504 



BELL SYSTEM TECHNICAL JOURNAL 



At the present time this system of voice frequency signaling is 

 empIo\'eci for regular use on the Chicago-Los Angeles circuit and a 

 few others. The s\stem employing 135-cycle current alternately 

 relayed and am|)lified at repeater points also is installed on these 

 circuits and prol)al)l\' w ill \>v retained for emergency use and to permit 

 temporary changes in circuit layout. 



Maintenance. The continuity of the many important services 

 routed over the facilities used in making up these long circuits is 

 dependent upon continuous and efficient maintenance methods and 

 performance. Coordination of the work of the different offices is 

 most essential in order to obtain best results, especially on the longer 

 direct circuits and on those built up by the connecting together of 

 several circuits, as there are a large number of variable factors. To 

 assist in obtaining best results, accurate records of the circuit make-up 



TOLL CIRCUIT LAYOUT Ri^CORD 



Chloago ^J ItOLtogslsa 



Fig. 10 



from end to end, including a complete description of the types of 

 equipnu'iu and transmission data are prepared and furnished to the 

 terminal and repeater stations. These are made on cards of con- 

 \enient size, as illustrated by Fig. 10, which is one of the five cards 

 for the Chicago-Los Angeles circuit. To insure proper functioning 

 of the circuit and satisfactory overall transmission and signaling one 

 of the terminal offices of each circuit is designated as the controlling 

 office for that circuit and is responsible for the direction and super- 



