1、GENERAL SECRETARIAT INTERNATIONAL TELECOMMUNICATION UNION Subject: CORRIGENDUM No. 1 Geneva, 30 October 1997 Recommendation -T T.32 (08195) TELECOMMU N KATION STANDARDIZATION SECTOR OF ITU All occurrences of FCLASS value “2.0“ in T.32 should be replaced with FCLASS value “2.1“. Union internationale
2、des tlcommunications - INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU T.32 (08/95) TERMINALS FOR TELEMATIC SERVICES ASYNCHRONOUS FACSIMILE DCE CONTROL - SERVICE CLASS 2 ITU-T Recommendation T.32 (Previously “CCITT Recommendation“) STD-ITU-T RECMN T-32-ENG
3、L 1995 Li8b259L Ob18550 bU3 FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (rru). The -T is responsible for studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to standar
4、dizing telecommunications 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 th
5、e 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 T.32 was prepared by IT-T Study Group 8 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 1 lth of August 1995. NOTE In this Recommenda
6、tion, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. . O IT 1996 All rights reserved.,No part of this publicahn may be reproduced or utilized in any form or by any means, electronic or mechanical, includi
7、ng pkmcopying and mfcrofilm, without permission in writing from the ITU. STD-ITU-T RECMN T-32-ENGL 1995 9 48b257L Ob38553 5qT 1 CONTENTS Introduction and scope . 1.1 Facsimile teminais . 1.2 Facsimile DCE 1.3 Scope 1.4 Overview 1.4.1 Service Class 1 1.4.2 Service Class 2 Normative references . Defin
8、itions Abbreviations . Facsimile DTE-DCE interchange circuits 5.1 Communication link data rates . 5.2 Asynchronous to synchronous conversion . 5.3 Flow control 5.4 Serial data interchange circuits . 5.4.1 Mandatory circuits 5.4.2 Optional circuits 5.4.3 Optional circuit behaviour Autodialler service
9、s 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.1 1 -. Command syntax 6.1.1 Character set and format . 6.1.2 DTE command lines 6.1.3 Basic command syntax 6.1.4 Extended command syntax . 6.1.5 Extended command parameter values . 6.1.6 Issuing commands . Command execution . 6.2.1 Command execution time .
10、 . 6.2.2 Aborting commands 6.3.1 Information text responses 6.3.2 Result code responses . Capabilities identification and control Call answering Call origination . Call termination DCE autodialier result codes Serial port flow control . Serial port rate control . . Y. . 6.10.1 Autobaud operation, +I
11、PR= 6.10.2 Fixed rate operation. +IpRO Data stream transparent commands 611 1.1 DTE to DCE strhs . 6.1 b.2 -DCE to DTE str DCE Group 3 Facsimile; Modem; Programmable Communications Interface. e . : - iv Recommendation T.32 (08195) STD-ITU-T RECMN T-32-ENGL 1995 = qBb259l1 Ob18555 195 Recommendation
12、T.32 ASYNCHRONOUS FACSIMILE DCE CONTROL - SERVICE CLASS 2 (Geneva, 1995) 1 Introduction and scope 1.1 Facsimile terminais Group 3 Facsimile terminals were developed for sending digitized documents over the General Switched Telephone Network (GSTN). These facsimile terminais are now in widespread use
13、 around the world. The operation of Group 3 Facsimile terminals has been standardized in Recommendations T.4, T.6 and T.30. 1.2 Facsimile DCE There are two types of adapters which allow Data Terminal Equipment (DTE) to communicate as Group 3 facsimile terminals. Some of these adapters are installed
14、inside the DTE, on the processor bus; these are called “fax boards”. Others are configured as an external “facsimile DCE”, connected to the DTE by a standard serial port (e.g. Recommendation V.24). using serial data interchange and start-stop framing as defined in Recommendation V.4. 1.3 Scope This
15、Recommendation contains protocols for use between a DTE? and a facsimile DCE. It supports automatic calling and answering. This Recommendation defines the commands that the DTE may issue to configure and control the DCE and the responses the facsimile DCE shall issue to those commands. This Recommen
