TRACING GRAMOPHONE AND PHONOGRAPH RECORDS. 



37 



The celluloid cylinders are 55mm. in diameter and 43mm. in length. 

 The speech groove consists of depressions just as in the ordinary wax 

 phonograph. They reproduce the voice with great truthfulness. For 

 tracing the speech groove the cyhnder is removed from its brass frame 

 and placed on the " rotator." This is a steel barrel having a tapered end 

 for the cyhnder. It is rotated by a motor. The speed of the motor is 

 twice reduced to jj^ and finally to ^ by the pulleys, giving a total reduction 

 to ^. The speed of the motor is so adjusted that the cylinder turns 

 once in 4^ hours. 



As the barrel turns, it is made to move axially by a thread turning 

 in a brass " nut." An additional " bearing" takes the strain of the pulleys 

 and relieves the nut» The celluloid cyhnder thus turns and moves axially 

 in such a way that the speech groove passes under a sapphire point, which 



Belt guides 



Belt from motor 



Phonograph 

 cylinder 



C L J -.U. • ^ I'll i L' ' 'J"™ 



Smoked paper with tracing ^^^ 



Far drum 



Rotator Near drum 



Fig. 42. — Machine for tracing phonograph records. 



follows the rise and fall in the bottom of the groove and moves a light 

 " tracing lever." The point of this lever records the movement on a 

 long band of smoked paper passing over two drums. The vertical " near 

 drum" is run by a belt from the rotator. The speech curves appear 

 in great magnification on the band of smoked paper. 



The tracing lever is the critical part of the apparatus. The sapphire 

 at the end of a steel point follows the speech groove. The fulcrum 

 of the lever to which it is attached is just to the left of it. The 

 long arm is made of selected German straws of unusual Ughtness and 

 rigidity. This is balanced by a weight. The end of the straw arm carries 

 a somewhat modified hinge point. 



Fig. 43.— Piece of curve obtained by apparatus in figure 42. 



A piece of curve reduced to three-eighths size from tracings made by 

 this apparatus is given in figure 43; it is from the record of the French 

 poem " Le Roi d'Yvetot." 



