Loud-speaking Long-distance Telephone.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Loud-speaking Long-distance Telephone.
I, PAUL DE KILDUCHEVSKY of the Hotel Victoria, Northumberland Avenue, S.W.
Electrician; do hereby declare the nature of this Invention to he as follows:-
This Invention relates to improvements having for object the establishment of
clear, loud-speaking long distance telephonic communication, and as regards the
transmitter consists essentially in means whereby strong currents necessary for long
distance communication and loud speaking may be used without danger of injury to
the microphone, and whereby the power of the transmitter may be readily regulated
to suit requirements.
The diaphragm is providel with independent microphones each composed of carbon
rods whose journailed ends are supported loosely in carbon blocks braced together by
glass rods, the carbon rods being electro-plated and connected so as to vibrate
together as one by being laced or bound together by wires and wrapped in asbestos
cloth.
Each microphone is enclosed in an exhausted glass bulb by which the carbon
supports are held and through which the vibrations of the diaphragm are transinitted
to the carbon rods, connecting wires being sealed through the glass and connected to
the carbon supports through metal plates preferably of aluminiumn, a current being
passed through the microphone during the process of exhaustion to enable occluded
guses and moisture to be extracted. Each inicrophone is coupled through a switch
to a separate battery and to a separate primary winding of an induction coil, the
several windings corresponding to the different microphones being parallel whilst a
single secondary winding common to all is connected to the line. Means are provided
for enabling the number of microphones in circuit in the transmitter to be varied
according to distance or the effect to be produced. The core of the induction coil is
composed of isolated segmental bundles of wires.
The diaphragmn is mounted on elastic cushions within the case of the transmitter
so as to be shielded from external vibrations through the sides of the case, and in
order to damp the vibrations of the diaphragin and thus ensure clearness of articulation
and improve the timbre, the inside of the case and the back of the diaphragmn are
coated with powdered glass or the like attached by glue rendered non-hygroscopic
by the admixture of bichromate of potash.
In the receiver the ordinary permanent magnet is replaced by an electro-magnet
having a laminated core and two sets of windings the one in circuit with the battery
and the other with the line, the object being to enable the weight of the magnet and
the diaphragmn to he made as nearly as possible equal, at the same time that the
weight and dimensions of the diaphragm are so far reduced as to greatly increase the
sensitiveness of the instrument.
Dated this 10th day of November 1900
A. M. & WM. CLARK,
53 Chancery Lane, London, Chartered Patent Agents.

page_text: I, PAUL DE KILDUCHEVSKY, Hotel Victoria, Northumberland Avenue, S.W.
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 :-
This Invention has for its object to enable clear articulate loud speaking telephonic
communication to be established over longer distances than it has heretofore been
possible to communicate by existing telephones.
The Invention comprises:-
(1) An improvement in the microphone whereby the use of powerful currents is
rendered possible without danger of injury to the microphone which is moreover
completely protected from external causes by which its efficiency might be impaired ;
(2) the combination of a plurality of microphones and batteries with an induction
coil having multiple primary circuits and a single secondary circuit whereby the
electromotive force of the transmitter may be readily regulated according to the
varying resistance of the circuit or otherwise as may be required; (3) means of
rendering the vibrations of the diaphragmn more sharp and defined so as to ensure
clearness of articulation and improve the timbre.
The Invention also comprises an improved construction of receiver for use in
combination with the above mentioned transmitter, and other combinations of parts,
as hereafter described and specified in the claims.
Reference is to he had to the accompanying drawings forming part of this
Specification in which
Figure 1 is a general diagram of the whole system and
Figures 2 and 3 are a part rear and cross-sectional views of one of the
microphones.
Figure 4 is a cross-section of the transmitter case shewing the inclined position of
the diaphragm and microphones.
Figure 5 is a cross-section of the core of the induction coil.
Figure 6 is a sectional elevation of the receiver.
Figure 7 is an end view of the electro-magnet and
Figure 8 an elevation of the magnet core separately.
The same letters of reference indicate the saine parts in all the figures.
Upon the back of diaphragm D are mounted a plurality of microphones M' M2 M³
(say three) in parallel circuits each circuit comprising a microphone, a battery, and a
separate primary winding of an induction coil C having as many parallel primary
windings pp2 p3 as there are microphones in the transmitter. The diaphragm D is
of wood, has a marginal wood frame d, and is mounted preferably in the rearwardly
inclined position shewn in Figure 4 by being fixed to corner cushions a of rubber
there being clearance left between the edges of the diaphragm and the sides of the
case so that the diaphragm shall be shielded as much as possible from external
vibrations.
In order to render the vibrations of the diaphragm more sharp and defined, and
so ensure clearness of articulation, the inside of the front and sides of the case and
the surfaces of the diaphragm are coated with a layer of crushed glass (such as used
for inedium quality glass paper) corundum or other granular non-hygroscopic
substance attached by glue bichromated to render it non-hygroscopic.
