. The Bell System technical journal . AL when the speed was 60 The marking and spacing frequencies of thetwo-source, one-source two-band, and frequency-shift arrangements were SIGNAL SPEED IN DOTS PER SECOND 25 30 35 40 46 50 55 60 65 2826 242220 1 T 1 1 1 1 1 1 / 1 / / y / / 16 / / / 1614 / / / 199801 SINGLE SIDEBAND: / / 12 (A) ZERO SPACING CARRIER-,^ (B) SPACING CARRIER J^ / / / ^^^ 6 DECIBELS BELOW-,^.^-^ / y 108 MARKING CARRIER/ ^1 / y > / r V. / ,- / i * / 1 ^^-{C) I955-V LINEAR ON-OFF 6 / . / ,^- WITHOUT CHANNEL FILTERS / / X>t- y J. 4 2 ,/^ —^^ < .^^^ 7 /-- ^ ^^ ^^ y 0
. The Bell System technical journal . AL when the speed was 60 The marking and spacing frequencies of thetwo-source, one-source two-band, and frequency-shift arrangements were SIGNAL SPEED IN DOTS PER SECOND 25 30 35 40 46 50 55 60 65 2826 242220 1 T 1 1 1 1 1 1 / 1 / / y / / 16 / / / 1614 / / / 199801 SINGLE SIDEBAND: / / 12 (A) ZERO SPACING CARRIER-,^ (B) SPACING CARRIER J^ / / / ^^^ 6 DECIBELS BELOW-,^.^-^ / y 108 MARKING CARRIER/ ^1 / y > / r V. / ,- / i * / 1 ^^-{C) I955-V LINEAR ON-OFF 6 / . / ,^- WITHOUT CHANNEL FILTERS / / X>t- y J. 4 2 ,/^ —^^ < .^^^ 7 /-- ^ ^^ ^^ y 0 90 100 no 120 130 140 150 SIGNAL SPEED IN WORDS PER MINUTE Fig. 7—Distortion vs. speed characteristics of single-sideband arrangements andon-off arrangement without channel filters. both varied by the same amount from their normal values without changingtheir relative separation. It is evident from Fig. 8 that the arrangementsranked in the following order as regards the permissible carrier frequency CARRIER TELEGR^iPH METHODS 503. a3d Ni NOiiaoxsia nvioi indv^ixviai 504 BELL SYSTEM TECHNICAL JOURNAL variations when the distortion was about 20 per cent: two-source withoutHmiter on a par with two-source with Umiter, one-source two-band withlimiter, level compensated on-off, linear on-off, frequency-shift, and single-sideband with — 6 db spacing carrier. This comparison includes only thosearrangements using the same type of filter (with loss per curve A, Fig. 1).Figure 9 shows the results obtained by making similar tests on the wide-bandfrequency-shift (with loss per curve B, Fig. 1) and on the narrow-band two-
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