LONG DISTANCE CABLE CIRCUIT 573 



program must not be allowed to spill over unduly as crosstalk into 

 neighboring circuits which may be carrying telephone messages or 

 other programs. The volume may also be limited by the requirement 

 that serious non-linear distortion be not introduced by effects pro- 

 duced in the vacuum tubes of the amplifiers or in any magnetic-core 

 coils either in the apparatus or in the line. On the other hand, the 

 minimum volume which a wire program circuit can handle is limited 

 by the tendency of the noise present on the circuit to annoy the 

 listener when the program volume is very weak. Crosstalk from 

 other circuits into the program circuit also enters as an important 

 consideration, since radio listeners must not be able to pick up intelli- 

 gible conversations during those times when the program volume is 

 very weak or when actual pauses occur in the programs. 



From this, it is seen that the matter of widening the volume range 

 of a wire program transmission system involves not only added cost 

 to keep non-linear distortion and noise within limits but also, and 

 perhaps even more important, added cost to isolate the circuit from 

 other circuits on the same route. 



From the standpoint of the radio part of broadcasting systems 

 handling very wide volume ranges also presents difficulties. Radio 

 transmitter and other radio equipment noises become more serious 

 as the volume range is widened. More important, however, widening 

 the volume range without corresponding increase in the radio trans- 

 mitter capacity reduces the effective range of a radio broadcasting 

 station, since this increases the tendency for the faint parts of the 

 programs to sink below the level of atmospheric and receiver-set 

 noises. 



At present it is understood that most radio broadcast programs 

 where no long distance wire circuits are involved are being delivered 

 with a volume range of about 30 db.^ In order to anticipate improve- 

 ments which may come in the broadcasting art, however, it has 

 seemed desirable to provide wire circuits in cable which will handle 

 a wider volume range than this and, accordingly, 40 db has been taken 

 as a working standard. This volume range appears to satisfy almost 

 everybody with the possible e.xception of some who listen to broad- 

 casts of symphony orchestras and the like. With the present limi- 

 tations of volume ranges to about 30 db, there has been some complaint 

 that much of the artistic quality and effectiveness of broadcasts of 

 such high-grade music has been lost because of the fact that the 

 operator manipulating the volume range control seemed to reduce the 

 range an undue amount. 



2 O. B. Hanson, "Volume Control in Broadcasting," Radio Broadcast, March, 

 1930. 



