passing a battery current
through his line wire to the bar coupling, and so through the electro-magnet coils,
is able to release the shutter, and the attendant then removes the connections
which he had previously made, as above described, and replaces the shutter. The
earth connection of the coupling bar being through the coils of a magnet in no way
interferes with the telephonic conversation.
When this system of telephonic conversation is carried out on an extensive
scale some modifications in the arrangements above described become necessary.
Where there are a large number of subscribers several attendants are required,
and the coupling bars are so long that an attendant cannot conveniently see which
of the coupling bars are disengaged and which are already in use; consequently I

page_text: so arrange the coupling bars that when brought into use they shall be turned partly
round or otherwise moved so that at a glance it is apparent whether a bar is or is
not in use.
A convenient arrangement is to substitute for the flat bars d fixed to the board,
round bars carried out in bracket bearings from the board. The holes for the pegs
are formed all on the same side of the bar, and on the other side a broad stripe is
painted on the bar from end to end, so that one side is readily distinguishable from
the other. The attendant, when bringing a coupling bar into use, turns it so as to
bring the holes to the upper side, and similarly when he removes the connections
he turns the holes down or to the back, and so at any time the position of the bar
which can be seen at a glance shows whether it be in or out of use. The coupling
bars are also marked with numbers at convenient distances, so that any required
bar can be found without difficulty.
Also, when the number of subscribers is large it becomes necessary to divide
them into sets, so that one attendant inay attend to the calls of one set, another to
those of another set, and so on. I then have a separate board for ench sot, and on
the board are tho call indicators of the set, and those only; but the line wire of
each subscriber is brought to the board for a subscriber belonging to the set may
desire to speak with another subscriber out of the set, and it is the duty then of
his attendant to make the necessary connections. But a difficulty arises when the
subscribers are thus divided into sets having different attendants, for when a
subscriber is called for at one board the attendant does not know whether he inay
not be already engaged and coupled for conversation at another board. To avoid
inconvenience arising from this cause I provide for each subscriber two blocks on
oach board, an upper and an under one, they are coupled in series, the upper block
on the first board makes contact for the upper block on the second board, and this
for the upper block on the third board, and so on. Then, at the end of the set of
boards the connections are continued through the lower blocks, each in succession
until last in the series, the lower block upon the subscriber's own board is arrived at
where (as previously described) the connection is made with the call indicator and
so to earth. Now, for the purpose of calling a subscriber the peg is inserted into
the hole in the lower block, and so will not interfere with any connection which
may have been previously made at either of the upper blocks, but when such a
connection exists the call will not pass, the connection with the subscriber's line
having been previously broken.
It is obvious that for upper and lower, right and left may be substituted. The
arrangement of the connections as above described to be used when multiple boards
are used is clearly shown by Figure 4 of the Drawings.
a, a, b, b, c, c, d, d', are eight blocks, all belonging to one subscriber, and each
subscriber has a similar series of blocks, that is to say, twice as many blocks as
there are coupling boards. The blocks a, a, are on one board, the blocks b, b', on
the next board, and so on; these blocks are in all respects similar to those shown
at Figures 2 and 3, except that there is but one peg hole in each block. The
connections are carried from board to board in the manner shown; first, the line
wire is brought to the body of one of the blocks, namely, the right hand block of
the first board; from the contact screw of this block connection is made with the
body of the right hand block on the next board, and so on to the end of the set of
boards; from the contact screw of the right hand block of the end board connection
is made with the body of the left hand block on the same board, and from this the
same method of connection is continued back, first, to the left hand block of the
next board, and so on to the end of the series, where the contact screw is connected
with the indicator, and so to earth. The attendant then when calling a subscriber
inserts the peg of his flexible connector into the hole of the left hand block on his
board. By so doing he cannot interrupt any conversation, but at the same time
if the subscriber be disengaged he gets into communication with him.
Or in place of this arrangement another requiring but one block to each
subscriber on each board may be adopted. Thus, a small finger key or contact

page_text: maker may be provided in connection with each subscriber's block, and the attendant
when he desires to know if a subscriber is at liberty places his finger on this key
or contact maker; if the subscriber be occupied the contact thus made completes a
circuit in which is a battery and a small bell or "buzzer;" and the sounding of this
bell or buzzer indicates that another councction ought not to be made. This
circuit however only becomes complete when one of the knife like blades corre-
sponding to this line wire is pegged out on one or other of the boards, the blade
being by this movement brought against a contact point and so completing the
circuit; but when by the removal of the peg the blade is permitted to spring back
this local test circuit is broken, and although the finger key or contact maker may
he pressed down the "buzzer " will not sound.
