5% 



lUU.I. SYSTEM TF.CIIXIC.il .IOURX.IL 



general the harder to fulfil. Frequency-amplitude distortion has been 

 practically eliminated as we have seen from each of the three essential 

 parts of this apparatus; and although it was found impracticable to 

 make each part of the apparatus free from frequency distortion in 

 phase, it was possible to give the complete set good frcqucnc\^ char- 

 acteristics in both amplitude and phase as will be explained. 



In a vibrating system of one degree of freedom when we wish to 

 a\oid frequency distortion in amplitude, we usually adjust the resonant 



Fig ,S — riciu-ral dianrani of recording apparatus showing circiiil <ktails 



frequency so that it is above the range of frequencies within wliirli we 

 desire to work; in addition, it is desirable in most cases to in.ikc the 

 dami^ing of the system large. With these adjustments made it is 

 found that there is a phase lag between amplitude and dri\ing force 

 which rises with frec|uency and reaches a maximum above the resonant 

 frecjuency, and it is possible tfi make this jihasc lag nearly jirfiportional 

 to the frequency over llu- r.ini^i' of fri(|iiencies within whicli it is 

 desired to work. 



It is well known that il e(|u.il driving forces produce e(|ii,il aniiili- 

 tudes at all fretiuencies, and if the phase lag of the ami)litude with 

 respect to the dri\ing force is proportional to frequency, then a dri\ing 

 force of c(jmple.\ wave form is. reproduced without distortion of wave 

 form in the \ibrating system. These conditions held very well over 

 the desired range of frcc|uencies in the oscillograph vibrator, as shown 

 in Fig. 4. In the case of the condenser transmitter, however, there 



