The motive power is supplied by a small air cooled petrol or
gasoline motor developing eight horse-power, and coupled direct
to a 2-kilo watt alternator. At one end of the shaft of the
latter the disk discharger is mounted, its function being to
break up the train of waves into groups of waves, so as to impart
a musical sound to the note produced in the receiver. A flexible
cable transmits the electric current from the generator to the
wagon containing the instruments. The aerial is built up of
masts carried in sections.
The Germans employ a mobile apparatus which is very similar, but
in this instance the mast is telescopic. When closed it occupies
but little space. By turning the winch handle the mast is
extended, and can be carried to any height up to a maximum of
about 100 feet. The capacity of these mobile stations varies
within wide limits, the range of the largest and most powerful
installations being about 200 miles. The disadvantage of these
systems, however, is that they are condemned to territories where
the ground at the utmost is gently undulating, and where there
are roads on which four-wheeled vehicles can travel.
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