1、GENERAL SECRETARIAT INTERNATIONAL TELECOMMUNICATION UNION Subject: Erratum Recommendation ITU-T G.136 (09/99) TE LEC0 M M U N I CATI ON STANDARDIZATION SECTOR OF ITU Geneva, 25 May 2000 ITU-T Recommendation G. 136 (09/99) Application rules for Automatic Level Control Devices Replace NOTE on page (ii
2、) by the following: NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Union internationale des tlcommunications Place des Nations 121 1 GENVE 20 Suisse - Switzerland - Suiza STD-
3、ITU-T RECMN G-13b-ENGL 1997 I Ii8bi571 Obb8104 bTO S GENERAL SECRETARIAT INTERNATIONAL TELECOMMUNICATION UNION Subject: Erratum Geneva, 25 May 2000 Recommendation ITU-T 6.136 (09199) TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU ITU-T Recommendation G. 136 (09/99) Application rules for Automatic L
4、evel Control Devices Replace NOTE on page (ii) by the following: NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Union internationale des tlcommunications Place des Nations 121
5、 1 GENVE 20 Suisse - Switzerland - Suiza STDmITU-T RECMN GmL3b-ENGL 1777 48b2571 Obb8105 537 INTERNATIONAL TELECOMM U N CATION U NION ITU-T TELECOMMUNICATION STAN DARD IZATIO N SECTOR OF ITU G.136 (09/99) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS International telephone
6、connections and circuits - General characteristics of the 4-wire chain formed by the international circuits and national extension circuits Application rules for automatic level control devices ITU-T Recommendation G.136 (Previously CCITT Recommendation) ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION S
7、YSTEMS AND MEDIA, DIGITAL SYSTEMS AND NEIWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS General definitions General Recommendations on the transmission quality for an entire international telephone connection General characteristics of national systems forming part of international connectio
8、ns General characteristics of the 4-wire chain formed by the international circuits and national extension circuits General characteristics of the 4-wire chain of international circuits; international transit General characteristics of international telephone circuits and national extension circuits
9、 Apparatus associated with long-distance telephone circuits Transmission plan aspects of special circuits and connections using the international telephone connection network Protection and restoration of transmission systems Software tools for transmission systems INTERNATIONAL ANALOGUE CARRIER SYS
10、TEM TRANSMISSION SYSTEMS INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE WITH METALLIC LINES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TESTING EQUIPMENTS TRANSMISSION MEDIA CHARACTERISTICS DIGI
11、TAL TRANSMISSION SYSTEMS TERMINAL EQUIPMENTS DIGITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION G.lOO-G. 1 99 G. 1 OM. 1 O9 G.110-G.119 G.120-G. 129 G.13O-G.139 G. 1404.149 G.
12、 150-4.159 G. 1 60-G.169 G. 1 704.179 G. 1 804.1 89 G.19O-G.199 G.200-G.299 G .300-G .399 G.400-G.449 G.450-G.499 G.600 - G.699 G.700-G.799 G.80O-G.899 G .go04 .999 For further details, please refer to ITU-T List of Recommendations. STD=ITU-T RECMN G-13b-ENGL 1979 qBb2591 Obb8107 30T ITU-T RECOMMEND
13、ATION G.136 APPLICATION RULES FOR AUTOMATIC LEVEL CONTROL DEVICES Summary This Recommendation provides a set of general application guidelines for network based Automatic Level Control Devices. These network based ALC devices are expected to comply with Recommendation G. 169 “Automatic Level Control
14、 Devices“. Source ITU-T Recommendation G.136 was prepared by ITU-T Study Group 12 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 30 September 1999. Keywords ALC, automatic level control, application rules, planning guidelines. Recommendation G.136 (09/99) 1 FOREWORD ITU (I
15、nternational Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The TU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Reco
16、mmendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these top
17、ics. The approval of Recommendations by the Members of the RU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recom
18、mendation the term recognized operating agency (ROA) includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms Administration, ROA and public correspondence are defined in the Constitution of the ITU (Geneva, 1992). a INTELLEC
19、TUAL PROPERTY RIGHTS The IT draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights
20、, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implement
21、ors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 2000 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photoco
22、pying and microfilm, without permission in writing from the ITU. 11 Recommendation 6.136 (09/99) 1 2 3 4 4.1 5 CONTENTS Page Introduction . References . Effects of level control Automatic Level Control devices . Application guidelines Insertion of ALC devices in a connection 1 2 2 2 3 . Recommendati
23、on (2.136 (09/99) 111 SFD-ITU-T RECMN G-13b-ENGL 1997 qBb2591 ObbBLLO 9T4 9 Recommendation G.136 APPLICATION RULES FOR AUTOMATIC LEVEL CONTROL DEVICES (Geneva, 1999) 1 Introduction This Recommendation applies only to network based Automatic Level Control (ALC) devices that are placed within networks
24、. For the purposes of this Recommendation an ALC device is defined as any piece of signal processing equipment located in the digital transmission path which automatically adjusts the level of a signal towards a pre-determined value, or which modifies the frequency response or spectral content of th
25、e signal in such a way as to affect the overall level of the signal. In a communication system one of the significant transmission parameters that can affect perceived quality is the overall loudness rating of the connection. This loudness level is controlled by the characteristics of the originatin
26、g terminal, the loss of the network which is comprised of accesses, switches, circuits, and the terminating terminal. The purpose of the audio path associated with the end-to-end connection is to facilitate the transfer of intelligence. Transfer of intelligence by communication involves not just the
27、 content of what is said but is affected by the ability of the speaker to rapidly change the volume of the speech, to convey emotion for example. This Recommendation has been prepared to provide planning guidance for the placement of network based ALC devices that can arbitrarily change the signal l
