. The Bell System technical journal . s. At the right of the chart are shown typical characteristics for NewYork-Washington (about 225 miles) two-wire cable circuits withvarious loadings. The now obsolete heavy-loaded system, H-245, gavean effective range of 1,400 cycles, the medium-heavy loaded or H-174gave 1,900 cycles while a new system which is being considered, calledB-88, will give about 2,700 cycles. (At the present time H-174 two- * The limiting frequencies are taken as those at which the loss is 10 db greaterthan the loss at 1,000 cycles. 32 487 488 BELL SYSTEM TECHNICAL JOURNAL wire
. The Bell System technical journal . s. At the right of the chart are shown typical characteristics for NewYork-Washington (about 225 miles) two-wire cable circuits withvarious loadings. The now obsolete heavy-loaded system, H-245, gavean effective range of 1,400 cycles, the medium-heavy loaded or H-174gave 1,900 cycles while a new system which is being considered, calledB-88, will give about 2,700 cycles. (At the present time H-174 two- * The limiting frequencies are taken as those at which the loss is 10 db greaterthan the loss at 1,000 cycles. 32 487 488 BELL SYSTEM TECHNICAL JOURNAL wire circuits are restricted to shorter lengths, the curve being givensimply for comparative purposes.) In addition to this matter of frequency band width, there has beenimprovement in the 1,000-cycle efficiency of long distance circuits andalso improvement with respect to noise and crosstalk. The originalloaded transcontinental circuit, for example, gave, during good weather. NEW YORK TOSAN FRANCISCO 165-MIL I OPEN-WIRENON-LOADED CARRIER. 2-WIRE LOADED CABLE —19 YORK-WASHINGTON 10 -I400CYCLES- 1 H-245 i H-174/ B-86 1f 1900 CYCLES07nn r*V(i re / J J / 7 / / T 5 , / \ \1 1 \ i 1 1111 0 \ ^ J. J /• / -5 1000 2000 CYCLES PER SECOND 3000 1000 2000 3000 CYCLES PER SECOND Fig. 1—Transmission-frequency characteiistics of representative types of telephone circuits. a 1,000-cycle transmission loss of about 20 db with a variation fromthis of at least 10 db during bad weather. The non-loaded circuit gaveabout 12 db during good weather with smaller variations. With bothof these circuits the noise was somewhat in excess of 1,000 noise carrier and cable systems compare very favorably with non-loadedvoice-frequency circuits in the matter of transmission loss and aremuch quieter. With the two-wire cable circuits shown, the H-245 circuit gave about12 db loss at 1,000 cycles, the H-174 circuit 10 db loss and it is ex-pected that the B-88 circuit will give about 9 db loss at 1,0
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