WIDE-BAND OPEN-WIRE PROGRAM SYSTEM 369 



line and associated pad will have the same 1,000-cycle loss as the 

 other line. As indicated, only one of these pads is required. This 

 building out of the shorter line minimizes attenuator adjustment when 

 the direction of transmission is reversed. The line amplifier in this, 

 as well as the other layouts to be discussed, is always set for a gain of 

 30 db. 



On Fig. 16 is shown the layout of a typical intermediate non- 

 bridging station where the gauges of the wires on the two sides of the 

 repeater station are different. As mentioned earlier each gauge of 

 wire has its own particular low-frequency attenuation equalizer. Con- 

 sequently, where the gauges of the wires on the two sides of the 

 repeater station are not alike, it is necessary to arrange the station 

 layout so that the proper low-frequency equalizer will be associated 

 with the proper direction of transmission. This association of appa- 

 ratus may be readily observed from Fig. 16. 



On Fig. 17 is shown the layout of a typical terminal station. This 

 layout differs from the intermediate station layout largely in the fact 

 that provision must be made for the introduction of predistortion 

 when the terminal station is transmitting a program to the open-wire 

 line and in the provision of a restoring network when the terminal 

 station is receiving a program from the open-wire line. The general 

 layout of the apparatus may readily be observed by reference to the 

 figure. The monitoring facilities at this type of station, in general, 

 differ from those provided at the normal intermediate station in that 

 a two-unit loudspeaker is provided for use as desired. 



On Fig. 18 is shown the layout of a typical intermediate bridging 

 station where the gauge of the wires in the two directions is the same. 

 This arrangement differs largely from the arrangement shown on Fig. 

 15 in that the bridging amplifier is inserted immediately ahead of the 

 line amplifier so as to provide the necessary additional branches as 

 required. The general circuit arrangements involved to take care of 

 the different types of branches which may be encountered are indicated 

 on this figure. The photograph. Fig. 19, shows the program equip- 

 ment layout at an intermediate bridging station, which is of the type 

 just discussed in Fig. 18, utilizing, however, only one branch circuit 

 which is connected to a local broadcasting station. 



In certain of the layouts just discussed, one apparatus unit desig- 

 nated as "Aux Filter" is shown which has not previously been men- 

 tioned. This is an 8,000-cycle low-pass filter somewhat similar to the 

 low-pass line filter, except that it is not designed to operate in parallel 

 with any high-pass filter. This filter is required at the transmitting 

 and receiving terminals, in the branches feeding the radio station and 



