Robison's Manual of radio telegraphy and telephony for the use of naval electricians (1918)
Robison, S. S. (Samuel Shelburne), b. 1867, United States Naval Institute, Todd, David Wooster, Hooper, Stanford Caldwell · Annapolis, Md. : The United States Naval Institute · leaf 149
an can be detected by thehuman ear, but their combination, producing a maximum of current inthe aerial 1000 times per second, can be read easily. The resultant 144 MANUAL OF RADIO TELEGRAPHY AND TELEPHONY. frequency would be the same (1000) if the frequency of the heterodyne,were 299,000. If it… … Fig. 90.—Fessenden.
