508 



BELL SYSTEM TECHNICAL JOURNAL 



The number of cords per operator is dependent on the average time 

 required to set up and disconnect each call (known as the average 

 work time per call) and the average communication time per call. 

 Whereas the former can be forecast quite accurately by the operating 

 characteristics of the circuits, the latter is dependent on the com- 

 mercial application of the service. To insure the provision of an 

 adequate number of cords it was necessary to allow for the longest 

 average communication time which could be reasonably anticipated. 

 The analysis of the average work time per call together with the fore- 

 cast communication time resulted in the requirement being set up for 

 a maximum of 18 cords per operator. 



Fig. 2 — Keyshelf arrangement of No. 1 Teletypewriter Switchboard. 



With the requirement for the position equipment established at 18 

 cords (and one teletypewriter for communication purposes), the 

 width of the position was determined to be approximately 34 inches, or 

 the width of four panels of the jack field, each panel being 8| inches in 

 width. The division into an even multiple of panels is for construc- 

 tional purposes, to separate the switchboard into sections for manu- 

 facturing. It was, however, necessary to adopt a new type of keyshelf 

 construction, shown in Fig. 2, to provide for the operator's tele- 

 typewriter. 



Because of its large size, the teletypewriter was located as low as 

 possible to minimize blocking the jack field. This required the pro- 



