Method of and Apparatus for Transmitting Vocal and other Sounds Electrically.
Year: 1892

page_text: Date of Application, 16th Nov., 1892
Complete Specification Left, 16th Sept., 1893-Accepted, 21st Oct., 1893
PROVISIONAL SPECIFICATION.
A Method of and Apparatus for Transmitting Vocal and other
Sounds Electrically.
1, JAMES GRIEVE LORRAIN, M. Inst. E.E. etc., of Norfolk House, Norfolk
Street, Strand, in the County of Middlesex, Chartered Patent Agent, do hereby
declare the nature of this invention (as communicated to me by Charles Clamond,
of 15 Rue Picot, Paris, in the Republic of France, Engineer) to be as
follows:-
My invention relates to a method of transmitting vocal and other sounds
electrically and to apparatus therefor, by which certain advantages are obtained:
and it has special reference to what are generally known as telephonic resistance
variers and used as transmitters.
The action of the microphone transmitter, as is well known, depends upon the
variation of the electrical resistance of the microphonic elements, the said variation
being produced by varying, under the influence of sound waves, the pressure or the
amount of contact surface between two or more elements or the length of an
element embraced in a circuit. In most cases two of these actions form factors
difficult to differentiate from one another. In instruments producing such variation
as aforesaid the elements have been free and separable from one another so to
speak.
A distinction between my invention and those which have preceded consists, in
so far as my apparatus is concerned, in employing what I may term an integral
telephonic resistance varier (which in itself constitutes the equivalent of the micro-
phonic elements as usually understood) without having any parts free or readily
separable in the sense in which such elements or parts are free and readily
separable in the existing forms of microphone.
A distinction between my invention and those which have preceded it consists,
in so far as my method is concerned, in varying the length and at the same time
the cross section of a conductor forming part of a circuit and constituting a
telephonic resistance varier.
In carrying my invention into effect I employ in a circuit a plastic, viscous, or
what I may term a semi-fluid, conducting mass; and this I place between two
parts which I shall hereinafter term "holders." In order to cause a variation of
resistance through such plastic mass, hereinafter called the integral element, I
cause the said holders, by the movement of one or both of them, to approach to or
recede from one another in accordance with sound vibrations impressed upon or
transmitted to the same.
To understand the action of my invention let us assume that the holders consist
of two simple cylindrical conducting bodies A and B (see Figure 1 of the accom-
panying sheet of drawings) and that between these place the integral element
consisting of a plastic viscous conducting body C so that it will adhere to the
adjacent ends of the two holders. The passage of a current through A, C, B, will
meet with a certain resistance. Now let us cause A and B to approach one
another. C will now be altered in shape as is shown in Figure 2. It will be of
shorter length and of greater cross section, and its electrical resistance will be
decreased. If now we cause A and B to recede from one another, till they are at
a greater distance apart than is shown in Figure 1, then the shape of C will again
be changed. Its length will be increased and its cross section decreased, and con-
sequently its electrical resistance will be increased. It will be seen that the
approach and recession of the holders will produce the same effect as the approach
D

page_text: and recession of the elements of an ordinary microphonic transmitter as used in
telephony and all that is necessary to make the parts described into a practical
telephonic transmitter is to mount the said parts in a manner similar to those
employed in the case, of ordinary microphonic transmitters, and with the same
accessories.
It will be seen that the resistance between the surfaces of contact of the integral
element and the holders does not vary, as the extent of contact surface remains
constant whether the holders approach to or recede from one another.
My integral element may be composed of any suitable ingrédients such for
example as finely divided solid bodies and liquid or viscous bodies, one or more of
the said bodies being, capable of conducting electricity. Care must of course be
taken not to employ materials capable of electrolytic decomposition on the passage
of the current.
To prevent the integral element from flowing or being knocked away from the
holders surround it and the adjacent ends or surfaces of the holders with an
elastic envelope, which may consist of any convenient material, such for example
as india-rubber, flexible collodion, elastic varnish or the like.
I may vary the shape of the holders within wide limits. For example, a
convenient form of my invention may have one holder of the form of a cup in
which is placed the integral element and the other holder of the form of a plunger
entering loosely into the said cup and in contact with the integral element. When
the holders are of this form the integral element takes the shape of a thimble as it
were and it is to be understood that when I speak of the length of such integral
element being varied I apply the term length as referring to the direction in which
the electric current is supposed to flow; and when I speak of the cross section of
'the integral element being varied, the cross section is supposed to be a plane to
which the direction of the assumed flow of the current is normal.
