JOINT DEVELOPMENT AND NOISE FREQUENCY INDUCTION 187 



the edges of the band is not sharp, however, so that extraneous currents 

 at frequencies outside of this band may also give rise to noise. This is 



POWER SYSTEM USAGE 



100.000,000 

 50,000,000 



10,000,000 ^ 

 5,000,000 



1,000,000 

 500,000 



POWER 



LINE 



CARRIER 



NORMAL 

 RANGE 



LIMITED 

 USAGE 



10,000 

 5,000 



1,000 

 500 



COMMUNICATION SYSTEM USAGE 



FREQUENCY IN 

 CYCLES PER SECOND 



RADIO COMMUNICATION 



f RANGE IN WHICH 

 SHORT-WAVE 

 TRANSATLANTIC 

 TELEPHONE 



+ CIRCUITS LIE 



SHORT 

 WAVE 



BROADCAST 



LONG 



LONG-WAVE WAVE 



TRANSATLANTIC 



TELEPHONE 



WIRE COMMUNICATION 



PRESENT 



CARRIER 



TELEPHONE 



HIGH-SPEED TOOLS — 



POWER SUPPLY — 



SINGLE POWER SYSTEMS 

 RAILWAY AND 

 OTHER POWER SUPPLY 



DIRECT-CURRENT 

 SYSTEMS 



lOPEN-WlRE 

 CARRIER 

 TELEGRAPH 



MESSAGE 

 TELEPHONE pROGRAM 

 TELEPHONE 



CABLE 

 CARRIER 

 TELEGRAPH _ LONG - DISTANCE 

 RINGING 



— TOLL RINGING 



— TRAIN CONTROL 



SUBSCRIBER 

 RINGING 



DIRECT _ 

 CURRENT _ 

 TELEGRAPH 



Fig. 1 — Frequencies used for electrical transmission. 



particularly true at the lower end with some of the local exchange cir- 

 cuits. High quality telephone circuits for program transmission cover 

 a wider range. This may be on certain circuits as much as from about 



