1、STDOITU-T RECMN V-IL-ENGL L97b 48b257I Ob284b5 051 m INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU SERIES V: DATA COMMUNICATION OVER THE TELEPHONE NETWORK Interfaces and voiceband modems v.11 (1 0196) Electrical characteristics for balanced do u ble-cu r
2、rent i n te rc hange ci rcu i ts opera ti ng at data signalling rates up to IO Mbit/s ITU-T Recommendation V.1 I (Previously “CCITT Recornmendation”) STD-ITU-T RECMN V=LL-ENGL L77b M Li8b257L Ob28gbb T78 m ITU-T V-SERIES RECOMMENDATIONS DATA COMMUNICATION OVER THE TELEPHONE NETWORK 1 - General Il 2
3、- Interfaces and voice 3 - Wideband modems 4 - Error control 5 - Transmission quality and maintenance 6 - Intenvorking with other networks For further details, please refer to ITU-TList of Recommendations. STD-ITU-T RECMN V-LL-ENGL L77b Itil 48b251L Ob28Lib7 724 FOREWORD The ITU-T (Telecommunication
4、 Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The World Tele
5、communication 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 topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down i
6、n WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation V.ll was revised by ITU-T Study Group 14 (1993-1996) and was approved by the WTSC (Geneva, October 9-18, 1996). NOTE 1. telecommunication administration and a recognized operating agency. In this Recommendation, the expressio
7、n “Administration” is used for conciseness to indicate both a 2. follows: The status of annexes and appendices attached to the Series V Recommendations should be interpreted as - an annex to a Recommendation forms an integral part of the Recommendation; an appendix to a Recommendation does not form
8、part of the Recommendation and only provides some complementary explanation or information specific to that Recommendation. - O ITU 1997 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 mi
9、crofilm, without permission in writing from the ITU. Recommendation V.ll (10/96) i 1 2 3 4 5 6 7 8 9 10 CONTENTS Introduction Field of application Symbolic representation of interchange circuit Generator polarities and receiver significant levels . 4.1 Generator 4.2 Receiver Generator 5.1 Resistance
10、 and d.c. offset voltage . 5.2 Static reference measurements 5.3 Dynamic voltage balance and rise time measurements . Load . 6.1 Characteristics . 6.2 Receiver input voltage - Current measurements 6.3 D.C. input sensitivity measurements . 6.4 Input balance test 6.5 Terminator Environmental constrain
11、ts Circuit protection . Detection of generator power-off or circuit failure Measurements at the physical interchange point 1 O . 1 Listing of essential measurements 10.2 Listing of optional measurements . Annex A . Compatibility with other interfaces . Compatibility of V.10 and V . 1 1 interchange c
12、ircuits in the same interface . Appendix I - Cable and termination A.l A.2 Recommendation V.11 interworking with Recommendation V . 10 1.1 Cable . 1.2 Cable length 1.3 Cable termination Appendix II - Multipoint operation Reference . 11 Recommendation V.ll (10/96) Page 1 1 1 2 2 2 2 2 3 5 6 6 7 7 8 8
13、 9 9 9 10 10 10 11 11 11 11 11 11 13 13 13 Recommendation V.ll ELECTRICAL CHARACTERISTICS FOR BALANCED DOUBLE-CURRENT INTERCHANGE CIRCUITS OPERATING AT DATA SIGNALLING RATES UP TO 10 Mbit/si) (Geneva, 1976; amended Geneva, 1980, at Melbourne, 1988, at Helsinki, 1993 and at Geneva, 1996) 1 Introducti
14、on This Recommendation deals with the electrical characteristics of the generator, receiver and interconnecting leads of a differential signalling (balanced) interchange circuit with an optional d.c. offset voltage. The balanced generator and load components are designed to cause minimum mutual inte
15、rference with adjacent balanced or unbalanced interchange circuits (see Recommendation V.10) provided that waveshaping is employed on the unbalanced circuits. In the context of this Recommendation, a balanced interchange circuit is defined as consisting of a balanced generator connected by a balance
16、d interconnecting pair to a balanced receiver. For a balanced generator, the algebraic sum of both the outlet potentials, with respect to earth, shall be constant for all signals transmitted; the impedances of the outlets with respect to earth shall be equal. The degree of balance and other essentia
17、l parameters of the interconnecting pair is a matter for further study. Annex A and Appendices I and II are provided to give guidance on a number of application aspects as follows: 0 0 NOTE - Generator and load devices meeting the electrical characteristics of this Recommendation need not operate ov
