TEJJiTYFEU-RlTKR KXCIIANGE SYSTEM 511 



the sccoikI half of the subscriber hues in u second Hnc-ni) of s\\ itchboard 

 in which they are equipped with answering lamps. The first half of 

 the lines also are multipled in this line-up but on a callinj^-only basis; 

 that is, without lamps. With this arrangement, calls originated by 

 the first half of the subscribers are answered in the first line of switch- 

 board, and those originated by the second half are answered in the 

 second line. Any operator may complete a connection to any line 

 eis there is a full multiple of jacks in both boards. In the second 

 line-up the two halves of the multiple are inverted as to location in 

 order to place the lines with answering lamps within easy reach. 

 The upper line of Fig. 3 shows the capacities obtainable with this 

 arrangement. It may be seen that, with a ratio of 7.5 subscriber lines 

 to one inter-toll trunk, a subscriber line capacity of approximately 

 3,800 is possible. It was necessary, however, to reduce this to 3,600 

 lines in order to obtain a division in a multiple of 600 lines to simplify 

 the numbering of the jacks. With this arrangement 300 lines are 

 provided in each panel without answering lamps and 300 lines with 

 answering lamps. 



This multiple arrangement is illustrated in Fig. 4, which shows 

 schematically the cabling for the first half of the subscriber multiple 

 (lines to 1,799). It may be noted that a third line of switchboard, 

 the inward and through board, is provided. Experience has shown 

 that the most efificient operation is obtained if the inward and through 

 trafific is segregated when the switchboard grows to 30 or more posi- 

 tions. As the subscriber multiple is used here for calling purposes 

 only, the answering lamps may be omitted from the entire subscriber 

 multiple, thus making additional space available for increased inter-toll 

 trunk capacity as discussed in the following. The subscriber lines are 

 cabled from the main distributing frame (MDF) to the relay equipment 

 and from there to the TWX intermediate distributing frame. Here 

 cross connections are provided to permit the assignment of any sub- 

 scriber line relay equipment to any multiple jack for flexibility in 

 assigning numbers. The distributing frame terminal strip also serves 

 as a doubling-up point for the cable to the switchboards. 



A somewhat similar arrangement used for the inter-toll trunk mul- 

 tiple is shown schematically in Fig. 5. The standard telegraph line 

 facilities and terminating repeaters designed for private line service 

 are used for the TWX trunks. Connections to these trunks are made 

 at the test board distributing frame and the trunks are cabled to the 

 TWX distributing frame. Here arrangements are provided for in- 

 serting a single-line repeater, which is necessary for converting the 

 positive and negative 130-volt signals to positive and negative 48-volt 



