IMPROVEMENTS IN ELECTRIC TELEPHONE TRANSMITTING AND RECEIVING INSTRUMENTS
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Arthur French St. George at the
Office of the Commissioners of Patents on the 1st November 1883.
ARTHUR FRENCH ST. GEORGE, of Bucklersbury, in the City of London,
"IMPROVEMENTS IN ELECTRIC TELEPHONE TRANSMITTING AND RECEIVING
INSTRUMENTS
"
My present invention relates to telephonic apparatus, in which articulate specch
or other audible signals are to be transmitted to distant places by means of elec-
tricity, and it has for its object improvements in the construction of parts of such
apparatus so that the audible signals are clearer and more distinct than has
ordinarily heretofore been the case.
In some forms of transmiting instruments used for so sending audible articulate
siguals it has been usual to direct the voice through a conical mouthpiece upon a
vibrating disc or plate the vibrations of which cause corresponding disturbances in
a current or currents of electricity which disturbances are reproduced and rendered
audible in a receiving instrument at any desired distance. "I have found however
that the human voice directed through such a mouthpiece is concentrated too much
upon the centre only of the vibrating disc or plate carried in a frame or support
and is liable to cause too great vibration and movement of the disc or plate at the
centre only with the result that certain sounds reproduced by the electrical
disturbances so caused, are more or less uncertain and indistinct.
According to the first part of my invention I use for the transmitting apparatus
a vibrating disc, or plate preferably of the kind described in the specification of
Letters Patent granted to me and dated February 21st A.D. 1883 and numbered
965 and I arrange this disc or plate in a suitable frame or support with a mouth-
piece in front through which the sounds of the human voice can be made to
impinge upon the disc or plate but I make the mouthpiece cylindrical or parallel
instead of conical or bell-mouthed, and in this way I find that the vibrations are
less concentrated upon the centre of the disc or plate than when a mouthpiece of the
Latter shape is used, and they are more uniform and even in character. And in
order to prevent, as the result of certain loud sounds or combination of sounds, too
great condensation of air in the tubular mouthpiece and consequent excessive or
incorrect flexures or disturbances of the disc or plate, I make one or more holes or
perforations through the disc or plate so that a certain vent is afforded to tho air

page_text: which would be otherwise too much alternately condensed and rarified in front of
the disc or plate.
I prefer to arrange the hole or holes in irregular positions in the disc or plate.
Another part of my invention relates to a novel form of transmitting apparatus
by which sounds such as the human voice causo variations or disturbances in a
current or currents of electricity, which variations are coverted into corresponding
audible sounds at any distant point. I take a sheet of paper of sufficient size and
I roll it up until it forms a tube, either parallel or somewhat conical, of several
thicknesses, and I carbonize the tube so formed preferably in the manner described
in the specification of Letters Patent granted to me dated February 21** A.D. 1883
and numbered 965. I connect one wire of the electrical circuit in which variations
are to be produced to the edge of the carbonized paper in the interior of the tubo
and the other wire to the edge at the exterior of the tube, and I use the tube so
arranged as a mouthpiece into and through which the sounds of the human voice
can be directed.
Vibrations produced by sounds so directed cause corresponding variations in the
electric current or currents which in turn are converted into audible sounds at
distant receiving instruments.
Another form of transmitting instrument which I sometimes use for the same
purpose consists of a sheet of paper folded backward and forward in a series of
folds and then carbonized in the way already described, the conducting wires of the
electric circuit being connected to its opposite ends. Or a disc of paper corrugated
by means of dies or in other convenient manner and then carbonized may be used
for the same purpose, the conducting wires being connected to opposite sides of
the disc.
Another part of my present invention relates to instruments for receiving and
rendering audible variations in an electric current or currents produced by means
of the human voice or other audible sounds at a distant point; and it has reference
to such receiving instruments in which the variations of the electric current cause
corresponding variations in the friction between a conductor of metal such as
platinum and a piece of chalk or other equivalent absorbent material through which
the electrical current is made to pass.
I take an ordinary telephonic disc or plate by the vibrations or movements of
which the electrical variations are converted into audible sounds, supported in a
suitable frame or support in the ordinary way, and to this disc or plate at or near
its centre I attach the end of a cylinder of chalk or other equivalent absorbent
material having the properties required, so that it projects at or nearly at right
angles from the face of the plate. Surrounding the chalk cylinder I fit a hollow
cylinder of platinum so that the latter can only turn upon the former with a
certain amount of friction, and I connect one end of the wire, through which the
electric current or currents pass in which the variations are produced as described,
to the chalk cylinder, and the other end of the wire to the platinum cylinder. As
is well understood, the friction between the two cylinders will vary in proportion to
the variations of the current or currents of electricity passing through them, and
in order that such variations in friction may cause corresponding vibrations or
movements in the disc or plate I attach to the external platinum cylinder a forked
bar or connecting piece the other end of which is provided with an arrangement
by which a certain amount of torsion can be communicated to it and to the
platinum cylinder, consisting for instance of two flexible strings twisted together.
It will be seen that when the friction between the two cylinders is sufficient the
tortional movement is communicated through the platinum cylinder to the chalk
cylinder and to the disc or plate and causes in the latter a certain amount of
buckling or flexure, which ceases and the plate or disc returns to its normal
position when the friction between the cylinders ceases.
A series of such bucklings or flexures takes place therefore, corresponding
accurately with the variations in the electrical current or currents passing through
the cylinders, and these bucklings reproduce audibly and clearly the sounds at the

page_text: distant transmitting instrument by which the electric variations are produced in
the telephone conducting wire.
The method of arrangement described may be somewhat modified. For instance,
the chalk or other analogous cylinder may have a torsional strain imparted to it in
the way described, this torsion causing flexures or bucklings of the plate or disc
corresponding to the variations in the electric current or currents passing between
the cylinder and a conducting connecting piece attached to the disc or plate.
In telephone transmitting instruments it has heretofore been usual to uso a
vibrating disc, plate, or acoustic equivalent to actuate the electrical apparatus, and
another part of my present invention consists in a novel method of using
vibratory pieces of tubular conducting carbonized organic material instead of a
plate or disc.
For this purpose I group one or more such tubes severally or collectively, in
suitable supporting sockets; or I group them together without such sockets, and I
arrange them so that all the tubes are included in the electric circuit in which it is
desired to set up electric variations by the action of sound.
The tubes described may be formed of carbonized organic material of either
natural or artificial structure. Where tubes of natural structure are used, I prefer
to employ pieces of dried grass, straw, or reeds, carbonized by the method described
in the specification of Letters Patent granted to me, dated February 21" A.D. 1883
and numbered 965. Where tubes of artificial structure are to be used, I prefer to
employ pasteboard, paper, or other analogous organic material similarly carbonized.
In all cases I prefer to arrange the one or more such tubes employed so that
their mouth or mouths are adjusted immediately opposite to a mouthpiece in such
manner that sonorous vibrations of the air contained in the mouthpiece will
produce corresponding vibrations in the columns of air contained in the tube or
tubes; and in this way corresponding variations in the electric current or currents
passing through the latter are also produced and are transmitted to the distant
receiving instruments.
I prefer sometimes to perforate the tubes as and for the purpose already
described.
By the improved methods of construction and arrangement described, I am
enabled to obtain great clearness and distinctness in the sounds of the human voice
or other sounds transmitted.
That part of my improvements relating to perforations as described may in some
cases be applied to telephonic receiving apparatus as well as to the transmitting
apparatus as described.