Year: 1887

page_text: Date of Application, 30th Nov., 1887
Complete Specification Left, 20th Aug., 1888
Complete Specification Accepted, 21st Sept., 1888
ALAN ARCHIBALD CAMPBELL SWINTON, Engineer, 75 Queen Victoria Street,
London, E.C. do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in Electric Telephones and has for its object
increased efficiency in working and greater simplicity in construction.
According to my invention 1 dispense with the separate induction coil or trans-
former usually employed in connection with microphone transmitters, and I sometimes
also dispense with the permanent magnets generally used in telephone receivers, and I
wind the electro magnets of my telephone receivers each with two wires, one a com-
paratively short and thick wire of small resistance which I arrange in circuit with a
battery and the microphone transmitter, and the other a long and thin wire of high
resistance which I put in circuit to line and earth, the arrangement being such that
variations in the resistance of the transmitter, consequent on the sonorous vibrations,
produce corresponding fluctuations in the strength of the battery current circulating
round the thick wire of the receiver electro magnet, and thus induce other currents
of high electro-motive-force in the fine wire coil which passing to line or earth and
thence through the fine wire coil of a similarly wound and arranged receiver at a
distant station actuate the said distant receivers in the ordinary manner.
Under ordinary circumstances I find that the magnetism produced in the core of the
electro-magnet, by the battery current circulating through the thick wire coil is
sufficient to render the instrument properly sensitive but I sometimes find it
advantageous to additionally polarise the said core by means of permanent magnets
suitably applied.
1024

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Telephones.
ALAN ARCHIBALD CAMPBELL SWINTON, 75 Queen Victoria Street London, E.C.
Engineer, 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:-
This invention relates to improvements in electric Telephones & has for its object
increased efficiency in working & greater simplicity in construction.
According to my invention I dispense with the separate induction coil or trans-
former generally employed in connection with microphone or variable resistance
transmitters and I sometimes also dispense with the permanent magnet usually used in
telephone receivers and i wind the electro-magnets of my telephone receivers each
with two wires, one a comparatively short and thick wire of small resistance wound
to comparatively few convolutions, which I arrange in circuit with a battery and the
microphone or variable resistance transmitter, and the other a long and thin wire of
high resistance wound to many convolutions which I connect in circuit to line and
earth, the arrangement being such that variations in the resistance of the trans-
mitter consequent on the sonorous vibrations produce corresponding fluctuations in
the strength of the battery current circulating round the coil of thick wire with which
the receiver electro-magnet is wound, and thus induce other currents of high electro
motive force in the fine wire coil, which passing to line and earth and thence through
the fine wire coil of a similarly wound and arranged receiver at a distant station,
actuate the said distant receiver in the ordinary manner.
The arrangement of connections at each station may be as shewn in Fig. 1, where a
is the soft iron core of the receiver magnet b the fine wire coil of many convolutions
in circuit with line and earth and wound on the core a, preferably at the end thereof
nearest to the diaphragm or armature d. c is the coil of thick wire and few convo-
lutions in circuit with the battery B and the microphone or variable transmitter M.
In this arrangement there is no electrical connection between the circuits in which
the coils and c are respectively situated, but in some cases I find it advantageous to
arrange the connections as shewn in Fig. 2 where the line currents after passing
through the coil & pass to earth partially through the coil c and partially thro' the
battery and transmitter.
I do not confine myself to the use of one receiver or electro magnet at each station
as several with their respective coils joined either in parallel or series may evidently
be employed without departing from my invention.
The two wires forming the two coils &c may be wound on the core a as shewn
in the Figs. 1 & 2 or they may be laid parallel to one another and wound on to the
core together. I however find it advantageous to wind them as shewn in figure 3
where a is the core d the diaphragm or armature, e the thick wire coil and & the

page_text: thin wire coil which is wound in two sections one of which, b, is wound on the end of
the core next to the diaphragm d and the remainder is wound over the thick
wire coil c.
Under ordinary circumstances I find that the magnetism produced in the core of
the electro magnet, by the battery current circulating through the thick wire coil is
sufficient to render the instrument properly sensitive, but I sometimes find it
advantageous to additionally polarise the said core by means of permanent magnets
applied to the core according to the manner that is usual in ordinary telephone
receivers.
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 electric telephones, receivers with double wound electro magnets arranged
and connected substantially as and for the purpose set forth.
(2) The method of winding the two coils with special reference to Fig. 3 of the
accompanying drawings & substantially as described.
(3) The subject matter of the two preceding claiming clauses in combination with
permanent magnets suitably applied for additionally polarising the receiver cores
substantially as set forth.
Dated this 20th day of Anoust 1888