IMPROVEMENTS IN ELECTRIC TELEPHONES
Year: 1884

page_text: I CHARLES LEVER of Bowdon in the. County of Chester, Electrician do hereby
declare the nature of said invention for "IMPROVEMENTS IN ELECTRIC TELEPHONES,
to be as follows:―
This invention has for its object improvements in the electric transmission and
reproduction of sound and articulate speech, and differs in principle and construction
from any form of telephonic apparatus at present in use.
Instead of employing a carbon transmitter in conjunction with an electro
inagnetic receiver as is usually the case, I take advantage of the electro-capillary
action of a polarized column of mercury in a tube of non-conducting material with
dilute sulphuric acid or equivalent electrolyte floating upon the mercury the whole
It is well known as was discovered
being of course included in an electric circuit.
by M. Lipmann that if a column of mercury and dilute acid be enclosed in such a
tube, preferably of glass, and the said column be included in an electric circuit any
variation of current or rather of electro-motive force will cause the mercurial
column to rise and fall in the tube proportionately, the cause being attributed to
the liberation of small quantities of gas at the surface of the mercury and dilute
acid or equivalent electrolyte thus altering the surface tension and causing a
movement from the capillary forces.
According to my invention the transmitter is made as follows:-
A tube of non-conducting material of small internal diameter, preferably a glass
tube; is at its lower end fixed to a small metal cylinder (the internal diameter of
which may be slightly larger than the external diameter of the glass tube) having
a screw thread cut in its interior into which may be screwed a small metal cap
which may be hollowed in its interior and is provided on its outside with à
terminal or binding screw. The metal cap being secured in its place, mercury is
poured in the tube so as to fill the hollow part of the metal cap and glass tube to
within a short distance from its open end. It will be seen then that if the said
metal cap be screwed backwards or forwards the mercurial column in the glass
tube will fall or rise proportionately. This arrangement is provided in order to
adjust the transmitter as will be described further on.

page_text: Floating on the top of the thin mercurial column is a thin float plunger or piston
made of wire or other piece of conducting material whose specific gravity is less
than that or mercury and which fits easily but accurately into the bore or interior
of the glass tube. I prefer an aluminium wire on account of its lightness although
other conductors will answer the same purpose.
The diaphragm of the transmitter is made of any suitable electric conductor
such as thin ferrotype plate and is secured by means of metal rims to a case of
insulating material of any suitable shape, such for instance as that used for Bell's
telephone. The glass tube with its attachments may be fixed in this case in a
similar manner to the permanent bar magnet in the Bell telephone but it is
cemented in the case so as to be perfectly rigid.
The piston floating in the column of mercury may either bear against the centre
of the conducting diaphragm by its buoyancy, in which case it is desirable to
platinise the contacts of the wire and diaphragm, or the piston may be electrically
connected with and fixed to the diaphragm. In the latter case it is immaterial
whether the specific gravity of the float piston be greater or less than that of
mercury. A binding screw fixed in the insulating case is connected. electrically to
the conducting diaphragm, the other binding screw being fixed to the small metal
cap as herein before described. The current entering then at the terminal fixed to
said metal cap passes through the mercurial column in contact therewith and
through the piston and the diaphragm to the terminal in connection therewith or
vice versa. An electrolyte may be substituted in the transmitter for the mercury
but the latter is preferable. The diaphragm may also be made of thin vulcanite or
other non-conductor, but in this case the thin piston must be electrically connected
to the terminal on the insulating case by means of a very fine flexible conductor.
The action of the transmitter is as follows:-
The small metal cap having been adjusted so that the float piston just touches
the surface of the mercury, the current from a battery passes through the
diaphragm, the piston and the mercurial column and through the primary circuit
of an induction coil and back to the battery or vice versa. It is evident however
that any sound waves produced by the voice or other sound producer directed into
the mouthpiece of the transmitter will by impinging on the diaphragm cause the
same to vibrate. These vibrations of the diaphragm will cause the float piston to
dip more or less into the mercury thus varying the resistance of the mercurial
column and causing variations in the current flowing through the primary circuit
of the induction coil the secondary circuit of which is connected to line and receiver,
thus causing variations of electric tension or electro motive force in this secondary
circuit which will be transmitted through the line to the receiver.
The receiver is according to my invention constructed in a similar manner to the
transmitter but the space at the open end of the glass tube containing the mercury
should be filled with dilute sulphuric acid or other equivalent electrolyte, or the
glass tube may contain a thin column of mercury then a similar column of the
dilute acid or equivalent electrolyte and another column of mercury as in
Lipmann's electrometer. A float piston of non-conducting material, not easily
affected by the acid solution, rests upon the lower column of mercury as in the
transmitter and reaches through the tube fitting its bore easily but accurately, to
the centre of the diaphragm which may be made of any suitable material. The
sulphuric acid solution or mercury above the said electrolyte is in electrical
connection with a binding screw fixed on the insulating case as in the transmitter.
The metal cap is then similarly adjusted so that the column of mercury upon which
rests the float piston causes the same to gently bear against the centre of the
diaphragm. The float piston must not be pressed into the mercurial column on
which it rests by the pressure of the diaphragin, this being an essential feature in
the adjustment of the receiver. The action of the receiver is as follows:-
The variations of electric tension proceeding from the secondary circuit of the
induction coil caused by the transmitter as hereinbefore described and coming

