1、ITU-T RECMN*R*L15 93 I 4862591 0573270 547 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPHY TELEGRAPH TRANSMISSION R.115 (03/93) MAINTENANCE LOOPS FOR TDM-SYSTEMS ITU-T Recommendation R.115 (Previously “CCIlT Recommendation”) ITU-T RECMN*R=115 93
2、 m 4862591 O593271 485 FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The IT-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizin
3、g telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Recommendation R.115 was revised by
4、the IT-T Study Group IX (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCIT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization
5、 Sector (IT-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text to references containing the acronyms “CCITT, CCI
6、R or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a recognized operating agency. In this Recommendation, the expressio
7、n “Administration” is used for conciseness LO indicate both a O IT 1994 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 IT. 2 3 4 5 6 CON
8、TENTS Location of the loops Names, types and definitions ofthe loops 3.1 Loop a - Digital multiplexer aggregate loop 3.2 Loop b - Analogue aggregate modem loop 3.3 Loop c - Analogue line loop 3.4 Loop d - Digital aggregate modem loop 3.5 Loop f - Tributary analogue loop . 3.6 Loop g - Tributary digi
9、tal loop towards the Muldex 3.7 Loop h - Tributary digital loop towards the tributary interface unit Use of the loops Page 1 1 1 1 2 2 2 2 3 3 Methods of control . 3 Control signalling . 3 6.1 Alternative A 3 6.2 Alternative B . 4 6.3 Maintenance channel signalling 5 Routing of the maintenance contr
10、ol signais . 6 Application . 6 Use of the maintenance channel . 6 Recommendation R.115 (03/93) - 1 ITU-T RECMN*R.LLS 93 = 4862593 0573273 258 m Recommendation R.115 MAINTENANCE LOOPS FOR TDM-SYSTEMS (Malaga-Torremolinos, 1984; amended at Melbourne, 1988 and at Helsinki, 1993) The CCITT, considering,
11、 (a) (b) (cl (d) involved in maintenance questions for the networks; te) the increasing use of TDM transmission systems; the volume of information circulating on data and telegraph transmmission networks; the savings to be made by reducing interruption time on such links; the importance of being abl
12、e to determine responsibilities between the several parties who, of necessity, are the advantages of standardization regarding maintenance, unanimously declares the following: 1 The locating of faults can be facilitated in many cases by looping and other maintenance procedures in the TDM equipments.
13、 These maintenance facilities allow local or remote measurements to be carried out optionally by the Administrations and/or users concerned. 2 Location of the loops following function blocks: The maintenance loops are positioned in order to make it possible for the Administrations to locate faults t
14、o the - aggregate modem; - TDM central logic; - tributary interface unit; - aggregate line; - subscriber line. The loops necessary to fulfil the above listed demands are shown in Figure 1. Additional loops may be used for the location of faulty boards but these loops are relevant to each particular
15、manufacturer?s implementation and are not included here. The number of maintenance loops may be extended to include the subscriber terminai equipment. These loops are left for further study. 3 See Figure 1. Names, types and definitions of the loops 3.1 This loop is a one-way or optionally an echo-ba
16、ck loop (see Figures 2 and 3) that shall connect the aggregate data output to the aggregate data input of the TDM central logic. This loop shall be accomplished as close as possible to the digital aggregate interface. Loop a - Digital multiplexer aggregate loop 3.2 This loop is a one-way loop or opt
17、ionally an echo-back loop (see Figures 2 and 3). With this loop, the line signal from the output of the aggregate modem is looped back to the input of the aggregate modem. The loop should include the maximum number of aggregate modem components used in normal working. Loop b - Analogue aggregate mod
18、em loop Recommendation R.115 (03/93) 1 ITU-T RECMN*R*LL5 93 4862593 0593274 194 -c + Tributory - _+ Tributory -, interace interface Subscriber - +- unit +- line unit +- NOTES 1 2 A symmetrical set of loops exists as seen from the remote side. Figures within parenthesis are the loop numbers according
19、 to Recommendation V.54. TM iogict ntral FIGURE 1R.115 Mainteuance loops TOM Amrwb AcKmgate central 7 wesaie fine, _+ - logic madem - - rodem . ,. 3.3 ,Loop c - Analogue line loop 4 *- This loop is a one-way loop or optionally an echo-back loop (see Figures 2 and 3). With this loop, the incoming lin
