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(90/4(%4)#!,G0G02%&%2%.#%G0G0#)2#5)43G0G0&/2&2%15%.#9G0G13G0$)6)3)/.G0G0-5,4)0,%82!$)/G0G13G02%,!9G0G03934%-3)45G134G0G0RecommendationG0G0 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation G.431 was published in Fascicle III.2 the Blue Book. This file is an extract from theBlue B
3、ook. While the presentation and layout of the text might be slightly different 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 concis
4、eness to indicate both atelecommunication administration and a recognized operating 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 w
5、riting from the ITU.Fascicle III.2 - Rec. G.431 1Recommendation G.431Fascicle III.2 - Rec. G.431HYPOTHETICAL REFERENCE CIRCUITS FOR FREQUENCY-DIVISIONMULTIPLEX RADIO-RELAY SYSTEMS1)(modified at Geneva, 1964)1 Hypothetical reference circuit for radio-relay systems providing 12 to 60 telephone channel
6、sThe hypothetical reference circuit defined in CCIR Recommendation 391 1, for frequency-division multiplexradio-relay systems with a capacity of 12 to 60 telephone channels per radio channel, has a length of 2500 km.This circuit has for each direction of transmission:- three pairs of channel modulat
7、ors,- six pairs of group modulators,- six pairs of supergroup modulators,it being understood that a “pair of modulators“ comprises a modulator and a demodulator (see Figure 1/G.431).Note - The meaning of the symbols used in this Figure is given in the Preliminary notes to this fascicle.FIGURE 1/G.43
8、1Hypothetical reference circuit for frequency-division multiplex radio-relay systemswith a capacity of 12 to 60 telephone channels per radio channel_1)This Recommendation applies only to line-of-sight or near line-of-sight radio-relay systems.2 Fascicle III.2 - Rec. G.431This circuit also has six se
9、ts of radio modulators and demodulators, for each direction of transmission, so thatthey divide the circuit into six homogeneous sections of equal length (see Recommendation G.322).2 Hypothetical reference circuit for radio-relay systems providing more than 60 telephone channelsThe hypothetical refe
10、rence circuit defined in CCIR Recommendation 392 2, for frequency-division multiplexradio-relay systems with a capacity of more than 60 telephone channels per radio channel, has a length of 2500 km.This circuit has for each direction of transmission:- three pairs of channel modulators,- six pairs of
11、 group modulators,- nine pairs of supergroup modulators,it being understood that a “pair of modulators“ comprises a modulator and a demodulator (see Figure 2/G.431).Note - The meaning of the symbols used in this Figure is given in the Preliminary notes to this fascicle.FIGURE 2/G.431Hypothetical ref
12、erence circuit for frequency-division multiplex radio-relay systemswith more than 60 telephone channels per radio channelThis circuit also has nine sets of radio modulators and demodulators for each direction of transmission so thatthey divide the circuit into nine homogeneous sections of equal leng
13、th (see Recommendation G.322).References1 CCIR Recommendation Hypothetical reference circuit for radio-relay systems for telephony using frequency-division multiplex with a capacity of 12 to 60 telephone channels, Vol. IX, Rec. 391, Dubrovnik, 1986.2 CCIR Recommendation Hypothetical reference circuit for radio-relay systems for telephony using frequency-division multiplex with a capacity of more than 60 telephone channels, Vol. IX, Rec. 392, Dubrovnik, 1986.