18、er the entire data signalling rate range specified. They may be designed to operate over narrower ranges to satis requirements more economically, particularly at lower data signalling rates. Reference measurements are described which may be used to verifj certain of the recommended parameters but it
19、 is a matter for individual manufacturers to decide what tests are necessary to ensure compliance with this Recommendation. Annex A - Compatibility with other interfaces. Appendix I - Cable and termination. Appendix II - Multipoint operation. 2 Field of application The electrical characteristics spe
20、cified in this Recommendation apply to interchange circuits operating with data signalling rates up to 10 Mbits. Typical points of application are illustrated in Figure 1. Whilst the balanced interchange circuit is primarily intended for use at the higher data signalling rates, its use at the lower
21、rates may be necessary in the following cases: 1) 2) 3) where the interconnecting cable is too long for proper unbalanced circuit operation; where extraneous noise sources make unbalanced circuit operation impossible; where it is necessw to minimize interference with other signals. 3 See Figure 2. T
22、he equipment at both sides of the interface may implement generators as well as receivers in any combination. Consequently, the symbolic representation of the interchange circuit, Figure 2 below, defines a generator interchange point as well as a load interchange point. Symbolic representation of in
23、terchange circuit 1 This Recommendation is also designated as Recommendation X.27 in the X-Series Recommendation s. Recommendation V.ll (10/96) 1 , Circuits to this Recommendation FIGURE 1N.11 Typical applications of balanced interchange circuits For data transmission applications, it is commonly ac
24、cepted that the interface cabling will be provided by the DTE. This introduces the line of demarcation between the DTE plus cable and the DCE. This line is also called the interchange point and physically implemented in the form of a connector. The applications also require interchange circuits in b
25、oth directions. This leads to an illustration as shown in Figure 3. 4 Generator polarities and receiver significant levels 4.1 Generator The signal conditions for the generator are specified in terms of the voltage between output points A and B shown in Figure 2. When the signal condition O (space)
26、for data circuits OT ON for control and timing circuits is transmitted, the output point A is positive with respect to point B. When the signal condition 1 (mark) for data circuits or OFF for control and timing circuits is transmitted, the output point A is negative with respect to point B. 4.2 Rece
27、iver The receiver differential significant levels are shown in Table 1, where VA and VB are respectively the voltages at points A and B relative to point C. 5 Generato-2) 5.1 Resistance and d.c. offset voltage 5.1.1 The total generator resistance between points A and B shall be less than or equal to
28、 100 ohms and be adequately balanced with respect to point C. The degree of balance required, both static and dynamic, is left for further study). 2, For test purposes other than specified in this Recommendation (e.g. signal quality measurement), a transmitter test load of 1 O0 ohms may be used. 2 R
29、ecommendation V.11 (10196) STD-ITU-T RECMN V-LI-ENGL 177b Sl 48b257L Ob284731 355 NOTES 1 - It is assumed that the value of the dynamic source impedance is in the same range. 2 - In the event that reflections are experienced on V. 1 1 circuits, either the use of a terminating network at the receiver
30、 (in the range of 120 to 126 ohms) or the use of series resistors (approximately 33 ohms) added to the generator output leads, should alleviate this problem. This latter solution has the addtional benefit of providing protection from over-voltages but creates a problem with meeting the Test-terminat
31、ion measurement specified in 5.2.2. Balanced interconnecting Generator cable Load 4 1 WT I r7 y I I I I Cable I I I termination Receiver I I 14 -7 ab ”Ca dl 4 Cable termination impedance vg Ground potential difference A, B and A, B c, C Generator output voltage between points A and B Generator volta
32、ge between points C and A Generator voltage between points C and B Interchange points Zero volt reference interchange points NOTES 1 - Two interchange points are shown. The output characteristics of the generator, excluding any interconnecting cable, are defined at the “generator interchange point”.
