430 BFXL SYSTEM TECHNICAL JOURNAL 



was directed by a suitable optical system upon the plate of the cell. 

 The voltage generated was amplified and attenuated as in the case of 

 the pure tones. 



The relative magnitudes of the components were of course fixed by 

 the form of the wave inscribed upon the disk, but this was modified 

 when desired, by the insertion of elements in the electrical circuit which 

 gave the desired characteristic. Greater flexibility in the control of 

 the amplitude of the components was obtained by inscribing each 

 component on a separate disk with a complete optical system and 

 cell for each. Frequency and phase relations were maintained by 

 mounting all of the disks on a single shaft. Such a generator having 

 ten disks is shown in Fig. 23. 



An analysis of the voltage output of the optical tone generators 

 showed an average error for the amplitude of the components of about 

 ± 0.5 db, which was probably the limit of accuracy of the measuring 

 instrument. Undesired harmonics due to the disk being off center or 

 inaccuracies in the wave form were removed by filters in the electrical 

 circuit. 



All of the tests on complex tones described in this paper were made 

 with the optical tone generator excepting the audiometer, and two 

 tone tests. For the latter tests, two vacuum tube oscillators were 

 used as a source. 