I have spoken of the described parts of my invention. as being mounted in a
manner similar to those employed in the case of ordinary microphonic transmitters;;
and shall now refer to two forms of telephonic transmitter embodying my
invention. In the first of these forms I take a case one wall of which consists of
an ordinary telephone diaphragm. To the centre of the said diaphragm is affixed
the one holder an ! to the back of the case is attached the other holder. This is a
very simple form, but it will be obvious that in such a case the diaphragm itself
might constitute the one holder, and the back of the case might constitute the
fother holder. The said diaphragm and back of the case, when constituting the
two holders, would of course require to be of conducting material and insulated
the one from the other. In the other convenient form of telephonic transmitter
herein before referred to, 1 support each of the holders on springs attached to the
case of the instrument, and I employ a third spring to press the holders (with the
integral element between them) against the centre of the diaphragm..
I have hereinbefore described my invention as though the holders were
necessarily composed of conducting material; and I have spoken of the electric
current as traversing the said holders as well as the integral element. I desire it
to be understood, however, that the said holders may consist of insulating material;
but it will of course be understood that when such is the case conductors must be
employed which shall dip into the integral element at points apart from one
another.
בז

page_text: .
COMPLETE SPECIFICATION.
A Method of and Apparatus for Transmitting Vocal and other
Sounds Electrically.
I, JAMES GRIEVE LORRAIN, M. Inst. E.E., etc. of Norfolk House, Norfolk
Street, Strand, in the County of Middlesex, Chartered Patent Agent, do hereby
declare the nature of this. invention as communicated to me by Charlés Clamond, of
15 Rue Picot, Paris, in the Republic of France, and in what manner the same is
to.be performed to be particularly described and ascertained in and by the following
statement:-
My invention has reference to improvements in the method of and apparatus for
transmitting vocal and other sounds, electrically; and it also embraces special
improvements in telephonic transmitters of that class in which the vibrations of the
air which accompany the utterance of sound produce electrical undulations similar
in form to the sound-waves by variations of electrical resistance in a charged
electric circuit. Instruments of this character have been called "variable-resistance
telephones," and the variation of resistance was heretofore produced, mainly, in
two ways. The principal method was to vary the contact and pressure between
two or more discrete bodies inserted in, an electric circuit, and these bodies were
then called the "telephonic electrodes." Another method of varying the resistance
of the circuit was to use one solid and one fluid electrode, both of comparatively-
high resistance, and to partly immerse the solid electrode in the fluid and to vary
the extent of immersion by the action of sound-waves.
By the first method great variations of electrical resistance were obtained; but
these variations were not always exactly proportionate to the amplitudes of the
sound waves, whereby the quality of the sound uttered against the instrument
became somewhat modified in, the receiver. Another difficulty in this mode of
telephonic transmission was that it was difficult to maintain the, electrodes at all
times in contact, and when the latter was broken and again established it gave rise
to such violent electrical impulses, which had no relation to the sound-waves which
produced the same, as to cause in the receiver a very loud and disagreeable sound,
which rendered the speech or other sounds which it was intended to transmit
sometimes inaudible or so blended with the accidental sounds caused by the makes
and breaks as to make the speech unintelligible. By the second method of tele-
phonic transmission the variations of electrical resistance produced were weak:
The electrical undulations, therefore were very faint, and consequently the'
reproduced sounds, while they were very clear, were almost inaudible...
:
It is the object of my invention to overcome these difficulties, and I do overcome
the same by resorting to a mode of producing great variations of electrical
resistance by sound-waves which are accurately proportionate to the amplitudes of
said sound waves without at any time breaking the circuit. By my method there-
fore the advantages of the two old methods are combined, while the disadvantages
of the same are completely avoided. I accomplish this result by connecting
permanently with two electrodes of the telephonic circuit and between the same a
plastic semi-fluid electrical resistance which at all times completely bridges the two
electrodes, which at no time varies the resistance of transition between itself and
either of the electrodes, but which varies its shape-that is to say, its length and
or cross-section-under the influence of sound-waves, and thereby varies the
electrical resistance of the circuit. The variations which I thus produce I have
found to be very accurately proportionate to the amplitudes of the sound-waves
and to be very great. All this will more fully appear from the following detailed
description, in which reference is made to the accompanying drawings, in which I
have illustrated some of the forms of apparatus suitable for the practice of my
invention, and.in which-
Figures 1, 2 and 3 represent the electrodes with the variable resistance interposed i

page_text: and varied in shape corresponding to different phases of operation, the whole
included in an electric circuit.
