Improvements in and relating to Telephony.
Year: 1895

page_text: Date of Application, 10th Aug., 1895
Complete Specification Left, 20th Sept., 1895-Accepted, 26th Oct., 1895
PROVISIONAL SPECIFICATION.
Improvements in and relating to Telephony.
I, JOHN STUART BIGGAR of 1260 Wilcox Avenue, Chicago, in the County of
Cook and State of Illinois, United States of America, Electrician do hereby
declare the nature of this invention to be as follows:-
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According to this invention, I employ as a section of a telephonic circuit a
material such as bismuth which is capable of changing its conductivity when cut by
magnetic lines of force, and arrange this section in the field of force of an electro-
magnet.
Dated out 7
improvements in and relating to Telephony.
I, JOHN STUART BIGGAR of 1260 Wilcox Avenue, Chicago in the County of
Cook and State of Illinois, United States of America, Electrician, do hereby
declare the nature of this invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:
According to this invention I employ as a section of a telephonic circuit, a
material, such as bismuth, which is capable of changing its conductivity when cut
by lines of magnetic force, and arrange this section in the field of force of an
electro-magnet.
I will describe in what manner I may carry my invention into practical effect,
with reference to the accompanying diagrams.
In the diagram Figure 1, a represents an ordinary magneto telephone, consisting
of the diaphragm a¹, the permanent magnet a³, and the coil a³ arranged on the
magnet. The circuit which includes the coil a³ also includes the coils of an
electro-maguet c. The poles of this magnet are constructed to face each other,
with an intervening space, in which is situated the block of bismuth d, or other
metal which similarly changes its conductivity with changes of magnetic stress or
influence to which it may be subjected. The block of bismuth is connected directly
and permanently in the main circuit e of the battery e¹.
The electric impulses or undulations which are set up in the circuit 6 by the
vibratory movement of the diaphragm a' caused by the sound waves, will create
corresponding maguetic impulses or undulations in the magnetic circuit of the
magnet c. Inasmuch as the block of bismuth d is cut by the lines of force
travelling in this magnetic circuit, it will be subjected to all such impulses or
undulations. Consequently, its resistance to the flow of current upon the main
circuit e will vary in accordance with the sound waves directed to the instrument a,
and a receiving instrument placed in the main circuit will be affected in the usual
manner and reproduce the sounds. The phenomenal action of bismuth herein
[Price 8d.]

page_text: referred to is well known and no attempt to explain it will be made or is
necessary.
It may be desirable to use an induction coil with the apparatus; if so, the piece
of bismuth will be in the closed primary circuit of the induction coil as indicated by
the dotted hues and the main line will as usual be connected with the secondary
coil s.
In Figure 2 I have illustrated a form of apparatus which is compact, in that it
embodies the magnet, the block of bismuth and the magneto-instrument in one
apparatus. The funnel or mouth piece g of the instrument is of metal and divided
in two parts, separated by insulating material, gl. There are two diaphragms,
one, , of bismuth, and the other, i, of soft iron and of the usual construction. The
latter is insulated from the mouth piece. Between the two diaphragms is an air
chamber which conducts the vibrations of one diaphragm to the other. Behind
the iron diaphragm the usual permanent magnet and coil are placed. A coil of wire j
wound upon the mouth piece of the instrument surrounds the bismuth diaphragm.
This coil is in a closed circuit with the coil upon the permanent magnet. The two
parts of the mouth piece form the terminals of the main circuit, and they are
bridged as shewn by the bismuth diaphragm. It will be seen that the bismuth
diaphragm is located in the magnetic circuit of the coil j and that it will therefore
be subjected to the variations in magnetic force, which will cause it to vary the
flow of current in the main circuit.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In telephony, a means for varying the resistance of an electric circuit, which
consists of an electro-magnet, in the magnetic path of which is located a portion
the said circuit consisting of material whose resistance to the flow of current can be
varied by the passage of magnetic lines of force through it.
2. In a telephone circuit, a section consisting of material capable of changing its
electric conductivity when cut by maguetic lines of force, arranged in a magneto
telephone in combination with an electro-magnet in whose field of force the said
section of the circuit is located, substantially as hereinbefore described.
3. In a telephone circuit, a section consisting of bismuth or other material having
similar properties, arranged in the field of an electro-magnet the coils of which are
included in the transmitter circuit, substantially as described.
Dated this 19th day of September A.D. 1895.
W. E. HEYS & SON,
Agents for the Applicant.