page_text: through the line pass through the mercurial column and sulphuric acid or vice
versâ. These variations of electric tension however cause the mercurial column on
which rests the float piston to be elevated or depressed in accordance therewith,
thus moving the piston which impinges against the centre of the diaphragm. The
float piston thus communicates these movements to the diaphragm causing the same
to vibrate in unison with the diaphragm of the transmitter, whereby the original
sound waves are reproduced. Any other form of transmitter may be used with
this receiver if desired, and both the transmitter and receiver as described may be
modified to intensify both the electrical and acoustic effects.

page_text: I, CHARLES LEVER of Bowdon in the County of Chester Electrician do hereby
declare the nature of said Invention for "IMPROVEMENTS IN ELECTRIC TELE-
PHONES and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
"
This Invention has for its object improvements in the electric transmission and
reproduction of sound and articulate speech, and differs in principle and construction
from any form of telephonic apparatus at present in use.
Instead of employing a carbon transmitter in conjunction with an electro-
magnetic receiver as-is usually the case, I take advantage of the electro-capillary
action of a polarised column of mercury in a tube of nonconducting material with
dilute sulphuric acid or equivalent electrolyte floating upon the mercury the whole
being of course included in an electric circuit. It is well known as was discovered
by M. Lipmann that if a column of mercury and dilute acid be enclosed in such a
tube, preferably of glass and the said column be included in an electric circuit any
variation of current or rather of electro motive force will cause the mercurial
column to rise and fall in the tube proportionately, the cause being attributed to
the liberation of small quantities of gas at the surface of the mercury and dilute
acid or equivalent electrolyte thus altering the surface tension and causing a
movement from the capillary forces.
According to my invention the transmitter is made as follows:-
་
Figure 1 of the accompanying drawing is a longitudinal section through one
form of transmitter constructed according to my invention.
A tube G of non-conducting material of small internal diameter, preferably a
glass tube, is at its lower end fixed to a small metal cylinder (the internal
diameter of which may be slightly larger than the external diameter of the glass
tube). The cylinder or socket C has a screw thread cut on its exterior as shown
or in its interior onto which or into which is screwed a small metal cap A which
is hollowed in its interior and is provided on its outside with a terminal or binding
screw B.
The metal cap A being screwed in its place mercury m m is poured into the
glass tube G so as to fill the hollow part of the metal cap A and glass tube G to
within a short distance from its open end. It will be seen then that if the said metal
cap A be screwed backwards or towards the mercurial column in the glass tube
will fall or rise proportionately. Or the cap A may be filled with mercury and the
latter made to rise as required in the tube G by screwing the cap further. onto
the tube.
This arrangement is provided in order to adjust the transmitter as will be
described further on.
Floating on the top of the thin mercurial column is a thin float plunger or
piston P made of wire or other piece of conducting material whose specific gravity
is less than that of mercury and which fits easily but accurately into the bore or
interior of the glass tube G. I prefer an aluminium wire on account of its lightness
although other conductors will answer the same purpose.
The diaphragm D of the transmitter is made of any suitable electric conductor
such as thin ferrotype plate and is secured by means of metal rims to a case F of

