Improvements in Telephonic and Phonographic Transmitters.
Year: 1889

page_text: COMT DUID DI BUITIVATION
Improvements in Telephonic and Phonographic Transmitters.
I, EDWIN STANDISH DRAKE of 151 Elm Street West Somerville in the State of
Massachusetts, United States of America, Inventor, do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
My invention relates to telephone and phonograph transmitters, so-called; and has
for its object the prevention of all counteracting impulses, which interfere with and
modify the vocalized impulses while they are being directed to the diaphragm of such
transmitter, and thereby to render more distinct and intelligible, and facilitate
telephonic and phonographic communications. And the invention consists in a trans-
mitter possessing the novel features hereinafter fully set forth and claimed.
In the accompanying drawings which form part of this specification-
Fig. 1 represents an elevation of a telephone transmitter front or door, embodying
iny invention.
Fig. 2 is a vertical section of the same, taken as on line xa, Fig. 1, and showing
my improved mouthpiece with its inlet and outlet air conduits.
Fig. 3 is a similar section of a Blake Transınitter, shown to enable me by comparison
to more clearly illustrate and describe my invention.
Fig. 4 is a vortical section of a transmitter embodying the principle of my invention.
in a modified form.
Although my invention is shown in the drawings as applied to the well known
"Blake Transmitter" it is equally well adapted to other forms of electric telephone
"Mechanical
transmitters, to phonograph recorders, and to what are termed
Telephones" wherein electricity is not employed as a transmitting agent.
My invention and improvements deal exclusively with that part of the construction
of a telephone or phonograph transmitter which relates to conducting the sound
impulses to and from the outward face of the diaphragm employed therein, and not to
the diaphragm itself and its telephonic and phonographic connections.
I construct in the door or front of the supporting case, or box A, of the
transmitter, to, or behind which, the diaphragm is secured, a rectangular mouth-
piece B, provided with an inlet passage C, and an outlet passage D, arranged at right
angles to each other, and at an angle of fortyfive degrees to the face of the
diaphragm E. The air conduit C receives the vocalized impulses imparted by the
speaker and conducts them to the diaphragm E, and, after having impinged
on the diaphragm, such utilized and spent. impulses are reflected therefrom
through outlet D), in practical conformity to the natural law of reflection of
sound waves or vibrations from plane surfaces. Thus the successive impulses
directed to the diaphragm are not counteracted, interfered with, or modified by
the returning reflected impulse; and, as a consequence greater purity of tone and
distinctness of modulation in the corresponding vocalized impulses imparted at the
opposite end of the telephonic line, (or, in case of a phonograph, reproduced by the
phonographic record,) is obtained, and the communications thus conveyed are more
clearly and intelligibly rendered, and the use of the telephone and phonograph as a
means of communication, is thereby greatly facilitated.
The backward bevels m, m, on the front exterior edges of the projecting mouth-
piece B, as well as the annular recess m' around the circular mouthpiece or aperture B
in the modification shown in Fig. 4, are for the purpose of deflecting the overplus of
impulses which do not enter the mouthpiece or aperture leading to the diaphragm,
and by so turning them aside preventing them from returning by reflection from the
immediately surrounding face or surface of the transmitter, into the path of, and
confusing the impulses which proceed directly from the speaker to the diaphragm.

page_text: The modification shown in Fig. 4 places the inlet passage of the mouthpiece in a
horizontal position, and the outlet in a vertical position, while the diaphragm is set
at an angle thereto, so that while the impulses directed toward the diaphragin are
received obliquely through the horizontal passage C, they are reflected through the
vertical passage D, thus securing the same result as is obtained by the construction
and arrangement shown in Fig. 2. Other forms of diaphragms and other arrange-
ments of independent inlet and outlet passages, relatively thereto and acting on the
same principle, may readily suggest themselves to skilful constructors of such
instruments for the same purpose and with the same results.
The advantages of my invention, above described, will be more readily understood
and appreciated by reference to Fig. 3, which represents the old form of mouthpiece
in its usual relation to the diaphragm. The vocalized impulses directed towards the
diaphragm, as illustrated by the broken lines, encounter the sides n, n, of the mouth-
piece B, and are in part reflected from side to side of the mouthpiece, and across
the path of the central impulses which move directly toward the diaphragm, thereby
disturbing and confusing the latter, and impairing the purity of tone and modulation
imparted by the corresponding vibrations at the opposite end of the telephonic line of
communication, or reproduced by the phonographic record.
And this difficulty is still further increased by the reaction of the impulses so
conducted directly against the diaphragm as they are reflected back in the opposite
direction from which they entered, and thus encounter and interrupt the successive
inward waves. The prevention of these difficulties in the manner, and by means
substantially as described, constitutes the essential feature of my invention.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is :-
―
1. A transmitter, embodying the combination of a diaphragm E, with a supporting
'case or front A, provided with separate but connecting inlet and outlet air conduits
or passages, so respectively arranged relatively to the diaphragin, that the vocalized
impulses directed to the diaphragm through the inlet passage, will be reflected
directly therefrom through the outlet passage, as and for the purposes specified.
2. The combination of diaphragm E, with door or front A, provided with air
passages C and D, leading obliquely to and from the diaphragm at equal angles
thereto, coinciding with the angles of incidence and reflection of the sound waves
conducted thereto and therefrom through said passages, as specified.
Dated this 11th day of June 1889
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London, Applicant's Agent.