1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 2 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(94%,%2!0(G0G042!.3-)33)/.#/%8)34%.#%G0G0/ amended at Geneva, 1964 and 1980)1 Common views1.1 Channels with higher modulation rates (100 or 200 bauds) must be capable of being inserted in systems ofamp
2、litude-modulated 50-baud/120-Hz channels conforming to Recommendations concerning them respectively as wellas in systems of frequency-modulated 50-baud/120-Hz channels (conforming to Recommendation R.35). However, it ispreferable that these high-speed channels should, as far as possible, be placed i
3、n a frequency-modulated system(conforming to Recommendation R.35). However, 200-baud/360-Hz channels can be set up only on systemsestablished on bearer circuits having a spacing of 3 kHz.1.2 If there are 50-baud channels on a mixed system, the distortion limits for the 50-baud channels onhomogeneous
4、 50-baud channel systems will have to be respected; hence, 100-baud and 200-baud channel equipmentwill have to be designed to this end. If this is not possible, the power levels on the 100-baud and 200-baud channelswill have to be reduced.1.3 The 100- and 200-baud channels should have performances c
5、omparable to those that could be obtained in ahomogeneous system, as specified in Recommendations R.37, R.38 A, R.38 B, provided that the condition indicatedunder 1.2 above is respected. They should, in particular, satisfy 13a) of Recommendations R.37, R.38 A, or R.38 Brespectively.1.4 The mean powe
6、r transmitted to line at a point of zero relative level is normally dependent on the transmissioncharacteristics of the bearer circuit as follows:a) 50 W total for FMVFT aggregates carried on circuits complying with the limits specified in Annex A toRecommendation R.35;b) 135 W total for other circu
7、its and for AMVFT.The mean normal power for each channel should not exceed the values specified in Table 1/R.36, for cases a)and b) above.TABLE 1/R.36VFT channel power levelsVFT channel power level (W)RelevantVFT channel characteristicsBearercase a)Bearercase b)RecommendationModulation rate(bauds)Ba
8、ndwidth(Hz)Type ofmodulation2.04.0 a)8.0a)95.610.8 a)19.2 a)21.6 a)R.31R.35R.37R.38BR.38A5050100200200120120240360480AMFMFMFMFMa)Provided that the condition mentioned under 1.2 is respected.2 Fascicle VII.1 - Rec. R.362 Combined use of channels with 240-Hz spacing and channels with 120-Hz spacing2.1
9、 Channels with 240-Hz spacing should be installed in the following preferred order: 12 (if possible), 11, 10, 9,8,7, The channel numbers1)are in accordance with Recommendation R.37 (100-baud channels with 240-Hz spacing).3 Combined use of 200-baud channels with 360-Hz spacing and channels with 120-H
10、z or 240-Hz spacing3.1 The characteristics of these channels with high modulation rates are defined in Recommendations R.37 on100-baud channels with 240-Hz spacing and R.38 B on 200-baud channels with 360-Hz spacing.3.2 The 200-baud/360-Hz channels should be installed in the following preferred orde
11、r: 5, 4, 6, 3, 2, 1 instead ofthe corresponding 50-baud channels. The channel numbers1)are in accordance with Recommendation R.38 B.3.3 In combined systems using channels with three different modulation rates, the order indicated in 3.2 aboveshould be used in preference to that indicated in 2.1 abov
12、e.4 Combined use of 200-baud channels with 480-Hz spacing and channels with 120-Hz or 240-Hz spacing4.1 For a combination of channels with 240-Hz spacing and channels with 480-Hz spacing, the channels with480-Hz spacing should be installed in the following preferential order: 4, 3, 5, 2, 62).4.2 For
13、 a combination of channels with 120-Hz spacing and channels with 480-Hz spacing, the order indicated in 4.1 above is applicable.Note In cooperation with a system using 6-channel group modulation, the preferred order would be: 4, 3, 6 (ifpossible), 12).4.3 In combined systems using channels with thre
14、e different modulation rates, the order indicated in 4.1 aboveshould be used in preference to that indicated in 2.1 above._1)For the numbering of channels that has been adopted in the international services see Recommendation R.70 bis.2)For the numbering of channels that has been adopted in the international services see Recommendation R. 70 bis.
