IMPROVE- MENTS. IN MICROPHONES OR TELEPHONES
Year: 1883

page_text: PROVISIONAL SPECIFICATION- left by Peter Jensen at the Office of the
Commissioners of Patents on the 22nd May 1883. Communicated to him
from abroad by Lars Magnus Ericsson of Stockholm Sweden
;
PETER JENSEN of 33 Chancery Lane in the County of Middlesex "IMPROVE-
MENTS. IN MICROPHONES OR TELEPHONES" (A Communication to me from abroad
by Lars Magnus Ericsson of Stockholm Sweden)
•
i
This invention consists firstly of an improved microphone, and partly of a
complete telephone arrangement with its receiving instrument and signalling or
call appliance and is principally to be used as a table apparatus.
The microphone itself which is fixed to an upright pillar joined to the frame-
work of the apparatus, is arranged in the following manner; the funnel or
mouthpiece used for speaking into is movably fastened to a cover so that it can
turn therein. The cover is screwed to a shell or chamber. Under the cover the
diaphragm is situated which is covered with a band of india rubber round the
edge and fastened to one edge of the cover by a screw and two springs, one of
which is provided with a set screw to regulate the pressure of the other spring
against the diaphragm. The latter spring forms a conductor from the diaphragm
to the cover and shell. There is a plate of carbon in the middle of the diaphragm,
against which a small platinum covered button is supported. A thin pin passes
down from the button and the lower end of it is provided with a small piece of
carbon. A small platinum-covered anvil is situated under the latter piece of
carbon which is pressed up against the button by means of a helical spring, capable
of being regulated as to tension by means of a screw. The pin is guided in a
socket. The helical spring and the lower part of the anvil carrier are contained
within the just named regulating screw on the upper part of which is mounted
an ebonite socket which carries and insulates the guide socket for the aforesaid
pin; the screw is also by an ebonite ring insulated from the shell of the
microphone.
In the foot or frame of the apparatus is placed an induction coil. A conducting
wire is connected to the zinc pole of the battery and to earth. A second wire is
connected to the carbon pole of the battery in such manner that the whole battery
can act through it. A third wire is connected to the carbon in one of the elements
LD 071

page_text: of the battery, so that only a part of the battery acts through it. A fourth wire
is connected to the line wire. As is usual in telephone arrangements it is only
the induction currents from the induction coil which are admitted to the line.
The current through the microphone passes along as follows: first from the carbon
in one element (a part of the battery only being closed through the microphone) to
the third conducting wire through two contact springs (when the receiving or
hearing telephone is taken off its staple or crutch these two springs are in contact
with each other) thence through the induction coil, the primary wire, along a wire
up through the interior of the pillar, to the regulating screw, the helical spring,
the anvil, the lower carbon contact, the pin, the platinum contact, the carbon disc
under the diaphragm through the latter the adjustable spring, the screw for fixing
it, the cover, the shell and then through the metal of the hollow pillar down to
the body of the apparatus, which by a spring is connected to the first wire that
leads to the zinc pole of the battery.
:
It will thus be observed that the primary current through the microphone must
pass through two platinum-carbon contacts, whereby the action becomes excellent.
By means of the regulating. screw the pressure of these contacts may also at any
time be adjusted thus ensuring the efficient working at all times.
The current path for the secondary line which is admitted to the line for acting
on the hearing telephone at the other end consists of the following parts: first
from the earth wire to the spring connected to the said first wire, then through
the secondary line to the induction coil from the other end of the latter through a
wire and through one or more hearing telephones then through two springs (which
when the hearing telephone is lifted off its crutch are in contact) and then into the
line wire.
The first four wires named above are placed in a flexible hose so that the
apparatus when placed on the writing desk or table may be shifted about.
As regards the call or signal appliance the bell with its internal hammer is
placed on the foot of the apparatus, the hammer being fixed on the keeper of the
working electro-magnet. There is a relay electro-magnet with keeper for closing
the current path for the working electro-magnet. A knob serves to close the line
when, it is desired to ring. Instead of galvanic ringing appliance a magnet
induction ringing appliance may be used, or the relay may be omitted for short
lines.