ITU-T G.343-1988 1.2/4.4mm标准同轴电缆线对上的4 M Hz系统 4 MHz systems on standardized 1.2/4.4 mm coaxial cable pairs

pdf标准 ITU-T G.343-1988 1.2/4.4mm标准同轴电缆线对上的4 M Hz系统 4 MHz systems on standardized 1.2/4.4 mm coaxial cable pairs

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ITU-T G.343-1988 1.2/4.4mm标准同轴电缆线对上的4 M Hz系统 4 MHz systems on standardized 1.2/4.4 mm coaxial cable pairs  第 1 页 ITU-T G.343-1988 1.2/4.4mm标准同轴电缆线对上的4 M Hz系统 4 MHz systems on standardized 1.2/4.4 mm coaxial cable pairs  第 2 页 ITU-T G.343-1988 1.2/4.4mm标准同轴电缆线对上的4 M Hz系统 4 MHz systems on standardized 1.2/4.4 mm coaxial cable pairs  第 3 页 ITU-T G.343-1988 1.2/4.4mm标准同轴电缆线对上的4 M Hz系统 4 MHz systems on standardized 1.2/4.4 mm coaxial cable pairs  第 4 页 ITU-T G.343-1988 1.2/4.4mm标准同轴电缆线对上的4 M Hz系统 4 MHz systems on standardized 1.2/4.4 mm coaxial cable pairs  第 5 页
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INTERNATIONAL TELECOMMUNICATION UNION )45 4 ' TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU ).4%2.!4)/.!, !.!,/'5% #!22)%2 3934%-3 ).$)6)$5!, #(!2!#4%2)34)#3 /& ).4%2.!4)/.!, #!22)%2 4%,%0(/.% 3934%-3 /. -%4!,,)# ,).%3  -(Z 3934%-3 /. 34!.$!2$):%$  MM #/!8)!, #!",% 0!)23 )45 4 Recommendation ' (Extract from the "LUE "OOK) NOTES 1 ITU-T Recommendation G.343 was published in Fascicle III.2 of the Blue Book. This file is an extract from the Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, the contents 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 a telecommunication administration and a recognized operating agency. © ITU 1988, 1993 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Recommendation G.343 Fascicle III.2 - Rec. G.343 4 MHz SYSTEMS ON STANDARDIZED 1.2/4.4 mm COAXIAL CABLE PAIRS (Geneva, 1964; further amended) Preliminary note The present Recommendation describes a system designed to carry a maximum of 960 carrier telephone channels on a 1.2/4.4 mm coaxial pair (see Recommendation G.622). A system of this kind is produced by halving the length of the repeater section of a 1.3 MHz system (as described in Recommendation G.341) if this length is 8 km, corresponding to a nominal repeater spacing of 4 km for a 4 MHz system. 1 Line frequencies The CCITT recommends the two plans in Figure 1/G.343. Plan 1 shows the supergroup allocations and Plan 2 the mastergroup allocations. It may be desirable to make provision for the through-connection of entire mastergroups or a supermastergroup to this system. This can be effected in accordance with the frequency arrangement of Plan 2 in Figure 1/G.343. Plan 2 uses the three lowest mastergroups in the 12 MHz system on a 2.6/9.5 mm coaxial pair. It permits, in particular, direct interconnection with a 12 MHz coaxial system using the Plan 1A frequency allocation shown in Figure 1/G.332 and with a radio-relay link of 900 or 1800 channels operated according to Recommendation G.423 (Figures 4/G.423 and 8/G.423). 2 Pilots and additional measuring frequencies 2.1 Line-regulating pilots The frequencies recommended for the various cases indicated in § 1 above and shown in Figure 1/G.343 are as follows: Plan 1 - The CCITT recommends the use of the following frequencies: i) 60 kHz or 308 kHz for the lower line-regulating pilot; ii) 4092 kHz or 4287 kHz for the upper line-regulating pilot. However, each Administration, when so requested by another Administration, should permanently send a lineregulating pilot at 4287 kHz. Plan 2 - The line-regulating pilots recommended in Recommendation G.332 for the 12 MHz system in the same frequency band. Fascicle III.2 - Rec. G.343 1 In every instance, the recommended stability is ± 1 x 10-5, the power level recommended is -10 dBm0, while the tolerances at this level are the same as in Recommendation G.332, § 2.1. The harmonics of the 60 and 308 kHz pilot should each have a level not higher than -70 dBm0. 2.2 Frequency comparison pilots Plan 1 - For a national routine frequency cheek as described in Recommendation G.225, a frequency of either 60 kHz or 308 kHz may be used for the frequency-comparison pilot. The power level of a frequency-comparison pilot should be adjusted at the output of the transmit amplifier, to a nominal value of –10 dBm0. The harmonics of the frequency-comparison pilots should each have a level not higher than -70 dBm0. The frequency 1800 kHz is provisionally reserved for international frequency comparisons, as required. However, if the Administrations concerned so desire, this frequency 1800 kHz may be used for the frequencycomparison pilot. Administrations concerned with an international carrier system on coaxial cable may agree to use (if they consider it desirable) one of the lower line-regulating pilots (either 60 or 308 kHz) for level control as well as for frequency checking. In any case, it is desirable that one of the following two solutions should always be applied, so as to allow the line-regulating pilots to be used at the same time for frequency checking: - - 2 provide, in each regulated-line section, a master oscillator which is regularly compared, directly or indirectly, with a national frequency standard; if there is no master oscillator in a regulated-line section, then beyond the junction between the two regulated-line sections considered, reintroduce the lower line-reg

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