IMPROVEMENTS IN TELEPHONIC APPARATUS
Year: 1882

page_text: LETTERS PATENT to William Robert Lake, of the firm of Haseltine, Lake,
and Co., Patent Agents, Southampton Buildings London, for an Invention of
"IMPROVEMENTS IN TELEPHONIC APPARATUS "-A communication to him from
abroad by Morris Franklin Tyler, of New Haven, Connecticut, United States
of America
COMPLETE SPECIFICATION filed by the said William Robert Lake at the
Office of the Commissioners of Patents on the 20th December 1882.
WILLIAM ROBERT LAKE, of the firm of Haseltine, Lake, and Co, Patent Agents,
Southampton Buildings, London, ** IMPROVEMENTS IN TELEPHONIC APPARATUS,”
communicated to me from abroad by Morris Franklin Tyler, of New Haven,
Connecticut, United States of America
This Invention relates to transmitters for telephonic communication.
. In the usual construction of telephonic transmitters several difficulties exist.
The best effect is produced upon a transmitter by having the mouth in a certain
position with relation to the diaphragm, and any variation from this position
detracts from the efficiency of the instrument, making the conversation more
difficult to be heard. Also the best results are attained by a certain strength of
voice; if the voice be too loud, then the vibrations are so strong as to produce &
rattling sound in the receiver which interferes with hearing; on the other hand, if
the voice be too low, then the vibrations are not of sufficient strength to be heard
distinctly. A large number of transmitters are used in offices or public places,
where, speaking even in the required tone of voice, the talking will interfere with
the business of the office, or expose the object of the conversation which it is desired
should be secret. It frequently occurs that a person desires to communicate to
another person something concerning the business of a person presont, which com-
munication he desires to make and receive a reply to but which, he cannot do
without that person having some knowledge of the nature of the communication.
Other difficulties in the use of the ordinary telephonic communication exist, and are
too well known to require further illustration.
The object of this Invention is to overcome these difficulties, and render the

page_text: telephone a strictly secret mode of communication, as well as to avoid disturbance
to the parties near, or in, the same apartment where communication is being made.
The said Invention consists in constructing a chamber outside of, and surrounding,
the exposed part of the diaphragm of a telephonic transmitter, the said chamber
having an opening (preferably upon the side opposite the diaphragm) formed to
receive the mouth and the adjacent parts of the face as hereinafter described, so
that the lips of the person making a communication are within the said chamber
and the opening is substantially closed by the face, whereby the vibrations imparted
to the atmosphere by the voice will be confined within the chamber and directed to
the diaphragm independently of the surrounding atmosphere. Communications
may then be made in a whisper, and consequently will not be heard except by the
party listening at the receiver at the other end of the line.
In the accompanying drawing
Figure 1 is a perspective view, and
Figure 2, is a longitudinal vertical central section, of a telephonic transmitter
constructed with a mouth piece according to this Invention.
Figure 3, is a longitudinal vertical central section of a removable chamber
constructed for attachment to a telephonic transmitter.
A represents a transmitter box of ordinary construction, a the diaphragm, b the
opening through the front of the transmitter to the exposed portion of the
diaphragm.
In front of the opening b is a chamber B, which may be, and preferably is, an
extension of the transmitter box, and forms practically the door thereof, it being
hinged, as shown in Figure 1, in the usual manner of hinging the door or mouth
piece of a transmitter.
In the front of the chamber B is an opening C so formed as to allow the lips and
the adjacent parts of the face of the speaker to enter. The opening C is elongated
upward as shown at d to receive, and conform substantially to, the shape of the nose,
so that as a person places his lips within the said opening, the elongation thereof
permits the introduction of the nose; the face will then fit the edge of the said
opening and practically close it when a person is speaking. For the convenience of
the speaker the front of the chamber B should be inclined backward towards the
diaphragm as shewn. The inner wall of the chamber B is funnel-shaped, as shown
at D, to concentrate the air waves upon the diaphragm.
The opening C is preferably provided with a light flexible cushion in order to
easily fit the face of a speaker, a soft material such as felt or leather being best for
this purpose. A hole is cut through the said material of the same shape as the
opening in the front of the chamber, but of smaller dimensions; the material is then
attached to the front of the chamber so as to leave an inwardly projecting edge e to
form the cushion; this cushion readily yields as the face is presented, and the
opening is thus more perfectly closed than would be the case if there were no such
cushion.
A small opening f is provided at some convenient part of the chamber for the
admission of air, but not sufficiently large to interfere with the vibrations imparted
by the voice to the air within the chamber.
The depth of the box, that is the distance from the opening in the front to the
diaphragm, must be such as will determine the proper position for the mouth
relatively to the said diaphragm, By thus confining the air around the diaphragın so
that the entire vibration produced by the voice will be concentrated upon the
diaphragm, a whisper produces the best result. In whispering there is very little, if
any, difference in persons; the strength of the whisper will be substantially the same
in all cases, differing therefore from the voice in speaking, hence when the opening
has been properly adjusted to the diaphragm as described, the transmitter is fitted
for all persons. On account of the vibrations being comfined within the chamber
without possibility of escape, no sound produced by whispering inside the box can
be heard outside, and communications can thus he most readily carried on by
Whispering, yet if persons so desire they may, by standing at a distance from the

