1、- 3404583 0029081 3 - I-ETS 300 004 ELECOMMUNICATION August 1991 STANDARD UDC: 621.395 Key words: BT, PABX, transmission characteristics, 2-wire Business Telecommunications (BT); Transmission characteristics at 2-wire analogue interfaces of a digital Private Automatic Branch Exchange (PABX) ETSI Eur
2、opean Telecommunications Standards Institute ETSI Secretariat: B.P.152 . F - 06561 Valbonne Cedex . France TP. + 33 92 94 42 O0 TF. + 33 93 65 47 16 Tx. 47 O0 40 F European Telecommunications Standards Institute 1 99 1 . All rights reserved. No part may be reproduced or used except as authorised by
3、contract or other written permission. The copyright and the foregoing restriction on reproduction and use extend to all media in which the information may be embodied. Whilst every care has been taken in the preparation and publication of this document, errors in content, typographical or otherwise,
4、 may occur. if you have comments concerning its accuracy, please write to ETSI Standards Management Dept.“ at the address shown on the title page. Contents 1 2 3 4 5 Foreword . 5 scope . 5 Definitions . 7 Definitions of interfaces 7 Parameters relevant for echo and stability . 7 Terminal Balance Rer
5、um Loss (TBRL) 8 4.2.1.1 Related standards . 6 4.1 4.2 Definition of parameters 7 4.2.1.2 Stability loss 9 Parameters for interference . 9 4.2.1 4.2.2 5.2 . 5.2.1 5.2.2 5.2.3 %wire interface specifications 9 Characteristics of interfaces K2 and M2 . lo 5.1.1.1 PABX impedance 10 Impedance unbalance a
6、bout earth . 11 Characteristics of interface L2 . 13 5.1.2.1 PABX impedance 13 Impedance unbalance about earth . 13 Characteristics of half connections . 15 Characteristics common to all 2-wire analogue interfaces 15 5.2.1.2 Group delay . 19 Single frequency noise 20 5.2.1.4 Crosstalk 20 the input i
7、nterface 22 output interface . 23 Characteristics of interfaces K2 and M2 . 25 5,2.2.2 Noise 25 Characteristics of interface L2 . 28 Values of total distortion . 30 Characteristics of interfaces . 5.1 9 5.1.1 5.1.1.2 5.1.1.3 Relative levels 12 5.1.2 5.1.2.2 5.1.2.3 Relative levels 14 5.2.1.1 Transmi
8、ssion loss . 15 5.2.1.3 5.2.1.5 5.2.1 $6 5.2.1.7 5.2.1.8 5.2.2.1 5.2.2.3 Values of total distortion . 26 . 5.2.3.1 Nominal value of transmission loss . 28 5.2.3.2 Noise 28 5.2.3.3 Total distortion including quantizing distortion 22 Discrimination against out-of-band signals applied to Spurious out-o
9、f-band signals received at the Echo and stability . 23 Nominal value of transmission loss . 25 Annex A: Test netwois for PABX input impedances at interfaces K2 and M2 32 Annex E: Relative levels for K2 and M22 interfaces in dBr . 33 Annex C: Test networks for PABX input impedances at interface U 34
10、Annex D: Relative levels at interface L2 and M21 in dBr 35 . 3404583 O029084 9 Page 4 I-ETS 300 ow:l991 Annex E: Test networks for TBRL in different European Administrations . 36 Annex F: Compensation of losses on long or short 2-wire lines . 38 Annex G: Impedance unbalance about earth in different
11、European Administrations . 39 Annex H: Discrimination against out-of-band signals applied to the input interface: Signals below 300 Hz . 40 Annex J: Single frequency noise (dBmO) 41 Annex K: Return loss 42 3404583 O029085 O W Page 5 - I-ETS 300 OW:1991 1 Foreword This Interim-European Telecommunicat
12、ion Standard (I-ETS) was produced by the Business Telecommunications (BT) Technical Committee of the European Telecommunications Standards Institute (ETSI), and was adopted, having passed through the ETSI standards approval procedure. This Standard was first prepared in the format of a CEPT Recommen
13、dation and was later converted into an ETSI standard. Consequently, it does not fully conform to the guidelines for the structure of ETSI standards although the ETSI “stylesheet” has been applied. This Standard was submitted for Public Enquiry as an ETS, but, as it contains transmission parameters w
14、ithout specifying the exact measurement method it was decided to convert the standard into an I-ETS, thus allowing a two year period during which the BT Technical Committee can gain further experience with a view to modifying the parameter values and finalising the test method. This Standard is inte
15、nded-to be used as a specification for the design of digital PABXs and for the harmonization of PABX transmission parameters throughout Europe. Parameters which ar8 only of an informative instead of a normative character are highlighted as such. During its preparation this I-ETS has been circulated
16、to other European Standardization bodies (European Computer Manufacturers Association (ECMA) and European Committee for Eiectrotechnical Standardization (CENELEC) who are also involved in the preparation of European Standards on ISPBXs. There are three other standards directly connected with this St
