Improvements in Telephonic Transmitters.
Year: 1892

page_text: Date of Application, 26th Nov., 1892-Accepted, 7th Jan., 1893
COMPLETE SPECIFICATION.
Improvements in Telephonic Transmitters.
I, ALBIN GRÖPER, of 28, Alexanderstrasse, Dusseldorf, in the Empire of
Germany, Manufacturer, 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 :—
This invention relates to improvements in microphonic telephone transmitters, or
those in which variation of the resistance of the electric circuit in which they are
placed is caused by subjecting bodies of carbon through which such circuit passes.
to various pressures; and has for its object the construction of a transmitter which.
shall be capable of accurately transmitting the sound or words spoken into it to a
great distance and at the same time be free from external or secondary sounds or
noises.
In the drawings hereto annexed
Figure 1 illustrates in vertical section one form of telephone transmitter according
to my invention,
Figure 2 being a cross section through same, taken on the line A. B., Figure 1.
Figure 3 illustrates a modified form of the instrument shewn at Figure 1, and
Figure 4 is a cross section of same, taken on the line C. D., Figure 3.
With reference to the drawings, e and d are metallic plates carrying between them.
the ebonite ring 9 to which they are screwed. A recess is formed in the ring g for
the reception of an india rubber washer f, carbon diaphragm b, india rubber
washer 1, and mica diaphragm a. The diaphragm a is the first to receive the sound
waves entering the transmitter, and measures about 04 millimetres in thickness-
and is therefore influenced by the slightest sound wave. The carbon diaphragm b
is separated from a by an air space c, and thus the vibrations of a are transmitted
to b and the carbon balls o are subjected to greater and less pressure alternately..
The current passes by way of the diaphragm b, balls o, case h, and plate d.
A case is attached to the rear plate d for the reception of the carbon balls o..
The case may be formed in various shapes, for instance it may be rectangular and.
provided with inclined shelves s as shewn in Figures and 2, or be of solid form
and circular in shape, as shewn in Figures 3 and 4, and provided with holes or
cavities for the reception of the carbon balls. In the form of case shewn at
Figures 1 and 2, the inclined surface of the shelves s is utilized for keeping the
balls o in loose contact with the diaphragm b, whilst in the form of case shewn in
Figures 3 and 4 this is effected by means of a carbon plate o and spring m, the force
exerted by the spring being regulated by the nut and bolt r.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
In a telephonic transmitter of the type described, the disposition of a mica
diaphragm and a carbon diaphragm so that an air space exists between them, the
mica diaphragm being adapted to receive sound waves and to transmit them to such
carbon diaphragm, which in turn communicates them to a number of carbon balls
adapted to be kept in contact with such carbon diaphragm, whereby such carbon
balls are subjected to varying pressures and the electric current passing through

page_text: them to a varying resistance; substantially as and for the purposes herein set forth
with reference to the drawings hereto annexed.
Dated this 25th day of November 1892.
CHEESBROUGH & ROYSTON, Fels. Chart. Inst. P.A.,
15, Water Street, Liverpool, Applicant's Patent Agents.