WIDE-BAND OPEN-WIRE PROGRAM SYSTEM 



365 



■A/W 



Fig. 12 — Restoring network. 



1000 2000 3000 4000 5000 6000 7000 80( 

 FREQUENCY IM CYCLES PER SECOND 



Fig. 13 — Attenuation characteristics of predistorting and restoring networks. 



Line Filters 



As a rule, on open-wire circuits other transmission channels are pro- 

 vided on the same wires which carry the program transmission. 

 These other channels operate at frequencies above the program range 

 and in order to direct the various currents to their proper channels 

 at a terminal or repeater station carrier line filter sets are inserted at 

 the ends of the line wires. The carrier line filter sets include a low- 

 pass and a high-pass filter. The low-pass filter, cutting off somewhat 

 above 8,000 cycles, directs the program transmission to the program 



