The Hawaiian gazette., 1898-01-14
I" GROUND" WIRES
An Electrician Speaks Of a TRlR-
phone Improvement.
SOME SCIENTIFIC DATA
Parallel Induction Not the Great
Trouble 1t is said to be-Earth
as an Interfering Conductor.
SCIENTIFIC DATA
by an electrician.


When the telephone was first used
on a telegraph circuit. it was noticed
that kissing and frying sounds could
be heard as well as Geographic signals
of all sorts. all of which had their
origin in other electric circuits. Some
times these extraneous noises were so
much stronger than the telephone
speech that they quite overpowered
il The din destroyed the articulation.
This was the case when the automa-
tic Wheatstone transmitter was en-
ployed on a telegraph circuit parallel
TO a telephone circuit on the same
poles. This was at first interpreted as
being due wholly TO induction and for
business purposes telephone lines were
removed as far as practicable from
telegraph lines. The trouble did not
cease, in some cases it was nearly as
bad as before and then it was appar-
ent that the source Of the disturbance
was the earth itself. Both circuits
made use OF it as a part of their sys-
TENS and their ground connections
were adjacent, oftentimes practically
the same When the telephone
ground" as it was technically called
was moved away there was some relief
but it was found possible TO detect
Geographic signals from lines separ-
ated by miles of earth.
When compared with Geographic in
struments the telephone is found to
be exceedingly sensitive. a sounder
requires about the tenth part of an
ampere 10 work it properly. a relay
about the hundredth of an ampere but
a telephone will render speech audible
with less than the millionth of an am
pere and is therefore more than ten
thousand times more sensitive than a
Geographic relay. When the earth is
made 10 form a part of an electric cir
cult the current does not go in a mar
row strip from one ground terminal
10 the other but spreads out in a wide
sheet much broader than perhaps most
have imagined. Thus if the grounds"
be no more than three or four miles
apart the spreading earth current can
be traced in a sheet as much as two
miles wide. If the grounds be still
further apart with streams of water
gas and water pipes and other cOnduc-
tors better than the eartr itself, and
these will conduct some of it but not
all, the stronger the current the more
II is spread and telephone ground con-
nection anywhere in its path will re-
ceiye its share unavOidably. In cities
and towns employing the Trolley rail-
way system, the rails form part of the
circuit. As they lie upon the earth,
the earth necessarily conducts away a
notable part of the current no matter
how large the rails and good the con-
nections. For instance, in Boston,
where great pains has been taken to
provide ample metallic conductors in
rails and return wires a thousand am
peres has been found to return through
the earth to the pOwer-house. and this
is something like ten per cent of the
whole output How widely such a cur
rent may spread may be imagined, and
one may compare such a current with
the minute one needed for telephone
work. One must remember that a
steady current does not effect the tele-
phone al all, it is only when the cur
rent varies in strength above certain
rate 80 or 40 times a second that it
begins TO be troublesome The Yaria-
tons in strength come from the Morse
Key or its substitutes in telegraphy.
from some types of arc lighting dyna-
mos, from alternating dynamos for in
candescent lighting and from the mot
ors in railway work. Though there be
thousand amperes in the earth. if the
variation be but one ampere. the nine
hundred and ninety-nine which are
constant are not offensive, hence ii does
not matter so much how much current
Is in the earth as how rapidly it varies.
There are other currents in the earth
due 10 natural causes such as light
ming, auroras, ETC., which have some
times been destructive to the telephone
and its connections.
To protect both service and the tele-
phone itself here, there is one remedy.
namely TO cease using the ground as
part Of the needful circuit and to pro-
vide each instrument with a complete
wire circuit Telephone companies are
adopting this method everywhere as
fast as practicable. 1t is more costly
to establish and maintain, but it has
been made necessary by the nature of
electrical action and by the Increase
in industrial enterprises within the
past ten years.
This matter should be given atten
ton.