Wireless Telegraphy and Telephony

WIRELESS TELEGRAPHY II oscillations flow back and forth through the aerial and ground, striking the mineral detector on their journey. The high frequency oscillations are alternating currents, be- cause they reverse their direction many thousand times per second. Such a current will not pass through the telephone receiver, because the little magnets contained therein exert a choking action on alternating currents of high frequency and effectually block their passage. The mineral detector acts as a valve, allowing the current to pass through in one direction, but not permitting it to return or go in the oppo- site direction. The result is a series of impulses flowing in one direction only, and therefore called a direct current. Such a current will flow through a telephone receiver and produce a motion of the diaphragm which imparts its mo- tion to the surrounding air, the result being sound waves audible to the ear. By varying the periods during which the key is pressed and the oscillations are being produced, according to a prearranged code, the sounds in the receiver may be made to assume an intelligible meaning.