1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Q.552 (I 1/2001) SERIES Q: SWITCHING AND SIGNALLING Digital exchanges - Transmission characteristics Transmission characteristics at 2-wire analogue interfaces of digital exchanges ITU-T Recommendation Q.552
2、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Q.552 SERIES Q: SWITCHING AND SIGNALLING Digital exchanges - Transmission characteristics (1 1/2001) Transmission characteristics at 2-wire analogue interfaces of digital exchanges ITU-T Recommendation Q.552
3、ITU-T Q-SERIES RECOMMENDATIONS SWITCHING AND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN SPECIFICATIONS OF SIGNALLING SYSTEM No. 4 SPECIFICATIONS OF SIGNALLING SYSTEM No. 5 SPECIFICATIONS OF SIGNALLING SYSTEM No. 6 SPECIFICATIONS
4、 OF SIGNALLING SYSTEM R1 SPECIFICATIONS OF SIGNALLING SYSTEM R2 DIGITAL EXCHANGES INTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING CLAUSES APPLICABLE TO ITU-T STANDARD SYSTEMS Introduction and field of application Exchange interfaces, functions and connections Design objectives and measurement Tra
5、nsmission characteristics INTERWORKING OF SIGNALLING SYSTEMS SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 Q3 INTERFACE DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 PUBLIC LAND MOBILE NETWORK INTERWORKING WITH SATELLITE MOBILE SYSTEMS INTELLIGENT NETWORK SPECIFICATIONS OF SIGNALLING RELATED TO BEARER INDE
6、PENDENT CALL CONTROL (BICC) BROADBAND ISDN SIGNALLING REQUIREMENTS AND PROTOCOLS FOR IMT-2000 Q.1-Q.3 4.4-4.59 Q.60-Q.99 Q. 100-Q.119 Q. 120-4.139 Q. 140-4.199 Q.250-Q.309 4.310-4.399 Q.400-Q.499 Q.500-Q.599 Q.5 OO-Q.509 Q.SlO-Q.539 Q.540-Q.549 Q.55O-Q.599 4.7004.799 4.600-4.699 4.800-Q.849 Q.850-Q.
7、999 Q.1000-Q.1099 Q.1100-Q.1199 4.1200-4.1699 Q. 1700-4.1799 Q. 1900-Q. 1999 4.2000-4.2999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Recommendation Q.552 Transmission characteristics at 2-wire analogue interfaces of digital exchanges Summary This Recommendation pr
8、ovides characteristics for 2-wire analogue interfaces, input and output connections with 2-wire analogue interfaces and half-connections with 2-wire analogue interfaces in accordance with definitions given in ITU-T Q.55 1. This Recommendation is valid for equipment that may terminate an internationa
9、l long-distance connection via 4-wire circuits interconnected by 4-wire exchange. It also includes, in a separate category, characteristics for interfaces which cannot terminate an international connection and are therefore entirely national in application. Source ITU-T Recommendation 4.552 was prep
10、ared by ITU-T Study Group 15 (2001-2004) and approved under the WTSA Resolution 1 procedure on 29 November 2001. ITU-T Rec. Q.552 (11/2001) 1 FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunicatio
11、n Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and. issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (W
12、TSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In Some areas of information technology which fall
13、 within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and LEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RI
14、GHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by I
15、TU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this
16、 may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 2002 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. 11 ITU-T Rec. 4.552 (11/2001) CONTENTS P
17、age 1 General 1 2 3 Characteristics of interfaces 2.1 Characteristics of interface C2 2.1.1 Exchange impedance 2.1.2 Impedance unbalance about earth . 2.1.3 Relative levels . 2.2 Characteristics of interface Z 2.2.1 Exchange impedance 2.2.2 Impedance unbalance about earth . 2.2.3 Relative levels . C
18、haracteristics of half-connections . 3.1 Characteristics common to all 2-wire analogue interfaces . 3.1.1 Transmission loss 3.1.2 Group delay . 3.1.3 Single frequency noise 3.1.4 Crosstalk . 3.1.5 3.1.6 3.1.7 Total distortion including quantizing distortion . Discrimination against out-of-band signa
19、ls applied to the input interface . Spurious out-of-band signals received at the output interface 3.1.8 Echo and stability 3.2 Characteristics of interface C2 3.2.1 Nominal value of transmission loss 3.2.2 Noise . 3.2.3 Values of total distortion . 3.3 Characteristics of interface Z 3.3.1 Nominal va
20、lue of transmission loss 3.3.2 Noise . 3.3.3 Values of total distortion . Appendix I . Impedance strategy in 2-wire networks . I . 1 Introduction . 1.2 General equations for unloaded cables . 1.3 General impedance considerations of a hybrid . 1.3.1 Cable input impedance 22 and the hybrid input imped
