. The Bell System technical journal . Figs. 4 and5, high and low group assignments are used for the two directions ofeach four-channel system. A repeater is provided for each four-channelsystem and, except in the case of OA, the high and low frequency groupsare frogged at each repeater, as in the N system. Figure (5 shows a block diagram of a complete 0 system. On this figure,and in general on other figures showing filters, a letter code is assignedto designate the kind of filter, with a subscript letter to indicate theparticular system in which the filter is used. The several filter designa-t
. The Bell System technical journal . Figs. 4 and5, high and low group assignments are used for the two directions ofeach four-channel system. A repeater is provided for each four-channelsystem and, except in the case of OA, the high and low frequency groupsare frogged at each repeater, as in the N system. Figure (5 shows a block diagram of a complete 0 system. On this figure,and in general on other figures showing filters, a letter code is assignedto designate the kind of filter, with a subscript letter to indicate theparticular system in which the filter is used. The several filter designa-tions and number codes are collected for reference in Table I. Much ofthe apparent complexity of the system, particularly as regards filters,arises out of the use of a single pair for both directions of complexity is occasioned by the requirement that a completecomplement of O systems will not always be provided. For example,OB, OC, and OD systems may be used above an existing C system, orsimilar systems. O 100 -. ■-TERMINAL Fig. 5—^Type-0 modulation plan. 696 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1952 lotj -Jx: LU^ ^IS? 1/1 -I 2 UJ 0 52 ■7 1- :£. > Q- , a. UJ 0 3 tOZ 1- 0 < u
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
