1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 - TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#% ).4%2.!4)/.!,G0G0,%!3%$G0G0#)2#5)43490%3G0G0/&G0G042!.3-)33)/.G0G0/.,%!3%$G0G0#)2#5)43)45G134G0G0RecommendationG0G0- (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation M.1015 was published i
2、n Fascicle IV.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 identical to the Blue Book version and copyright conditions remain unchanged (see below).2 In
3、 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 this publication may be reproduced or utilized in any form or by any means, electronic orm
4、echanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle IV.2 - Rec. M.1015 1Recommendation M.1015Fascicle IV.2 - Rec. M.1015TYPES OF TRANSMISSION ON LEASED CIRCUITS1 A leased point-to-point or multiterminal circuit can be provided in some instances for on
5、e type of service only,such as: telephony (that is, speech transmission), voice-frequency telegraphy, data transmission, facsimile.(The list is not complete but it includes the most common types of service.)2 In other instances leased circuits are used for different transmission purposes at differen
6、t times, in which casethe circuit characteristics should in principle be determined by the requirements of the more exacting form oftransmission (when there is a difference in requirements).Note The North American expression for this type of operation is alternate-use.3 Although special quality leas
7、ed circuits are not provided for normal telephony, it is recognized that they willbe used for voice communication for service coordination purposes and for the alternate-use type of operation envisagedin 2 above. The prescribed circuit limits in Recommendations M.1020 and M.1025 are not intended to
8、define a circuitto be used to carry normal telephony, although a circuit which meets these limits will be adequate for voicecommunication purposes.4 In some instances the bandwidth provided by the circuit is divided into two or more bands thus providing twoor more circuits which may be used for diff
9、erent types of transmission.If the band is divided among two or more classes of transmission by means of equipment under the control ofthe Administration, then band-dividing filters should wherever possible be used in preference to hybrid transformersbecause their use affords the possibility, in som
10、e circumstances, of carrying out maintenance operations on one circuit(obtained by frequency division) without affecting another.In those cases in which the frequency division is effected by the renters apparatus in the renters premises theAdministrations should make it clear that even though the re
11、nters apparatus must be approved by the Administration,this latter is not responsible for faults or the wrong operation of equipment attributable to the arrangement adopted by therenter.2 Fascicle IV.2 - Rec. M.10155 Figures 1/M.1015 to 3/M.1015 illustrate some typical arrangements.d01-scFIGURE 1/M.1015.D01d02-scFIGURE 2/M.1015.D02Fascicle IV.2 - Rec. M.1015 3d03-scIGURE 3/M.1015.D03
