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)%2G1342!.3-)33)/.G0G03934%-3!22!.%-%.4G0G0/ further amended)1 Carrier-system racks (formerly Part A)Th
2、e CCITT,consideringthat countries not having a national industry for the construction of carrier systems must obtain them fromdifferent factories, and that the variations of the dimensions of the racks between different sources of supply do notallow of a simple and economical layout of the cables an
3、d efficient use of accommodation,unanimously recommendsthat in future the dimensions of carrier-system racks should meet the requirements as follows:1) Space between suites - The minimum space between suites should be such that it is possible to move testtrolleys from place to place (between two sui
4、tes), and also for maintenance staff to be able to workcomfortably between two suites. A spacing of 75 cm at least seems reasonable.2) Overall height - The overall height of a rack above the floor (not including the space provided foroverhead cable runs) should not exceed 320 cm.In principle, 30 cm
5、should be allowed for overhead cable runs, and also about 30 cm for access to thesecables, which makes at the most 60 cm between the top of the rack and the ceiling; nevertheless, someAdministrations consider that a total height of 40 cm between the top of the rack and the ceiling issufficient in ce
6、rtain cases. In main repeater stations (or terminal equipment stations), where, in addition tocables connecting one rack to another, general distribution cables have to be allowed for, it isrecommended that the height of the building between the floor and the ceiling should be at least 4 m tofacilit
7、ate access to the various cables.3) Thickness - The thickness of a rack should not be greater than 45 cm. For racks which may be placed backto back the total suite thickness may be up to 52 cm, including all maintenance controls, cooling fins, etc.,which may protrude from the nominal face of the equ
8、ipment.2 Use of standard components in transmission equipment1)(formerly Part B)While acknowledging that the International Electrotechnical Commission (IEC) is competent to devisestandards for components or devices generally used in electrical engineering, the CCITT nevertheless reserves the rightto
9、 issue recommendations dealing with such equipment and with transmission systems which, if componentsstandardized by the IEC were used, may prove impossible to create.Furthermore, manufacturers and Administrations wishing to use components specified by the IEC or by anotherbody will still be respons
10、ible for ensuring that the recommendations issued by the CCITT are met._1)This recommendation applies both to carrier systems and to audio equipment.2 Fascicle III.2 - Rec. G.231Hence the CCITT recommendsthat Administrations and manufacturers should ensure that all components used in transmission sy
11、stems andequipments (even if such components have been standardized by some other national or international body) are such thatthe requirements of CCITT recommendations will be complied with in the conditions of use envisaged, throughout thelife of the equipment or systems, i.e. twenty years or more
12、3 Power supply (formerly Part C)Information on noise at the terminals of the battery power supply system is given in Supplement No. 13 1.For carrier system equipment, it is recommended that power supply equipment should provide a no-breaksupply when the power mains fail.Note - Much existing equipme
13、nt has been designed in accordance with the old recommendation in Volume IIIof the Blue Book (1964) which is reproduced below:“In countries where the main power supply is unreliable and where it is the normal source of supply for thecoaxial system, it is recommended that in each power-feeding statio
14、n there should be equipment to transfer from thenormal source of supply to a standby source or vice versa in such a manner that breaks in transmission on voice-frequency telegraph circuits or on telephone circuits with automatic signalling carried by the system do not exceed about150 milliseconds.“4
15、 Repeater station cabling2)(formerly Part D)The Administrations mentioned in the list kept by the CCITT Secretariat are prepared to supply otherAdministrations and technical assistance experts working under the ITU with information on the national standards theyapply to the wiring of repeater statio
16、ns. However, they would warn users that cable specifications and wiring diagramsare not always the best way of giving them the information they desire. The documentation available is very bulky andrequests for information should be reasonably precise, since it is essential to know exactly on what po
17、int information isrequired in order to decide what form the reply should take.A proper understanding of how wiring is done in repeater stations cannot be acquired from documents aloneand the persons concerned should get in touch with the Administrations on the list in order to see the methods put in
18、topractice.Administrations are invited to supply information to keep this list, which is deposited with the CCITTSecretariat, constantly up to date.Reference1 Noise at the terminals of the battery supply, Orange Book, Vol. III-3, Supplement No. 13, ITU, Geneva, 1977._2)This recommendation applies both to carrier systems and to audio equipment.