21、ance 2, 1.3.2 Balance impedance ZB 1.4 Echo considerations 1.4.1 Talker echo loudness rating TELR . ITU-T Rec . Q.552 (11/2001) 7 7 7 9 10 10 12 12 12 12 15 15 15 16 17 17 18 18 19 19 22 23 23 23 23 23 . 111 1.4.2 1.5 1.6 1.7 1.8 1.8.1 1.8.2 1.8.3 1.8.4 Sidetone masking rating STMR and listener side
22、tone rating LSTR . Applications Analysis of loop impedance variation by means of a special impedance Conclusions . Examples of impedances 22 and compromise nominal impedances Zr and 2, Cable input impedance 2, and hybrid input impedance 2, Balance impedance 2, Echo considerations diagram . Applicati
23、on of the special impedance diagram . Page 24 25 25 27 27 28 30 30 32 iv ITU-T Rec . Q.552 (11/2001) ITU-T Recommendation Q.552 Transmission characteristics at 2-wire analogue interfaces of digital exchanges 1 General This Recommendation provides characteristics for: - - - in accordance with definit
24、ions given in ITU-T Q.55 1 particularly in Figure UQ.55 1, The characteristics of the input and output connections of a given interface are not necessarily the same. The characteristics of half-connections are not necessarily identical for different types of interfaces. This Recommendation is valid
25、for equipment that may terminate an international long-distance connection via 4-wire circuits interconnected by 4-wire exchanges. It also includes, in a separate category, characteristics for interfaces which cannot terminate an international connection and are therefore entirely national in applic
26、ation. 2-wire analogue interfaces (Type C2 and Z); input and output connections with 2-wire analogue interfaces; and half-connections with 2-wire analogue interfaces; 2 Characteristics of interfaces NOTE - For measuring 2-wire analogue interface conditions it is necessary to apply a quiet code, i.e.
27、 a PCM signal corresponding to decoder output value O (p-law) or output value 1 (A-law), with the sign bit in a fixed state, to the exchange test point Ti, when no test signal is stipulated. 2.1 Characteristics of interface C2 The recommended values of interfaces C2 are valid for digital exchanges i
28、ncluding PABXs with transit functions and routing capabilities for originating and terminating traffic. Depending on the type of traffic to be handled, two different sets of relative levels are required. This suggests subdivision into C21 and C22 interface specifications. The interface C21 provides
29、the termination of outgoing and incoming international long-distance connections and possible national connections, with the exchange acting as transit switch. The interface C22 provides for the connection of a 2-wire trunk line. A typical example is the interconnection of a Z interface with a C22 i
30、nterface in a local exchange for routing through the 2-wire analogue trunk network. A C22 interface cannot be part of the international 4-wire chain (see Figure 2/Q.55 1). 2.1.1 Exchange impedance 2.1.1.1 Nominal value Nominal values of exchange impedance should be defined depending on national cond
31、itions. The definition shall include a test network for the exchange impedance. Network operators may want to adopt different test networks corresponding to the cable types used (e.g. unloaded and loaded). 2.1.1.2 Return loss The return loss of the impedance presented by a C2 interface against the t
32、est network for the exchange impedance should comply with the limits given in Figure 1. ITU-T Rec. 4.552 (11/2001) 1 300 500 2000 3400 Hz Frequency (f) T1515480-94 Figure UQ.552 - Minimum value of return loss against the test network for the exchange impedance at a 2-wire interface 2.1.2 Impedance u
33、nbalance about earth The Longitudinal Conversion Loss (LCL) at the interface, defined in 4.1.3/G. 1 17, should exceed the minimum values of Figure 2 with the equipment under test in the normal talking state, in accordance with ITU-T K. 1 O. NOTE 1 - A network operator may adopt other values and in s
34、ome cases a wider bandwidth, depending on actual conditions in its telephone network. NOTE 2 - A limit may also be required for the Transverse Conversion Loss (TCL), as defined in 4.1.2/G. 1 17, if the exchange termination is not reciprocal with respect to the transverse and longitudinal paths. A su
35、itable limit would be 40 dB to ensure an adequate near-end crosstalk attenuation between interfaces. dB 50 I 3 O0 600 Frequency (0 3400 Hz TI 515490-94 Figure 2/Q.552 - Minimum values of LCL measured in the arrangement shown in Figure 3 Test method Longitudinal conversion loss at the C2 equipment po
