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(7). The Magneto system is now regarded as obsolete for
exchange working on a large scale. It is still employed at
a number of exchanges, chiefly in tropical countries where it
is retained because of it's being less liable to humidity
troubles, referred to later on, than either the Common Battery
(C.B.) Manual or the Automatic Systems. Even in these countries
it is giving way more and more to these more modern systems in
view of the better service they afford and of the fact that
methods are now available for controlling the humidity condi-
tions on these systems. For small exchanges in certain situa-
tions there is still a field of usefulness for it.
(8). For the principal Exchanges in this Colony the C.B.
Manual and the Automatic should be considered and further on
I deal with the main features of these systems.
Climatic Conditions.
(9). As already stated the Magneto system is less subject to
the harmful effects of humidity than either the C. B. Manual
or the Automatic. With the two latter systems a Central
Battery is employed which keeps much of the Exchange apparatus
and cables continuously under electrical pressure. Where
excessive humidity occurs there is a liability for the dampness
to penetrate the wiring and coil windings and, due to the elec-
trical pressue being continuously applied, cause electrical leakage which may in time set up electrolytic action and cause
a breakdown of the cables and coils. There is also a liability
for the moisture to cause surface leakage between electrical
contacts and also to set up corrosion of the various metal
parts of the equipment. With the Magneto system these severe
electrical conditions do not apply, but nevertheless it is
usual where high humidites occur to provide appliances for
At the keeping the cables and apparatus as dry as possible. present Victoria Central Exchange a Calcium Chloride plant
which extracts the moisture from the air and pumps the dried air
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