IMPROVEMENTS IN TELEPHONES
Year: 1879

page_text: "
LETTERS PATENT to Arnold White, of Queen Victoria Street, in the City of
A com-
IMPROVEMENTS IN TELEPHONES.
London, for the Invention of
munication from abroad by Thomas Alva Edison, of Menlo Park, in the State
of New Jersey, in the United States of America.
Sealed the 19th March 1880, and dated the 31st December 1879.
PROVISIONAL SPECIFICATION left by the said Arnold White at the Office
of the ('ominissioners of Patents on the 31st December 1879.
"IMPROVE
ARNOLD WHITE, of Queen Victoria Street, in the City of London.
A cominunication from abroad by Thomas Alva Edison,
MENTS IN TELEPHONES."
of Menlo Park, in the State of New Jersey, in the United States of America.
This Invention relates to improvements in and connected with the receiving
apparatus of telephones, in respect of which Letters Patent were granted to the
said Thomas Alva Edison, dated respectively the 30th July 1877, No. 2909. and the
15th June 1878, No. 2396.
According to the first of the said former Letters Patent the receiving apparatus
was provided with a frictional surface moved by power, and acting in connection
with the electric current to vibrate a tympan and produce tones corresponding to
those actuating the transmitting apparatus. According to the second of the said
former Letters Patent the said frictional surface was composed of chalk combined
with a chemical substance and kept moistened with water.
Now according to the present Invention it is proposed to dispense with the
chemical substance previously employed in combination with the chalk, and to use
the latter alone moistened with distilled or pure water.
In carrying out the said former Invention it has been customary to use a metul
spring or arm tipped or faced with platinum in contact with the chalk body of the
receiving apparatus. Now, according to the present Invention, it is proposed to
employ a metal spring or arın tipped or faced with paladium, whereby the degree
of frictional variation is increased under the action of a given strength of electric
current, and a corresponding augmentation in the volume of sound is obtained.
Another part of the present Invention relates to the arrangement of the con-
nections of the induction coil in which the several parts of the apparatus are placed.

page_text: In carrying out this part of the Invention it is found advantageous to place the
receiving apparatus in a tertiary circuit in lieu of in the secondary circuit: but it is
found that by reason of the presence of two continuous circuits, viz., the primary
and tertiary circuits, the full effect of the current from the distant station is not
obtained upon the receiving apparatus, a portion of it passing from the secondary to
the primary circuit. In order to obviate this defect, a key is placed in the primary
circuit, so arranged as to keep that circuit open while the current from the distant
station is acting upon the receiving apparatus, the said key being depressed for the
purpose of closing the primary circuit when it is desired to actuate the transmitting
apparatus. It has been found, however, that upon opening or closing this key a
powerful inductive discharge is directed upon the receiving apparatus at the same
station, which discharge has a deteriorating effect upon the surface of the chalk
body of the receiving apparatus.
According to this part of the present Invention the defect before mentioned is
obviated by opening the tertiary circuit prior to the closing of the primary circuit,
and closing the tertiary circuit to leave it in condition to be acted upon by a
current from the distant station, immediately after the closing of the primary
circuit, and also by opening the tertiary circuit prior to the opening of the primary
circuit, and closing the tertiary circuit immediately thereafter.
In carrying this part of the present Invention into effect, these conditions are
fulfilled by the employment of a single key arranged in the following manner,
2. One of the wires from the tertiary coil, and one of the wires from the primary
coil, are permanently attached to the lever of the key, and the other wire of the
tertiary coil is bifurcated, and the ends of its two lengths are provided with contact
points placed one at each side of the lever of the key, but at such a distance i
therefrom as to admit of a third contact point connected with the other wire of the
primary coil being brought into contact with the lever of the key while it is
passing from one to the other of the two contact points of the bifurcated tertiary
wire.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Arnold White in the Great Seal Patent Office on the 14th April
1880.
ARNOLD WHITE, of Queen Victoria Street, in the City of London. "IMPROVE-
MENTS IN TELEPHONES. communication from abroad by Thomas Alva Edison,
of Menlo Park, in the State of New Jersey, in the United States of America.
