678 



BELL SYSTEM TECHNICAL JOURNAL 



FREQUENCY IN KILOCYCLES PER SECOND 



2000 KC 

 CARRIER 



PHOTO- 

 ELECTRIC 

 CELL 



c^ 



,ST 

 MODULATOR 



COAXIAL 

 LINE 



Fig. 19 — Double modulation method for translating television signals for wire line 



transmission. 



Other Communication Facilities 



The telephone channels provided by the system may be used for 

 other types of communication services, such as multi-channel tele- 

 graph, teletype, picture transmission, etc. For the transmission of a 

 high-quality musical program, which requires a wider band than does 

 commercial telephony, two or more adjacent telephone channels may 

 be merged. The adaptability of the broad-band system to different 

 types of transmission thus will be evident. 



As already noted, the commercial application of these systems for 

 wide-band transmission over coaxial lines must await a demand for 

 large groups of communication facilities or for television. The re- 

 sults which have been outlined are based upon development work in 

 the laboratory and the field, and it is probable that the systems when 

 used commercially will differ considerably from the arrangements 

 described. 



