IMPROVEMENTS RELATING TO ELECTRICAL CIRCUITS AND APPARATUS FOR USE WITH SUCH ELECTRICAL CIRCUITS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Alexander Muirhead at the Office
of the Commissioners of Patents on the 14th April 1882. A communication
from abroad by James Alfred Briggs and Frederick Kinsman Electricians,
both of Bombay in the Empire of India.
•
ALEXANDER MUIRHEAD of 29 Regency Street in the City of Westminster
"IMPROVEMENTS RELATING TO ELECTRICAL CIRCUITS AND APPARATUS FOR USE
WITH SUCH ELECTRICAL CIRCUITS" [A communication from abroad by James
Alfred Briggs and Frederick Kinsman Electricians, both of Bombay in the Empire
of India.]
1st The improvements herein referred to are applicable when wo or more
electrical circuits are carried by the same line of supports, trough, or cable and
have two main objects vis.
(a) To obviate the disturbing effects of induction, split currents, earth currents
&c thus affording certain highly advantageous methods of utilizing the same one
trough cable or line of supports for carrying two or more electrical circuits
irrespective of the nature of the said circuits.
(b) To increase the carrying capacity of the supports by affording a means of
erecting aerial wires close together.
2nd In securing the above mentioned objects I use certain special apparatus or
certain special dispositions of the circuits or a combination of these two methods.
The following is a description of the special apparatus employed.
Vide diagram No 1. This represents forms of an insulator intended to carry two
or more wires-this insulator is called the improved Compound Insulator.
Vide diagram No 2. This represents forms of an insulator which is called the
Improved Aerial Insulator and which consists of a rod or any geometrical figure
which may be derived from a combination of rods, the improved aerial insulator is
made for use with two or more wires and is intended to be fixed at one or more
(preferably three) distinct and isolated points in each any or every span in other
words at certain points between the supports, its use is confined to aerial lines and
it is devised with the objects of retaining the wires in their proper relative
positions and of keeping them insulated from each other. These improved forms
of insulators may be of any substance which is sufficiently insulating but in
practice it is preferred to use porcelain or stone ware.

page_text: Vide diagram No 3 this represents an arrangement for use at any convenient
point on the line or in any office into which two or more line wires enter. The
principle involved may be stated as follows.
A B, is a portion of the circuit of one line wire, CD is a portion of the circuit
of the second line wire, it is evident that on approximating the two said portions
the induction set up between them will be in the same sense as that set up on the
other portions and the effect will be to increase the inductive disturbances, if
however A B and C D can be so arranged that the mutual inductive action
between them be in the reverse sense to that set up in the other portions of the
circuits it is evident that the mutual induction between the lengths A B and C D
can be opposed to and made, by 'suitable adjustments; to neutralize the mutual
induction on the two lines to which A B and C D are respectively attached, this
necessary reversal of the induction between A. B and C D is brought about by the
method illustrated in diagram No 4, which shows two coils one of which A B is
attached to one line wire, and the other C D is attached to a second line wire-the
_two_coils are usually wound in opposite senses that is. to say one is a right handed
coil, the other a left-handed-coil-but-sometimes I wind the coils in the samo sense,
adjustment is obtained by altering the relative position of-the-coils-either_by_
moving one or both bodily or by rotating them, or one of them, or any axis or
axes, Another modo of adjustment is the employment of a conducting plate which
can be introduced or moved, between the two coils so as to screen more or less of
the one coil from the other, or any combination of those several modes of
adjustment may be employed.
It is important to notice that in this arrangement I make use of the direct
_nction of one circuit upon another, without the intervention of a core of any magnetic
substance by which means-I-avoid the_rotardation invariably attending the use of
electro magnets.
"
This arrangement is called the Improved Induction Guard, any number of such
induction guards may be joined up or combined into a single instrument adapted
for a number of line wires.
Diagram. No. 5 represents a special arrangement of circuits in which A A¹
represent the wires forming one complete circuit, B B¹ the wires forming a second
complete circuit, it will be noticed that the two wires forming one circuit are
situated on the perpendicular bisecting the straight line joining the other two.
C is the point of bisection, and at or about this point one or more circuits may
bo carried.
It is important to notice that the circuits A A' B B' are joined up in such a way
that in any case there is no resultant inductive action between them.
If required B B' may be replaced by any number of single wires forming
portions of electrical circuits which would also have no resultant inductive action
on A..A!.
Diagram No 6 represents an arrangement of mixed circuits in which the two
wires of the complete telephone circuit A A¹ are crossed at one or more points—
the points being so selected that the sum of the induced currents set up or tending
to be set up in one of the telephone wires A, shall be equal to the sum of the
induced current set up or tending to be set up in the other telephone wire A¹ and
shall be in such directions that they either neutralize each other or tend to
neutralize each other.
Diagram No 7 represents another arrangement in which the wires constituting
one or more complete circuits are fitted to one and the same insulator at each point
of support; the arrangement being of-such nature that no two wires are in metallic
contact with each other at or between the point of support. The wires are further
retained in their proper relative positions by the use of the improved aerial
insulators previously referred to, and further between each pair of support the
system or any particular portion of the system of wires above described is revolved
or turned round the geometrical axis of the system through any desired angle,
though in practice certain angles are preferred as that of 180°, each wire or one or

page_text: more particular wires thus lie or tend to lie in a spiral round the geometrical axis
of the system.
Vide diagram Nos 8, 9 and 10 these show the telephone or other receiving
instrument joined up in the null branch of any duplex arrangements, by this system
the minimum number of contacts are made and broken when using the telephone or
other receiving instrument and the core of the latter may be retained in an entirely
neutral or unpolarized condition--the telephone in this arrangement is protected
from induction, from lines adjacent to its own by an induction guard placed in the
artificial side and having the coils wound in the same sense or by an induction
guard placed on the line side and having its coils wound in different senses.