28、evel and bandwidth of a communication channel. This Recommendation provides guidelines which, if followed, should ensure that network implemented with ALC devices will result in implementations that continue to be aligned with published ITU- T Recommendations. 2 References The following ITU-T Recomm
29、endations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are
30、 therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. - - - - ITU-T Recommendation G. 101 (1996), The transmission plan. ITU-T Reco
31、mmendation G. 120 ( 1998), Transmission characteristics of national networks. ITU-T Recommendation G. 121 (1993), Loudness ratings (LRs) of national systems. ITU-T Recommendation G. 122 (1993), Influence of national systems on stability and talker echo in international connections. ITU-T Recommendat
32、ion G.126 (1993), Listener echo in telephone networks. ITU-T Recommendation G. 13 1 (1996), Control of talker echo. ITU-T Recommendation G. 165 (1993), Echo cancellers. ITU-T Recommendation G. 168 (1997), Digital network echo cancellers. ITU-T Recommendation G. 169 (1999), Automatic level control de
33、vices. - - - - - Recommendation G.136 (09/99) 1 - ITU-T Recommendation P.3 1 O (1996), Transmission characteristics for telephone band (300-3400 Hz) digital telephones. - ITU-T Recommendation P. 340 ( 1996), Transmission characteristics of hands-pee telephones. ITU-T Recommendation P.342 (1 996), Tr
34、ansmission characteristics for telephone band (300-3400 Hz) digital loudspeaking and hands-free telephony terminals. - 3 Effects of level control The design and implementation of the PSTN was shaped by international agreements which were formulated as ITU-T Recommendations relating to overall transm
35、ission performance and transmission planning guidance. In this regard the network related Recommendations, viz. G. 1 O1 - The transmission plan; G.121 - Loudness ratings (LRs) of national systems; G.120 - Transmission characteristics of national networks, and the terminal, viz. Recommendations P.3 1
36、0 - Transmission characteristics for telephone band (300-3400 Hz) digital telephones; P.340 - Transmission characteristics of hands-free telephones; P.342 - Transmission characteristics for telephone band (300-3400 Hz) digital loudspeaking and hands-free telephony terminals, have by default defined
37、the range of acceptable end-to-end connection losses. The ITU-T has accepted the concept that customers may wish to modify the end-to-end connection loss and thus ITU-T Recommendations now make provision for the use of volume controls on terminal equipment, e.g. on telephone sets and automatic level
38、 control devices on audio conference bridges. Further, the placement of ALC devices should be consistent with the planning guidance provided in the following Recommendations, viz. G.122 - Influence of national systems on stability and talker echo in intemational connections, G.126 - Listener echo in
39、 telephone networks, G.131 - Control of talker echo, and G.175 - Transmission planning for private/public network interconnection of voice traffic. It is recognized that the use of ALC devices can change the real time dynamics of a conversation and as a result, the transmission impairments that resu
40、lt from ALC devices must be controlled. Further, it is recognized that unless the placement of ALC devices within networks is performed in an orderly fashion, the integrity of the networks can be compromised. The following guidelines present a set of rules which if followed should result in acceptab
41、le network implementations. 4 Automatic Level Control devices Specific guidelines for deployment of ALCs may vary between national networks and even between networks within the same country. These guidelines are usually established in consideration of performance and customer expectations, competiti
42、ve pressures, specific business goals, economic and technological constraints, etc. As a practical matter they must take into consideration the routing and the technology used to provide the connection. 4.1 Application guidelines The following are a set of general application guidelines for Automati
43、c Level Control devices which are compliant with Recommendation G.169. It is recognized that while there may be a need to develop application guidelines for ALC devices within national networks, that the generation of national guidelines is a national matter and thus is outside the scope of this Rec
44、ommendation. 1) An ALC device should only be placed on connections which are equipped with active echo cancellers, e.g. echo cancellers which are compliant with Recommendation G.165 - Echo cancellers or G. 168 - Digital network echo cancellers. 2 Recommendation 6.136 (09/99) 2) An ALC device should
45、not be placed in the tail path of the echo canceller that is performing the echo control function for that connection. (When echo cancellers are tandemed only one of the echo cancellers is performing the echo cancelling functionality for that connection. The ALC device must not appear in the tail of
46、 the canceller that is performing the echo control function,) ALC devices should never operate in tandem. An ALC device should operate on signals received from other Administrations and should not modify a signal that is to passed to another Administration, unless there is a bilateral agreement to d
47、o so. 3) 4) 5 An ALC device is a particular type of device that incorporates a speech processing function that acts upon a unidirectional speech signal. Thus, it is expected that ALC devices placed within the network will operate at a 4-wire point in the connection. This Recommendation is not intend
48、ed to preclude any implementation scheme and recognizes that there may be implementation benefits if the ALC functionality is integrated into a device which also performs other speech processing functions, e.g. an echo canceller function. Insertion of ALC devices in a connection Recommendation G.136
49、 (09/99) 3 STD-ITU-T RECMN G=L3b-NGL 1999 = 48b2591 Obb8LL3 b03 Series A Series B Series C Series D Series E Series F Series G Series H Series I Series J Series K Series L Series M Series N Series O Series P Series Q Series R Series S Series T Series U Series V Series X Series Y Series Z ITU-T RECOMMENDATIONS SERIES OrganizaGon of the work of the ITU-T Means of expression: definitions, symbols, classification General telecommunication statistics General tariff principles Overall network operation, telephone service, service operation and human factors Non-telephone telecommunicati