20、e signal at the receiver input of the aggregate modem is looped back to the outgoing direction of the line. It is noted that it -may not be possible to correctly receive data that has been sent over the looped circuit. Analogue - +- 3.4 Loop d - Digital aggregate modem loop This loop is a one-way lo
21、op or optionally an echo-back loop (see Figures 2 and 3). In this loop the received aggregate digital data from the modem is looped back to the originating side. This loop shall be located as close as possible to the digital aggregate interface. 3.5 Loop f - Tributary analogue loop This loop is a on
22、e-way loop (see Figure 2). With this loop, the tributary signal to a set of two characters (a and ) constituting the wanted information to be transmitted; a character depending solely on the system configuration (frame, type of channel: format, speed and alternative operation), which therefore makes
23、 it possible to check that both multiplexers have identical programming. Maintenance information a) Checking the state of the aggregate channel Character a: bO to b7 = “o” (or “W) Character : bo: return to O of the system bl: programming fault b2: loss of frame alignment b3: regrouped alarm b4: firs
24、t (“errored interval”) fault threshold reached (see Note) b5: second (“severely errored interval”) threshold reached (see Note) b6: request for aggregate channel state b7: even parity Therefore, in normal operation, the character will have the value “00”. transmission performance. NOTE - The TDM equ
25、ipment monitors the errors on the synchronization channel, for assessing the b) Monitoring of link errors Character a: bO = “ 1 ” bl to b6 = “O” b7 even parity = “i” Character : bO to b5 modulo 32 counter, aggregate of errors detected on the frame alignment word b6: unused = “O” b7: even parity If t
26、here are no errors in the opposite direction, the meter will keep the same value. Checking and maintenance of telegraph channels Character a: (No. of channel + i) (2 to 47) expressed in binary c) bO to b5 from “02” to “2F b6 = “0 b7 = even parity Recommendation R.115 (03/93) 5 ITU-T RECMN*RlLL5 93 4
27、8b259L 0593278 83T D Character : bo: analogue telelooping (loop f) bl: digital telelooping (loop e) b2: exceeding an adjustable limit (maximum 25%) b3: local looping in progress b4: reserved for subsequent use b5: reserved for subsequent use b6: request for telegraph channel state b7: even parity In
28、 the absence of any command, messages on the maintenance channel must be less than 15 seconds apart and they will be alternatively of typea) and b). This will enable each end of the link to obtain information on both directions of transmission. In the event of a command (telelooping of a telegraph c
29、hannel), messages for telegraph channels must never be more than three seconds apart. 7 Routing of the maintenance control signals One 50 baud channel, or a channel of more than 50 bauds may be allocated (on an optional basis) for maintenance purposes, where possible on a separate system using a par
30、allel route. Where this option is exercised the allocation of the maintenance channel is specified within the respective CCIlT Recommendation or bilaterally between Administrations. The selected maintenance channel should only be used for the transmission of alarms, supervision and remote control si
31、gnais. When there is no possibility to use a separate telegraph system on a parallel route, the c and d loop control can be performed by periodical carrier switching on and off during a period of time from 1.5 to 2 s by the following way: switch on the loop c - “There is no carrier” - 40 ms, “There
32、is a carrier” - 40 ms, etc; switch on the loop d - “There is no carrier” - 80 ms, “There is a carrier” - 80 ms, etc; switch ofSthe loops c und d - There is no carrier” - 120 ms, “There is a carrier” - 120 ms, etc. - - - The diagrams of the signals are given in Figure 7. 8 Application It may be possi
33、ble to apply the described maintenance technique to multiplexors conforming to Recommendations R. 101, R.111 and other standardized multiplexors. It may be possible to apply the described maintenance technique to multiplexors conforming to Recommendations R. 101, R.lll and other standardized multipl
34、exors. 9 Use of the maintenance channel Use of the maintenance channel for purposes other than loop control is left for further study. 6 Recommendation R.115 (03/93) ITU-T RECMN*R-LLS 93 4862591 0593277 77b E 1500 - rns k a) Command to switch on the ioop c. b, Command to switch on the ioOp d. Command to swikh of the loops c and d. Shaded area demtes the carrier sigial transmission. FIGURE 7m.115 Recommendation R.115 (03/93) 7 ITU-T RECRN*R.LLS 73 W 4862593 0593280 478 W Printed in Switzerland Geneva, 1994
