. An elementary book on electricity and magnetism and their applications. tate about an axis so thatby turning the knob on topany desired amount of themovable plates can be in-cluded between the fixedplates. Finally, the receiving telephones used in wireless tele-graphy must be doubles-head telephones (Fig. 416) with a Mo table ][.. 11. — Variable receiving condenser. ELECTROMAGNETIC WAVES 561. Fig. 41G. — Double-headtelephone receivers. resistance of from 1000 to 2500 ohms. Besides these importantinstruments one usually finds in a modern installation numer-ous switches, rheostats, and meters
. An elementary book on electricity and magnetism and their applications. tate about an axis so thatby turning the knob on topany desired amount of themovable plates can be in-cluded between the fixedplates. Finally, the receiving telephones used in wireless tele-graphy must be doubles-head telephones (Fig. 416) with a Mo table ][.. 11. — Variable receiving condenser. ELECTROMAGNETIC WAVES 561. Fig. 41G. — Double-headtelephone receivers. resistance of from 1000 to 2500 ohms. Besides these importantinstruments one usually finds in a modern installation numer-ous switches, rheostats, and meters tomeasure current, voltage, and wavelength. 379. The service of ocean seems to be the peculiarfield of service for radiotelegraphy, andit has already come into extendedcommercial use on the water. Ofcourse wire telegraphy has for a longtime been extensively used on land,but a moving ship cannot keep up wirecommunication with the land and sothe ether waves have been seized uponas a medium for sending sending out daily time signals, weather reports, and stormwarnings, as well as by responding to calls for aid from shipsin distress, radiotelegraphy has been of inestimable service tomariners and already has saved thousands of human lives. In a certain sense radiotelegraphy has removed the seaand destroyed distance. For example, radio stations havebeen erect
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
