LINE FILTER FOR PROGRAM SYSTEM 



385 



The filter consists of four parts, each with distinguishing functional 

 characteristics. The separate parts, or sections, have image im- 

 pedances such that when they are joined together no current is 

 reflected at the junctions. Figure 1 shows the filter in block sche- 



IMPEDANCE 

 CORRECTING 

 TERMINATION 



PEAK 

 SECTION 



DELAY 



AND LOSS 



EQUALIZING 



LATTICE 



SECTION 



IMPEDANCE 

 CORRECTING 

 TERMINATION 



Fig. 1 — Block schematic diagram of filter. 



matic form. Each part of the filter provides some of the attenuation 

 required to exclude carrier currents from the program circuit, the 

 attenuation of the complete filter being the sum of the attenuations 

 of all parts. On Fig. 2 are shown the loss-frequency characteristics 

 of the various sections and of the complete filter. 



O 50 



30 



Z 20 



2 4 6 8 10 12 14 16 18 20 22 24 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 2 — Loss in filter and in component sections. 



Delay Equalization 



Likewise, the phase shift of the complete filter is the algebraic sum 

 of the phase shifts of all sections. The phase shift of the filter exclu- 

 sive of the delay and loss equalizing section is similar to that of the 



