404 BELL SYSTEM TECHNICAL JOURNAL 



and amplifier and for converting the signals delivered by that system 

 into a permanent printed record. 



With the combination of cable and signal shaping amplifier, signals 

 which are transmitted into the sending shaping network and the cable 

 as square topped impulses as shown in Fig. 1 emerge from the amplifier 



Fig. 1 



as rounded impulses from which the high frequency components have 

 been removed as a result of the attenuating effect of the cable. The 

 receiving and printing system must therefore be capable of accurately 

 translating rounded signals of this nature into printed characters. 



Requirements of Operating System for Loaded Cables 



The outstanding characteristic of the loaded cable is the enormously 

 increased speed of transmission which may be as high as 2,400 letters 

 per minute or more. For practical utilization of such high speeds the 

 operating system must include some means for dividing the line time 

 to provide a number of traffic channels. This is necessary in order 

 to facilitate the distribution of the work of preparing the perforated 

 transmitting tapes and checking the received message records among 

 the required number of operators. The system must also provide for 

 efficient two-way operation to avoid delay in the transmission of 

 traffic from either terminal and should be capable of being joined 

 with other cables or land lines through automatic repeaters to avoid 

 the delay and expense introduced by manual methods of repetition. 



As the shape of the received signal is determined by the cable- 

 amplifier system and also by the character and amount of interference 

 present which cannot be eliminated by the distortion correction net- 

 works, the operating system must be able to take the partly corrected 

 signals delivered to it by the amplifier and accurately restore them to 

 the form in which they were originally transmitted before using them 

 to control the final recording mechanism. 