The said Invention relates to improvements in and connected with the receiving
apparatus of telephones, in respect of which Letters Patent were granted to the
said Thomas Alva Edison, dated respectively the Thirtieth July One thousand eight
hundred and seventy seven, No. 2909, and the Fifteenth June One thousand eight
hundred and seventy eight, No. 2396.

page_text: According to the first of the said former Letters Patent the receiving apparatus
was provided with a frictional surface moved by power and acting in connection
with the electric current to vibrate a tympan, and produce tones corresponding to
those actuating the transmitting apparatus. According to the second of the said
former Letters Patent the said frictional surface was composed of chalk combined
with a chemical substance, and kept moistened with water.
Now, according to the present Invention, it is proposed to dispense with the
chemical substance previously employed in combination with the chalk, and to use
the latter alone moistened with distilled or pure water.
In carrying out the said former Invention it has been customary to use a metal
spring or armi tipped or faced with platinum in contact with the chalk body of the
receiving apparatus. Now, according to the present Invention, it is proposed to
employ a metal spring or arm tipped or faced with paladium, whereby the degree
of frictional variation is increased under the action of a given strength of electric
current, and a corresponding augmentation in the volume of sound is obtained.
Another part of the present Invention relates to the arrangement of the con-
nections of the induction coil in which the several parts of the apparatus are
placed.
In carrying out this part of the Invention it is found advantageous to place the
receiving apparatus in a tertiary circuit in lieu of in the secondary circuit; but it
is found that by reason of the presence of two continuous circuits, viz., the
primary and tertiary circuits, the full effect of the current from the distant station
is not obtained upon the receiving apparatus, a portion of it passing from the
secondary to the primary circuit. In order to obviate this defect a key is placed in
the primary circuit, so arranged as to keep that circuit open while the current from
the distant station is acting upon the receiving apparatus, the said key being
depressed for the purpose of closing the primary circuit when it is desired to actuate
the transmitting apparatus. It has been found, however, that upon opening or
closing this key a powerful inductive discharge is directed upon the receiving
apparatus at the same station, which discharge has a deteriorating effect upon the
surface of the chalk body of the receiving apparatus.
According to this part of the present Invention the defect before mentioned is
obviated by opening the tertiary circuit prior to the closing of the primary circuit,
and closing the tertiary circuit to leave it in condition to be acted upon by a current
from the distant station immediately after the closing of the primary circuit, and
also by opening the tertiary circuit prior to the opening of the primary circuit, and
closing the tertiary circuit immediately thereafter.
In carrying this part of the present Invention into effect these conditions are
fulfilled by the employment of a single key arranged in the following manner,
videlicet One of the wires from the tertiary coil and one of the wires from the
primary coil are permanently attached to the lever of the key, and the other wire
of the tertiary coil is bifurcated, and the ends of its two lengths are provided with
contact points placed one at each side of the lever of the key, but at such a
distance therefrom as to admit of a third contact point, connected with the other
wire of the primary coil, being brought into contact with the lever of the key
while it is passing from one to the other of the two contact points of the bifurcated
tertiary wire.
In order that the said Invention may be perfectly understood, I shall describe a
complete set of instruments for the purposes of telephonic communication with the
Invention applied thereto, and in so doing shall refer to the several Figures on the
accompanying Sheet of Drawings, the same letters of reference in which indicate
corresponding parts in all the Figures.
Figure 1 of the accompanying Drawings represents in sectional elevation a
general view of the instruments and their connections for the purpose of telephonic
communication between two stations, marked respectively No 1 and No. 2, the
transmitters being drawn to their natural size, whilst the other parts of the
apparatus are drawn to a scale of one half size.

page_text: Figure 2 represents an elevation of one of the receivers, shewn detached with the
cover removed, and Figure 3 is a transverse section of the same.
A, A, are the transmitters; B, B, are the receivers ; C, C, are the batteries; D, D,
are the induction coils, a being their primary circuit (shewn in thick lines) in which
the transmitter is placed; b, their secondary circuit (indicated in thick dotted lines),
which constitutes the main line, and c, their tertiary circuit (denoted by series
of short thick lines and dots) in which the receiver is placed; E, E, are relays, and
F, F, are call bells or sounders, d, d, being local circuits (indicated by a series
of short fine lines in the Drawing), in which the call bell or sounders are placed.