17、andard: I-ETS 300 003: Business Telecommunications (BT); Transmission characteristics of digital Private Automatic Branch Exchange (PABX). I-ETS 300 005: Business Telecommunications (BT); Transmission characteristics at 4-wire analogue interfaces of a digital Private Automatic Branch Exchange (PABX)
18、. I-ETS 300 006: Business Telecommunications (BT); Transmission characteristics at digital interfaces of a digital Private Automatic Branch Exchange (PABX). This Standard is based on information from CCITT Recommendations and the relevant Recommendation numbers are quoted where appropriate. 2 Scope
19、This Standard provides characteristics for: 2-wire anaiogue interfaces (Type K2, M2 and U); . input and output connections with 2-wire analogue interfaces; and - half-connections with 2-wire analogue interfaces. in accordance with definitions given in I-ETS 300 003 particularly in figure 2 of I-ETS
20、300 003. 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 Standard is valid for digital PABXs that may terminate a public switched n
21、etwork 4-wire connection, It also includes, in a separate category, characteristics for 2-wire interfaces which are involved in 2-wire connections with the public switched telephone network (PSTN). -_ I H 3404583 0029086 2 Page 6 I-ETS 300 004:1991 3 Related standards I-ETS 300 003 (i 99 1 ): “Busin
22、ess Telecommunications (BT); Transmission characteristics of digital Private Automatic Branch Exchange (PABX)“. I-ETS 300 005 (1 99 1 1: “Business Telecommunications (BT); Transmission characteristics at 4-wire analogue interfaces of a digital Private Automatic Branch Exchange (PABX)“. I-ETS 300 005
23、 (i 99 1 I: “Business Telecommunications (BT); Transmission characteristics at 4-wire analogue interfaces of a digital Private Automatic Branch Exchange (PABXI . I-ETC 300 006 (i 991 1: “Business Telecommunications (BT); Transmission characteristics at digital interfaces of a digital Private Automat
24、ic Branch Exchange (PABX)“. nS 300 132: “Equipment Engineerhg; Power supply interface at the input to telecommunications equipments“ . CCITT Recommendation G. 1 O1 : The transmission plan. CCITT Recommendation G. 103: Hypothetical reference connections. CCITT Recommendation G.111: Loudness ratings (
25、LRs) in an international connection. CCITT Recommendation G. 1 17: Transmission aspects of unbalance about earth (definitions and methods). CCITT Recommendation G.121: Loudness ratings (LRs) of national systems. CCITT Recommendation G.122: Influence of national systems on stability, talker echo, and
26、 listener echo in international connections. CCITT Recommendation G.123: Circuit noise in national networks. CCITT Recommendation G.223: Assumptions for the calculation of noise on hypothetical reference circuits for telephony. CCIT Recommendation G.714: Separate performance characteristics for the
27、encoding and decoding sides of PCM channels applicable to 4-wire voice- frequency interfaces. CCITT Recommendation G.715: Separate performance characteristics for the encoding and decoding side of PCM channels applicable to 2-wire interfaces. CCITT Recommendation K.4: Disturbance to signalling. CCIT
28、T Recommendation K. 1 O: Unbalance about earth of telecommunications installations. CCITT Recommendation 0.9: Measuring arrangements to assess the degree of unbalance about earth. CCIlT Recommendation 0.81 : Groupdelay measuring equipment for telephone-type circuits. CCITT Recommendation O. 131 : Qu
29、antizing distortion measuring equipment using a pseudo-random noise test signal. CCITT Recommendation O. 1 32: Quantizing distortion measuring equipment using a sinusoidal test signal. Page 7 ias 300 004.1981 3404583 0029087 4 _ - CCIT Recommendation 0.133: Equipment for measuring the performance of
30、 PCM mcoders and decoders. CCITT Recommendation 0.45bis: Transmission characteristics of an analogue intemational exchange. CCITT Recommendation 0.543: Digital exchange performance design objectives. CCIlT Recommendation 0.552: Transmission characteristics at 2-wire analogue interfaces of a digital
31、exchange. CCIlT Fascicle 1.3: Terms and definitions. CCITT Fascicle V1.5: Digital local, transit, combined and international exchanges in integrated digital networks and mixed analogue-digbl networks. CCTTT Fascicle 111.3 (Orange Book, 1980) Supplement 13 to the G Series: Noise at the terminals of b
32、attery supply. NOTE: All references to CCIlT recommendations refer to the 1988 editions (“Blue Bod“) except if expressly otherwise noted. 4 Definitions 4.1 Definitions of interfaces Interface K2: As defined in subclause 4.6.1.3 of I-RS 300 003, the interface K2 provides for the direct connection of
33、2-wire analogue circuits to the public network. Interface M2: As defined in subclause 4.6.1.2 of I-ETC 300 003, the interface M2 is subdivided into the interfaces M21“ and “M22“. These interfaces may have different transmission characteristics. - The interface M21 provides the termination of connect
