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BELL SYSTEM TECHNICAL JOURNAL 



4. Transmisson Equivalent — When the balance tests have been 

 completed, a measurement of the overall transmission loss is 

 made between the terminal stations. 



5. Talking Test — In order that the quality and noIuiiu' of trans- 

 mission from a service standpoint may be determined, a talking 

 test is made over the entire circuit using standard subscriber 

 sets at each end. 



6. Signaling — As a tinal check, ringing tests are made over the 

 circuit in both directions to insure that satisfactor\- signaling 

 is being obtained. 



This testing routine has been perfected to such an extent that the 

 circuit need not be kept out of service for more than about lo minutes 

 even in the case of the longest circuits. Results of measurements 

 over the period of a year on the Chicago-San Francisco circuit are 

 shown in Fig. 11. The overall transmission measurements, which 



Kig. 1 1— -Monthly Ranges in Temperature and Repeater Gain on the Chicago-San 

 Francisco Circuit 



are shown as variations from normal, were made at the conclusion of 

 semi-weekly tests and after any necessary adjustment in repeater 

 amplification had been made to compensate for changes in attenua- 

 tion loss. The other curves show the average temperature along 



