1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%2.!4)/.!,G0G0!.!,/5%G0G0#!22)%2G0G03934%-3%.%2!,G0G0#(!2!#4%2)34)#3G0G0#/-/.G0G04/G0G0!,!.!,/5%G0G0#!22)%2G0G13G042!.3-)33)/.G0G03934%-32%#/-%.$!4)/.3G0G0#/.#%2.).42!.3,!4).G0G0%15)0-%.43)45G134G0G0Recommen
2、dationG0G0 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation G.233 was published in Fascicle III.2 of the Blue Book. This file is an extract fromthe Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are ide
3、ntical to the Blue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of
4、this publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle III.2 - Rec. G.233 1Recommendation G.233Fascicle III.2 - Rec. G.233RECOMMENDATIONS CONCERNING TRANSLATING EQU
5、IPMENTS(amended at Geneva, 1964; further amended)This Recommendation concerns translating equipments with the exception of:- channel-translating equipment, in respect of which Recommendations G.232, G.234 1 and G.235 shouldbe consulted;- equipment for translation into the line-frequency band; the Re
6、commendations relating to the various linesystems should be consulted.1 Translating procedureThe procedures whereby the translating equipments defined in Recommendation G.211 translate basic groups,supergroups and mastergroups or a basic 15-supermastergroup assembly (No. 1) are represented by the fo
7、llowingfigures:1) Figure 1/G.233 for group-translating equipments (procedures 1 and 2);2) Figure 2/G.233 for supergroup-translating equipments (procedure 1);3) Figure 3/G.233 for mastergroup-translating equipments (procedure 1);4) Figure 4/G.233 for supergroup-translating equipments (procedure 2);5)
8、 Figure 5/G.233 for translating equipments for basic 15-supergroup assembly (No. 1) (procedure 2).Note - Equipments 4 and 5 above are peculiar to procedure 2 described in Recommendation G.211. Theconditions in which this procedure is used are described in that Recommendation.FIGURE 1/G.233Constituti
9、on of the basic supergroup2 Fascicle III.2 - Rec. G.233FIGURE 2/G.233Constitution of the basic mastergroupFIGURE 3/G.233Constitution of the basic supermastergroupFascicle III.2 - Rec. G.233 3FIGURE 4/G.233Constitution of the basic 15-supergroup assembly4 Fascicle III.2 - Rec. G.233FIGURE 5/G.233Cons
10、titution of 15-supergroup assembly No. 3Note to Figures 1/G.233 to 5/G.233 - The virtual carrier frequencies shown in Figures 1/G.233 to 5/G.233 will normally be thefrequencies actually used. However, they are all shown as virtual frequencies to allow for the possibility of using cheaper ways ofcons
11、tituting basic groups, supergroups, etc., in the future.2 Adjustment of level at basic group-frequency pointsWhen a group passes through different carrier systems, it is necessary to provide for an adjustment of level: forexample, between the limits of about 4 dB, wherever the group passes through t
12、he basic frequency range.3 Relative power levels at group distribution frames and supergroup distribution framesAlthough the standardization of the relative power levels at group distribution frames and supergroupdistribution frames would be desirable to facilitate the setting-up and maintenance of
13、international carrier systems androuting changes of groups or supergroups from one system to another, it was not possible before the Plenary Assemblyof 1972 to recommend such a standardization internationally, because of the diversity of carrier systems already inservice. Table 1/G.233 shows, for in
14、formation, the level used by different Administrations.The CCITT concerned itself solely with recommending preferred values for countries which have not yet fixedthese values for their national networks. Accordingly:- a relative sending level of -36 dBr is recommended at group and supergroup distrib
15、ution frames;- for reception, it is recommended that a choice be made between -23 dBr and -30 dBr;- the following values are recommended for the impedance:150 ohms balanced for group distribution frames,75 ohms unbalanced for supergroup distribution frames.Fascicle III.2 - Rec. G.233 5TABLE 1/G.233R
16、elative power levels at the basic group and supergroup distribution framesin the carrier systems of various AdministrationsCountryRelative power level atgroup distribution frameImpedance at groupRelative power level atsupergroup distributionframeImpedanceatsupergroupTransmit(dBr)Receive(dBr)distribu
17、tion frameTransmit(dBr)Receive(dBr)distributionframeFederal Republicof Germany-36 -30150 ohms,balanced-35 -3075 ohms,unbalancedAustraliaDenmark a)System 1 -36.5 -30.5150 ohms,symetrique-35 -30.5 id.System 2 -42 -5135 ohms,balanced-35 -30 id.Austria -37-36-8-3075 ohms,unbalanced150 ohmsbalanced-35 -3
18、0 id.Belgium -37 -8 150 ohms,balanced-35 -30 id.Peoples Republicof Bulgaria-36 -23 150 ohms,balanced-36 -23 id.Spain, Ireland,New Zealand, Norway,United Kingdom-37 -8 150 ohms,unbalanced-35 -30 id.USA(American Telephone andTelegraph Company)-42 -5 135 ohms,balanced-25 -28 id.France -33 -15 150 ohms,
