The transformer must not be connected directly to the line. An instrument such as this is not designed for continuous service and is intended to be disconnected as soon as you are through using it.
Fig. 192.—Side View of the Transformer.
It will be found a great convenience in operating many of the electrical devices described, wherever direct current is not essential.
CHAPTER VIV WIRELESS TELEGRAPHY
Probably no branch of electrical science ever appealed more to the imagination of the experimenter than that coming under the heading of wireless telegraphy. Wherever you go, you are likely to see the ear-marks of amateur wireless telegraph stations in the aerials and masts set up in trees and on house-tops. It is estimated that there are nearly a quarter of a million such stations in the United States.
There is really no great mystery about this wonderful art which made possible the instantaneous transmission of messages over immense distances without any apparent physical connection save that of the earth, air, or water.
Did you ever throw a stone in a pool of water? As soon as the stone struck, little waves spread out from the spot in gradually enlarging circles until they reached the shore or died away.
By throwing several stones in succession, with varying intervals of time between them, it would be possible so to arrange a set of signals, that they would convey a meaning to a second person standing on the opposite shore of the pool.