1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD IZATION SECTOR OF ITU SERIES V: DATA COMMUNICATION OVER THE TELEPHONE NETWORK Interaces and voiceband modems V.24 (02/2000) List of definitions for interchange circuits between data terminal equipment (DTE) and data circuit-term
2、inating equipment (DCE) ITU-T Recommendation V.24 (Formerly CCITT Recommendation) STD-ITU-T RECMN V.24-ENGL 2000 M 4Ab259L Ob83951 T14 m ITU-T V-SERIES RECOMMENDATIONS DATA COMMUNICATION OVER THE TELEPHONE NETWORK 11 General v.1-v.9 Wideband modems Error control Transmission quality and maintenance
3、Simultaneous transmission of data and other signals Interworking with other networks Interface layer specifications for data communication Control procedures Modems on digital circuits v.35-v.39 V.40-V .49 V.50-V. 59 V.60-V .99 V.100-V.199 V.20-V.249 V.25Q-V.299 V.300-V.399 For further details, plea
4、se refer to ITU-T List of Recommendations. STD-ITU-T RECMN V.24-ENGL 2000 4862591 Ob83952 950 I ITU-T RECOMMENDATION V.24 LIST OF DEFINITIONS FOR INTERCHANGE CIRCUITS BETWEEN DATA TERMINAL EQUIPMENT (DTE) AND DATA CIRCUIT-TERMINATING EQUIPMENT (DCE) Summary This Recommendation applies to the interco
5、nnecting circuits being called interchange circuits at the interface between DTE and DCE for the transfer of binary data, control and timing signals as appropriate. This Recommendation also applies to both sides of separate intermediate equipment, which may be inserted between these two classes of e
6、quipment. Source ITU-T Recommendation V.24 was revised by ITU-T Study Group 16 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 17 February 2000. STD-ITU-T RECMN V.24-ENGL 2000 II 4Bb259L Ohfi3953 897 U FOREWORD ITU (International Telecommunication Union) is the United Natio
7、ns Specialized Agency in the field of telecommunications. The ITU 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 Recommendations on them with a view to standardizing telecom
8、munications 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 topics. The approval of Recommendations by the Members of t
9、he ITU-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 Recommendation, the expression “Administration“ is used for
10、conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU 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
11、takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, 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 intellectua
12、l property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 2001 All rights reserved. No part of this public
13、ation 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. 1 1.1 1.2 1.3 1.4 2 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.1 1 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 3.22 3.2
14、3 3.24 3.25 3.26 3.27 Page Scope Range of application . Applicable electrical characteristics . Applicable mechanical characteristics Allocation of functionalities . Line of demarcation Definitions of interchange circuits . Circuit 102 . Signal ground or common return Circuit 102a . DTE common retur
15、n . Circuit 102b . DCE common return Circuit 102c . Common return . Circuit 103 . Transmitted data . Circuit 104 . Received data Circuit 105 . Request to send . Circuit 106 . Ready for sending , Circuit 107 . Data set ready . Circuit 108/2 . Data terminal ready . Circuit 11 1 . Data signalling rate
16、selector (DTE source) Circuit 1 12 . Data signalling rate selector (DCE source) Circuit 108/1 . Connect data set to line . Circuit 109 . Data channel received line signal detector . Circuit 1 13 . Transmitter signal element timing (DTE source) . Circuit 1 14 . Transmitter signal element timing (DCE
17、source) . Circuit 1 15 . Receiver signal element timing (DCE source) . Circuit 1 16/1 . Back-up switching in direct mode , Circuit 1 16/2 . Back-up switching in authorized mode . Circuit 1 17 . Standby indicator Circuit 11 8 . Transmitted backward channel data . Circuit 11 9 .- . Received backward c
18、hannel data Circuit 120 . Transmit backward channel line signal Circuit 12 I . Backward channel ready . Circuit 125 . Calling indicator . Circuit 126 Select transmit frequency . Circuit 122 . Backward channel received line signal detector 2 2 4 4 4 4 4 5 5 5 5 6 6 7 7 7 7 8 8 8 9 9 9 9 9 9 10 10 10
19、. 3.28 3.29 3.30 3.31 3.32 3.33 3.34 3.35 3.36 3.37 4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 5 Circuit 128 . Receiver signal element timing (DTE source) . Circuit 13 1 . Received character timing (DCE source) . Circuit 133 . Ready for receiving Circuit 134 . Received data present . Circuit 135 . Received energ
20、y present . Circuit 137 - Transmitted character timing (DTE source) . Circuit 138 - Transmitted character timing (DCE source) Circuit 140 - LoopbaclMaintenance test Circuit 141 - Local loopback . Circuit 142 - Test indicator Operational requirements . Data circuits and timing circuits . 4.1.1 Data c
21、ircuits . 4.1.2 Timing circuits Control and indication circuits . 4.2.1 Operation of circuits 107, 108/1 and 108/2 . 4.2.2 Circuit 125 - Calling indicator 4.2.3 Usage of circuit 126 4.2.4 Circuit 140 - LoopbacMMaintenance Test . Miscellaneous . 4.3.1 Interrelationship of circuits 103, 105 and 106 .
