1、ITU-T RECMN*V*L2 75 4862573 Obob545 563 W INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU DATA COMMUNICATION OVER THE TELEPHONE NETWORK v.12 (08195) ELECTRICAL CHARACTERISTICS INTERCHANGE CIRCUITS FOR INTERFACES WITH DATA SIGNALLING RATES UP TO 52 Mbis FO
2、R BALANCED DOUBLE-CURRENT ITU-T Recommendation V.12 (Previously “CCIlT Recommendation”) ITU-T RECMNaV.12 95 4Bb259L ObOb54b 4TT H FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (IT). The ITU-T is responsible for studyin
3、g technical, operating and tariff questions and issuing Recommen- dations 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 IT-T Study Grou
4、ps 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 in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation V.12 was prepared by ITU-T Study Group 14 (1993-1996) and wa
5、s approved under the WTSC Resolution No. 1 procedure on the 29th of August 1995. NOTES 1. telecommunication administration and a recognized operating agency. 2. follows: In this Recommendation, the expression “Administration” is used for conciseness to indicate both a The status of annexes and appen
6、dices attached to the Series V Recommendations should be interpreted as - - an annexes to a Recommendation forms an integral part of the Recommendation; an appendix to a Recommendation does not form part of the Recommendation and only provides some complemetary explanation or information specific to
7、 that Recommendation. 0 ITU 1995 Ail 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 ITU. ITU-T RECMN*V*L2 95 W 4862593 Obob547 336 W CONTENT
8、S 1 Scope 2 References 3 Definitions 4 Electrical charactenstics . 4.1 Generator characteristics . 4.1.1 Open circuit measurement 4.1.2 Test termination measurements . 4.1.3 Short-circuit measurement 4.1.4 Output signal waveform 4.2 Load characteristics 4.2.1 Input current-voltage measurements . 4.2
9、.2 Input sensitivity measurements . 4.2.3 Cable termination 4.2.4 Fail-safe operation Interconnecting cable electrical characteristics . 4.3 5 Circuit protection . Example on an interconnecting cable . Appendix I - Guidelines for application . 1.1.1 Length I . 1.2 Cable physical characteristics . I
10、. 1.3 Cable termination Examples of generators and receivers 1.2.1 ECL - Emitter coupled logic technology 1.2.2 Fail-safe biasing of receivers 1.1 1.2 Page 1 2 2 2 3 3 3 4 4 5 5 6 7 7 8 8 8 8 8 9 9 9 9 9 Recommendation V.12 (08/95) i ITU-T RECMN*V.L2 75 m 4862573 Obob548 272 m SUMMARY This Recommend
11、ation specifies the electrical characteristics of a balanced digital interchange circuit, that may be employed when specified for the interchange of seriai binary signals between Data Terminal Equipment (DTE) and Data Circuit-Terminating Equipment (DCE) or in any point-to-point interconnection of se
12、rial binary signais between data equipments. The balanced digital interchange circuit will normally be utilized on data and timing, or control circuits where the data signalling rate is up to a maximum limit of 52 Mbit/ 2) generator in power-off condition. Recommendation V.12 (08/95) 7 ITU-T RECMN*V
13、=L2 75 m 4862593 0606556 347 When detection of one or more of the above fault conditions is required by specific applications, additional provisions are required in the load, and the following items must be determined and specified. 1) 2) Which interchange circuits require fault detection? What faul
14、ts must be detected? 3) What action must be taken when a fault is detected? The method of detection of fault conditions is application-dependent and is therefore not further specified. (See 1.2.2.) 4.3 Interconnecting cable electrical characteristics The cable shall consist of twisted pair conductor
15、s and have an overall shield. The two wires of each pair shall be connected to the same signal, one to the MA and the other to the B/B signal poles. Maximum single conductor DC Resistance (DCR) at 20 “C 3.5 R 110Rf 11 IR 4.5 dB 47.6 t 6.5 pF/m Differential Impedance at 50 MHz Maximum Signal Attenuat
16、ion at 50 MHz Mutual Capacitance within pair at 1 kHz Propagation Delay maximum: 79 ns Skew (pair-to-pair) 2.0 ns See Appendix I. 1.2 for further guidance on an example of an interconnecting cable. 5 Circuit protection Balanced digital interchange generator and receiver devices, under either the pow
17、er-on or power-off condition, complying to this Recommendation shall not be damaged under the following conditions: a) generator open circuit; b) short-circuit across the balanced interconnecting cable; c) short-circuit to circuit common. Appendix I Guidelines for application 1.1 Example on an inter
18、connecting cable The following subclause provides further information to 4.3 and provides additional guidance concerning operational constraints imposed by the cable parameters of length and termination. 1.1.1 Length The nominal length of cable separating the generator and the load is 15 metres. 8 R
19、ecommendation V.12 (08/95) ITU-T RECMN*V.L2 95 48b2591 0606557 285 1.1.2 Cable physical characteristics The following physical characteristics apply to the cable: Conductor: Insulation: 0.08 mm2,7 strands of O. 13 mm, tinned annealed copper, nominal diameter 0.38 mm. Polyethylene or polypropylene; 0
20、.24 mm nominal wall thickness; 0.86 mm f 0.025 mm outside diameter. Foil Shield: Braid Shield: 0.05 1 mm nominal aluminiudpolyester laminated tape spiral wrapped around the cable core. Braided 0.13 mm, tinned plated copper in accordance with 80% minimum coverage, in electrical contact with the alumi
21、nium of the foil shield. Outside Diameter: 5 10.6 mm. 1.1.3 Cable termination The characteristic impedance of twisted pair cable is a function of frequency, wire size and type as well as the kind of insulating materials employed. For example, the characteristic impedance of average 0.08 mm2, copper
22、conductor, plastic insulated twisted pair cable, to a 50 MHz sine wave will be approximately 110 s1. 1.2 Examples of generators and receivers 1.2.1 Emitter Coupled Logic (ECL) families such as 10K, 10H, and 100K have been developed that meet the requirements of this Recommendation by a number of int
23、egrated circuit manufacturers. The 100K family is compensated for both Power Supply Voltage and Operating Temperature variations; offering constant thresholds and output levels over both ranges. Some other families are only Power Supply Voltage compensated. The 100K family also accepts a wide range
24、of power supply voltages (Vee) from -4.2 V to -5.7 V. ECL - Emitter coupled logic technology 1.2.2 In the event that the interchange cable is not present, the receiver must default to a known state. The method of fail-safe biasing is application and component specific, therefore is beyond the scope
25、of this Recommendation. External resistors can be used to bias the receivers input into a known state (2 150 mV differential) for the case of the disconnected cable. For example, a 1.5 162 pull-up and pull-down resistor will bias the receiver to 177 mV, defaulting the receiver to an OFF state. Fail-
26、safe biasing of receivers (Figure I. 1) FIGURE I.lN.12 Receiver fail-safe biasing It should be noted that it is not necessary to use external resistors on all families of receivers. Some receiver integrated circuits have this feature internal to the integrated circuit. Recommendation V.12 (08/95) 9
