1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%2.!4)/.!,G0G0!.!,/5%G0G0#!22)%2G0G03934%-3%.%2!,G0G0#(!2!#4%2)34)#3G0G0/&G0G0).4%2.!4)/.!,#!22)%2G0G04%,%0(/.%G0G03934%-3G0G0/.2!$)/G0G13G02%,!9G0G0/2G0G03!4%,)4%G0G0,).+3G0G0!.$).4%2#/%#4)/.G0G07)4(G0G0-%4
2、!,)#G0G0,).%3-%4(/$3G0G0/&G0G0).4%2#/%#4)/.)45G134G0G0RecommendationG0G0 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation G.421 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 differe
3、nt from the Blue Book version, thecontents of the file are identical 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 op
4、erating agency. ITU 1988, 1993All rights reserved. No part of 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.421 1Recommendation G.421Fascicl
5、e III.2 - Rec. G.421METHODS OF INTERCONNECTIONIn studying the interconnection of radio-relay systems, either with one another or with systems on metallic lines,distinction should be made between the following cases:1 Interconnection at audio-frequenciesThis is the normal method, at the present stage
6、 of technical development, whenever a radio-relay system usingtime-division multiplex is involved1). Operational requirements may be such that it is also necessary in the case offrequency-division multiplex and of systems on metallic lines.2 Interconnection by through-group connectionWith present te
7、chnical development only radio-relay links having frequency-division multiplex can providetelephone channels assembled in groups, supergroups, mastergroups, and in some cases, supermastergroups or in15-supergroup assemblies1).Interconnection between a radio-relay system using frequency-division mult
8、iplex and a system on metallic linescan be carried out by through-connection of groups, supergroups, etc. This is possible because, according to theprovisions of Recommendation G.423, the baseband of such a radio-relay system corresponds to that of a certain numberof groups, supergroups or mastergro
9、ups transmitted to line in coaxial cable systems. These groups can be obtained fromthe relevant basic frequency band by means of translating equipment already standardized for cable systems inaccordance with CCITT Recommendations.Through-connection should then be carried out in accordance with Recom
10、mendation G.242, via the basicfrequency range for groups (12 to 60 kHz or 60 to 108 kHz), for supergroups (312-552 kHz), etc. (see RecommendationG.211 and Figure 1/G.211, in particular).3 Interconnection in the basebandThe baseband of frequency-division multiplex radio-relay links is the same as the
11、 frequency band of carriersystems on metallic lines, and interconnection in this band is possible in the conditions specified in RecommendationG.423.Direct through-connection may also be made in this baseband, between metallic-line systems and radio-relaylinks, in accordance with the general provisi
12、ons of Recommendation G.242, 7.For time-division multiplex radio-relay links, the baseband had been defined by the CCIR as “the series ofmodulated pulses before it is applied to the carrier frequency“. Interconnection in the baseband of time-divisionradio-relay links with metallic-line systems has n
13、ot yet been studied._1)Note from the Secretariat - This text relates to FDM radio-relay systems which were the subject ofRecommendations G.432 and G.443 (now both deleted). As far as PCM radio-relay systems are concerned see CCIRReport 378 1.2 Fascicle III.2 - Rec. G.4214 Interconnection at intermediate frequencies5 Interconnection at radio frequencies 4 and 5 concern cases arising only in the interconnection of two radio-relay systems and are the concern ofthe CCIR.Reference1 CCIR Report Characteristics of digital radio-relay systems, Vol. IX, Report 378, Dubrovnik, 1986.