22、4.3.2 Idle periods 4.3.3 Clamping . Circuit failures (electrical) Provision of interchange circuits in DCEs and DTEs Data flow control Power-up considerations References Page 10 10 11 11 11 11 12 12 12 13 13 13 13 13 14 14 15 15 15 15 15 16 16 17 17 17 17 17 Recommendation V.24 LIST OF DEFINITIONS F
23、OR INTERCHANGE CIRCUITS BETWEEN DATA TERMINAL EQUIPMENT (DTE) AND (Geneva, 1964, amended at Mar del Plata, 1968, Geneva, 1972, 1976 and 1980, Malaga-Torremolinos, 1984, Melbourne, 1988, Helsinki, 1993, Geneva, I996 and 2000) DATA CIRCUIT-TERMINATING EQUIPMENT (DCE) 1 Scope 1.1 Range of application T
24、his Recommendation applies to the interconnecting circuits being called interchange circuits at the interface between DTE and DCE for the transfer of binary data, control and timing signals as appropriate. This Recommendation also applies to both sides of separate intermediate equipment, which may b
25、e inserted between these two classes of equipment (see Figure 1). Line of demarcation V.24 interface I V.24 interface Line T1400030-93 NOTE - Without intermediate equipment, the selections A and B are identical. Selection C may be a selection specifically for automatic calling. Figure 1N24 - Illustr
26、ation of general layout of equipment The range of interchange circuits defined in this Recommendation is applicable, for example: a) b) c) to synchronous and asynchronous data communications; to data transmission on leased line service, either 2-wire or 4-wire, either point-to-point or multipoint op
27、eration; to data transmission on switched network service, either 2-wire or 4-wire; A DTE/DCE interface conforming to this Recommendation may also be used for attachment to a Public Data Network (PDN). For these cases, additional information on interchange circuit implementation and operational requ
28、irements may be found in Recommendations X.20 bis and x.21 his. In any type of practical equipment a selection will be made from the range of interchange circuits defined in this Recommendation, as appropriate. The actual interchange circuits to be used in a particular DCE are those indicated in the
29、 appropriate Recommendation. STD-ITU-T RECMN VeZY-ENGL 2000 D 4862591 0683957 432 w The required interchange circuits specified in the DCE Recommendations which make reference to this Recommendation apply only to the DCE side of the interface. Only those circuits necessary to assure satisfactory ope
30、ration of the application the DTE is intending to support need be controlled or monitored by the DTE (see 4.5 for proper handling of unimplemented circuits). The usage and operational requirements of certain interchange circuits and the interaction between them are specified in clause 4. For proper
31、operation of the DCE it is important that the guidelines in clause 4 be observed. 1.2 Applicable electrical characteristics Electrical characteristics for interchange circuits are specified in Recommendations V. 1 O, V. 1 1, V.12, V.28, V.31 andV.31 bis. 1.3 Applicable mechanical characteristics For
32、 mechanical characteristics of the interface, refer to ISO/IEC 21 10 (25-pole), ISO/IEC 11569 (26-pole), ISO/IEC 13575 (50-pole) or ISO/IEC 4902 (37-pole) as appropriate. 1.4 Allocation of functionalities The DCE may include signal converters, timing generators, pulse regenerators, and control circu
33、itry, together with equipment to provide functions such as error control, automatic calling and automatic answering. Some of these functions may be implemented in separate intermediate equipment or in the DTE. 2 Line of demarcation The interface between DTE and DCE is located at a connector, which i
34、s the interchange point between these two classes of equipment. The interface connector will not necessarily be physically attached to the DCE and may be mounted in a fixed position near the DTE. An interconnecting cable or cables will normally be provided with the DTE. It is recommended to keep the
35、 cables as short as possible. Their lengths should be limited by the load capacitance and other electrical Characteristics specified in the relevant Recommendation on electrical characteristics (see 1.2). 3 Definitions of interchange circuits A list of these interchange circuits is presented in Tabl
36、e 1. NOTE - Compared to earlier versions of this Recommendation, Table 1 and the definitions below summarize fewer interchange circuits, and some circuit numbers are void. Interchange circuits for which no practical application has become known or whose application has ceased have been removed, e.g.