The arrangements to be made when this system of local circuits is applied to
ascertain when a subscriber is at liberty is illustrated by Figure 5. Here portions
of three boards are represented, and two blocks, belonging to different subscribers
are indicated on each board. The blocks employed are similar to those shown at
Figures 2 and 3, except that in each case an insulated peg is provided upon the
blade which, when the blade is lifted off its contact screw by the insertion of a
peg, raises a spring a into contact with a metal stud b. The three studs bon the
different boards appertaining to each subscriber are connected by an insulated
wire c; two of these wires are seen in the Drawing.
The springs a of all the blocks on all the boards are connected to one common
wire . Over each block there is a finger key e which when pressed down makes
contact with the corresponding stud b. Each board has its battery f, and one pole
of the battery is connected with all the finger keys e on the board, whilst the other
pole of the battery is connected through the electric bell or "buzzer" g, (of which
also there is one to each board) to the common wire d. The attendant at either
board, when wishing to acertain if a subscriber be disengaged, presses down the
finger key corresponding to this subscriber's block, and thereby causes the bell
or "buzzer" g belonging to the board to sound if at either of the boards the
subscriber's wire is already coupled, but otherwise the bell or "buzzer" does
not respond.
A modification of the arrangement above described is shown at Figure 6. Here
the insertion of a pin into either of the blocks of a series completes a local circuit,
and so operates an indicator at each of the boards. In the Figure a, b, and c are
three blocks on as many different boards, forming a series belonging to one
subscriber. Behind these blocks contact springs are placed in such positions that
the insertion of a peg into either block deflects the spring into contact with a stud d.
e is a battery; all the springs are connected with one pole of the battery, and all
the studs & with the other pole. The closing of the circuit by the insertion of a
peg may operate indicators at each board in any well known manner. A very
suitable way is to arrange an electro-magnet in the local circuit to operate on a
valve and so admit air under pressure to a pipe leading to small cylinder and piston
indicators, of which one is provided in the vicinity of each block. When air is
admitted to the pipe the pistons are raised to the tops of the cylinders, where they
remain until by another movement of the valve the air is allowed to escape from
the pipe, when the pistons fall by their own weight.
I will now proceed to describe the apparatus with which each subscriber is
furnished, and with which he works.
The apparatus with which the subscriber works consists of the following com-
bination of parts, namely:-1, a telephone transmitter of the carbon type, and
hereinafter more fully described; 2, an induction coil with the primary of which
the telephone is connected when transmitting, the secondary being to line so that
the pulsations induced in it flow to the correspondent's receiving telephone; 3, a call
bell; 4, a local battery; 5, a relay to complete the bell circuit; 6, a key to transmit
a call current from the battery into the line wire to gain the attention of the
attendant at the central office; 7, a switch to put the transmitting telephone in
and out of circuit; 8, a receiving telephone. These parts are coupled in such a

page_text: manner that the battery serves three purposes:-1, when the relay is brought into
action by an incoming current it puts the battery into circuit with the call bell,
which then sounds; 2, when the key is depressed it, as already stated, sends a
current to line, calling, or answering the call, of the central station; 3, when the
transmitting telphone is switched in the battery is put into local circuit with this
telephone and the primary of the induction coil. In working on the central office
system this set of instruments is used on open circuit, the battery being only applied
to the line when a call signal has to be given or answered, but provision is made
in the combined instrument admitting of its being also worked on private lines on
the closed circuit system, the battery being then always in the line circuit when the
apparatus is not in use.
A diagramatic view of this instrument is shown at Figure 7. The several parts
of which it is composed, (with the exception already mentioned,) are separately
of well known construction, so that detailed description or Drawings of them is
unnecessary. The connecting wires (of which the arrangement is somewhat com-
plicated) are indicated by lines. These wires are for the most part insulated the
one from the other, except through the apparatus which they serve to connect and
combine. Where in the diagram one line representing a wire crosses another
similar line a double bend formed in one of the lines indicates that the wires do not
come into electrical contact. On the other hand where the lines indicating wires
meet without this indication actual electrical connection is to be inferred. Tracing
these connections it will be seen that when the finger key 6 is moved from the
position in which it is shown so as to change its contacts that one pole of the
battery 4 becomes connected with the line wire and the other pole is put to earth.
The line circuit is then complete through the corresponding indicator c at the
central office, and the shutter falls.
The battery has thus served to give the call or answer as the case may be.
When the arm of the switch 7 is making contact with the two studs to the left of
it (which is the position in which the instrument stands ready to receive a call) the
line circuit is complete through the key 6, the bobbin of the relay 5, the switch
arm 7, and the primary wire of the induction coil 2. A local circuit also stands
ready to be completed by the relay. The tongue of the relay 5 is connected through
the switch arm 7, and the primary of the induction coil 2 with one pole of the
battery 4, whilst the other pole of this battery is connected through the bobbin of
the call bell 3, and the bell apparatus with the contact point of the relay 5, so that
immediately a current from the central office causes the tongue of the relay to be
attracted the battery 4 acting in local circuit causes the bell to sound. When the
switch arın is shifted to the right so as to make contact with the two studs to the
right of it the instrument is ready for telephonic conversation. The line circuit is
complete through the key 6, the receiving telephone 8, the secondary wire of the
induction coil 2, the switch 7, and the primary wire of the induction coil. At the
same time the battery 4 is on short circuit through the primary of the induction
coil 2 as is required in order that the telephone transmitter 1 may be operative.
