Line Filter for Program System

Open wire circuits recently have been developed for transmitting radio broadcast programs with greater naturalness and over greater distances than heretofore. The simultaneous utilization of these circuits for the transmission of broadcast programs and carrier telephone messages requires the use of line filters to restrict the program and carrier currents to the proper circuits. The low pass line filter developed for the program circuits and its contribution to the maintenance of good quality in the programs transmitted are described in this paper. 1 transmission PROGRAMshare them not systems operated on openusewire telephone lines ordinarily are assigned the exclusive of the lines, but usually with other communication facilities. The 1 wide-band system described in an accompanying paper transmits currents in the frequency band extending from 35 to 8,000 cycles per second, while the lines over which it is routed possess useful transmission ranges extending from 35 to considerably above 30,000 cycles. In order that the range above 8,000 cycles shall not be wasted, carrier telephone systems utilizing these frequencies usually are operated on the same wires with the program systems. Line filters are used at each terminal and repeater point in the program system to separate the program currents from the carrier currents and to guide each to the proper channel. They are operated in sets consisting of a low-pass filter and a high-pass filter connected in parallel at one end, the end that faces the line.