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Updated: May 25, 2025
Kendall cast a glance over his detector-instruments. The radio network was undisturbed, the magnetic and electric fields recognized only the slight disturbances occasioned by the planet itself. There was nothing, noth Five hundred miles away, a gigantic ship came into instantaneous being. Simultaneously, and instantaneously, the various detector systems howled their warnings.
The way a simple vacuum tube detector receiving set works is like this: when the filament is heated to brilliancy it gives off electrons as previously described.
Shunt the potentiometer around the A battery and connect the sliding contact with the or zinc pole of the B battery and the + or carbon pole with one terminal of the headphone; connect the other terminal to one of the posts of the variometer and the other post of the variometer to the plate of the detector. Finally shunt a .001 mfd. fixed condenser around the headphones.
Next connect a wire to the aerial between the variable condenser and the stator and connect this to one post of a .0005 microfarad fixed condenser, then connect the other post of this with the grid of the detector and shunt a 2 megohm grid leak around it.
In this way then are the faint incoming signals, speech and music which are received by the amplifying receiving set reproduced and magnified enormously. The Telemegafone is shown complete at B. From the foregoing chapters you have seen that the vacuum tube can be used either as a detector or an amplifier or as a generator of electric oscillations, as in the case of the heterodyne receiving set.
Along the detector line a visibeam sped, and Costigan's face hardened as he saw the unmistakable outline of Nerado's interstellar cruiser, far behind them. "Well, a stern chase always was a long one," Costigan said finally. "He can't catch us for plenty of days yet ... now what?" for the alarms of the detectors had broken out anew. There was still another point of interference to be investigated.
Also, I'm going to send out all four courses, instead of only one then I'll know we're all right." "Suppose they find our one band, narrow as it is? Of course, if that were shut off automatically by the detector, we'd be safe; but would we not be out of control?" "Not necessarily I see you didn't get quite all this stuff over the educator.
To the devices of Carty and his associates was added the extremely delicate detector that was needed. This was the invention of Dr. Lee de Forest, an American inventor and a graduate of the Sheffield Technical School of Yale University. De Forest's contribution was a lamp instrument, a three-step audion amplifier. This is to the wireless telephone what the coherer is to the wireless telegraph.
The six great lookout plates into which the alert observers peered were blank, their far-flung ultra-sensitive detector screens encountering no obstacle the ether was empty for thousands upon thousands of kilometers. The signal lamps upon the pilot's panel were dark, its warning bells were silent.
Thus sound is converted into waves, and the receiving station, as you see here, with its aërial on the roof, its detector, its 'phone and its tuner, gets these waves and turns them again into sound. That is the outline of the thing, which you will understand better 'after' than 'before using.
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