Band Concerts from an Electric

Light Bulb

��M

��By George F. Worts

USIC that ranges from the pierc- does not stop there. If several of the ing wail of a taut violin string tubes are connected in the correct way to the grumbling bass of a mon- and adjusted with great care, the wire-

��ster horn has been added to the re- markable achievemnts of an electrical instrument so small and so insignifi- cant in appearance that it could be passed by scores of times without arousing so much as a lingering glance. Despite its innocent appearance, however, its technical name is more

��less signals will be increased in loud- ness several hundred times. This ar- rangement is known as the Audion amplifier.

In both of these uses, the construc- tion and operation of the audion are practically the same. In fact, for all of the uses to which the audion is put.

��than formidable. Scientists know it as its fundamental structure, apart from the "oscillating vacuum tube," al- size, does not vary. In appearance it though this name has been changed closely resembles an ordinary electric and shortened to a simple compound lamp bulb. There is a brass base with word, "audion." "Audion" is derived threads, so that it can be screwed into from audio, to hear, and ion, the tini- a socket, a round glass bulb and a fila- est division of electricity ; in other ment burning brightly in a partial vac- words, to make audible the action of uum. But beyond this point, the an- ions. This, in a word, is exactly what dion and the electric light are strangers, the oscillating vacuum tube accom- Built into the bulb close to the fila- plishes. ment are tw^o metal electrodes. One Before proceeding directly to a dis- is a tiny replica of the grids that are cussion of the latest marvel of the au- used in coal stoves .... and it is called dion, — electrical music — let us pass a grid ; while the other is a small plate

��hurriedly over some of the achievements that have preceded it, which, in a round-about way, have led to the discovery.

Amateur and profes- sional wireless opera- tors know the audion well, although numbers of them are not aware that it has other uses than the reception of radio signals.

Connected with the proper wireless instru- ments, the audion will receive and strengthen the weak signals of a distant radio station to a degree several times as loud as any other detector. But its abil- ity in this direction

���Dr. Lee DeForest, inventor

of electrical music, and his

audion bulb

71

��The grid and the plate are connected to the other apparatus in such a way that a per- fect balance, electric- ally speaking, is main- tained between them. When an outer influ- ence, such as an in- coming wireless wave, is brought into the bulb, this balance is disturbed, and in a strengthened form, the disturbance is heard in the telephone head re- ceiv ers a s the dots and dashes of the wireless code.

Strange to say, this same balancing princi- ple is made use of in another application di- rectly opposite in na-

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