=426. The Action of the Wireless Telephone.=--In the wireless telephone we have a continuous stream of electric waves of high frequency. (See Fig. 425_A_.) This stream of electric waves corresponds to the current that flows through the transmitter in the wire telephone. These waves are of such high frequency that even though we had a receiver diaphragm vibrating in step with the waves, we could not hear the sound because the human ear cannot hear a sound which consists of more than about 40,000 vibrations per second. The sound waves act upon this stream of waves very much, as in the wire telephone, the transmitter acts to modify the line current. The impulses caused by the voice are much slower than the electric waves first mentioned and these slower impulses are reproduced in the receiver. Not only are these slower impulses reproduced but they are _amplified_, that is, produced with greater energy than the impulses impressed on the stream of waves. Fig. 425_A_ represents as nearly as is possible in a diagram the continuous stream of electric waves. Fig. 426_B_, represents the impulses produced by the sound alone, and Fig. 426_C_, shows how these voice impulses are impressed on the stream of waves. [Illustration: FIG. 425.--_A_, unmodified high frequency waves; _B_, waves of voice frequency; _C_, high frequency waves modified by waves of voice frequency.] [Illustration: FIG. 426.--Vacuum tube, transmitting type. (_Western Electric Co._)] [Illustration: FIG. 427.--Vacuum tube, receiving type. (_Western Electric Co._)] [Illustration: FIG. 428.--Diagram of wireless telephone transmitting set.]