16、dation is useful for intelligent DTEs and DTE software, facsimile DCEs and facsimile terminais with digital connection to DTEs. This Recommendation assumes that the DTE and DCE are connected via serial asynchronous connection using V.24 circuits; it requires the provision of the Packet Protocol (cla
17、use 9) when used on serial ports. However, the protocols defined may be implemented in any environment that provides a character serial bidirectional data stream, including processor-bus-attached “fax boards”, local area networks, Small Computer Systems Interface (SCSI, IS0 93 16), IEEE 1284, etc. T
18、he adaptation of these protocols and procedures to these alternative communication schemes is beyond the scope of this Recommendation. 1.4 Overview A system including a DTE and a facsimile DCE partitions Group 3 facsimile functions between the two devices. There are several levels in the Communicati
19、ons path where a functional partition can be made. This Recommendation describes a protocol for use at one of those levels, Service Class 2. Each level is described as a “Service Class” based on the increasing number of functions performed by the DCE. .- 1.4.1 Service Class 1 Service Class 1 is defi
20、ned in Recommendation T.31. Asynchronous Facsimile DCE Control Standard, Service Class 1, which describes a-set of services at the phBical and data link layers: waiting, signalling and HDLC data formatting. T.30 session managemeet and 7.4 or T.6 image data handling are done by the DE. 2- - _ - Recom
21、mendation T.32 (08/95) 1 1.4.2 Service Class 2 Service Class 2, as defined in this Recommendation, manages a set of services defined by Recommendation T.30. In Service Class 2 the facsimile DCE makes and terminates calls, manages the communication session, transports image data and may optionaily co
22、nvert between T.4 or T.6 image formats. The DTE prepares and interprets image data in compressed form, as described in Recommendation T.4 or T.6. The DTE transfers the image data as required by Recommendation T.30, prompted by the DCE. 2 Normative references The following ITU-T Recommendations, Inte
23、rnational Standards and National Standards contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and Standards are subject to revision and parties to agreements based
24、on this Recommendation are encouraged to investigate the possibility of applying the most recent edition of the Recommendations and Standards listed below. Members of IEC and IS0 maintain registers of currently valid International Standards. The TSB maintains a list of the currently valid ITU-T Reco
25、mmendationdCCIT Recommendations. - -T Recommendation T.4 (1993), Standardization of Group 3 facsimile apparatus for document transmission. - CCIT Recommendation T.6 (1988). Facsimile coding schemes and coding controlfunctions for Group 4 facsimile apparatus. -T Recommendation T.30 (1993), Procedures
26、 for document facsimile transmission in the general switched telephone network. - - - -T Recommendation T.3 1 (1993, Asynchronous facsimile DCE control - Service Class I. CCITT Recommendation T.50 (1992). International Reference Alphabet (IRA) (formerly International Alphabet No. 5 or IA5), Informat
27、ion technology - 7-bit coded character ser for information interchange. - CCIT Recommendation V.4 (1988), General stucture of signals of International Alphabet No. 5 code for character oriented data transmission over public telephone networks. CCITT Recommendation T.434 (1992), Binaryfile transfer f
28、ormat for the relematic services. ITU-T Recommendation V.8 (1994). Procedures for starting sessions of data transmission over the general switched telephone network. ITU-T Recommendation V.24 (1993), List of definitions for interchange circuits between Data Tenninal Equipment (DTE) and Data Circuit-
29、Tenninating Equipment (DCE). - - - - CCIT Recommendation V.25 (1988), Automatic answering equipment ador parallel automatic calling equipment on the general switched telephone network including procedures for disabling of echo control devices for both manually and automatically established calls. IT
