Microphone Worked by Granular Coal.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Microphone Worked by Granular Coal.
I, JULIUS OTTO ZWARG, of Freiberg, Kingdom of Saxony, Empire of Germany,
Manufacturer, do hereby declare the nature of this invention to be as follows:-
The object of the present invention is a microphone worked by granular coal
with contactual holes inclined towards the front side of the granular cavity, with
an opening for the filling and openings for removing the dust.
In the above microphone the granular coal is placed in a closed case of metal,
one side of which is formed by a removable lid and the other side is provided with
numerous perforations of whatever division which assure a great magnitude of con-
tact between the granular coal and the membrane which is screwed by means of
the board outside against the case.
All the perforations are inclined toward the membrane which causes the granular
coal thus introduced to undergo in the simplest manner à certain drag toward the
hindpart opposite the membrane whilst the granules find a proper support at the
hindpart of the perforated partition.
The large number of holes have as a natural result, as is well known, the supply-
ing a greater magnitude of contact and consequently a slight resistance to the
current between the coal and the membrane so that the electric current for the
ringing of the call may pass without any impediment.
The outside board which is electrically isolated from the case by a diaphragm
non-conductor and by isolated fastening-screws, serves to join one of the extremities
of the electric circuit whilst its other extremity is joined at the top to the case by
means of a screw. This screw likewise acts as a closing to an opening passing
through the jacket of the lid or revetment and which easily allows of the case
being filled with granular coal, which becomes necessary from time to time in
order to compensate for the losses resulting from the pulverization of the coal.
In this way the filling may easily be performed without taking the apparatus
to pieces.
To allow of the dust, caused by the coal during the working of the microphone
to make its way outside the case it is provided at its lower extremity with open-
ings (or rather fissures) large enough to allow of the dust passing but not the
granular coal. Of these apertures there is one or several according to the number
required, which open on to the interior hollow of the case, in order to secure it.
against dust, the others lead, to the space between the perforated side of the case
and the membrane, to effect the removal of the dust entering this space by the
inclined perforations.
The characteristic of the above microphone is its simplicity it being composed
of but few metallic pieces.
Besides which, owing to the inclined perforations, with a view to the drag of
the granular coal opposite the membrane, it may be regulated of itself and that
the filling of coal may be regulated in the simplest manner by the fillinghole, it

page_text: results that the superintendence and ruling of the microphone may be entrusted
to any workman or any other person.
Dated 1:00
ו
100%
L. DUVINAGE,
Agent for Applicant.
I, JULIUS OTTO ZWARG, of Freiberg, Kingdom of Saxony, 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 a microphone with granulated carbon, carrying con-
tact holes, which are inclined toward the diaphragm of the fore race of the
chamber holding the granulated carbon, an opening being provided for the filling
of said chamber. The accompanying drawing shows this microphone. Fig. 1 is a
transverse vertical section of it and Fig. 2 is a section according the line x-y of
Fig. 1.
The granulated carbon g is laid into a movable metallic box a the hind face b
of which is provided with an opening for the filling, the other face a¹ showing
numerous perforations a² no matter what may be their section-forming a large
surface of contact between the granulated carbon, the wall a¹ and the diaphragm p
which is fastened between the box a and the plate e serving to fix the apparatus. The
plate e is provided at its center with a screw-threaded opening receiving the mouth-
piece c. All the perforations a² are inclined toward the diaphragm; the effect
of this inclination is to render slower, by this simple device, the motion toward
the back opposite the diaphragm, of the granulated carbon, that may go into them,
whereas this carbon settles at the lower part of the perforated side. As it is well
known, the great number of holes spreads the contact surface and decreases con-
sequently the resistance to the electric current between the carbon and the
diaphragm, so as the electric current for the call bell may go through it easily.
The plate e with the mouth piece c is electrically insulated from the envelope by
means of a non conducting diaphragm e¹ and of insulated set-screws f; its duty
is to connect one of the ends of the electric circuit, whereas the other end is in
connection with the upper part of the box a through the screw d. This screw d
also serves to shut the filling opening of the box a.
What characterises this microphone is its great simplicity for it is composed
of but a few pieces of metal. Besides this the apparatus is self regulating on
account of the inclined perforations a³ intended to prevent the falling of the granu-
lated carbon against the diaphragm: finally as the filling of carbon can be very
easily regulated by means of the filling hole, any workman or other person may
be trusted to take care of the apparatus and regulate it.
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 microphone with granulated carbon characterized by a metallic box a
holding the granulated carbon g and carrying a number of perforations a² on the
face a near the diaphragm p so as to gain a great contact surface between the
granulated carbon, the wall a¹ and the diaphragm.

page_text: 2. A microphone with granulated carbon in which the perforations a³ of the
carbon box a are inclined toward the diaphragm p in order to create a natural
down motion of the granulated carbon opposite the diaphragm.
3. A microphone with granulated carbon in which the carbon box a has in its
upper part an opening for the filling of the granulated carbon, said opening being
closed by means of a conductible pressure screw d.
L. DUVINAGE,
Agent for Applicant.