page_text: opening speak in the usual tone of voice, and make their communications in the
usual manner.
As there are very many transmitters in use, it will be desirable in some cases to
provide whispering chambers for such transmitters; in this case they are formed as
shown in Figure 3, with a recess F at the rear, corresponding with the sizes of the
transmitters, and are placed over the front thereof bringing the opening in the back
of the chamber into line with the opening in the transmitter.
The said opening into the chamber may be made on other sides than the front
if desired, but the best results are attained by having it directly in front of the
diaphragm as shown.
Having thus fully described the said Invention, as communicated to me by
my foreign correspondent, and the manner of performing the same, I wish it
understood that I claim
First. The combination, with the diaphragm of a telephonic transmitter, of. a
chamber arranged in front of the said diaphragm and constructed with an opening
to receive the mouth and adjacent parts of the face of a speaker, whereby the
sounds will be produced entirely within the said chamber, substantially as
described.
Second. The combination, with the diaphragm of a telephonic transmitter, of a
chamber arranged in front of the said diaphragm and constructed with an opening
to receive the mouth and adjacent parts of the face of a speaker, whereby the
sounds will be produced entirely within the said chamber, the inner side of the
said chamber being funnel shaped and contracting toward the opening for the
diaphragm, substantially as described.
Third. In combination, with the diaphragm of a telephonic transmitter, of a
chamber arranged in front of the said diaphragm and constructed with an opening
to receive the mouth and adjacent parts of the face of a speaker, whereby the
sounds will be produced entirely within the said chamber, the said opening
being provided with a cushion against which the the face may rest, substantially
as described.
Fourth, The combination, with the diaphragm of a telephonic transmitter, of a
chamber arranged in front of the said diaphragin and constructed with an opening
to receive the mouth and adjacent parts of the face of a speaker, whereby the
sounds will be produced entirely within the said chamber, the said chamber being
provided with an opening, substantially as described.
Fifth. The combination, with a transmitter for vocal communication, comprising
a diaphragm arranged in rear of an opening in front of the transmitter box, of a
detachable chamber arranged to be placed over the front of the transmitter, the
said chamber being constructed with an opening to receive the mouth and adjacent
parts of the face of a speaker, whereby the sounds will be produced entirely
within the said chamber and concentrated upon the diaphragin, substantially as
described.
In witness whereof I the said William Robert Lake have hereunto set my
hand and seal this Twentieth day of December in the year of our Lord
One thousand eight hundred and eighty two