Figure 4 is a vertical section of a telephone transmitter embodying my invention
included in a working circuit.
Figures 5 and 6 are longitudinal sections showing two forms of electrodes with
the plastic variable resistance interposed, and
Figure 7 is a vertical section of another form of telephonic transmitter embodying
my invention and included in a working circuit.
Like numerals of reference indicate like parts all throughout the drawings.
The principle element of the apparatus is a plastic pasty electrical conductor,
which consists of an intimate mixture of a finely-divided solid and of a liquid, con-
stituting as a whole a plastic viscid pasty body of such consistence as is sometimes
called a "semi-fluid." The plasticity may be due either entirely to the fluid or to
the mixture of the fluid with the solid, and the conductivity may also be due either
to the solid or to the fluid, or to both, and I am not confined to any particular
fluid or to any particular solid in the composition of my improved telephonic
resistance. Thus I might use ordinary potters' clay, the plasticity of which is due
to a particular property of silicate of alumina in contact with water and the con-
ductivity of which is due to both the silicate of alumina and the water.
By
preference, however, my improved telephonic resistance is not made of native
compounds, but is artificially compounded. Good results are obtained by mixing
concentrated solutions of salts-such as solutions of silicate of soda, silicate of
potash, chloride of calcium, or acetate of magnesia-with powders of either con-
ducting or non-conducting bodies in sufficient quantities to make a viscid plastic.
body of such consistence that it will not flow spontaneously, but will resist only
very lightly the action of forces tending to distort their shapes. Such compounds,
in which the powders employed may be of metal or of carbon or oxides of metals,
or of any non-conducting substance, undergo a considerable change when, used for
some time in telephonic transmission on account of the electrolytic action of the
current upon the salt solution, and for this reason I prefer to employ for com-
mercial use pastes in which no electrolytic action takes place. This result I obtain
by mixing conducting-powders with syrupy and viscid liquids which are
non-conductors of electricity, such as glycerine, viscid oils like castor-oil, or a
plastic viscid body, such as vaseline. In addition to the powders already specified
may use the powders of metallic alloys, or I may use conducting-metalloids, such
as tellurium, silicium, or binary combinations of conductors which are easily pul-
verized, such as certain sulphides or oxides of metal; but I give the preference to
metals, simple or alloyed, and to metalloids which are not decomposed by the
current, and among these metals or alloys or metalloids I use, by preference, those
which give powders having the least weight, for the lighter the elements of the
paste are the lighter the whole mass is, and the more readily can its form be
changed by the action of sonorous waves upon the same.
In Figure 1 a plastic viscid button made in accordance with my invention is
represented at 1. It may, as shown, have the shape of a short but rather thick
cylinder. 2 and 3 represent the terminals of an electric circuit charged by a
battery 4, with which the terminals are connected by the wires 5 6, and a
galvanometer or other current indicator 7 is also included in the circuit. If one of
these terminals 2, 3, is fixed and the other is free to move axially under the action
of sound-waves, then the arrangement shown in Figure 1 becomes a telephonic
transmitter constructed upon the principle of my invention. The resistance
changer 1, being pasty, adheres at each end to one of the electrodes, and if one of
these electrodes moves axially toward or from the other the shape of the resistance-
changer, which for convenience of description may be called a "Inicrophonic"
element, changes. If, for instance, one of the electrodes approaches the other
under the action of sound-waves, the microphonic element 1 becomes shorter and
thicker, and consequently its electrical resistance, and therefore that of the circuit,
is decreased. This phase of operation is represented in Figure 2. If, on the other

page_text: hand, one of the electrodes recedes from the other under the action of sound-waves,
the microphonic element. becomes elongated, as shown in Figure 3, and assumes a
hyperboloidal form-that is to say, a shape resembling two truncated cones joined
at their small ends, as represented in Figure 3. The microphonic element there-
fore has increased. in length. and decreased in thickness, whereby its electrical
resistance and that of the circuit is increased. The galvanometer 7, included in
the circuit, will indicate an increased amount of current under the conditions
shown in Figure 2, and a decreased amount of current under the conditions shown
in Figure 3. While such variations of the total resistance of the body of the
microphonic element take place no variation of resistance takes place at the surfaces
at which the microphonic element is connected with the electrodes 2 and 3--that is
to say, the transition resistance to the passage of. the current from electrode 2 to
the microphonic element 1, and. the transition resistance to the passage of the
current from the microphonic element. I to the electrode 3 remains constant during
all phases of operation, since by reason of the pasty nature of the microphonic
element the contact of the same with the electrodes is not varied whether these
electrodes approach to or recede from each other.
