652 BELL SYSTEM TECHNICAL JOURNAL 



obvious from Fig. 9. It will be seen that a wider frequency band is 

 actually employed with this system than was required for two separate 

 channels. Furthermore, this wider band is much less effectively 

 utilized. Two bands are required for the voice channel in place of 

 one. At the receiver, one of these bands was disregarded. To have 

 received both would have required apparatus accepting twice the 

 band width and the gain in signal would have been offset by the 

 corresponding increase in noise level. For all useful purposes, there- 

 fore, the energy radiated in the form of the second band is wasted. 



To proceed further with a discussion of multi-channel radio trans- 

 mission is beyond the scope of the present paper. Whatever the 

 system employed, however, one conclusion illustrated by these experi- 

 ments may be pointed to with confidence: television by radio requires 

 a discrete and fairly wide frequency band. Hence the frequently 

 predicted introduction of television as an adjunct to radio broad- 

 casting without extensive changes in existing channel arrangements is 

 extremely unlikely. 



