AN IMPROVED APPARATUS FOR TRANSMITTING ACOUSTIC SIGNALS
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Charles Marie Courtot at the Office
of the Commissioners of Patents on the 19th October 1876.
CHARLES MARIE COURTOT, of Paris, Boulevard de Strasbourg, No. 23, Electrician.
"AN IMPROVED APPARATUS FOR TRANSMITTING ACOUSTIC SIGNALS."
It has been the custom for some time to employ in offices and other places
speaking tubes, the ends of which come into the two rooms between which com-
munication is desired. These pipes are terminated at each end by a bell mouth in
which a whistle is inserted by pushing, so that a person blowing through the tube
from one end sounds the whistle at the other end as a signal that he wishes to
make a communication. On withdrawing the whistle and putting the bell mouth
to the car the listener can hear what the person speaking at the other end of the
tube says.
In ordinary times the whistle is therefore in the bell mouth, as it is
necessary to be always ready to hear the signal; but it frequently happens that the
whistle falls out and prevents the person blowing through from the other end being
heard. It is to avoid this inconvenience that I have invented a bell mouth and
whistle in one piece, which can be made to act at will either as a whistle to signal
or as a bell mouth to transmit the words, and this without the necessity of removing
a single part.
The apparatus is fixed in a casing of wood or metal terminated by a bell mouth
at one end; at the other end the casing receives a threaded socket, to which the
accoustic tube is fastened. The casing is hollowed out to receive the whistle.
The whistle is formed by a metallic plate cut in a suitable manner, and by
another piece, also of metal, hollowed on the inside, the end of which piece is
adjusted in such a manner as to form a whistle. These two pieces are soldered
together.
The air which is blown in from the opposite end of the pipe is directed upon the
whistle by an inclined plate arranged in a metallic tube. The parts forming the
whistle close the rectangular part of this tube.
I will now explain how the apparatus works as a bell mouth. The inclined plate
is pivotted and can be raised by the push-in action of a rod, which is caused to act
upon a lever or tail piece. This rod simply penetrates by its thin end the eye of
the lever, and is stopped by a shoulder against the plate. To facilitate manipulation
the rod carries a button. The plate is cut so as to embrace as exactly as possible

page_text: the interior shape of the pipe portion of the bell mouth. It rests in the circular
part of this pipe or conduit upon a semi-cylindrical socket soldered to the pipe and
cut obliquely. By the side of the joints the plate rests upon a caoutchouc pad fixed
in a cavity. This caoutchouc is compressed when the button is pressed so that the
natural position of the plate is an inclined position, that is to say, the apparatus if
left to itself will whistle upon a person blowing through the pipe from the opposite
end. It is only necessary to press upon the button to raise the plate if it be desired
to use the apparatus as an ordinary bell mouth for receiving or conveying messages
from one end to the other of the accoustic tube.
The metallic part which constitutes the whistle and the conductor of the wind
can be fastened to the casing in two different ways. Either the plate is soldered
to the tube, and thus the whole can be maintained by a screw, or else the plate is
independent of the tube, in which case the latter is simply placed in the casing and
the plate to which is soldered; its whistle plate is fixed by screws, thus dispensing
with the necessity of the first-named screw.