The transmitter is constructed in the following manner :-
e is a shell of metal (by preference cast iron), on which is secured a disc ✓ of
brass (for example) platinized on its top surface f³, around which disc is arranged a
ring 9 of vulcanite or other suitable non conducting material projecting above the
surface of the disc for a sufficient height to form a cup. Into this cup is inserted a
button of carbon (by preference the finest lamp black, moulded and consolidated
under pressure), and upon the top of this button is placed another metal disc e',
platinized upon its surface it. The terminal a¹ of the divided portion at of the
wire a is connected to the disc i by means of a strip of platinum, whilst the
terminal a of such portion of the said wire is attached to the shell e. The carbon
button h, with the inetal disc i, is thus interposed in the electric circuit, and it is so
arranged as to be susceptible of mechanical influence from the exterior in the
following manner :-
On the rim of the shell e is placed a membrane or tympan of mica or iron (tor
example), which is held firmly at its edges by the mouth piece m, attached by screws
to the shell e, the tympan being thus clamped between the mouth piece and the
shell. The tympan is provided with a boss at its centre, through which passes a
screw n, the point of which bears upon the disc i faced with nonconducting
material. In fitting the parts together, the screw n is turned until the tympan,
the disc i, and the carbon button are brought into such relationship as to produce
a minimum, but actual contact between the surfaces of all, but not to establish the
contact to such an extent as to constitute an initial degree of pressure.
The apparatus operates in the following manner :-
By producing sound (say for example, speaking) into the mouth piece m, the
tympan is thrown into vibration, and the effect being transmitted to the disc i,
and the carbon button h, their positions in relation to each other are varied, greater
or less intimacy of contact being produced between the two surfaces of the carbon
button h and the discs i, f, on opposite sides of it. By these means a greater or less
number of points in the contiguous surfaces are brought into contact as the tympan
is vibrated, whereby the resistance to the passage of the current is varied, and the
current passing through the primary circuit a is transformed into an undulatory
one; the induced current passing through the secondary circuit or main line bis
also converted into an undulatory current, and thence a similar change takes place
in the induced current passing through the tertiary circuit c, in which the receiver
at the distant station is placed, the undulations of which current exactly correspond
to the waves of sound which originally actuated the tympan at the sending
station.
The receivers B, B, are constructed in the following manner, reference being had
to the general view, Figure 1, and the details, Figures 2 and 3 :-
o is a cylinder of chalk, moulded upon a shaft p, which is supported in bearings
q, q, attached to the casing r, and is extended beyond the casing, and provided at
its outer extremity with a worm wheels, with which engages a worm a on a
spindle t, the latter being provided with a crank handle t₁ for the facility of turning
the worm s¹, and thence imparting rotary motion to the chalk cylinder. u is a disc
or tympan of mica, which is attached at its edges by the cover v, and screws to the
casing and carries at its centre a strip or arm of brass faced or tipped with
paladium at, which projects over the cylinder o, and is maintained in yielding
contact with the chalk by means of an india rubber spring or cushion w, the pressure

page_text: of which is regulated by means of a screw w³. The terminal of the divided
portion of the tertiary wire is connected with the brass strip or arm . and the
terminal of such portion of the said wire is connected to one of the bearings 9, 9?
of the shaft on which the chalk cylinder o is mounted, the chalk cylinder o and
the brass strip or arm are thus in the circuit, so that the electric current is caused
to pass from the brass strip or arm to and through the chalk cylinder at the point
of contact with the strip or arm. The chalk is moistened with pure or distilled
water at long intervals, so as to maintain it in a humid condition, and when the
electric current passes, a chemical action is produced on the surface of the cylinder,
and among other parts at the point of contact of the strip or arin therewith.
The receipt of an oral cominunication takes place under the following conditions,
videlict-The crank handle t is turned by hand in either direction at pleasure
so as to impart rotary motion to the chalk cylinder whereby the disc or tympan u
is drawn forwards or thrust backwards according to the direction in which the
cylinder is rotated, when now an undulatory current the result of the actuation
of the tympan at the sending station, as herein before described. traverses the
tertiary circuit, a variable degree of lubricity in accordance with the undulations
of the current is produced on the surface of the chalk, and the metal strip or arm
proportionately released, allowing the tympan to return towards its normal
position. This action being continued so long as the cylinder is rotated and the
current is passing, the tympan u is caused to vibrate in unison with the tympan of
the transmitter at the sending station and audible sounds are produced at corre-
-ponding to the vocal sounds which originally actuated the tympan of the transmitter
at the sending station.
