THE L3 SYSTEM — DESIGN 817 



regulator is mounted on the other. This requires access to both sides of 

 the bay, but results in an overall saving in the number of bays and over- 

 all floor space. 



All of the transmission components and a heater and bias supply unit 

 are mounted in one 7' bay for each coaxial. The plate and primary ac 

 power for two of these bays is mounted in another 7' bay. 



3.33 Equalizing Main Repeater 



This repeater contains exactly the same transmission equipment as 

 the equalizing auxiliary repeater (see Table IV). It differs in the func- 

 tion noted before, that is, it is equipped to feed power to the cable. 

 The equipment to perform this function will be described later in the 

 paper. Since the repeater can feed power to the cable it can also supply 

 the power for its own operation. This power is derived from the primary 

 ac supply used for the line by means of conventional metallic rectifiers 

 for dc circuits and transformers for the ac heater supplies. These power 

 supplies are not a part of the power loop containing auxiliary repeaters, 

 so no special arrangements are required to obtain good waveform or 

 high power factor. 



The equipment arrangement uses the same units as the equalizing 

 auxiliary repeater, but here conventional ll'-6'' frames are used. 



3.34 Switching Main Repeater 



Usually, this type of repeater is supplied at the point where circuits 

 are dropped or terminated. In order to permit switching from a working 

 line to a spare line in case of trouble, see Section 3.4, more complex 

 equalization is required so that the Knes will be as nearly alike as pos- 

 sible when the switch takes place. Furthermore, the signal delivered 

 to the terminal must meet equalization limits that will result in a satis- 

 factory grade of service. 



Where the repeater is part of a system required to transmit only 

 message circuits the basic equipment shown in Table IV (telephone 

 only case) is required. In addition to these units facilites are provided 

 which indicate and alarm pilot levels and provide for patching and other 

 maintenance arrangements. Since this repeater always feeds power to 

 the cable it uses the same power arrangements as the equalizing main 

 repeater. 



When the system is being used for the combined telephone and tele- 

 vision signal this repeater is the same as the "all telephone system" 

 repeater except that it has additional equalization equipment to adjust 



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