Year: 1887

page_text: Date of Application, 25th Oct., 1887
Complete Specification Left, 23rd July, 1888
Complete Specification Accepted, 31st Aug., 1888
A communication from abroad by LARS MAGNUS ERICSSON, of Stockholm, Sweden,
Electrician.
I, CHARLES BELL, of 29 Waterloo Street, Glasgow, Lanarkshire, Merchant, do
hereby declare the nature of my invention to be as follows:-
This Invention comprises a new or improved construction, or arrangement and
combination of the parts of a microphone, which may be used to transmit speech or
magnify minute telephonic sounds, or for other telephonic purposes; and which will
be simple in construction and more efficient and reliable in action than those hitherto
in use.
a
And in order that the nature and novelty of this invention may be properly
understood, there is hereunto appended an explanatory Drawing representing
sectional elevation of the new or improved construction of microphone, and in which
reference lotters are used to indicate the various parts of the instrument hereinafter
referred to.
Referring to the Drawings:-A is the outer case of the diaphragm and its fittings,
which is preferably bowl-shaped in the upper part and covered by an enclosing lid
or cap B, which is screwed on to it. In the centre of the lid is a hole or loose joint
in which the sound funnel C is loosely fixed or jointed at C in such a way that it can
be swivelled round. Between the upper part of the bowl A and the lid B the
diaphragm D is placed within an india-rubber ring D' at the edges pressed against
the cover B by two points G G¹ of the spring G and an india-rubber ferrule or other
equivalent at the screw G2, and in the centre on the under side there is a carbon
block E fixed. G is a spring as seen detached in Figure 2, which presses against the
diaphragm D, and is fixed at the bolt and screw F, which bolt is fixed in the lid and
passes through a hole in the diaphragm D. In the lower part of the outer case A is
à screwed tube H insulated by an ebonite tube H' from the outer case A and fitted

page_text: in this is an adjusting centre screw I, the upper part of which is hollow and contains
a metal cup K which is pressed up by a spiral spring I and guided by a small
spindle moving up and down in a hole or recess in the adjusting screw I. The pin
or pencil N, has its upper end N', which presses against the carbon block E on the
underside of the diaphragm D, covered with platinum, and its lower end N³ formed
of carbon, and resting in the motal-cup K, the bottom of which consists of platinum.
P is a cap of ebonite on the top of the screw I, and O is a plug screwed into the
cap P and serving as a guide for the pin or pencil N. A spiral spring L is fitted on
the guiding stem L of the cup K, so that this spring always presses the pin or
pencil N, N', against the carbon block E and diaphragm D, but this pressure can be
regulated by turning the adjusting screw I to press more or less on the spring L.
The microphone thus constructed is supported in the socket A' of the arm A² which
is a metallic tube with flange A³ fixed by the wooden tube B₁ on to the telephone.
The current enters the microphone by the wire a which passes through the tube A³
and is connected with the washer S between the securing nut S₁ and the screw
socket H of the adjusting screw I. From the screw I the current runs to the contact
in the metal-cup K and from thence to the contact carbon E on the diaphragm D, and
returns through the case A, the tube A2 and the other wire fixed by the pin 61 on
the flange A³ of the tube A2 and connected with the induction-coil C¹.
Dated this 25th day of October 1887

page_text: A communication from abroad by LARS MAGNUS ERICSSON, of Stockholm, Sweden,
Electrician.
I, CHARLES BELL, of 29 Waterloo Street, Glasgow, Lanarkshire, Merchant, do
hereby declare the nature of my said 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 :-
This Invention comprises a new or improved construction, or arrangement and
combination of the parts of a microphone, which may be used to transmit speech or
magnify minute telephonic sounds, or for other telephonic purposes; and which will
be simple in construction and more efficient and reliable in action than those hitherto
in use.
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 Figure 1 represents
a sectional elevation of the new or improved construction of microphone, and in
which reference letters are used to indicate the various parts of the instrument herein-
after referred to. Referring to these Drawings:-A is the outer case of the
diaphragm and its fittings, which is preferably bowl-shaped in the upper part and
covered by an enclosing lid or cap B, which is screwed on to it. In the centre of the
lid B is a hole or loose joint in which the sound funnel C is loosely fixed or jointed
at C in such a way that it can be swivelled round. Between the upper part of the
bowl A and the lid B tho diaphragm D is placed within an india-rubber ring D¹ at
the edges pressed against the cover B by two points G¹, G¹, of the spring G, and an
india-rubber ferrule F or other equivalent at the screw G³, and in the centre on the
under side there is a circular carbon block E fixed. G is the spring as seen detached
in Figure 2, which presses against the diaphragm D, and is fixed by the screw G2 and
rubber block F, to the lid B, both passing through a hole in the diaphragm D. In
the lower part of the outer case A is an internally screwed tube H insulated by an
ebonite tube H from the outer case A and fitted in this is an adjusting centre
screw I, the upper part of which is hollow and contains a loose metal cup K, which
is pressed up by a spiral spring L and guided by a small spindle L' moving up and
down in a hole or recess in the adjusting screw I. The pin or pencil N, has its
upper end N, which presses against the carbon block E on the underside of the
diaphragm D, covered with platinum, and its lower end N2 formed of carbon, and
resting in the metal-cup K, the bottom of which consists of platinum. P is a cap of
ebonite on the top of the screw I, and O is a plug screwed into the cap P and serving
as a guide for the pin or pencil N. A spiral spring L is fitted on the guiding stem L¹

page_text: of the cup K, so that this spring always presses the pin or pencil N, N', against the
carbon block E and diaphragm D, but this pressure can be regulated by turning
the adjusting scrow I to press more or less on the spring L. The microphone thus
constructed is supported in the socket A¹ of the arm A2 which is a metallic tube with
flange A³ fixed by the wooden tube block B¹ on to the telephone.
The current enters the microphone by the wire a which passes through the tube A²
and is connected with the washer S between the securing nut S₁ and the screw
socket H of the adjusting screw I. From the screw I the current runs to the contact
in the metal-cup K and from thence to the contact carbon E on the diaphragm D,
and returns through the case A, the tube A² and the other wire fixed by the pin bí
on the flange A³ of the tube A² and connected with the induction-coil c.
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 a
microphone, substantially as herein described, in reference to and shown in the
accompanying Drawings.
Second. The construction and use of a microphone, in which the current is carried
to the carbon block E and diaphragm D by a pin or pencil N, the two ends of which
make loose contacts, the upper with the diaphragm E, D, and the bottom end with a
metal cup K supported on a regulating spiral spring L, the pin N, resting loosely in
the cup K, and the whole placed inside a caso A, and adjusted by a regulating
screw I, all substantially as herein described, in reference to and shown in the
accompanying Drawings.