34、ions toifrom the PSTN via 4-wire analogue (K4) or digital (KD) subscriber line access, with the PABX acting as a transit switch. The interface M22 provides the termination of connections other than those covered by M21. Typical is the interconnection of an i2 interface with an M22 interface in a PAB
35、X for routings through existing 2-wh analogue circuits to other PABXs (see figure 2 of LETS 300 003). Interface U: The interface L2 provides for the connection of 2-wire analogue extension lines and will carry signals such as speech, voice-band analogue data and multi-frequency push-button signals,
36、etc. In addition, the interface L2 provides for ordinary functions such as DC feeding, OC signalling, ringing, etc, See also I-ETS 300 003, subclause 4.6.1,l. 4.2 Defimition of parameters 4.2.1 Parameters relevant for echo and rtabdity Terminal Balance Return Loss TTBRL) is introduced in order to ch
37、aracterize the PABX performance required to comply with the network performance objective of CCIlT Recommendation G.122 with respect to echo, The TBRL of an equipment port is measured in the talking state as in an established connection through a digital PABX. The parameter “Stability Loss as define
38、d in CCITT Recommendation G.122, applies to the worst terminating conditions encountered at a 2-wire interface in normal operation. I Page 8 3404563 0029088 b I-ETS 300 Ow:1991 4.2.1.1 The term TBRL is used to characterize an impedance balancing property of the 2-wire analogue equipment port. Temhal
39、 Balance Return Loss TBRL The expression for TBRL is: dB Za+Z, ?+Za 2*Za ?-Z, TBRL = 20 log where: za = z,= PABX impedance of a 2-wire equipment port. impedance of the balance network presented at a 2-wire equipment port. z,= NOTE: impedance of the balance test network. Some Administrations have fou
40、nd that it is advantageous to choose Za= - with reference to the interfaces M21 and M22, to terminate the analogue lines between PABXs, to ensure that every PABX will have adequate values of stability margin and echo. At present no unique component values can be recommended. However, Annex A include
41、s a model of the test network and a list of the nominal values specified by different European Administrations. 6.1.1.1.2 Return loss The return loss of the impedance presented by K2 and M2 interfaces against the test network for the exchange impedance shall comply with the limits given in figure 2.
42、 Annex K includes the requirements for Sweden. dB I 18 14 Frequency (0 Logarithmic Scale Figure 2: Minimum value of return loss against the test network for PABX impedance at a 2-wire interface 3404583 0029091 b I PSge i 1 I-ETS 300 004:1991 6.1 $1.2 The Longitudinal Conversion Loss (LCL), defined i
43、n CCITT Recommendation G.117, 4.1.3 shall exceed as a minimum requirement the following values : Impedance unbalance about earth 300- 600H 40 dB 600 - 3400 HZ 46 dB with the equipment under test in the normal talking and quiescent state, in accordance with CCIlT Recommendation K, 1 O. Some administr
44、ations specify other values and in some cases wider bandwidth (see Annex GI. NOTE: A limit may also be required for the Transverse Conversion Loss TTCL), as defined in CCITT Recommendation G.117, 4.1.2, if the PABX termination is not reciprocal with respect to the transverse and longitudinal paths.
45、A suitable limit would be 40 dB to ensure an adequate near-end crosstalk attenuation between interfaces. Test method Longitudinal Conversion Loss shall be measured in accordance with the principles given in CCIn Recommendation 0.9, 0 2.1 and 3. Figure 3 shows an example of the basic measuring arrang
46、ement for digital PABXs. Transverse Conversion Loss shall be measured in accordance with the principles given in CCITT Recommendation 0,9, P 2.2 and 0 3. Measurements of the longitudinal and transverse voltages should preferably be done with a frequency selective level meter. Page 12 I-ETS 300 004:1
47、991 LCL 20 loglo Item under test I Sinusoidal - I i “Ll - dB “Ti I -9- I PABX test points I I i i - - output relative level : - 0,7 to + 0.3 dB. NOTE 1 : These differences may arise, for example, from design tolerances, cabling (between cabinet and the Distribution Frame (DF), and adjustment increme
48、nts. Level adjustment procedures are given in CCIlT Recommendation G.715, 2.1. NOTE 2: 5.1.2 Characteristics of hterface L2 5.1.2.1 PABX impedance 6.1.2.1.1 Nominal value The use of the preferred configuration shown in Annex C will minimize the diversity of types of PABX impedances, At present no un
49、ique component values can be recommended. However, the table in Annex C includes a list of the nominal values specified by different European Administrations. NOTE 1: The principal criterion Qoveming the choice of the nominal value of the PABX 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 extension lines fitted with voice band modems. NOTE 2: As a general rule a complex PABX impedance with a capacitive reactance is