36、rt should be measured in accordance with the principles given in 4.U0.9. Figure 3 shows an example of the basic measuring arrangement for digital exchanges. Arrangements containing two resistors each of value R/2 may also be used (see 5.1/0.9). Measurements of the longitudinal and transverse voltage
37、s should preferably be done with a frequency-selective level meter. 2 ITU-T Rec. 4.552 (11/2001) Item under test Sinusoidal oscillator I 1 + * 7 T1515500-94 R should be in the range of 600-900 Q Longitudinal conversion loss (LCL) = 20 logl, IcldR VL, NOTE 1 - Provisions should be made for representa
38、tive DC currents to be present. NOTE 2 - Special care must be taken in those applications using active hybrids. Figure 3/Q.552 - Arrangement for measuring LCL 2.1.3 Relative levels 2.1.3.1 Nominal levels 2.1.3.1.1 Interface C21 compensation comparable to 2.2.3.3 is provided. 2.1.3.1.2 Interface C22
39、To adjust the transmission loss of a digital transmission section to the values of national transmission planning for local or national traffic, depending on the relative levels given in 2.1.3.1.1 and 2.2.3.1, the following ranges encompass the requirements for C22 interfaces of a large number of ne
40、twork operators: - input level: - In order to compensate loss on long toll or junction lines, a network operator may, to satis local conditions, choose values of relative levels derived from the basic values as follows: LI = Li +xdB interfaces should meet the recommended values for Z interfaces in 2
41、.2.3.1 if no loss Lj = +3.0 to -7.0 dBr in 0.5 dB steps; Lo = +1.0 to -8.0 dBr in 0.5 dB steps. output level: Li =Lo -xdB where x should take a negative value. The value of x is in national competence. Such compensation of loss requires careful selection and application of balance networks. It has b
42、een recognized that it is not necessary for a particular design of equipment to be capable of operating over the entire level range. 2.1.3.2 Tolerances of relative levels The difference between the actual relative level and the nominal relative level should lie within the following values: 3 ITU-T R
43、ec. Q.552 (11/2001) - input relative level: -0.3 to +0.7 dB; - output relative level: -0.7 to +0.3 dB. These differences may arise, for example, from design tolerances, cabling between analogue ports and the (DF), and adjustment increments. NOTE - Level adjustment procedures are given in clause 3/G.
44、712. Austria, FRG BT NTT USA ETSI 2.2 Characteristics of interface Z The recommended values of interface Z are valid for digital local exchanges, PABXs and digital remote units. For PABXs, see 2.1.uQ.55 1. 2.2.1 Exchange impedance Guidance for network operators can be found in Appendix I. 2.2.1.1 No
45、minal value The principal criterion governing the choice of the nominal value of the exchange impedance is to ensure an adequate sidetone performance for telephone sets, particularly those operated on short lines. If this criterion is met, the impedance will also be suitable for subscriber lines fit
46、ted with voiceband modems. As a general rule a complex exchange impedance with a capacitive reactance is necessary to achieve satisfactory values of stability, echo and sidetone. For additional information, see ITU-T G. 1 1 1 and ITU-T G. 12 1. The use of the preferred configuration below will minim
47、ize the diversity of types of exchange impedances. At present no unique component values can be recommended. However, to provide guidance for network operators, examples of nominal values chosen by some network operators are given in Table 1. Rs (ohms) Rp (ohms) Cp (farads) 220 820 115 n 300 1 O00 2
48、20 n 600 infinity IC1 900 infinity 2.16 p 270 750 150 n CP TlblSSlhM NOTE 1 - The test network and the component values represent a configuration that exhibits the required exchange impedance. It need not necessarily correspond to any actual network provided in the exchange interface. 4 ITU-T Rec. Q
49、.552 (11/2001) Table UQ.552 - Test networks for exchange impedances being considered NOTE 2 - The range of component values reflects the fact that there are substantial differences in the sensitivity and sidetone performance of the various telephone instruments throughout the world. In general, the combination of short lines and sensitive telephone sets might be rather common in the future due to increased use of remote concentration. In order to control sidetone performance, network operators need to take into account telephone set parameters. Not only should the parameters of exist
