. Bell telephone magazine . the nature of any difficulty toa control office where telephone peopleare ready to take the necessary may involve sending craftsmen tothe station or merely operating a switchwhich will handle the problem by remotecontrol. At the receiving terminal station theenergy sent along the route must be de-modulated—that is, the original infor-mation, whether telephone conversations,data messages, or television programsmust be retrieved from the carrier radiowave. This involves a process of elec-trical conversion; the world of super-highfrequencies is left behind
. Bell telephone magazine . the nature of any difficulty toa control office where telephone peopleare ready to take the necessary may involve sending craftsmen tothe station or merely operating a switchwhich will handle the problem by remotecontrol. At the receiving terminal station theenergy sent along the route must be de-modulated—that is, the original infor-mation, whether telephone conversations,data messages, or television programsmust be retrieved from the carrier radiowave. This involves a process of elec-trical conversion; the world of super-highfrequencies is left behind as the micro-waves are stepped down in stages by con-verters to the lower frequencies used byregular telephone equipment or by tele-vision stations. Electrical filters sort outeach particular telephone or data mes-sage for its ultimate destination. In thecase of television, only one demodulationstep is necessary because this signal oc-cupies an entire transmission band, andit is sent on to the broadcasting Traveling wave tube used in TH and TD-3systems has a far greater power output thanelectron tubes used previously. For Em ergencies Transmission by means of microwavesoffers problems as well as , for example, the signalfades, as irregularities in the atmosphereprevent all or part of it from reachingthe receiving antenna. Again, the micro-wave equipment is also subject to suchdifficulties as the failure of a , at least one channel on aradio relay route is usually assigned toserve as a standby. Ordinarily, on multi-channel routes, sections of protectionchannels are automatically substitutedfor sections of any working channels thathave become disabled. Substitutions canalso be made by push-button remotecontrol. In the six-channel TD-2 system, it willbe recalled, a protection channel was setaside to act as a substitute in the eventof the failure of any of the five workingchannels. Again, on a route with twelvechannels,
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Keywords: ., bookauthoramerican, bookcentury1900, bookdecade1920, bookyear1922