Any kind of microphone may be employed, that is to say the carbon may either
be granular or in the form of pencils the latter form being preferred and the essential
feature being that each microphone is enclosed in vacuo, or in an inert atmosphere
in a bulb e by which the supports of the carbon pencils are held and through which

page_text: the vibrations of the diaphragin are transmitted to the pencils. In the example
shewn each microphone comprises a plurality of carbon pencils f whose cylindrical
ends of reduced diameter are received loosely in corresponding holes in a pair of
carbon blocks g braced rigidly together, as shewn in Figure 2, y rods of glass.
The carbon pencils fare electro-plated with copper (except the contact portions) and
are connected so as to vibrate in unison by being bound together by wires i of
aluminium laced through a jud; of asbestos cloth upon which presses a spring .
The carbon supporting blocks are also copper plated (except the holes and the side
next the pencils) and are embraced by clips k of aluminium rivetted to the blocks g
the one member of the clip being extended to form the spring which presses
against the side of the g'ass bulbe and against the asbestos pad so as to transmit
vibrations directly from the bulb to the pencils f. The bulb e is contracted or pinched
in as at el so as to grip the pencil supporting blocks g and the ends of the bulb are
dmwn down so as to embrace the tapered bowed portions of the clips kk. The
clips & serve to make electrical communication with the platinum leading-in wires
sealed through the ends of the bulb in the usual way of sealing in those of incan-
descent lamps. During the operation of exhausting he bulb a current is passed
through the microphone to enable occluded gases and moisture to be extracted from
the carbon. The microphone being enclosed in an exhausted bulb the power of the
current may be increased to any required extent without liability of oxidation of the
carbons and the carbon pencils are protected from atmospheric moisture, from dust,
and from derangement. It is however to be understood that instead of a vacuum
the bulb may contain an inert atmosphere such a nitrogen but a
preferred.
For the purpose of mounting the microphones on the diaphragm and making
electrical connection the leading-in wires may terminate externally in convex copper
contact discs which are held between and make electrical contact with corresponding
concave holders 2 formed by spring brackets fixed to the back of the diaphragın D.
The bulbs e are mounted so as to touch the back of the diaphragm D, say, by the
teat eat which the exhausting tube was sealed off or otherwise in order that the
Lulb shall participate as fully as possible in the vibrations of the diaphragm. The bulb
holders are connected by wires 1-1, 2-2, 3-3, on the one hand with the
batteries B1, B2, B3, and on the other with the primary windings p, p, p, of the
induction coil C, switches m³, m³, m³, being interposed and having their contacts so
arranged that any one or more of the microphones may be cut out as required. In
shunt to the microphones is placed a siren call device being a make-and-break formed
by a toothed wheel N and spring contacts n, n', n³, n³, connected to the respective
members of the shunt circuits. The wheel may be rotated by a handle so that by
rapidly making and breaking the circuits of all the batteries B',B,B,simultaneously
the resulting induction currents produced in the coil C will cause the diaphragm of
the receiver at the other end of the line to produce a siren call. The wheel N has a
seginent of insulating material which is brought opposite to the spring contacts
by the weight of the handle n whereby the short circuit through the call device is
automatically broken when the handle is released.
O is a telephone switch hook interposed between the batteries and the induction
coil, having a multiple switch ol, o, o, and whereby the circuits through the several
primary windings of the coil and the circuit of the receiver battery V are automatically
completed when the receiver is taken off the hook. The switches are formed of
insulated metal rings each of which makes contact with a pair of springs connected
to the respective members of the circuits.
The induction coil C bas, as above mentioned, as many independent parallel primary
windings p, p, p, as there are inicrophones in the transmitter, each in circuit with
each and with its own battery as above described. By the employment of independent
multiple primary circuits the current power in Watts may be increased in order to
obtain with a small coil the inductive action required for very long distance telephony,
the resistance of the primary circuit being correspondingly decreased. The coil has
a single secondary winding a commnou to all the primary windings and in connection

page_text: with the line L. Z is a switch connected with the coils u of the receiver and
movable over a row of contacts 12345 connected respectively to different points in
the length of the secondary wire 8 of the coil C so that when the resistance is variable,
as in the case of trunk lines, the effective length of the secondary coil, and consequently
its electromotive force, may be varied to suit the conditions of working. By placing
the switch on the contact, the coil C is cut out altogether so that the currents
received only pass through the receiver.
The induction coil has a core formed of segmental bundles c of shellac-coated soft
iron wires, as shewn in Figure 5, the bundles being insulated by being wrapped in
shellac-coated paper to prevent self-induction and Foucault currents. The ends of
the wires project beyond the ends of the coil and form divergent brush-like poles.
which have the effect of facilitating the magnetic discharge of the core and so
diminishing retardation and consequently increasing the loudness and clearness of
articulation.
