LONG DISTANCE TELEPHONE CIRCUITS 533 



TABLE II 

 Transmission Standards 

 Bell System C. C. I. 



Number of Regional Centers ^8 Number of European National Outlets 



—29 



NIsT LOSS 



Circuits Between Regional Centers International Circuits 



(On effective transmission basis) (Based on 800-cycle transmission 



equivalent) 



Future Plant Future Plant 



Terminating Switched Terminating 



or Switched Business 



Two-Wire 8.7 db 



Four- Wire 6.9 db 



Existing Plant Existing Plant 



9.0-1 1 .0 3 .0-5 db Two- Wire U .3 db 



Four- Wire 9.6 db 



MAXIMUM OVERALL NET LOSS BETWEEN SUBSCRIBERsf 



Regional Center Transmitting National Transmitting Loss. . . 17 db 



Loss 16 db National Receiving Loss 1 1 db 



Regional Center Receiving Loss 12 db International Circuit 7-11 ^^ 



Circuit Between Regional Cen- 



ters (Via Net Loss) 3-5 db Total 35-39 db 



Total 31-33 db 



FREQUENCY BAND WIDTH 



250 to 2750 cycles 300 to 2400 cycles 



Loss at extreme frequencies 10 db greater Loss at extreme frequencies 8.7 db 

 than at 1000 cycles. greater than at 800 cycles. 



For narrower bands the effective trans- 

 mission equivalent reflects the effect 

 on transmission of band width. 



DELAY DISTORTION 



Direct circuit connection (terminal cir- Overall Connectioti 



cuit) — -20 milliseconds. 30 milliseconds as the difference between 



Via circuits (in switched connections) the time of propagation for the highest 



10 milliseconds. frequency effectively transmitted and 



(Differences between 1000 cycle delay the time of propagation for 800 cycles. 



and the highest frequency effectively 



transmitted.) 



NON-LINEAR DISTORTION 



No fixed limits at present on message No fixed limits at present on message 



circuits but consideration is being circuits but consideration- is being 



given to methods of measuring and given to methods of measuring and 



evaluating the impairment due to this evaluating the impairment due to this 



effect. effect. 



* Via net loss is the loss which the circuit contributes to an overall connection 

 when switched to toll lines at both ends. 



t The regional center and national outlet transmitting and receiving losses are 

 the maximum losses between the most distant subscriber in the particular area 

 served by the regional center or national outlet and the particular regional center 

 or national outlet. 



