510 



BELL SYSTEM TECHNICAL JOURNAL 



The lower line of Fig. 3 shows the inter-toll trunk and subscriber 

 line capacities obtainable within the permissible reach limits on a 6- 

 panel multiple basis where the complete subscriber multiple is equipped 

 with answering lamps. The capacity shown is based on various 

 ratios of subscriber lines to inter-toll trunks. Because of the essentially 

 toll character of the teletypewriter exchange service, it was anticipated 

 that there would be a high ratio of inter-toll trunks to subscriber lines 

 and comparatively little local traffic. The traffic studies indicated that 

 the average ratio would be in the order of seven or eight subscriber lines 



4000 



a. 3600 

 tlJ 



CD 



a. 



u 



<i> 3200 



CD 



^ 2800 

 a. 



(Q 



2 



2 2400 



t 2000 



1600 



1200 



4 6 8 10 12 14 16 



RATIO OF SUBSCRIBER LINES TO INTER-TOLL TRUNKS 



20 



Fig. 3 — Curves showing variation of subscriber line capacity for No. 1 Teletype- 

 writer Switchboard. ^4— Inverted multiple. B- — Conventional multiple. 



to one trunk. It may be seen from Fig. 2) that, with this ratio, a 

 capacity of only 2,200 subscriber lines is obtainable with the entire 

 multiple equipped with answ'ering lamps. 



By providing answering lamps for only the first half of the sub- 

 scriber lines and installing the second half without answering lamps in 

 the upper portion, the total space for a given number of lines can be 

 reduced and advantage taken of the additional space afforded by the 

 34-inch vertical reach permissible for calling multiple. This arrange- 

 ment, known as the inverted multiple, provides answering facilities for 



