IMPROVEMENTS IN THE CONSTRUCTION OF APPARATUS FOR TRANSMITTING SOUNDS.
Year: 1880

page_text: LETTERS PATENT to Frederick Robert von Wreden, M.D., Actual Councillor of
State, of 6, Zvenigovodskaya Vulitza, Saint Petersburg, in the Empire of
Russia, for an Invention of "IMPROVEMENTS IN THE CONSTRUCTION OF
APPARATUS FOR TRANSMITTING SOUNDS.'
PROVISIONAL SPECIFICATION left by the said Frederick Robert von
Wreden at the Office of the Commissioners of Patents on the 23rd August
1880.
FREDERICK ROBERT VON WREDEN, M.D., Actual Councillor of State, of 6,
Zvenigovodskaya Vulitza, Saint Petersburg, in the Empire of Russia. " IMPROVE-
MENTS IN THE CONSTRUCTION OF APPARATUS FOR TRANSMITTING SOUNDS."
The improved instrument is an electro-acoustic apparatus, the construction of
which is based on the principle of the microphone, and which has the property of
collecting all acoustic vibrations, even the slightest and most distant ones, which
the hunian ear can scarcely perceive, and of transmitting the same with increased
strength to one or more telephones at any desired distance.
The apparatus is constructed anologically with the ear, and consists of three
essentially important parts, viz. :-
1. A very thin (from 0.0002 to 0.003 of an inch thick) and tightly stretched
membrane T (Figs. 1 and 2), which corresponds to the tympanum in the ear, its
size and material being determined according to the different kinds of sounds to be
transmitted.
2. An electrically conducting piece K of Jablotchkoff's coal or some other material
of variable electrical resistance (acoustic ossicles in the ear) fixed on the membrane T,
and communicating by means of a fine wire a with a contact screw 8 for a
conductor from an electric battery.
3. A regulator of contact H, the sensibility of which can be accurately adjusted,
as hereinafter described; this regulator is the most important part of the
apparatus, because on it depends the purity and clearness of articulated and other
sounds transmitted by the instrument.

