Year: 1887

page_text: Date of Application, 25th Oct., 1887
Complete Specification Left, 23rd July, 1888
Complete Specification Accepted, 31st Aug., 1888
Dereby declare the nature of my invention to be as foNOWS.
The Microphones hitherto commonly in use require adjusting frequently to work
satisfactorily, and this cannot be done by every one, but requires an experienced
workman or electrician.
This invention comprises a new or improved construction of microphone, which can
work for years without such repeated adjustments.
And in order that the nature and novelty of this invention, may be properly
understood, there is hereunto appended an explanatory Sheet of Drawings, in which
the same reference letters are used to indicate corresponding parts in all the Figures
where shown. Figure 1, represents a sectional side elevation through the middle of
the new or improved construction of microphone and Figure 2 an end view looking
from behind, while Figure 3 is a plan corresponding to Figure 2, but with some of the
parts broken off and removed.
Referring to these Drawings:-A is the sound funnel or trumpet secured at its
contracted end in the centre of a shallow recessed frame B; C is the diaphragm with
the usual india-rubber ring round its edges D. E is a spring pressing against the
diaphragm to steady it and suppress irregular sounds and vibrations, and P is a piece
of metal fixed in the middle of the diaphragm and carrying a semi-circular grooved
bar of metal, which acts as a support for a small bar of carbon O. F is a metal bar
fixed on the frame B carrying a bar of ebonite G, on which there are two pieces of
metal H and H fixed. One of these two pieces H', is by a screw H connected
with the metal bar F, whereas the other piece H" is insulated by the ebonite bar G.
On each of the metal pieces H' and H" are one or more metal-pins 1, three being

page_text: shown in the Drawings, on which rest metal-cylinders K, with holes in their bottoms
for the pins I, and at the top they have pieces of carbon L by which they loosely lean
against and have contact with the carbon bar O. M is a flat bar of ebonite with pieces
cut out forming small recesses for the pieces of carbon I which serve to keep the
cylinders K in position or from touching each other, or falling out even if the micro-
phone is taken from its place. N and Qare the two pole wires. The current runs,
as can be easily seen from the wire N to H, through the three pins I, to the right,
thence to the cylinders K, and carbon pieces I, the carbon bar 0, and through the
corresponding left parts of the instrument, to the screw H, and thence through the
metal frame B of the instrument to the wire Q.
It can now easily be understood why this microphone can work satisfactorily for a
long period without requiring adjustment. The power of gravity presses the carbons L,
against the carbon bar O, and thus a more uniform and safe effect is secured than
could be obtained by using springs, as is the case in a great number of other micro-
phones. The carbon pieces I are made in the shape of cylinders and arranged so as
to make them revolve on their pins I, by a slight shaking and thereby giving another
contact surface to the other carbon, which also prevents dust or such like from sticking
to the carbon contacts. As mentioned above, two or more cylinders K with carbons L
may be used, but of course it is of advantage to use more than two as if one of the
contacts should be out of order, the instrument can nevertheless work. In the
drawing there are six cylinders K, three on each side, which are quite sufficient. The
carbon bar O is fixed at one point, which is placed in the centre of the diaphragm C
in order to make the effect of the vibrations of the diaphragm C as uniform as possible
at all the carbon contacts.
Datal the OE:1.
1007

page_text: Improvements in Microphones.
A communication from abroad by LARS MAGNUS ERICSSON, of Stockholm, Sweden,
Electrician.
I CHARLES BELL, of 29 Waterloo Street Glasgow, Lanarkshire, Mercbant,. 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 in writing, reference. being had to the accompanying Sheet of Drawings,
and to the letters and figures marked thereon, that is to say:-
The microphones hitherto commonly in use require adjusting frequently to work
satisfactorily, and this cannot be done by everyone, but requires an experienced
workman or electrician.
This invention comprises a new or improved construction of microphone, which can
work for years without such repeated adjustments.
And in order that the nature and novelty, and the manner of performing or carrying
this invention into effect or practice may be properly understood, there is hereunto
appended an explanatory Sheet of Drawings, in which the same reference letters are
used to indicate corresponding parts in all the figures where shown.
Figure 1 represents a sectional side elevation through the middle of the new or
improved construction of microphone and Figure 2 an end view looking from behind,
while Figure 3 is a plan corresponding to Figure 2, but with some of the parts broken
off and removed.
Referring to these Drawings :-A is the sound funnel or trumpet secured at its
contracted end in the centre of a shallow recessed frame B; C is the diaphragm with
the usual india-rubber ring round its edges D; E is a spring pressing against the
diaphragm to steady it and suppress irregular sounds and vibrations; and P is a piece
of metal fixed in the middle of the diaphragm and carrying a semi-circular grooved
bar of metal, which acts as a support for a small bar of carbon O. F is a metal bar
fixed on the frame B carrying a bar of ebonite G, on which there are two pieces of
metal Hand H fixed. One of these two pieces H' is by a screw H¹ connected with
the metal bar F, whereas the other piece H" is insulated by the ebonite bar G. On
each of the metal pieces H' and H are one or more metal pins I, three being shown
in the Drawings, on which rest metal cylinders K, with holes in their bottoms for the
pins 1, and at the top they have pieces of carbon L by which they loosely lean against
and have contact with the carbon bar O. M is a flat bar of ebonite with pieces cut
out forming small recesses for the pieces of carbon L which serve to keep the
cylinders K in position or from touching each other, or falling out even if the
microphone is taken from its place. N and Q are the two pole wires. The current
runs, as can be easily seen from the wire N to H", through the three pins I, on
the right of Figure 2, thence to the cylinders K, and carbon pieces L, the carbon

page_text: bar O, and through the corresponding left side parts of the instrument, to the
screw and thence through the metal frame B of the instrument to the
wire Q.
It can now easily be understood why this microphone can work satisfactorily for a
long period without requiring adjustment. The power of gravity presses the carbons L,
against the carbon bar O, and thus a more uniform and safe effect is secured than could
be obtained by using springs, as is the case in a great number of other microphones.
The carbon pieces L are made in the shape of cylinders and arranged so as to make
them revolve on their pins I, by a slight shaking and thereby giving another contact
surface to the other carbon, which also prevents dust or such like from sticking to the
carbon contacts. As mentioned above two or more cylinders K with carbons L may
be used, but of course it is of advantage to use more than two as if one of the contacts
should be out of order, the instrument can nevertheless work. In the Drawing there
are six cylinders K, three on each side, which are found quite sufficient. The carbon
bar O is fixed at one point, which is placed in the centre of the diaphragm C, in order
to make the effect of the vibrations of the diaphragm C as uniform as possible at all
the carbon contacts.
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
First. The construction, or arrangement and combination of the parts of micro-
phones, substantially as herein described, in reference to and shown in the accompanying
Drawings.
Second. The construction and use of a microphone, in which the one contact is the
carbon bar O fixed at a point placed in the centre of the diaphragm C, and the other
contact is composed of two or more round carbon bars L, fixed in the upper ends of
the metal cylinders K, which are placed sloping, or at an angle with their bottom ends
resting upon metal pins I, so that they can easily revolve, all substantially as herein
described, in reference to and shown in the accompanying Drawings.
Dated this 23rd day of July 1888