IMPROVEMENTS IN TELEPHONIC APPARATUS
Year: 1878

page_text: LETTERS PATENT to William Morgan-Brown, of the Firm of Brandon and
Morgan-Brown, Engineers and Patent Agents, of 38, Southampton Buildings,
London, and 1, Rue Laffitte, Paris, for the Invention of "IMPROVEMENTS IN
TELEPHONIC APPARATUS." A communication from abroad by Antoine Breguet,
Electrician, Cornelius Roosevelt and Gabriel Lippinann, all of Paris, Republic
of France.
Sealed the 28th May 1878, and dated the 19th March 1878.
COMPLETE SPECIFICATION filed by the said William Morgan-Brown at the
Office of the Commissioners of Patents on the 19th March 1878.
WILLIAM MORGAN-BROWN, of the Firm of Brandon and Morgan-Brown, Engineers
and Patent Agents, of 38, Southampton Buildings, London, and 1, Ruc Laffitte,
Paris. "IMPROVEMENTS IN TELEPHONIC APPARATUS." A communication from
abroad by Antoine Breguet, Electrician, Cornelius Roosevelt and Gabriel Lippmann,.
all of Paris, Republic of France.
These improvements are based on the relation existing between electrical and
capillary phenomena.
The 4 Figures of the annexed Drawing represent in sectional elevation four
different forms of apparatus based on the above principle, the component parts of
which are a tube T charged with mercury M, terminated below by a capillary tube
or point, which is immersed in a vase V containing a lower layer of mercury N
covered by a charge of acidulated water A. Two platinum wires P, Q, communicate
respectively with the mercury M in the tube T, and the mercury N in the vase V ;
if these two wires are united the level of the mercury in the capillary tube will
maintain itself at an invariable height; but if an electrical source is interposed in the
circuit of the wires the level will assume another position of equilibrium, which will
depend on the difference of potential of this source. Consequently every variation
of the potential will produce a corresponding variation of the level of the under
surface of the mercury.
The apparatus above described is reversible, that is to say, if by the pressure
at S, Figures 2 and 3 being modified, the level of the mercury is displaced a

page_text: difference of potential, or in other terms, an electro-motive force is engendered in
the two conductors P and Q.
In practice two such instruments are coupled or united together by the con-
ducting wires P, P¹, and Q, Q, as shown in the accompanying Drawings. Pressure
is exerted at S, an electro-motive force proportionate to the amount of this pressure
is generated in the circuit, and this electro-motive force produces a change in the
level of the mercury M¹ of the second apparatus. The pressure at S' is consequently
also modified.
It will be easily understood that these phenomena can be made available for
telephonic purposes; thus, taking an instrument in its most simple form, as shown in
the Figures 2 and 3, by speaking in the uppper part of the tube T the air contained
therein at S is caused to vibrate. These vibrations are communicated to the
mercury which translates them in vibrations of electro-motive force, and these
vibrations engender in the receiving apparatus exactly corresponding vibrations of
the mass of air S₁, so that if the car be placed above the tube T¹ every word that
has been uttered in the tube T will be heard.
The mercury tube T may be terminated in different manners with reference to its
capillarity; for instance, with a cylindrical tube as shown in the transmitting
instrument Figure 2, with a long capillary slot as shown in the receiving
instrument of the same Figure, with a flat under surface containing a series of
capillary slots, as shown in the transmitting instrument, Figure 3, or as a square
conical tube terminated below by a capillary slot, as shown in the receiving instru-
ment of the same Figure.
Figure 4 represents a simpler arrangement of the instrument's transmittor and
receptor, both of which are hermetically closed and therefore portative; according
to this arrangement the capillary tubes T and T₁ are charged with drops of
mercury M and M' soparated by similar drops of acidulated water A; two platinum
wires P and Q are inserted through the capillary tube with their points in contact
with the upper and lower drops of mercury. A thin disc of wood, glass, or other
appropriate material substance C is fixed centrally to one extremity of the tube T
by means of sealing wax or any other similar adhesive substanco answering the
purpose. A small globule of air exists at either extremity of the tube. On speaking
against the membrane C this latter transmits its vibrations to the capillary tube T,
which thus vibrates in the direction of its length. If its mass is smaller than that
of the mercury with which it is charged it will be displaced with reference to the
mercury, and the effect produced is the same as if the mercury was displaced with
reference to the tube since the relative motion is the same. All the drops of
mercury separated by the acid represent so many capillary elements associated in
tension.
Figure 1 represents an instrument more especially constructed for portative
purposes, in which the upper opening of the tube T is closed hermetically by an
india-rubber cap B, above which is placed a thin metallic plate or membrane O with
a plug D adapted centrally on its under surface, bearing on the cap B, whilst this
latter in its turn bears on the mercury M, in such a manner that the vibrations of
the air produced in speaking on the membrane are transmitted to the mercury Min
the tube T, and made available in the instrument for telephonic purposes. A
partition T¹ established about midway in the tube T with a central hole serves to
prevent any air entering accidentally in this tube from passing to the lower
capillary part when the instrument is inverted. This separation Tacts in a similar
manner with respect to aqueous vapour. A separation V¹ of the same construction
is adapted in the lower part of the vase V for the purpose of preventing the
displacement of the mercury N when the instrument is inverted.