The local circuit of the battery 4 passes through the primary wire of the induction
coil 2, the switch arm 7, and the telephone transmitter 1. Thus, as before stated,
the battery 4 is made to serve three distinct purposes:-As a local bell battery;
as a call battery, communicating through the line wire with the central office;
and as a local battery for the transmitting telephone.
By a slight modification of the connections and adjustments of the combined
instrument above described, it becomes applicable for use on private lines, each
terminal being supplied with such a combined instrument, and the working being
on the closed circuit system; Figure 8 is a diagramatic view of the instrument
with the connections and adjustinents thus arranged. When the switch arm 7 is
to the right, as it is represented in the Drawing, the instrument is arranged for
telephonic correspondence. The line circuit is complete through the relay 3, the
key 6, the receiving telephone 8, the secondary wire of the induction coil 2, the
switch arm 7, and the telephone transmitter 1. The local circuit of the battery 4

page_text: is complete through the primary wire of the induction coil 2, the switch arm 7, and
the telephone transmitter 1. When the switch arm 7 is to the left the battery is to
line and earth through the relay coil 5. The current may be traced from line
through the relay bobbin 5, the key 6, the switch arm 7, the primary wire of the
induction coil 2, and the battery 4 to carth; when this line circuit is broken by
the movement of the finger key at either station, the tongue of the relay 3 is drawn
back by its spring and the local bell circuit is completed; it passes from the
battery 4, through the bell coil 3, by the tongue of the relay 5, and the switch
arın 7, to the primary of the induction coil 2, and so back to the battery, hence,
as before, the battery 4 serves three purposes; it is a local bell battery, also a call
battery, and also a local battery for the telephone transmitter.
.
The transmitting telephone which I employ consists of a metal cup closed at the
top by a thin metal diaphragm, immediately facing which there is a mouth piece,
so that the diaphragm can be thrown into vibration by the voice of a speaker. In
the centre of the diaphragm on the under side there is a rounded projection, and
this bears upon a button of hard carbon; this button, which is slightly roughened
on its under side, rests upon a button of soft carbon, and this upon a thin plate of
platinum, forming the face of an adjustable support within the cup; this support
has a screw stem passing through the bottom of the metal cup, and by turning the
stem the height of the support, and consequently the pressure exerted by the
diaphragm upon the carbon buttons can be adjusted. The upper face of the hard
carbon button is coated with copper by electro-deposition, and one of the circuit
wires is soldered to it; the other is attached to the metal cup in any convenient
position. The local battery and the primary of the induction coil being coupled in
circuit with this transmitting telephone, the flow of the current remains uniform
so long as there is no variation in the pressure of the carbon buttons the one on
the other; but when the pressure is caused to vary by the vibrations imparted to
the diaphragin by the voice, a corresponding variation takes place in the conduction
of the current through the carbon buttons, and a pulsation is set up in the secondary
or line circuit to which the receiving telephone at the other end responds. In some
cases I substitute for the rounded projection on the diaphragm three contact points
ranged around the centre, and these press on the upper or hard carbon button.
I sometimes form the stem of the support which carries the carbon buttons with a
globular end, which is received into a corresponding socket upon a lever where it is
held by a spring. This arrangement permits the carbon buttons to adjust them-
selves to the pressure of the points on the diaphragm so that the pressure may be
transmitted equally by all of them. The socket which receives the globular end
of the stem is formed upon a lever, and this is adjustable by a screw; thus the
button support can be set up to the diaphragm, and the pressure upon the carbon
buttons varied at pleasure.
Figures 9 show a transverse section and a back view of a hard and soft carbon
telephone transmitter of the form just referred to. a is the mouth piece, and
immediately in front of it is the ordinary telephone diaphragm b. To the centre
of the diaphragm there is cemented a picce c having three projecting points.