The several connections are clearly indicated in the Drawing, the presence of a
curve at the point of intersection of two lines denoting that the wires represented
pass one behind the other and are not connected with each other.
In using the apparatus the tertiary circuit is opened prior to the closing of the
primary circuit, and is closed to leave in condition to be acted upon by a current
from the distant station immediately after the closing of the primary circuit, and
the tertiary circuit is opened prior to the opening of the primary circuit and closed
immediately thereafter. These conditions are fulfilled by the employment of a
single key Garranged in the manner shown in Figure 1 of the Drawings and next
hereinafter described.
The wire of the tertiary circuit c and the wire a³ of the primary circuit a are
permanently attached to the lever y of the key G, and the other wire (c) of the
tertiary circuit is bifurcated, as shewn at c, c, and the ends of those two lengths
cc, are provided with contact points 3, 4, placed one at each side of the lever y
of the key G, but at such a distance therefrom as to admit of a third contact
point 5 connected with the other wire (a) of the primary circuit a being brought
into contact with the lever of the key while it is passing from one to the other of
the two contact points of the bifurcated tertiary wire. During the normal con-
dition of the apparatus the keys G are in the positions indicated in the Drawing, the
primary circuit being open and the tertiary circuit being closed. When now it is
required to send a communication from either station, the key G of that station is
depressed so as to cause it to leave the contact point 3 of the bifurcated wire c* of
the tertiary circuit c. and bring it into contact with the contact point 4 of the said
wire. By this movement the tertiary circuit is first opened, then the key being
brought into contact with the contact point 5 the primary circuit is closed, and
finally when the lever of the key arrives at the contact point 4 the tertiary circuit
is closed in readiness to be acted upon by a current from the distant station.
When the key is released in order to open the primary circuit the lever of the key
irst leaves the contact point 4. thus opening the tertiary circuit, then leaves the
contact point 5. thus opening the primary circuit and finally arrives at the point 3,
hereby closing the tertiary circuit and placing it in a condition to be acted upon
by a current from the distant station.
Before sending an oral communication the call bell or sounder F at the distant

page_text: station is actuated so as to notify that a communication is about to be sent. This
result is obtained by the act of depressing the key H at the sending station, thus
completing the secondary circuit whilst isolating the apparatus at the sending
station, and exciting the relay E at the distant station; by the action of this relay
the local circuit d is completed and the bell F is sounded, a notification being thus
afforded that a communication is about to be sent. The key H is then released
and the key G is operated, and the sender speaks into the mouth piece m of the
transmitter A, and the speech is heard at the receiver B of the distant station, as
hereinbefore explained.
Having now described and particularly ascertained the nature of the said
Invention and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that although I have described various devices
and arrangements which are necessary or desirable in carrying out the said
Invention, yet make no claim to any of the said devices or arrangements as
forming any part of the present Invention, except as hereinafter mentioned, but
what consider to be novel and original, and therefore claim as the Invention
secured to me by the hereinbefore in part recited Letters Patent is,-
First. Constructing the frictional surface of the rotary body of the receiver
of chalk moistened with pure or distilled water, substantially as hereinbefore
described.
Secondly. In a receiver constructed as herein set forth the employment in
contact with the surface of the moving chalk body of a metal strip or arm tipped
or faced with paladium, substantially as hereinbefore described.
Thirdly. The mode of controlling the opening and closing of the primary and
tertiary circuits by the use of a single key, so arranged that the tertiary circuit
shall be opened before the primary circuit is closed or opened, and shall be closed
immediately afterwards, substantially as and for the purpose herein before described.
In witness whereof, I, the said Arnold White have to this my Specification
set my hand and seal, this Twelfth day of April, One thousand eight
hundred and eighty.
Witness,
W. B. MERCER,
Clerk,
11, Queen Victoria Street,
E.C.
ARNOLD WHITE. (L.S.)