The receiver R is provided with an electro-magnetic field formed by the core rand-
the coils in the circuit of a local hattery V. The core of the electro-magnet is
laminated or formed of superposed strips of soft sheet iron separated by intervening
strips of shellac-coated paper the superposed strips being bent to U shape and united
by heating sufficiently to soften the shellac after bending. The limbs of the core are
provided with a second set of coils u .in circuit with the line L, the circuit of the
local battery V being closed through the coils t t by the contact of the hook switch O
at that end of the line when the receiver is removed from the hook. By the employ-
ment of an electro-magnetic field in the receiver the strength of the field may be
varied to any required extent to suit the strength of the induction current passing
through the receiving coils and the weight of the magnet core may consequently
be so small as not to exceed that of the diaphragm whereby the maximum degree
of sensitiveness of the instrument inay be obtained. The diaphragm w is clamped
between the front and back covers of the case in the usual way.
Having now particularly described and ascertained the nature of the raid
Invention and in what manner the same is to be performed I declare that what I
claim is :-
1. In a telephone transmitter, a microphone hermetically sealed up in vacuo or in
an inert atanosphere as and for the purpose specified.
2. In a telephone transmitter the combination, with a battery and induction coil, of
a microphone hermetically sealed up in vacuo or in an inert atainosphere and mounted
upon the diaphragm of the transmitter and provided with leading-in wires connecting
the microphone with the battery and coil as specified.
3. In a telephone transmitter the combination, with a battery and induction coil,
of a microphone hermetically sealed up in vacuo or in an inert atmosphere and
mounted upon the diaphragm, the microphone being constructed of carbon pencils in
parallel bound together so as to vibrate in unison as specified.
4. In a telephone transmitter the combination of a plurality of independent
microphones hermetically sealed in vacno or in an inert atmosphere and of an
induction coil having a plurality of independent parallel primary windings each in
circuit with a microphone and a battery as specified.
5. In a telephone transmitter the combination of a plurality of. independent
microphones euch hermetically sealed in vacuo or in an inert atmosphere and mounted
on the diaphragan of the transmitter and connected in parallel with as many batteries
and with as many independent pritnary windings of an induction coil as there are
microphones substantially as specified.
6. In a telephone transmitter the combination of a plurality of independent.
microphones each formed of carbon pencils in parallel bound together so as to
vibrate in unison and hermetically sealed in vacuo or in an inert atmosphere and
mounted on the diaphragm of the transmitter, the microphones being connected in
parallel with as many batteries and with as many independent parallel primary
windings of an induction coil as there are microphones substantially as specified.

page_text: 7. In a telephone transmitter the combination of a plurality of independent
microphones in vacco or an inert atmosphere and of an induction coil having a
plurality of independent parallel primary windings each in circuit through a switch
with an independent microphone and a battery, as specified, and of a make-and-break
formed of a rotary toothed contact wheel having an insulating segment and of spring
contacts in shunts to the several microphones substantially as and for the purpose
specified.
8. The combination, with a telephone transmitter, comprising a diaphragm, a
plurality of microphones in vacuo or in an inert atmosphere mounted on the diaphragm
and each in circuit with a separate buttery, of an induction coil having as many
parallel primary windings as there are microphones each primary winding being in
circuit with a battery and microphone, the coil having a single secondary winding in
connection with the line as specified.
9. In a telephone transmitter the combination, with the diaphragm and with the
walls of the case, of an attached lining of crushed glass, corundum, or other granular
non-hygroscopic material as and for the purpose specified.
10. In a telephone receiver the combination, with the diaphragm, of an electro-
magnet having two sets of coils the one set in circuit with the line and the other in
another circuit with a local battery substantially as and for the purpose specified.
11. In a telephone receiver the combination, with the diaphragm, of an electro-
magnet having a laminated core and two sets of coils the one set in circuit with the
line and the other in circuit through a switch with a local battery substantially as
and for the purpose specified.
12. A long distance loud speaking telephone consisting in the combination of a
transmitter comprising a diaphragm, a plurality of independent microphones in vacuo
or an inert atmosphere, an induction coil having a plurality of independent parallel
primary windings each in circuit through a switch with an independent microphone
and battery, and a single secondary winding in connection with the line through a
switch whereby various lengths of the secondary circuit may be utilized as required,
and of a receiver consisting in the combination, with a diaphragm, of an electro-magnet
having two sets of coils the one set in circuit with the line and the other in circuit
with a local battery substantially as specified.
Dated this 10th day of August 1897.
A. M. & WM. CLARK,
53 Chancery Lane, London, Chartered Patent Agents.