33、 The electrical characteristics to which the receiver must respond are defined at the “load interchange point”. 2 - Points C and C may be interconnected and further connected to protective ground if required by national regulations. FIGURE 2A7.11 Symbolic representation of a balanced interchange cir
34、cuit 5.1.2 conditions. The magnitude of the generator d.c. offset voltage (see 5.2.2) shall not exceed 3 V under all operating 5.2 Static reference measurements The generator characteristics are specified in accordance with measurements illustrated in Figure 4 and described in 5.2.1 to 5.2.4. 5.2.1
35、Open-circuit measurement See Figure 4 a). The open-circuit voltage measurement is made with a 3900-ohm resistor connected between points A and B. In both binary states, the magnitude of the differential voltage ( VO) shall not be more than 6.0 volts, nor shall the magnitude of Voa and Vob be more th
36、an 6.0 volts. Recommendation V.ll (10/96) 3 (Connector) (Note 3) A Data circuits 1 DTE and Cable VA* - VEt 5 -0.3 V VA, - VB 2 +0.3 V 1 O (Note21 Control and timing circuits I DCE I OFF ON I Line of demarcation T1400230-Q3/d03 NOTES 1 - The zero voit reference interchange point C, C may be interconn
37、ected via the signal ground conductor. 2 - Signal ground may be further connected to external protective ground if national regulations require. 3 - The type of connector with this electrical characteristic specification depends on the application. IS0 specifies, for data transmission over telephone
38、 type facilities, a 37-pin connector in IS0 4902 and, for data transmission over data network facilities, a 15-pin connector in IS0 4903. FIGURE 3N. 1 1 Practical representation of the interface 5.2.2 Test-termination measurement See Figure 4 b). With a test load of two resistors, each 50 ohms, conn
39、ected in series between the output points A and B, the differential voltage (V,) shall not be less than 2.0 volts or 50% of the magnitude of Vo, whichever is greater. For the opposite binary state the polarity of V, shall be reversed (-V,). The difference in the magnitudes of V, and -Vr shall be les
40、s than 0.4 volt. The magnitude of the generator offset voltage Vos measured between the centre of the test load and point C shall not be greater than 3.0 volts. The magnitude of the difference in the values of Vos for one binary state and the opposite binary state shall be less than 0.4 volt. NOTE -
41、 Under some conditions this measurement does not determine the degree of balance of the internal generator impedances to point C. It is left for further study whether additional measurements are necessary to ensure adequate balance in generator output impedances. 4 Recommendation V.11 (10196) STD.IT
42、U-T- RECMN V-11-ENGL 199b II 48bZ591 b28473 128 5.2.3 Short-circuit measurement See Figure 4 c). With the output points A and B short-circuited to point C, the current flowing through each of the output points A or B in both binary states shall not exceed 150 milliamperes. 5.2.4 Power-off measuremen
43、ts See Figure 4 d). Under power-off condition with voltages ranging between +0.25 volt and -0.25 volt applied between each output point and point C, as indicated in Figure 4 d), the magnitude of the output leakage currents (Ixa and I therefore, appropriate techniques should be implemented to prevent
44、 such behaviour. For example, adequate hysteresis may be incorporated in the receiver to prevent such conditions. 6.4 Input balance test See Figure 8. The balance of the receiver input resistance and internal bias voltages shall be such that the receiver shall remain in the intended binary state und
45、er the conditions shown in Figure 8 and described as follows: a) with Vi = +720 millivolts and Vcm varied between -7 and +7 volts; b) with = -720 millivolts and Vcm varied between -7 and +7 volts; c) with Vi = +300 millivolts and Vcm a 1.5 voit peak-to-peak square wave at the highest applicable data
46、 signalling rate (this condition is provisional and subject to further study); d) with Vi = -300 millivolts and Vcm a 1.5 volt peak-to-peak square wave at the highest applicable data signalling rate (this condition is provisional and subject to further study). I. C r- T140011093/d08 a) Matched. FIGU
47、RE 8N.11 Receiver input balance test 6.5 Terminator The use of a cable terminating impedance (ZJ is optional depending upon the specific environment in which the interchange circuit is employed (see Appendix I). In no case shall the total load resistance be less than 100 ohms. 8 Recommendation V.ll
48、(10196) 7 Environmental constraints In order to operate a balanced interchange circuit at data signalling rates ranging between O and 10 Mbit/s, the following conditions apply: I) 2) 3) For each interchange circuit a balanced interconnecting pair is required. Each interchange circuit must be appropr
49、iately terminated (see Appendix I). The total common-mode voltage at the receiver must be less than 7 volts peak. The common mode voltage at the receiver is the worst case combination of generator-receiver ground-potential difference ( Vg, Figure 2); longitudinally induced random noise voltage measured between the receiver points A or B and C with the generator ends of the cable A, B and C joined together; and generator d.c. offset voltage, if any. a) b) c) Unless the generator is of a type which generates no d.c. offset voltage, the sum of a) and b) above, whic
