IMPROVEMENTS IN APPARATUS FOR TRANSMITTING AND RECEIVING MESSAGES OR SIGNALS BY MEANS OF ELECTRICITY " AUDIBLE
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Arthur French St. George at the
Office of the Commissioners of Patents on the 2nd October 1883.
ARTHUR FRENCH ST. GEORGE, of Bucklersbury, in the City of London,
"IMPROVEMENTS IN APPARATUS FOR TRANSMITTING AND RECEIVING
MESSAGES OR SIGNALS BY MEANS OF ELECTRICITY "
AUDIBLE
My present invention relates to telephones, or apparatus used for transmitting
and receiving audible messages by means of electricity, and it has for its objects
novel methods of constructing and arranging such apparatus so that it is very
simple, cheap, and effective.
In order to put in operation that part of my invention which relates to
apparatus used for receiving and rendering audible messages transmitted from a
distance, I take a plate or membrane of non-metallic material, such as wood,
parchment, or paper, of convenient size and shape which may be varied to suit
varying circumstances, and I arrange this plate or membrane in a wooden or other
support which carries it by its edges. Upon the centre of one side of the plate or
membrane I attach, preferably by cement, a number of short pieces of iron wire
each covered with cotton, silk, or other material of the like kind, in order to damp
any metallic dominant note given out by the iron wire when vibrating.
I prefer to arrange the pieces of covered iron wire parallel and close to each
other, and of different lengths, the longest being in the centre and the others upon
each side diminishing gradually in length, so that the whole form a shape
approximately circular. I do not confine myself, however, to the particular
number and shape of the iron wires, for instance, a single spiral covered wire may
be used; but I prefer the arrangement first described for the reason that as the
different lengths of wire have different rates of vibration so each different piece is
capable of responding to a certain number of magnetic attractions per second; and
also that the method of using different lengths of wire and arranging them so as to
form approximately a circle allows of perfect action of the plate or membrane.
The plate or membrane carrying the wires as described is arranged in the usual
way opposite to the pole of a magnet or electro-magnet having round it a coil of
insulated conducting wire forming part of the telephone circuit through which
telephonic currents or variations in currents are transmitted by means of
transmitting apparatus of the kind which I will now describe.
[Pains 271

page_text: In order to produce electrical currents or variations in the currents, which
variations are to be resolved into corresponding audible sounds in the receiving
apparatus above described, I cause the sounds which are to be reproduced (such as
the human voice) to impinge upon an electric conducting substance which is
included in the circuit and through which a constant current of electricity is made
to pass from any convenient source.
I prefer to use such electric conducting substance in the form of a plate, disc,
film, reed, wire, or net work or gauze, and I find a very suitable material for the
desired purpose to consist of carbonized organic material capable of conducting
electricity. Or, sometimes I use lampblack, or plumbago, or any form of carbon
which can without difficulty be made into the form of a somewhat fragile disc or
plate.
I connect rigidly with the circuit the plates, discs or other form of conducting
substance described, and I make their junction with the wires of the circuit
" loose
perfectly rigid so as to prevent the possibility of what is known as
contact," or microphonic action, between the wires or connections and the disc,
plate, or other form of conducting material described.
I prefer to attach one wire of the circuit to one edge of the disc or plate and the
other wire to the opposite edge, and I support the disc or plate in a suitable frame,
in which it need not necessarily be held all round, a mouthpiece of convenient
form being added if desired.
Another novel method which I sometimes adopt to form the disc or plate consists
in dusting carbon powder or metallic or other suitable conducting powder over the
surface of a membrane, plate, or disc of nonconducting material. The edge of
the surface of conducting particles is electroplated and connected to the wires of the
telephonic circuit as already described. In this method of arrangement when
vibration takes place the conducting particles become more or less separated
between themselves, and their conducting power as a whole varies in proportion.
It will be seen that according to my invention sounds impinging upon a simple
conducting body inserted rigidly and permanently in the circuit set up an agitation
in the integral parts of the conducting body itself and alter their molecular
or mechanical conditions of electrical contact with each other, and the electrical
resistance of the body as a whole is thus varied by the impinging sounds but the
conducting body being itself a simple element permanently and rigidly connected
to the conducting wires or connections, no microphonic variations in the electric
contact and conductivity between two or more separate parts can take place.
In some cases I arrange a weight or equivalent device such as a pendent ball
to press lightly against the conducting body so as to cause the latter to be under
a slight constant strain. In this way sounds of very rapid period of vibration are
more readily transmitted; but the weight described in no way acts as an electrical
conductor. The transmitting apparatus described may in some cases be used as
receiving apparatus.