The L3 Coaxial System 



Television Terminals 



By JOHN W. RIEKE and R. S. GRAHAM 



(Manuscript received April 17, 1953) 



Television terminals are required at circuit ends of the L3 coaxial system; 

 at the transmitting end to condition video signals for carrier transmission 

 and at the receiving end to detect the transmitted signals. Special signal 

 characteristics, e.g., a degree of modulation which exceeds the value commonly 

 referred to as 100 per cent modulation, require departures from standard 

 modulating and detecting processes. The high degree of modulation requires 

 both careful control of transmitted wave form and at the receiver product 

 demodulation with phase synchronous carrier (homodyne detection). 



Carrier regeneration requirements result in the choice of one step fre- 

 quency translation from the video frequency spectrum to the allocated 

 vestigial sideband carrier spectrum. The one step process using a single 

 modulator results in unusual balance requirements for the modulator itself 

 and an unusual circuit configuration. 



Transmission quality objectives for the terminals are such as to permit 

 six pairs of television terminals to operate in tandem in a transcontinental 

 circuit. This permits a degree of interconnecting flexibility in operation 

 with other systems, e.g., LI coaxial or microwave systems. These objectives 

 place severe requirements upon the transmission stability of various filters 

 and other circuits within the terminals. New network techniques both in 

 design and fabrication are brought to bear in the effort to achieve required 

 performance. 



The transmitting and receiving terminals are described, illustrating the 

 functional operation and mechanical and electrical arrangements of the 

 equipment. 



Introduction 



The main features of the L3 coaxial cable transmission system have 

 been described in a companion paper/ This paper describes the television 

 transmitting and receiving terminal equipment of the L3 system. The 



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