IMPROVEMENTS IN TELEPHONIC TRANSMITTING AND RECEIVING APPARATUS
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Richard Theiler and Meinrad Theiler
at the Office of the Commissioners of Patents on the 30th April 1880.
RICHARD THEILER and MEINRAD THEILER, of 86, Canonbury Road, Islington,
in the County of Middlesex. "IMPROVEMENTS IN TELEPHONIC TRANSMITTING
AND RECEIVING APPARATUS."
The first part of our Invention relates to an improved method of constructing
telephonic transmitters in which the pressure of two contacts against one another
is made to vary by the vibrations of a diaphragın or sounding board. All such
transmitters as constructed by other inventors are affected and disturbed in their
action, either by any change in the tension of the diaphragm, or by the contacts
breaking away from one another when the vibrations exceed a certain amplitude.
The transınitters constructed according to our method are free from these faults, as
will be seen from the following description of the essential features of this part of
our Invention:-One of the contacts in connection with a battery and the primary
circuit of an induction coil is fixed to the surface of the diaphragm or sounding
board, while the other contact is suspended as a pendulum in such a manner that
it leans slightly against the contact on the diaphragm. The point of suspension of
this pendulum is also placed on the diaphragm, so that the same relation exists
between the, two contacts no matter what the tension of the diaphragm may bo.
In order to prevent the possibility of the contacts leaving one another when the
vibrations of the diaphragm come to bo of some considerable amplitude, as in speaking
very loudly or very near the diaphragm, we fix an adjustable limitting stop so
that the pendulum can be regulated to lean more or less against the other contact,
but is thereby prevented from leaving it entirely. This limitting stop we also
attach to the diaphragm, whereby any change in the temperature, and consequent
alteration of the tension of the diaphragm, is prevented from affecting the action of
the transmitter. By making the limitting stop slightly clastic the instrument can
be adjusted with greater nicety than if the limit was quite rigid. The contacts may
be made of any conducting substance. We found platinum sponge worked into a
stiff paste with white clay and baked an excellent inaterial for such contacts. We
also found that the contacts made of magnetic metals give better results for such
purposes than platinum or other non magnetic metals.
The second part of our Invention relates to an improved method or methods of
constructing electro magnetic telephone receivers. Instead of acting upon the

page_text: diaphragm by only one coil at the centre, or by two coils beside one another, as in
the Bell and Gower telephones, we place three coils behind, that is, concentrically
with one another, and construct the instrument so that the three coils all act upon
the centre of the diaphragm, whereby the amplitude of the vibrations received is
made considerably greater. For this purpose the iron diaphragm carries at its
centre a pin which consists for half its entire length of brass or other non-magnetic
substance, the other half being of soft iron or steel. This compound pin and iron
diaphragm are acted upon by the following arrangement of 3 coils:-A U shaped
permanent magnet carries on each pole or extremity an iron tube, the two tubes
being concentric with one another. One of these tubes almost touches the iron
diaphragm, while the other is brought very close to the end of the compound pin.
One of the coils is put on that tube which faces the diaphragm, the second coil is
fixed to the inside of the same pole of the permanent magnet, and the third coil is
put on that tube which faces the end of the compound pin.
By means of this construction the action of the current when passing through
the three coils upon the diaphragm is fourfold. The iron diaphragm is acted upon
in the first place by the magnetised tube immediately facing it, in the second place
by the elongation and contraction of the iron pin which passes through the second
coil, in the third place by the alteration in the magnetic polarization of the said
iron pin, and in the fourth place by the coil attached to the other pole of the s
magnet and facing the end of the pin.
The attraction between several electro-magnets and one common armature may
also be transferred to the centre of a diaphragm by attaching a non magnetic stud
to the latter, and fixing transversely thereon a light armature, for example, a
piece of iron wire, which is made to face the poles of the several electro magnets
very closely.