Exhibit of the Department of Interior Patent Office: Government Building, Louisiana Purchase Exposition, 1904, pages 6-7, 9:
|DE|| FOREST'S WIRELESS TELEGRAPHY.
This invention enables telegraphic messages to be transmitted between
distant stations, whether on land or on sea, and without any wires
connecting the same.
It has long been known that owing to the phenomena of induction, certain electrical disturbances at one point would cause like disturbances at a distant point, although no wires connected the two places. This invention utilizes this principle by sending out waves of induction in all directions from the transmitting station, and then receiving the same at the distant station on a suitable instrument. By properly proportioning the wave frequency and the self induction, and the capacity of the instruments, it is said to be possible to so tune the receivers electrically, that each will only respond to waves intended for the same, and thereby the messages intended for one station will not interfere with those intended for another. These induced waves readily pass through the wall of the Exposition buildings, and the public may communicate from the Patent Office space to other stations on the grounds.
|The||ory of Operation.
An accepted theory states that the surging of electric charges between
the spark gap in fig. 1, causes the current to flow up the sending mast
in the form of vortex rings in the hypothetical ether filling all space,
and that these rings expand in all directions, reaching the distant
station without wires and in a greatly attenuated condition. At the
receiving station, the aerial receiving conductor constitutes an
obstruction to a portion of the vortex ring, or ether wave, and
therefore the latter in part, follows down the mast, passes through the
receiving instrument and causes a signal to be sounded. Fig. 2 shows how
such vortex waves if generated in England with sufficient power, would
expand until they reached America, on one side, and probably India on
the other side, and would accommodate themselves to the earth's
curvature as they enlarged. Fig. 5 shows a hypothetical vortex ring in
The sending key is shown in fig. 3, with its contacts immersed in oil, and the generator is shown near the middle of fig. 1.
The receiving instrument consists of self-induction coils, a condenser in shunt, a telephonic receiver, a responder and a local battery closed on itself through the same, all as shown on the right of fig. 1. The responder, in a greatly enlarged section, is shown in fig. 4, and consists of a mixture of litharge, glycerine and alcohol, occupying the gap between the wires and carrying very fine tin filings. The local battery normally causes minute particles of metal to be projected from the anode wire to the tin filings and from the latter to the cathode wire, thus causing a metallic conducting bridge to be formed for the local circuit, through the glycerine mixture, as shown in the upper portion of the gap. Upon the passage of electrical energy from the vortex ring, down the aerial receiving conductor, and through this gap in a direction opposite to that of the local battery, this metallic conducting bridge is destroyed by the simple laws of electrolysis, and therefore the local battery circuit is suddenly broken, which causes its static charge to operate the receiver and sound the signal. After the vortex ring or induced wave has passed, the normal condition is restored, and the responder is ready for another signal wave.
Wireless telegraphy has been tested by the United States Signal Service, and preparations are now being made to try it in Alaska.