page_text: On one end of the contact regulator H is fixed a thick ring R, wherein is screwed
or fixed an electrically conducting piece K¹ of coal or some other material with
variable resistance to electricity (half conductors) which corresponds to the terminal
apparatus of acoustic nerves in the ear.
The piece K is in direct contact with the cylindrical piece K fixed on the membrane,
and through the metallic contact regulator H and a fine copper wire b is in con-
ducting connection with the contact screw s¹, to which is fixed a conducting wire
from a telephone or some distant station (receiving station).
The other end of the contact regulator is provided with a fine accurately cut
screw thread, on which a counterweight G can be moved to adjust the degree of
contact or pressure between the two coal or other pieces K, K³, (accomodation
apparatus of the ear).
As is obvious, the apparatus may be modified in various ways without departing
from the distinguishing characteristics, and in some cases the instrument may be
provided with several membranes (instead of one) of the same or of different
material, and with several electric contacts of variable resistance, and several
contact regulators; also a number of contact pieces and contact regulators may be
combined with one membrane.
All the acting parts of the instrument are fixed to the inside of the top part (or
cover) of a wooden box A, the lower part or bottom serving merely to protect them.
The cover is provided with a funnel shaped sound hole L, concentric with the
membrane T.
The form and material of the outer casing or support of the instrument are not
essential, and may be varied according to requirement. Instead of a round thick
sided box of veined birch-wood, mahogany, box wood, hard caoutchouc, or other
materials, the acting parts may be placed, for instance, in a square thin-sided box
of pine wood (resounding wood), which need not have any sound hole, and which,
by its resounding qualities, considerably increases the sound.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Frederick Robert von Wreden in the Great Seal Patent Office on the
10th February 1881.
FREDERICK ROBERT VON WREDEN, M.D., Actual Councillor of State, of 6,
Zvenigovodskayavulitza, Saint Petersburg, in the Empire of Russia.
"IMPROVE-
MENTS IN THE CONSTRUCTION OF APPARATUS FOR TRANSMITTING SOUNDS."
The improved instrument is an electro-acoustic apparatus, the construction of
which is based on the principle of the microphone, and which has the property of
collecting all acoustic vibrations, even the slightest and most distant ones, which the
human ear can scarcely perceive, and of transmitting the same with increased
strength to one or more telephones at any desired distance.
The apparatus is constructed analogically with the ear, and consists of three
essentially important parts, that is to say :-
(1.) A very thin and tightly stretched membrane (from 0·002 to 0.003 of an inch
thick) which corresponds to the tympanum of the ear, its size and material
being determined according to the different kinds of sound to be transmitted.
(2.) An electrically conducting piece of Jablotchkoff's carbon or some other
material of variable electrical resistance, which corresponds to the acoustic ossicles
in the ear.
(3.) A regulator of contact, the sensibility of which can be accurately adjusted, as
hereinafter described. This regulator is the most important part of the apparatus,
because on it depends the purity and clearness of articulated and other sounds
transmitted by the instrument.
Referring to the accompanying Sheet of Drawings, in which Fig. 1 is an
elevation, partly in section, of one form of the improved instrument, and Fig. 2 is a
plan of the same,→
T is the stretched membrane; K, K¹, are two pieces of carbon of variable
resistance (corresponding to the terminal apparatus of the acoustic nerves in the
ear), the former being attached to the membrane T, and the latter being fixed in
the thick ring R on the contact regulator H. The carbon K is connected by a
fine wire a with the contact screw, to which is also joined a wire from an electric
battery.
The carbon K¹ is in direct contact with the cylindrical piece of carbon K fixed on
the membrane, and through the metallic contact regulator H and fine copper wire b
is in electrical connection with the contact screw S¹, to which is fixed the
line or conducting wire from a telephone or some distant station (receiving
station).
The other end of the regulator is provided with a fine accurately cut screw thread,
over which a counterweight G can be moved to adjust the degree of contact or
pressure between the two carbon or other pieces K, K². This part corresponds to
the accommodation apparatus of the ear.
As is obvious, the apparatus may be modified in various ways without departing
from its distinguishing characteristics, and in some cases the instrument may be
provided with several membranes, instead of one, of the same or of different
materials, and with several electric contacts of variable resistance, and several
contact regulators; also a number of contact pieces and contact regulators may be
combined with one diaphragm.
All the acting parts of the instrument are fixed to the inside of the top part (or
cover) of a wooden box A, the lower part or bottom serving merely to protect them.
The cover is provided with a funnel shaped sound hole L concentric with the
membrane T.

page_text: The form and material of the outer casing or support of the instrument are not
essential, and may be varied according to requirement. Instead of being in a round
thick sided box of veined birch-wood, mahogany, boxwood, or other material, the
acting parts may be placed, for instance, in a square thin-sided box of pine wood
(resounding wood), which need not have any sound hole, and which, by its resonant
qualities, considerably increases the sound.
Having now described the nature of my said Invention, and the manner in
which it is to be or may be carried into practical effect, I would have it
understood that what I consider as novel and original, and therefore claim as
secured to me under the Letters Patent herein before in part recited is,―
(1.) The improved instrument or electro acoustic apparatus, constructed, arranged,
and operating substantially as hereinbefore described, for the purpose of collecting
acoustic vibrations and transmitting the same with increased strength to one or
more telephones.
(2.) In an electro-acoustic apparatus for collecting acoustic vibrations and trans-
mitting the same to one or more telephones the improved contact regulator,
consisting of a lever carrying a carbon or other contact piece, and means for
adjusting the degree of contact or pressure between the said contact piece and a
second contact piece, substantially as described and illustrated.
In witness whereof, I, the said Frederick Robert von Wreden, have hereunto
set my hand and seal, this Second day of February, Lord One thousand
eight bundred and eighty one.
FREDERICK ROBERT VON WREDEN. (L.S.)