IMPROVEMENTS IN APPARATUS FOR TRANSMITTING AND DEDIwth Car
Year: 1882

page_text: LETTERS PATENT to John Rapieff, of No. 35 Queen Victoria Street, in the
City of London, Electrician, for an invention of "IMPROVEMENTS IN APPARATUS
FOR TRANSMITTING AND DEDIwth Car
PROVISIONAL SPECIFICATION left by the said John Rapieff at the Office
of the Commissioners of Patents on the 3rd March 1882,
JOHN RAPIEFF, of No 35 Queen Victoria Street, in the City of London,
Electrician. "IMPROVEMENTS IN APPARATUS FOR TRANSMITTING AND RECEIVING
SOUND"
For the purpose of increasing the distinctness and intensity of transmitted
sounds I propose to use a microphone having two or more groups of contacts, parts
or branches, arranged in such a way that the vibrations set up by the sound waves
in one or several of these groups will increase or decrease the pressure of the
contacts and consequently decrease or increase their resistance, while the contrary
effect will be produced in the contacts of the other group or groups, and I connect
these different groups of contacts parts or branches of the microphone to separate
wires or parts of the primary coil or coils of an induction Bobbin, in such a way
that the effect of a divided current from a battery, passing through this
arrangement of microphone's contacts and primary coil or coils, when the microphone
is at rest, shall produce little or no magnetisation of the iron core in the, induction
Bobbin,
The result of this arrangement will be that when the sound waves or vibrations
act on the microphone the added or double effect of the changes of the microphone's
contacts pressure and resistance will produce a differential action of the current on
the primary coil or coils and consequently will effect a greatly intensified variation
of the magnetisation of the iron core and the induced currents in the secondary
coil or coils of the induction Bobbin.
For obtaining the same result any similar disposition of the microphone's contacts
in connection with the induction Bobbin can be used, as for instance :-the groups
of the microphone's contacts may be inserted in the sides of a "Wheatstone"
Bridge while the primary coil or coils of the induction Bobbin are placed in the
Bridge itself.

page_text: Instead of one battery I sometimes use two, or more, in which case they may be
connected in a suitable manner to increase the effect.
To obtain the contact m and n I use carbon, coke, charcoal, graphite, metal
their oxides or other conductor or semi-conductor, or other suitable material, either
in pieces, powder or grains, and more particularly in thin discs, plates, stars,
gridirons, spirals, filaments or fibres; but other suitable shapes may be used.
These may be obtained by the proper shaping and carbonization (before or
afterwards) of card board, pasteboard, veneers, saw dust, webs of silk, cotton, flax etc,
cocoa nut fibre, cotton, wool or other suitable material
These parts are arranged so as to form what is called a microphone and fixed to
a diaphragm, stand or soundboard etc.
The pressure between them is made by means of a weight or spring; or by
permanent or temporary magnetism.
The simplest form of the microphone will be two or more discs or plates of rigid
wire gauze or webb or properly shaped carbonized cardboard, the surfaces of which
may be plain, corrugated, granulated, curved or pierced with holes, and may touch
each other; or I may put between them carbon or other semi conductor, either
granulated, powdered, or in the form of fibre.
To increase the actions of the sound waves on the microphone I sometimes place
the latter in the focus of any suitably shaped sound reflector, or otherwise
constructed accumulator of the sound.
Figures 2 and 3 (which may be combined) show modifications which describe
themselves.
Having now described and ascertained the nature of my said Invention and in
what manner the same is or may be performed
I claim as secured to me by the hereinbefore in part recited Letters Patent.-
Firstly. The use of two or more groups or sets of microphonic contacts with
primary coil or coils differentially arranged, substantially as described and shewn
in figs 1. 4. 5. 6. 7 and 8 of the accompanying sheet of drawings, for the purpose
set forth.
Secondly.-The arrangement of microphonic contacts in the side or sides of a
Wheatstone Bridge, & the primary coil or coils of the induction bobbin in the
Bridge itself, substantially as set forth & shewn in figs 9.10 & 11 of accompanying
drawings.
Thirdly. The use for microphones of carbonized cardboard, web or organic
fibre &ct substantially as hereinbefore specified
Fourthly. The combinaiton of microphones with suitable sound reflectors or
accumulators as herein before described.
In Witness whereof I the said John Rapieff have hereunto set my hand
and seal this thirtyfirst day of August in the year of our Lord one
thousand eight hundred and eighty two.
JUHN KAPIEFF. (LS)