19、balanced-45 -35 id.Hungary, Italy, Netherlands -37 -30 150 ohms,balanced-35 -30 id.India -36.5 -30.4 150 ohms,balanced-34.8 -30.4 id.Japan (NipponTelegraph and TelephonePublic Corporation)-36 -18 75 ohms,balanced-29 -29 id.Mexico(Telfonos de Mxico)-47 -10 150 ohms,balanced-47 -24 id.6 Fascicle III.2
20、 - Rec. G.233TABLE 1/G.233 (continued)Peoples Republicof Poland-36 -23 150 ohms,balanced-36 -23 id.German Democratic Republic -36 -23 150 ohms,balanced-36 -23 id.Sweden -35 -30 id.Switzerland -36.5 -30.5 75 ohms,unbalanced-35 -26 id.USSR -36 -23 150 ohms,balanced-36 -23 id.a)System 1 only.4 Relative
21、 power levels at mastergroup distribution framesThe relative power levels at mastergroup distribution frames (see Figure 6/G.233) should be adjusted to thefollowing values:- transmit: -36 dBr,- receive: -23 dBr,across a 75-ohm impedance, unbalanced to earth.FIGURE 6/G.233Relative levels at mastergro
22、up distribution frameFascicle III.2 - Rec. G.233 75 Relative levels at supermastergroup distribution framesRelative power levels at supermastergroup distribution frames should be adjusted to the following values:- transmit: -33 dBr,- receive: -25 dBr,across a 75-ohm impedance, unbalanced to earth.6
23、Relative levels at the distribution frame of 15-supergroup assembly (No. 1)The relative power levels at the 15-supergroup assembly distribution frame should be adjusted to the followingvalues:- send: -33 dBr,- receive: -25 or -33 dBr,across a 75-ohm impedance, unbalanced to earth.7 Return lossIn rel
24、ation to the nominal impedance, the return loss at the input and output of the translating equipment ofsupergroups, mastergroups, supermastergroups and 15-supergroup assemblies should not be lower than 20 dB in thewanted frequency band for both directions (send and receive) of transmission.With resp
25、ect to the group translating equipment, the same limit applies at the high-frequency side; at the low-frequency side, it is also valid except in those areas in the vicinity of the group and supergroup pilots such as:- the band 103.7-104.6 kHz of group 3 when there is a stop filter for the 411.920 kH
26、z pilot;- the band 63.7-64.6 kHz of group 5 when there is a stop filter for the 547.920 kHz pilot.The above limits relate to the intrinsic return loss, i.e., that obtained when the cords connecting the measuringapparatus to the equipment are as short as possible. In view of the station cabling encou
27、ntered in practice, the return lossrecorded at the distribution frame of groups, supergroups, etc., may differ from the intrinsic return loss. This factorshould be taken into account in designing and establishing the links.8 NoiseRecommendation G.222, 4 gives information on the noise produced by gro
28、up, supergroup, mastergroup and15-supergroup assembly translating equipment.9 Interference related to supergroup reference pilotInterference from, or with, supergroup reference pilots may be avoided by taking suitable precautions inchannel terminal equipments or group-translating equipment (see Reco
29、mmendation G.232, 13.2 and theRecommendation cited in 2).9.1 Pilots at 411.860 and 411.920 kHz9.1.1 For the protection of pilots at a through-connection point (see Recommendation G.243), group 3 should at thereceive end of a supergroup link be through-connected without demodulation, for example to a
30、nother supergroup link;the modulating equipment for group 3 should present an attenuation of at least 20 dB at the frequency of the supergrouppilot.8 Fascicle III.2 - Rec. G.2339.1.2 Moreover, when an Administration wishes to route 8- or 12-channel groups free between one supergroup linkand another
31、with no restrictions on routing of group 3, then the group 3 modulating and group 3 demodulatingequipment should each provide in all cases at least 20 dB suppression at the frequency of the supergroup reference pilot.9.2 Pilot at 547.920 kHzIf this pilot is used in a supergroup transmitting five gro
32、ups (regardless of the use made of these groups) and nota wideband signal (for data, etc.) occupying most of the frequency band, the arrangements mentioned in 9.1 above forthe group 3 equipment should be adopted in the modulating and demodulating equipment of group 5.10 Accuracy of carrier frequenci
33、esSee Recommendation G.225, 1).11 Carrier leaks11.1 The carrier leak at the transmit side of a modulation stage should not exceed:-47 dBm0 for group modulation,-50 dBm0 for supergroup modulation,-45 dBm0 for mastergroup modulation,-50 dBm0 for supermastergroup modulation and 15-supergroup assembly m
34、odulation,-30 dBm0 for 15-supergroup assemblies Nos. 2 and 3 on 12-MHz and 60-MHz systems, and for the firstmodulation stage of 15-supergroup modulation on 60-MHz systems, since in this case the carrier leaksfall into bands of frequencies not used for traffic.11.2 Higher levels of carrier leaks can