37、 the 200-series of interchange circuits for parallel automatic calling in accordance with earlier versions of Recommendation V.25 and interchange circuits relevant for modems employing parallel data transmission in accordance with former Recommendation V.20. - STD*ITU-T RECMN V-24-ENGL 2000 YBb259L
38、Ob83958 379 Table 1N.24 - Interchange circuits by category _ signal ground or common return DTE common return DCE common return Zommon return ransmitted data Leceived data Lequest to send Leady for sending ata set ready Ionnect data set to line lata terminal ready )ata channel received line signal d
39、etector )ata signal rate selector (DTE) lata signal rate selector (DCE) rransmitter signal element timing (DTE) rransmitter signal element timing (DCE) ieceiver signal element timing (DCE) 3ack-up switching in direct mode 3ack-up switching in authorized mode Standby indicator ransmitted backward cha
40、nnel data Received backward channel data ransmit backward channel line signal Backward channel ready Backward channel received line signal detector Calling indicator Select transmit frequency Receiver signal element timing (DTE) Received character timing (DCE source) Ready for receiving Received dat
41、a present Received energy present Transmitted character timing (DTE source Transmitted character timing (DCE source LoopbacklMaintenance test Local loopback Test indicator nter- oange ircuit imber 1 02 02a 02b 02c 03 04 05 .O6 i 07 i0811 i0812 109 111 112 113 114 115 11 6/1 1 1612 117 118 119 120 12
42、1 122 125 126 128 131 133 134 135 137 138 140 141 142 Interchange circuit name 2 round 3 X X X X Data - rom ,CE 4 - - X X X X - Control - rom CE 6 - - X X X X X X X X X X X - - ro CE 7 - - X X X X X X X X X X X - Timing - rom ICE 8 - - X X X X - STDoITU-T RECMN V.24-ENGL 2000 I 4b259L Ob83959 205 I
43、3.1 This conductor establishes the signal common return for unbalanced interchange circuits with electrical characteristics according to Recommendation V.28 and the d.c. reference potential for interchange circuits according to Recommendations V. 1 O and V. 1 1. Within the DTE, this circuit should b
44、e brought to one point, and it should be possible to connect this point to protective ground or earth by means of a metallic strap within the equipment. This metallic strap can be connected or removed at installation, as may be required to meet applicable safety regulations or to minimize the introd
45、uction of noise into electronic circuitry. Caution should be exercised to prevent the establishment of ground loops carrying high currents. Circuit 102 - Signal ground or common return 3.2 This conductor is connected to the DTE circuit common return and is used as the reference potential for the unb
46、alanced V. 1 O-type interchange circuit receivers within the DCE. Circuit 102a - DTE common return 3.3 This conductor is connected to the DCE circuit common return and is used as the reference potential for the unbalanced V. 1 O-type interchange circuit receivers within the DTE. NOTE - Two arrangeme
47、nts exist for the case where a mixture of V.10 and V.11 circuits is used in the same interface: 1) The DTE common return and the DCE common return are both connected to circuit 102. This arrangement is particularly useful where the need to conserve pole assignments is a requirement IO and 12. It sho
48、uld, however, be noted that only category 2 receivers as specified in clause 9N.10 can be used in this case, and that the usable interface cable length may be shorter than specified in Appendix IW.10. Separate provision is made for the V.10 common return circuits 102a and 102b, and for a d.c. refere
49、nce potential conductor circuit 102 1 i. Circuit 102b - DCE common return 2) 3.4 Circuit 102c - Common return This conductor establishes the signal common return for single-current interchange circuits controlled by contact closure with electrical characteristics according to Recommendation V.3 1 , in cases where a common return is used. Within the equipment containing the signal source of the interchange circuit, this conductor shall be isolated fi-om signal ground and protective ground, irrespective of whether it is located within the DCE or within the DTE. 3.