Figure 10 shows the diaphragm b in plan, together with the triple horned bearing
piece c which it carries. The piece c is not in electrical connection with the metal
of the diaphragin, the japan and the cement by which it is attached being of an
insulating nature. The horns of the piece c bear upon a coin like disc d made of
hard carbon of such quality as is commonly employed in microphones and for
carbon electrodes for the display of the electric arc. One side of the disc d, namely,
that upon which the horns of the piece c bear, is thickly coated with copper by
electro-deposition; e is a metal button coated with platinum on the side next the
diaphragm, and it has a ring of vulcanite fixed around it as a rim, and so it is
converted into a shallow box into which soft carbon or lamp black is firmly com-
pressed in such manner as to form a soft carbon disc. The hard carbon disc d lies
upon the soft carbon disc, and it is connected (by a thin strip of plattinum soldered
to its back) to the insulated binding screw inserted into the vulcanite ring which

page_text: embraces the button e, and from this screw a fine wire passes to the insulated
binding post f by which the instrument is coupled in circuit. The stem of the
button e is received into a cup like hollow at the end of the metal arm g which is
screwed to the bar h, so that the two together form a stiff but not absolutely rigid
lever, and this is connected at one end to the frame of the instrument by the
spring strip . At the other end of the lever a spring i is interposed between it
and the frame, and it is clamped down to the frame by a screw . By means of
this screw & the pressure upon the carbon discs is adjusted by experiment until the
best effect is obtained. The electrical connection of the soft carbon disc is through
the button e, the lever g, h, and the metallic frame of the instrument. As already
stated the construction of the instrument may be simplified by substituting a
rounded projection for the triple horned piece con the diaphragm; also by adjusting
the pressure simply by a screw stem passing through the bottom of a cup like frame
and bearing directly upon the button c. The screw stem then takes the place of
the lever 9₁ h.
Sometimes it is advisable to arrange telephonic circuits with two line wires in
place of completing the circuit by means of earth connections. Figure 11 shows
the modification which it is then necessary to make in the knife like blocks a of
Figure 1 and in the flexible connectors by which these are coupled together. Each
knife block has a piece of vulcanite a fixed on its face, and one of the line wires is
brought to it and there connected with a small curved spring a*; the other line
wire is brought to the body of the bolt as before. The indicator c is connected
between the spring a* and the insulated screw all of the block, as the Drawing
indicates; thus when the blade like piece bears on the screw all the indicator c is
in the circuit of the two line wires. The pegs at the ends of the flexible connectors
are now constructed in the following manner :-Each is composed of a metal cone
having a stem surrounded with an insulating collar of vulcanite, and over the collar
there is a metal ring '. A handle screwed on the stem clamps the whole together.
There are two insulated wires runuing through the flexible connector connecting
together the cones and the rings respectively. When the pegs are inserted
into the holes in the blocks the springs come against the rings ', and so the
circuit of one line wire is closed whilst that of the other is complete through the
cones x.
Having thus described the nature of the said Invention, and the manner of
performing the same, I would have it understood that I claim,―
First. The knife like block with its blade completing the connection of the
subscriber's line through the indicator to earth, and breaking this connection
when the blade part is displaced by the application of the flexible connector.
Second. The combination upon a connecting board of the knife like blocks, the
subscriber's call, the indicators, the connecting bars, and the metal band coupled
with the call battery.
Third. The combination with each connecting bar of an indicator having an
earth connection and serving to show when the flexible couplers may be removed
from the bar.
Fourth. The combination with the connecting board of coupling bars which are
moveable in their bearings, and which are so arranged that the position of the bar
serves to indicate if it be in or out of use.
Fifth. The arrangement for use when the subscribers are so numerous that more
than one connecting board is required, consisting in providing for each subscriber
two connecting blocks on each board, one for use in coupling one subscriber's line
with another, and the other for connecting the apparatus used in calling and com-
municating from the central office, the whole so combined and arranged, as described
in respect to Figure 4; that calls from the office cannot interrupt the conversation
of subscribers.
Sixth. The arrangement, in combination with duplicate or multiple connecting
boards, of local circuits at the central office, substantially as described in respect

page_text: to Figures 5 and 6, by which either of the attendants can ascertain whether a
subscriber's line wire is at liberty or has already been coupled at another board.
Seventh. The arrangement of the combined instrument, described in respect to
Figures 7 and 8, by which the same battery is made to serve three uses; namely,
as a local battery to work the bell, as the call battery to open communication
with the distant station, and as the local battery for the telephone transmitter.
Eighth. The construction of telephone transmitters in such manner that the
vibrations imparted by the voice to the diaphragm are communicated to two discs,
one of hard and the other of soft carbon, and are made to influence an electric
current passing in a circuit of which the hard and soft carbon discs form part.
Ninth. The construction of a telephone transmitter, substantially as described and
indicated in the Drawing annexed.
Tenth. The knife like blocks and the coupling pegs in the modified form repre-
sented in Figure 11, for use when two line wires are in each case employed in
substitution for earth connections.
In witness whereof, I, the said Charles Ezra Scribner, have hereunto set my
hand and seal, this Tenth day of May, in the year of our Lord One thousand
eight hundred and eighty.
C. E. SCRIBNER. (L.S.)