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BELL SYSTEM TECHNICAL JOURNAL 



Electric Company theater system the direction of cutting is reversed. 

 After a record has been cut into the "wax," the "wax" may be 

 handled and with proper precautions readily shipped from place to 

 place. 



The shape of the groove varies somewhat in commercial practice. 

 The groove and stylus most commonly used with Western Electric 

 apparatus are shown in Fig. 5. The groove is approximately .006 in. 

 wide and .0025 in. deep. The pitch of the groove is between .010 in. 

 and .011 in. so that the space between grooves is about .004 in. Thus 



Fig. 4 — The recording machine. 



the maximum safe amplitude is about .002 in. If this occurs at 250 

 cycles the corresponding amplitude at 5,000 cycles, assuming constant 

 absolute intensity of sound over this range, would be .0001 in. 



It is important that a smooth groove be cut as any roughness in 

 the walls introduces extraneous noise in the reproduced sound. To 

 insure a truly smooth groove the surface of the "wax" must be shaved 

 to a high polish. The texture of the "wax" must be fine and homo- 

 geneous which requires not only that the "wax" composition be 

 correct, but that it be operated at the proper temperature. "Waxes" 

 may be obtained commercially which will operate satisfactorily over 



