TABLES OF PHASE 



879 



we see that it can be constructed by adding a number of semi-infinite con- 

 stant slopes of attenuation as shown in Fig. 4b. The first of these will be a 

 semi-infinite slope of magnitude ki commencing at the first critical frequency 



0.6 0.8 1 1.5 



FREQUENCY (f ) 



5 6 7 8 9 10 



Fig. 4 — (a) Straight line approximation to attenuation characteristic, (b) Individual 

 semi-infinite constant slopes of attenuation which add to produce the straight line approxi- 

 mation of Fig. 4(a). 



/o. The second will be a semi-infinite slope of magnitude —^1 commencing 

 at the critical frequency /i which must be added to correct for the fact that 

 the first straight line of slope +^1 does not extend to infinity, but terminates 

 at the critical frequency /i, where the straight line approximation assumes a 