page_text: insulating material of any suitable shape, such for instance as that used for Bell's
telephone. The glass tube G with its attachments C and A may be fixed in this
case in a similar manner to the permanent bar magnet in the Bell telephone but
it is cemented in the case so as to be perfectly rigid..
The piston P floating in the column of mercury m may either bear against the
centre of the conducting diaphragm D by its buoyancy in which case it is desirable
to platinise the contacts of the wire plunger P and diaphragm D or the piston P
may be electrically connected with and fixed to the diaphragm D. In the latter
case it is immaterial whether the specific gravity of the float piston P be greater
or less than that of mercury..
A binding screw fixed for instance in the insulating case F is connected
electrically to the conducting diaphragm D the other binding screw B being fixed
to the small metal cap A as herein before described. The current entering then at
the terminal B fixed to said metal cap passes through the mercurial column m in
contact therewith and through the piston P and the diaphragm D to the terminal
in connection therewith or vice versa. An electrolyte may be substituted in the
transmitter for the mercury but the latter is preferable. The diaphragm D may
also be made of thin vulcanite or other nonconductor but in such case the thin
piston must be electrically connected to the terminal on the insulating case by
means of a very fine flexible conductor. The action of the transmitter is as
follows.
The small metal cap A having been adjusted so that the float piston P just
touches the surface of the mercury m the current from a battery passes through
the diaphragm D the piston P and the mercurial column m and through the
primary circuit of an induction coil and back to the battery from the wire w¹ to
the line or vice versa. It is evident however that any sound waves produced by
the voice or other sound producer directed into the mouthpiece of the transmitter
will by impinging on the diaphragm D cause the same to vibrate.
These vibrations of the diaphragm will cause the float piston P to dip more or
less into the mercury thus varying the resistance of the mercurial column and
causing variations in the current flowing through the primary circuit of the
induction coil the secondary circuit of which is connected to line and receiver, thus
causing variations of electric tension or electro-motive force in this secondary
circuit which will be transmitted through the line to the receiver. For short lines
the induction coil may be dispensed with as is well known.
The receiver is according to my Invention constructed in a similar manner to
the transmitter and so that they may be interchanged or reversed in action as will
be seen from Figure 2 which is a longitudinal section through the receiver but
space S at the open end of the glass tube containing the mercury should be filled
with dilute sulphuric acid or other equivalent electrolyte. A float piston P in this
case made of non-conducting material not easily affected by the acid solution and
whose specific gravity is greater than that of the acid solution rests upon the lower
column of mercury as in the transmitter and reaches through the tube, fitting its
bore easily but accurately, to the centre of the diaphragm D which may be made
of any suitable material. The piston P may be made of vulcanite. The sulphuric
acid solution above the said eloctrolyte is in electrical connection with a binding
screw B' fixed on the insulating case as in the transmitter.
The metal cap A is then similarly adjusted so that the column of mercury upon
which rests the float piston P causes the same to gently bear against the centre of
the diaphragm. The float piston must not on any account be pressed into the
mercurial column on which it rests by the pressure of the diaphragm, this being an
essential feature in the adjustment of the receiver I prefer to make the insulated
case F of glass so that the adjustment may be assisted by the eye. The action of
the receiver is as follows:-
The variations of electric tension proceeding from the secondary circuit of the
induction coil caused by the transmitter as hereinbefore described and coming
through the line pass through the mercurial column and sulphuric acid or vice versa,

page_text: These variations of electric tension or current from the battery liberate corresponding
minute quantities of gas at the surface of the column m and liquid body S, thus
altering the surface tension at 8 m and causing the mercurial column on which rests
the nonconducting float piston P to be elevated or depressed in accordance there-
with, thus moving the piston which impinges against the centre of the diaphragm D.
The float piston P thus communicates these movements to the diaphragm D causing
the same to vibrate in unison with the diaphragm of the transmitter, whereby the
original sound waves are reproduced.
This action of the instrument shown at Figure 2 as a transmitter is as follows.
.The resistance of the mercury column m being less than that of the acid solution
or equivalent electrolyte S both having the same sectional area in the glass tube G
it is evident that the vibrations of the diaphragm D will produce the same effect
as described with reference to Figure 1, inasmuch as these vibrations will cause the
float piston P to depress or elevate the mercury column m in accordance therewith,
or in other words vary the resistance of the column of the electrolyte and mercury
combined. These variations will therefore produce the same effect as described
with reference to Figure 1.
The call bell connections and switch may be connected in any ordinary and well
known manner, and the mouthpiece may be provided with a trumpet shaped
projection in order to intensify the acoustic properties of the instruments whether
acting as transmitter or receiver. Any other form of transmitter may be used
with this receiver if desired.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
:-
First In an electric telephone receiver the combination of a column of mercury
enclosed in a tube of nonconducting material such as a glass tube, means for
adjusting this mercurial column; an electrolyte floating on the top of this mercurial
column both being included in an electric circuit and a float piston of nonconducting
material of greater specific gravity than the electrolyte but of less specific gravity
than that of mercury floating on the mercurial column which impinges against a
diaphragm by its buoyancy whereby the variations of current or electric tension
proceeding from the transmitter liberate by electrolysis proportionate minute
quantities of gas at the surface of the mercury and the said electrolyte, thus
.causing the said mercurial column to be elevated and depressed in accordance
therewith, and communicating by means of the said piston float these movements
to the diaphragm thus reproducing the original sound waves or articulate speech
substantially as described and set forth.
Second: In an electric telephone transmitter the combination of a column of
mercury enclosed in a tube of nonconducting material means for adjusting the
mercury column, an electrolyte floating on said mercurial column, both being
included in an electric circuit, and a float piston made of nonconducting material
and floating on the mercurial column and impinging against the diaphragm, whereby
the vibrations of the diaphragm causes the said mercurial column to be elevated or
depressed producing variations of resistance, current or electric tension in the
circuit to line and receiver in accordance with these vibrations substantially as
described and set forth.
Third: The constructions of transmitter and receiver shown on the drawings.
BREWER & JENSEN,
For the Applicant.