IMPROVEMENTS IN MICRO-TELEPHONIC APPARATUS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office of
the Commissioners of Patents on the 3rd August 1882. Communicated to
him from abroad by Doctor Arsène D'Arsonval of Paris in the Republic of
France.
"
JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman "IMPROVEMENTS IN MICRO-TELEPHONIC APPARATUS a communication
to me from abroad by Doctor Arséne D'Arsonval of Paris in the Republic of
Franco
In the provisional Specification which I deposited on the 2nd May 1882 with
my application for Patent No 2065 it was indicated that the regulation of the
pressure of the moveable bodies (that is to say the blocks of the manganesian
agglomerate containing bi-oxide of manganese destined to replace the carbon)
upon the bodies fixed upon the microphonic plates were regulated magnetically
that is to say by a magnet which operates more or less as required.
That substitution permits the microphone to be placed in any position and the
micro-telephonic apparatus to be made portable and of small dimensions capable of
being held by the hand
It has combined therewith an induction coil placed in a small automatic commu-
tator box which is also of small dimensions and having a telephonic receiver
constituting a new system of micro-telephonic portable post applicable to military
telephones and other purposes.
The microphonic plate or diaphragm of the transmitter has four moveable
blocks of the substance before named and having a cross-section of circular square
or other form and having the two extremities of each of them enter into the
supports of the same composition connected to the lugs which communicate with
the pile by means of wires passing through a long flexible connecting tube.
Each of the blocks is inclosed in a metallic envelope. The pressure of the said
moveable blocks upon the microphonic plate is regulated by two small magnetic
pieces tied to a magnet which constitutes or is set in the handle of the microphonic
transmitting apparatus.
The arrangement of microphone is connected to an induction coil placed in the
box of the automatic commutator the rod of which supports the telephonic portable

page_text: receiver put also into communication with the commutator box by ineans of wires
passing through another long flexible tube.
The microphonic plate of the transmitter is maintained in position upon a case
enclosing the parts by a shouldered ring screwed upon the said case.
With regard to the portable receiver the principal feature consists in the
employment of a circular coil placed in an annular magnetic field.
To effect this the two poles of a permanent magnet are utilized of which poles
the one is in the form of a cylinder and the other pole is fixed to the other end of
the magnet and envelopes the first of the poles in the form of a ring. The magnet
may take the general figure of the magnet of the transmitter.
These two poles are therefore concentrated and the variable space between them
constitutes an annular magnetic field of equal intensity in which is placed the
coil which in consequence itself is immersed in the magnetic field so that all its
parts are submitted to the induction avoiding, useless resistance and permitting
the apparatus to give the maximum of useful effect with the minimum of effort.
The vibrating plate of the receiver is in direct contact with the poles of the
magnet and rests also upon the edge of the casing which encloses the poles and the
coil. The receiver is to be applied directly to the car by means of the ear piece
screwed upon the casing (and serving to secure the vibrating plate). Or it may be
a double acoustic tube allowing with one single receiver the hearing with both cars
so that speaking can be heard from a great distance. It follows that by the
combination of the said microphonic transmitter of small dimensions with the said
portable receiver there is provided a micro-telephonic portable post capable of
various applications. And moreover the microphonic apparatus the receiver and
the annular magnetic field may be applied to. other telephonic posts of any other
system.