35、be tolerated at the output of a modulation stage at the receive side, providedno interference with adjacent groups, etc. occurs (e.g. by way of backward carrier leak, etc.)11.3 In the case of sound-programme transmission according to the Recommendation cited in 3 certain channelcarrier leaks, pregro
36、up carrier leaks etc. falling in adjacent groups may cause excessive interference. In order to meetRecommendation cited in 4 the level of such leaks, measured at the supergroup distribution frame or an equivalentpoint, should not be higher than the values indicated below:-75 dBm0 in the frequency ra
37、nges 73-82 kHz and 86-95 kHz,-55 dBm0 at 67 kHz and 101 kHz.In the frequency bands 67-73 kHz and 95-101 kHz the requirements are based on straight lines (linearfrequency and dB scales) connecting the limits indicated above.Note 1 - It is recognized that there are several possibilities of meeting thi
38、s recommended limit, such asallocating the necessary attenuation wholly or partly to the channel or group translating equipment respectively, to insertspecial filters at the group distribution frame, or by selection of groups.Note 2 - The above limit is applicable to the transmit side only.Note 3 -
39、The 7 dB margin between the Recommendation cited in 4 and 11.3 above allows for cumulation onthe group links involved.11.4 In the case of 3-kHz spaced channels, the following recommendations apply:When a baseband carries 3-kHz or a mixture of 3- and 4-kHz channels, the level of each carrier leak sho
40、uld notexceed the value given in Table 2/G.233 (limits apply to transmit path only).Fascicle III.2 - Rec. G.233 9TABLE 2/G.233Carrier leak of:Group and supergroupcarrying 3 kHz channelsRecommended limit,dBm0Groups 1, 2, and 3 ofany supergroupSame supergroup 60a)Groups 4 and 5 ofsupergroups 4 to 16Gr
41、oups 1 and 2 respectively of the adjacent lowersupergroup (i.e. supergroup 3 to 15)73a),b)Supergroup 1 Supergroup 360a),b)Supergroups 3 to 14 Group 4 of supergroups 5 to 16 respectively73a)a)Based on Recommendation G.235 relating to subgroup carrier leaks.b)Based on the assumption that the interfere
42、nce limit per single frequency is -73 dBm0p.The filters of the supergroup translating equipment may contribute to the suppression of the group 4 and 5carrier leaks.Special attention is also necessary to avoid backward carrier leaks in the demodulation stage that may result in aproduct falling into a
43、 3-kHz channel in either the group or supergroup demodulation stage.Note - No allowance has been given for cumulation. The effects of cumulation are offset at least in part by thenoise masking effect of long interconnected sections that commonly accompany the use of 3-kHz channel equipments.12 Go-to
44、-return crosstalkThe following limits are recommended for crosstalk ratios (single frequency measurements) for group andhigher order translating equipments; they will apply to both the low and high frequency sides:- group translation: 80 dB;- higher order translation stages: 85 dB.Note - On the basi
45、s of telephony considerations alone, a limit of 80 dB would have been proposed for alltranslation stages; this would also have sufficed to meet the recommended limit for intelligible crosstalk betweenprogramme circuits (74 dB in Recommendation J.21 5) in networks where programme circuits are systema
46、ticallyequipped with compandors. However, importance was attached to adopting a single requirement for each translationstage which would suffice for the most demanding network conditions to be encountered.10 Fascicle III.2 - Rec. G.23313 Group-delay distortion13.1 Group translating equipmentIt is re
47、commended that the limits in Figure 7/G.233 for the group-delay distortion (relative to the value at84 kHz) should not be exceeded by a group translating equipment consisting of a pair of group transmitting andreceiving equipments. The given values are applicable to groups 2, 3 and 4 (without additi
48、onal pilot stop filters). Groups1 and 5 are excluded due to additional distortions caused by various sources (pilot stop filters, position at the end of thesupergroup band, etc.); group 3 may be excluded, when the supergroup pilot 411.92 kHz or 411.86 kHz is used.Note - The range of measured values
49、on modern equipments is indicated in Supplement 17 at the end of thisfascicle.FIGURE 7/G.23313.2 Supergroup translating equipmentIt is recommended that the limits in Figure 8/G.233 for the group-delay distortion (relative to the value at412 kHz) should not be exceeded by a supergroup translating equipment consisting of a pair of supergroup transmittingand receiving equipments. The given values are not applicable to supergroups 1 and 3. Depending on the design ofsupergroup translating equipment this restriction may also ap
