Year: 1897

page_text: I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent Agents,
45, Southampton Buildings, in the County of Middlesex, do hereby declare the
nature of this invention to be as follows:-
This invention relates to an improved arrangement for reducing the apparent
resistance in systems of electrical conductors fed with telephonic currents and com
prising a large number of receivers.
In an electrical conductor into which there are switched a comparatively large
number of induction coils, say two hundred or more, the secondary convolutions
of which pass through telephonic receivers, any undulations of current entering
the conductor at certain points are audible at all receivers thus included in the
circuit.
In the performance of such systems of electrical conductors, the somewhat serious
disadvantage has been observed in practice that the sounds, audible though they
are at the receiving apparatus, lack power in consequence of the considerable
apparent resistance of the main conductor.
Now the applicant has ascertained by tests that the apparent resistance is
intensified mainly by the following two factors:
a. Each of the induction coils comprises two solenoids differing in size and in
self-induction, so that the current arriving through the conductor does not reach
the receivers until after it has undergone a noticeable transformation.
b. Induction coils such as these have hitherto been enclosed in sheet metal cases
for protection from external influences; and these cases, being metal were electrical
conductors.
It is therefore the removal of these injurious factors which the present invention
first and foremost aims at, as this alone is sufficient materially to reduce the apparent
resistance and proportionately to increase the power of the sounds transmitted to
the receivers. To this end so-called "double wire" solenoids are substituted for
the induction coils hitherto employed and referred to above, in paragraph (a). In
constructing these solenoids, two wires of precisely equal section, and properly
insulated from each other, are wound close together around an iron core of any;
suitable shape; the dimensions being so determined, that as regards transformation
the relation between the two wires may be as nearly as possible
1, and that, pro-
portionately to this relation, self induction may be reduced to the smallest possible
minimum, whilst being, however, approximately equal in both wire-convolutions
=

page_text: or coils. The induction coils of this construction, unlike those used hitherto, are
placed in cases, preferably non-metallic, but made of some other suitable material;.
though, if desired, they may be constructed of metal, but so that its several con-
stituent parts may in no event come into electrical contact with each other.
According to this invention a feeding conductor is joined on to the main wire on
cable preferably at or near the centre thereof; so that the main conductor or line
may be fed from three different directions at the same time.
A further improvement deemed desirable is to include in this feeding line or
circuit, as well as in the consuming or service line, condensers of sufficient capacity
which in an arrangement such as is herein described assist in tempering the apparent
resistance in a far greater degree than did the condensers in telephonic systems as
heretofore arranged.
Dated this 10th day of June 1807
Improvements relating to Telephonic Systems.
fault.
311-
...
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent Agents,
45, Southampton Buildings, in the County of Middlesex, 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::
A
This invention relates to a distributing system for telephone currents by means
of which a diminution of the apparent resistances occurring with the systems hitherto
employed is effected.
1.
The invention is illustrated in the accompanying drawing the figures of which
are hereinafter referred to.
If a considerable number (for example 200 or more) of induction or receive
coils t₁ to
t₁, are inserted upon a conductor a-b (Figure 1), the secondary winding
of which coils actuate telephone receivers ₁₂, the current undulations which
pass along the conductor are audible in the whole of the receivers so inserted.
As a consequence of this, the inconvenience that the sounds audible in the
telephone receivers do not possess the requisite strength, makes itself seriously felt,
this being the result of the excessive self-induction caused by the arrangement in
series upon the conductors of the induction coils, whereby the apparent resistance is
increased far beyond the necessary and useful extent.
This prejudicial effect upon the strength of the transmitted sounds is still further
increased owing to the fact that the induction coils or transformers of such distributing
systems are arranged within closed sheet metal casings, whereby the tendency to the
production of eddy currents is auginented.
In the distributing system which forms the subject of this invention, the defects
above mentioned are obviated by means of the devices hereinafter described:
Whereas in the distributing systems of this kind hitherto employed, the circuit
containing the induction coils of the telephone receivers is fed by means of induction
coils or transformers inserted upon the main circuit, in accordance with my invention
the induction coils of the receivers are inserted in circuits which are supplied by
means of condensers C (Figures 2, 3 and 4).
The dimensions of these condensers C are so calculated that the requisite degree of
resonance is produced in the inducing circuit of the receivers.

page_text: In cases in which a specially large number of receivers is required to be actuated
(Figure 3), the receivers coils tm, tn. to may advantageously be arranged suitably
grouped in shunt circuits, e tm, f, gt, h... i to j these latter being in parallel upon
the feed or main circuit. The condensers C which feed the receiver coils may then,
according to circumstances, either be arranged upon the main conductors only, upon
the parallel conductors branching off therefrom only or upon both the main conductors
and the branch conductors at the same time.
In such cases it appears to be advantageous also (for the purpose of facilitating the
management of the separate branch circuits) to employ one only (a b Figure 4) of
the two main conductors, whilst the other is replaced by distinct conductors
de, gh...jk corresponding in number to the branches c tm d, ftm g or groups of
branches it, toj arranged in parallel which are employed.
In order to increase the mutual induction and capacity of the induction coils and
thereby contribute to the diminution of the apparent resistances, the arrangement of
the receiver coils fed by condensers may be bifilar, that is with the two windings side
by side; such coils possess considerably greater mutual induction and capacity than
the coils ordinarily employed even if the latter have the same self-induction in the
two windings.
As already stated, the existence of eddy currents in the systems of this kind
hitherto employed is especially favored by the fact that the induction coils of the
telephone receivers are arranged in closed metal casings.
In accordance with my invention this defect also is obviated by arranging the
induction coils in casings which are either non-conductors or almost non conductors
of electricity.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is :-
1. A distributing system for several telephone receivers r₁₂.
intended to be actuated at the same time from one or more central telephone trans-
T₁ (Figure 2)
mitters, characterised by the fact that the receiver coils ₁, to... t₁ are inserted in
circuits which are supplied through condensers C.
2. A distributing system for several telephone receivers intended to be actuated at
the same time from one or more central telephone transmitters, characterised by the
fact that the receiver coils t₁ tm, t₁ tn, t₁ to (Figure 3) are suitably grouped in shunts
or branches arranged in parallel upon the main conductors a b, c d.
3. A distributing system for several telephone receivers intended to be actuated
at the same time from one or more central telephone transmitters, characterised by
the fact that one only (a b Figure 4) of the main conductors is common to all the
branch conductors, whilst in place of the second main conductor, as many con-
ductors d e, g h, j k are provided as there are distinct branches or distinct groups of
branches arranged in parallel.
4. A distributing system for several telephone receivers intended to be actuated at
the same time from one transmitter or from several central telephone transmitters
characterised by the fact that condensers C of suitable capacity are inserted either in
the main conductor or conductors only, or in the shunt circuits branching therefrom
in parallel or finally in both at the same time (Figures 3 and 4).
5. A distributing system for several telephone receivers intended to be actuated
at the same time from one or more central transmitters, characterised by the employ-
ment of receiver coils, formed by a bifilar winding around a core of any suitable
form.
6. A distributing system for several telephone receivers intended to be actuated
from one or more central telephone transmitters at the same time, characterised by
the fact that the receiver coils are arranged in non-metallic or in metallic but non-
conducting closed casings.
7. A distributing system for several telephone receivers intended to be actuated at

page_text: the same time from one or inore central telephone transmitters in which the arrange-
ments described in Claims 1 to 6 are combined as desired.
Dated this 10th day of March 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.