page_text: when placed vertically 2 millimeters, whilst there need scarcely be any minimum to
their smallness.
With a view of giving a greater intensity to these capillary instruments, if
necessary, to compensate as much as possible the obstacles which may arise in the
wires of aerial, subterraneous, or submarine lines, I apply thereto currents derived
from any ordinary batteries.
Instead of acting on the air in S the surface of the mercury M in the transmitting
apparatus may be acted on directly, and its action transmitted directly to the
surface of the mercury M³ of the receiving instrument.
Instead of leaving the surface of the mercury M and M' to the effect of the
ordinary pressure of the atmosphere I augment or I diminish, according to circum-
stances, the constant pressure exerted on these surfaces, and act in a similar manner
with regard to the acidulated water in the vases V and V. For this purpose either
the entire apparatus or merely the upper parts of M, M', and V, V₁, are enclosed
hermetically and in communication with a pressure gauge. These capillary
apparatus can be applied with advantage to the Bell telephone or to the receptor
of Edison's telephone; they may be coupled in tension or in quality, as required.
The sulphuric acid above mentioned for developing by contact with the mercury
the electro-motive power for working these instruments may be replaced by other
substances.
Among some of the advantages of this capillary telephone I will mention the
following:-
Firstly. They do not require a battery.
Secondly. The disturbing influence of the resistance in a long line is barely
perceptible with these capillary apparatus since they are influenced nearly
exclusively by the quality tension of the current and not by the quality quantity of
the current.
Thirdly. These instruments when coupled, are as above stated absolutely
correlatives, insomuch that even different positions of equilibrium of the surface
of the mercury in one instrument produce different positions of equilibrium in the
corresponding instrument. This advantage has been realized for the first time in
my capillary instruments; it does not exist in other instruments or in Bell's telephone.
Consequently not only they are capable of reproducing over long distances without
a battery faithful indications of pendular motion like Bell's apparatus, but also the
exact image of the most general motions.
Fourthly. The speed of transmission with these capillary instruments is necessarily
much greater than with the instruments hitherto in use, since they are operated by
the weakest possible amount of electricity.
I claim as the Invention,-
Firstly. The instruments above described and illustrated in Figures 2 and 3,
consisting in a tube T with a capillary lower. extremity of the different forms
indicated and charged or partially charged with mercury M, its_capillary lower
extremity being immersed in acidulated water A placed in a vase V over a layer of
mercury M, with platinum wires P and Q respectively in connection with the
charges of mercury M' and N' in a similar instrument, forming a receptor or
receiving instrument for telephonic purposes.
Secondly. The construction and use of instruments above described and illustrated
by Figure 4, forming a closed and portative series of transmitting and receiving
instruments for telephonic purposes.
Thirdly. The construction and use of the portable telephone above described and
illustrated in Figure 1.
Fourthly. The adaptation of a piston in the upper part of the tubes T and T"
above the air S and S' in both instruments, Figure 2, and in the transmitting
instrument, Figure 3, for the purpose of telephonic transmissions or others.
Fifthly. The different modes above described and illustrated in Figures 2 and 3
of augmenting capillary action by forming the under extremities of the tubes T and
T' with extended slots for the purposes above mentioned

page_text: Sixthly. Enclosing hermetically the instruments above described and illustrated
in Figures 2 and 3, or merely the upper parts of the tubes T and T, and their
vases V and 'V', and either augmenting or diminishing the pressure of the air
therein enclosed for the purposes above stated.
In witness whereof, I, the said William Morgan-Brown, have hereunto set my 5
hand and seal, this Nineteenth day of March, in the year of our Lord One
thousand eight hundred and seventy-eight.
WILLIAM MORGAN-BROWN. (L.S.)