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Page:Popular Science Monthly Volume 89.djvu/292

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^278

��Popular Science Monthly

��Music by Wireless

UNITED STATKS Patent 1,166,582, issued in 1916 to G. Desilels, shows an interesting "Wireless Apparatus for Producing and Transmitting Musical Sounds." By the use of this method, which is here shown diagrammatically, it is possible to play tunes the same as on a piano, and to have the nuisic thus played transmitted by wireless to a distant station and there reproduced. It is seen that alternating current power lines are led to the primary of trans- former 43 by way of the special piano- keyboard switches shown at 22. All of these are connected in parallel, and closing any of them serves to apply power to the transformer. The secon- dary charges condenser 47, which dis- charges with oscillations tlirough the primary portion of helix 46 and which- ever of the rotary spark gaps 3 to 10 is connected by the high-voltage switches of keyboard 22. It may be noted that in the drawing of the patent itself the condenser and spark gap are incorrectly connected to the helix and transformer; from the specification it is obvious, how- ever, that the wiring siiow^n was intended. The novel points of the system are in the rotary gaps 3 to lo and in the key- board 22. Each of the gaps has a different number of spokes, and the numbers are chosen so that the spark frequencies correspond to the notes of an octave in the musical scale. Thus if key 23 is pressed, disc 3 is connected; if this disc has 10 spokes and if the shaft revolves about 1500 r.p.m., 250 sparks per second will be produced. Since tin- spokes are evenly spaced, the sjiarks will occur regularly, and a musical note of about middle C on the musical scale will be produced. If key 30 were pressed, double the number of sparks would occur per second, and the musical tone would be one octave higher. Similarly the other keys connect the other gaps, wliich have their spark freciuencies pro])erly (-hosen so as to give the various notes of the scale. When more than one jjctave is desired additional gaps are made use of; instead of increasing the number of spokes indefinitely the in- ventor prefers to duiilicate the ocla\e of gaps but to rotate the next higher group at (Iciuble speed. This of course (l(nii)les

��the spark frequency and therefore doubles the pitch. By supi^lying suf- ficient power it is feasible to play chords by pressing several of the keys at the .same time. The loudness of the musical tone can be regulated by rheostats operated by pedals and connected so as to vary the intensity of the sparks. It is easily seen that the radiation from a transmitter of this sort would produce musical tone effects in any recei\er, using a telephone in comliination with any of the usual rectifying detectors.

���Music may be transmitted by means of this wireless apparatus

Lighting Audion Bulbs Cheaply

AMATEIRS who are not fortunate ^ enough to possess a storage battery often light their audions by the current from dr\- cells. When the detector is used for any length of time, howe\er, the expense of this method is almost pro- hil)iti^'e. The following is suggested as an exceedingly inexpensive substitute, which ma>' be used by those who can secure worn-out dry cells:

Cut the tops from fi\e one-quart jars or bottles, and fill tlieni one-third to one- half full with a saturated solution of sal- ammoniac. Next .scrape all the shellac from the zinc of five okl dry cells, and punch 1-8 inch holes about an inch apart all over the shell. W'hen these cells are placed in the prei^ared solution the\' will light till' bulb nearly as long as a new l)atter\', and at an expense of possi- bh' two cents for the (-hemical.

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