шечной of Neutraшzing inductive Disturbances in Telephone Circuits and Apparatus therefor.
Year: 1885

page_text: шечной of Neutraшzing inductive Disturbances
in Telephone Circuits and Apparatus therefor.
I, WILLIAM PHILLIPS THOMPSON, Fel. Inst P.A. of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool in the County of Lancaster, änd
323 High Holborn in the County of Middlesex, Civil Engineer do hereby declare
the nature of the said invention for AN IMPROVED METHOD OF NEUTRALIZING
INDUCTIVE DISTURBANCES IN TELEPHONE CIRCUITS AND APPARATUS THEREFOR
(a communication from abroad by William A. Jackson and Josephus C. Chambers
of Detroit; county of Wayne, State of Michigan, United States of America,
electricians) and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
The method or process consists in neutralizing the disturbing currents which are
generated in telephone circuits by induction from external wires and other objects
by opposing said disturbing currents by the reaction of electrical charges induced
by said disturbing currents in one or more insulated bodies which are capable of
being electrically charged by induction, and are also good conductors, which will bo
hereinafter called "inductive bodies" for brevity.
There are several forms of apparatus, all alike in principle but differing some-
what in construction, which can be used to carry out the process and the form
which has been chosen for illustration as being the best and most compact is that
which will be described.
Figure 1 is a perspective of the core of an induction coil, preferably made of
soft iron. Figure 2 is a cross section through a completed induction coil. Figure 3.
is a vertical section through the coil at right angles to Figure 2. Figure 4 is an
elevation of the core partially wound, and Figure 5 is a similar elevation of the
core and winding with some insulated conductors, or "inductive bodies" added.
K represents a core the body of which is made of a rectangular piece of thin
metal; the softest, iron is best, having at the corners broad pole pieces A of
similar metal, with their broader surfaces at right angles to the corresponding.
surfaces of K

page_text: I represents an electrical conductor, which may be either wire or one or more
metal plates wrapped around the part K of the core, but insulated therefrom. It
is found that soft iron is the best inaterial for I. When the coil is put to use as an
ordinary induction coil the part I reacts upon the primary in the same manner that
the ordinary core does, and becomes really the core of the induction coil, leaving
the core KA free from the effect of the primary to perform its peculiar functions
in the coil,
P represents the primary, wound over K I and passing between A A, insulated,
and connected with a battery and transmitter in the ordinary well known manner,
as indicated in Figure 3.
S represents the secondary, made of insulated wire, finer than the primary, and
wound over the primary and connected on one side with the line wire and on the
other side with the ground wire which leads through the receiving telephone in
the usual manner.
H represents a helix of insulated wire wound over the completed coil, and may
be used or not at pleasure. The ends of H, and also of I when I is made of wire,
may be connected together, or may be left disconnected. In practice usually the
ends of I or the ends of H are not connected, but led through the the wooden
'cap, B, at one end of the coil, as shown in Figure 3, and left free.
This arrange-
ment is a safeguard against either I or H coming into electrical contact with any
other part of the coil.
a a a a represents thin strips of iron, insulated from all other parts of the coil
and from each other, which are sometimes laid along the edges of K, but they are
not essential, and are only used when it is desired to increase the metallic surface
which is to be acted upon inductively.
The completed coil therefore consists of a core K, which may or may not have
the pole pieces A, a supplemental core I, a primary P, a secondary S, and an
enclosing helix H, this last being wound so that it crosses the convolutions of the
secondary, and each of these elements is insulated from every other element.
The wooden caps B and the additional pieces a a do not form essential parts of
the coil, though generally the first is used for convenience in making a finish, and
sometimes the second is used.
It will be noticed that there are in close proximity to that part of the telephone
circuit which consists of the secondary S, insulated "inductive bodies," represented
by K A and H; also by a a when used. The secondary is usually wound to a
resistance of from between 300 to 750 Ohms, the higher resistance having a greater
suppressing effect, but being less satisfactory in all respects than a lower resistance
say from 400 to 500 Ohms, and therefore have a large number of convolutions of
the circuit in electrical proximity to the "inductive bodies."
The disturbing currents caused in a telephone circuit by induction from other
wires, the earth etcetera, are generally of higher potential than the normal tele-
phonic current, and have therefore a much greater tendency to induce electrical
charges in "inductive, bodies" placed adjacent to the line traversed by such
currents than has the telephonic current. This is utilized by placing one or more
"inductive bodies" in electrical proximity to the telephone circuit, but insulated
therefrom, so that an inductive influence will be mutually exerted by said
telephonic circuit and said "inductive bodies
upon each other.
33
When a telephone circuit is put to use in talking, the receiving telephone is
affected both by the normal telephonic current from the sending station and by
currents generated in the circuit by induction from outside wires etcetera, and the
latter currents often cause in the receiving telephone rattling cracking sounds loud
enough to drown the sounds produced by the normal current.
When a telephone circuit through which these two classes of currents is flowing
is brought into electrical proximity to one or more insulated "inductive bodies,'
the said currents tend to cause induced charges in said "inductive bodies," and
these induced charges react upon the convolutions of the secondary or line
wire, and cause therein opposing and conflicting currents of like polarity as the

page_text: .
disturbing currents, by which the high tension disturbing currents are neutralized
and checked, while the normal telephonic currents, owing to their comparatively
low potential, are little affected, and flow on into the receiving telephone.
It is evident that the process can be practised by the use of various mechanical
appliances, and that, where a telephone circuit is already in position, and has a
telephone supplied with an induction coil, the primary P and at will either the
core KA or the supplemental core I can be omitted, and the remaining part of the
mechanism illustrated can be connected in the circuit by cutting the wire thereof,
and joining the severed ends to the ends of the secondary S. But it is preferred
to use the complete induction coil as illustrated, because it transmits with great
power, and because induction disturbances are more noticeable at the ends of a
telephone circuit, namely, in the receiving telephone, and the induction coil when
placed in the transmitter box is in the best position to give its maximum effect.
Having now particularly described and ascertained the nature of the said
invention, 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. The herein described process of neutralizing induction disturbances in telephone
circuits, consisting in opposing the disturbing currents by induced charges generated
by, and reacting upon, said disturbing currents.
2. The herein described method or process of neutralizing disturbing currents in
a telephone circuit by establishing an equilibrium between said disturbing currents
and electrical charges of opposite polarity inductively generated by said disturbing
currents.
3. In an induction coil the combination with a core, primary and secondary, of
a supplemental core interposed between and insulated from the core and primary,
substantially as shown and described.
4. In combination with the core K primary P and secondary S the insulated iron
strips a a, substantially as shown and described.
5. In combination with an induction coil an enclosing helix, insulated therefrom,
and wound at an angle to the convolutions of the primary and secondary, substan-
tially as shown and described.
6. In an induction coil for neutralizing induction disturbances in electrical
circuits, a compound core, consisting of a core and a supplemental core partially or
wholly surrounding the same, but insulated therefrom, substantially as shown and
described,
7. In combination with a telephone circuit an "inductive body" in electrical
proximity to, but insulated from said circuit, substantially as shown and described.
Dated this 20th day of July 1885.
WP. THOMPSON & Co.,
Agents for the Applicant.