Figure 4 represents one practical form of transmitter embodying my invention.
The cylindrical casing 8 has mounted at its open end the diaphragm 9, which in
this case is of resonant conducting material, and this diaphragm has secured to its
centre the electrode 2. A second electrode 3 is supported by a bracket 10, which
is secured to the casing as shown. Between the two electrodes and adhering to
each of the same is my improved microphonic element 1, and a. very thin sleeve. 11,
Fig. 5. of elastic non-conducting material-like soft rubber, or collodion-surrounds
the microphonic contact and a portion of each electrode, the purpose of which is to
maintain the normal shape of the microphonic element. in all positions of the
instrument and to protect that element against violent distortion, which might
otherwise be caused by violent shocks which the instrument may receive when
roughly handled or during shipment. This sleeve of elastic insulating material
may be produced by a coat of rubber or pyroxyline varnish applied with a brush
and which after evaporation of the solvent leaves behind a very thin film of rubber
or pyroxyline.
In the apparatus shown in Figure 4. no adjustment for the electrode is provided,
nor is such adjustment necessary. The circuit connections are from one pole of
the battery 12 by a wire 13 to bracket 10, and from the other pole of the battery
by wire 14 to the primary coil 15 of an inductorium, and from the latter by wire 16
to the diaphragm. The secondary of the inductorium is included in the line 17, in
which the receiving telephone 18 is placed. For short lines the induction-coil may
be omitted, and the telephone receiver is then placed in the battery-circuit.
In the apparatus shown in Figures 4 and 5 the electrodes and the microphonic
element are represented cylindrical in form; but this form is not essential, nor
am I confined to any particular form of either the electrodes or of the microphonic
element; but the form which I prefer and which I have found very effective is that
represented in Figure 6. In this case one of the electrodes 2 is a cylindrical body
shaped convex, semispherical at one end, while the other electrode 3 is, a block
having a concaved semispherical recess 3¹ of considerably-larger diameter than the
spherical end of electrode 2. This latter is with its spherical end arranged
centrally in the recess 3', and the space between the two electrodes is filled with
the microphonic pasty, viscid, and plastic microphonic element 1, which thus
assumes the shape of a thimble or, approximately, of a semispherical shell. The
thin elastic non-conducting sleeve 11 covers a portion of each electrode and the
otherwise exposed surface of the microphonic element. This construction may be
used in the apparatus shown in Figure 4, in which case the electrode 2 would be
made fast to the centre of the diaphragm, while the electrode 3. could be fixed to
the bracket 10. By preference, however, these two electrodes, with the intervening
microphonic element, are supported in the manner shown in Figure 7, that is to
say, the electrode 2 is suspended by a spring or wire 19 and-the electrode 3 by a

page_text: spring or wire 20,-and both of them are urged toward the diaphragm by a leaf-
spring 21, the tension of which may be adjusted by the screw 22. The outer end
of electrode 2 is in this case made conical, as indicated in Figure 6 at 2¹, and the
point of this cone is maintained in contact with the centre of the diaphragm, which
in this case may be of insulating material, such as mica for instance. The circuit
connections are or may be the same as those described with reference to Figure 4,
the wires 13 and 16 in this case connecting with the suspension springs or wires 20
and 19, respectively.
From the foregoing description it will appear that my novel method of
transmitting vocal and other sounds electrically consists in varying by and in
accordance with sound vibrations the cross-section and or the length of a conductor
included in the telephonic circuit, and thereby producing electrical undulations
corresponding with the sound waves which accompany the utterance of said vocal
and other sounds. It will furthermore be clear that I can practice this method of
telephonic transmission by means of a great variety of apparatus, and that while I
have hereinbefore shown and described some apparatus adapted for the practice of
my method, I am not confined to the use of any particular apparatus or means.
Having now particularly described and ascertained the nature of my said
invention, as communicated to me from abroad by Charles Clamond of 15 Rue.
Picot, Paris, and in what manner the same is to be performed I declare that
what I claim is :-
1. The hereinabove described method of transmitting vocal and other sounds
electrically substantially as set forth.
2. In apparatus for transmitting sounds electrically the employment of a
conductor of plastic viscid material substantially as set forth.
3. In apparatus for transmitting sounds electrically a plastic viscid conductor
composed substantially as described.
Dated this 16th day of September 1893.
J. G. LORRAIN.