The aerial, or antennae, as it is called in a wireless work, is made up
of copper wires. On a ship these are strung between the masts, usually
consisting of two, four or six wires held apart by crosspieces. Two or
more wires lead down from this to the wireless cabin.
The coil or transformer is the apparatus which produces the spark that
forms the electrical waves. In small stations, the length and thickness
of the spark and the speed of vibration is regulated by a thumb screw.
Transformers are used when the power is taken from the alternating
current of an electric light circuit.
The gap, which the electrical current jumps when the telegraph key is
pressed down, is composed of two rods which slide together or apart to
vary the length of the spark.
The simplest type of sending station consists of the antenna, battery,
coil, wireless key and spark gap. If a change in wave length is desired
a transmitting tuning coil must be added.
The receiving apparatus contains a detector, which is chiefly two
mineral points lightly touching and connected with a sensitive head
telephone. The incoming signals are heard as long and short buzzing
sounds corresponding to the dots and dashes. The receiving tuning coil,
used to adjust wave lengths, is operated by simply moving sliding
contacts along a bar until the signals are more plainly heard. While
the large stations have more complicated apparatus, the principle
remains the same.
[Illustration: The masts for the cavalry wireless sets are so attached
that they can be loaded and unloaded with the utmost rapidity; a
complete station can be erected or dismantled in less than ten minutes.]
[Illustration: The gasoline engine which supplies the power for
operating a cavalry wireless station is fitted to the saddle frame and
is light enough to be carried by one horse.