. Bulletin. Science. Figure 59.âReproductions of Bell's harmonic multiple telegraph transmitter and receiver. (USNM 208211, â ^08212; Smithsonian photo 1^204.) Ontario, to Boston, Massachusetts, Bell started experi- menting with such a telegraph. He first considered using tuning forks to interrupt the circuit at the transmitting end, for a tuning fork could produce a response only in another electrically driven tuning fork of the same frequency. A number of forks of different frequencies could thus be used for multiple telegraphy on a single telegraph line. In November 1873 Bell replaced the t
. Bulletin. Science. Figure 59.âReproductions of Bell's harmonic multiple telegraph transmitter and receiver. (USNM 208211, â ^08212; Smithsonian photo 1^204.) Ontario, to Boston, Massachusetts, Bell started experi- menting with such a telegraph. He first considered using tuning forks to interrupt the circuit at the transmitting end, for a tuning fork could produce a response only in another electrically driven tuning fork of the same frequency. A number of forks of different frequencies could thus be used for multiple telegraphy on a single telegraph line. In November 1873 Bell replaced the tuning forks with steel reeds. How- ever, difficulties in putting his concepts into practice caused Bell to drop his experimentation for a while. In the meantime, however, Bell did not cease developing his ideas. During the summer of 1874 it occurred to him that if a magnetized reed were vibrated before a coil of wire it would induce a fluctu- ating current in which the vibrations would corre- spond exactly to the sound waves causing the current. If this undulatory current could actuate at the end of the line an instrument similar to the one producing the current, such a receiver would produce a re- sponseâbut only in a receiver tuned to the same fre- quency as that of the transmitter. If those conditions were met, much of the auxiliary apparatus used in most electromagnetic communication devices to interrupt and power the circuit could be eliminated. Moreover, with such a device there would be an exact reproduction of the sound waves transmitted in the form of an undulatory current rather than by the set of pulses produced by a vibrating reed. Bell also speculated that if at one end of a line there were a set of magnetized reeds of varying lengths (like the reeds in a harmonica or Aeolian harp) acting as armatures for an electromagnet and a similar instrument at the other end of the line, such a "harp" apparatus (fig. 60) would be capable of transmitting and reprod
Size: 2944px × 849px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorunitedstatesdepto, bookcentury1900, booksubjectscience