30、U-T Recommendation V.25 ter (1995), Serial asynchronous automatic dialling and control. CCITT Recommendation T.81 (1992), Information technology - Digital compression and coding of continuous - tones still images - Requirements and guidelines. IS0 21 11:1985, Data communication - Basic mode control
31、procedures - Code independent information transfer. - - - 3 Definitions c. For the purposes of this Recommendation, the following definitions apply: 3.1 data to operate a DQ otfassimile DCE. In-practice, these are computers of any size. DTE (da. terminal equipment$ A DTE is any terminal or computer
32、capable of providing commands and _. - - 2 Recommendation T.32 (08195) 3.2 DCE (data circuit-terminating equipment): A DCE is any device which connects a DTE to a communications network. This Recommendation focuses on DCEs which connect to the GSTN. This class of DCEs includes DCEs compatible with t
33、he V-Series modem Recommendations and facsimile DCEs described below. 3.3 facsimile DCE A facsimile DCE is a device which provides facsimile communication facilities between a DTE and a remote Group 3 Facsimile terminal across the GSTN. A Class 2 facsimile DCE includes the following functions: contr
34、ol functions: interchange circuits to the DTE; HDLC data link layer functions; V-Series signal converters; autodialler functions; GSTN interface. 3.4 the facsimile DCE. The specific implementation of these functions is beyond the scope of this Recommendation. facsimile DTE: A facsimile DTE must prov
35、ide those Group 3 facsimile functions and services not provided by 4 Abbreviations For the purposes of this Recommendation, the following abbreviations are used: CCITT IRA IEEE IS0 International Organization for Standardization IT-T International Telegraph and Telephone Consultative Committee Intema
36、tional Reference Alphabet (Recommendation T.50) Institute of Electrical and Electronics Engineers Intemational Telecommunication Union Telecommunication Standardization XON XOFF IRA DC1 character, used to enable data flow on the opposite circuit IRA DC3 character, used to disable data flow on the op
37、posite circuit 5 Facsimile DTE-DCE interchange circuits A facsimile DCE described by this Recommendation uses an asynchronous serial connection between the DTE and the DCE. Use of this protocol on other DTE-DCE interfaces is beyond the scope of this Recommendation. 5.1 Communication link data rates
38、The communications link between the DTE and facsimile DCE shall provide full duplex character data at rates fast enough to accommodate the transfer of synchronous T.30 Phase C data. The DTE-DCE data rate shall be at least 25% faster than the maximum expected connection rate to accommodate the start
39、and stop bit overhead. For example, 12 O00 bit/s is the minimum rate needed to support synchronous rate of 9600 bit/s Phase C data; 19200 bids is sufficient to support facsimile signalling at up to 14400 bit/s. Since format conversion facilities can compress the transmit data, even higher rates may
40、be useful. It is preferred to use the highest data rate available. c Mechanisms to set the DTE-DCE serial rate are described in 6.10 and 6.2.10N.25 ter (IPR parameter). Because flow control is always used, changing the DTE-DCE communications link data rate during facsimile operation is not necessary
41、, notrecwrnended and DCEs are not required to support it (see 6.2.10N.25 ter). _. - ,- Recommendation T.32 (08/95) 3 STD*ITU-T RECMN T.32-ENGL 1995 48b259L Ob18558 9T4 V.24 circuit 102 5.2 Asynchronous to synchronous conversion Group 3 data communication is bit-synchronous. The DCE must delete start
42、 and stop elements from transmitted octets and add them to received octets. The bit order is by default unchanged between the DTE and the remote station, unless the DCE is directed otherwise by the +FBO parameter (8.5.3.4). Description Signal ground 5.3 Flow control 103 104 Flow control is necessary
43、 to match the DTE-DCE data rate to the line signalling rate and to the requirements of Group 3 data transmission (for example, provision must be made for minimum scan line times). In-band unidirectional DCl/DC3 (XON/XOm) flow control is mandatory; flow control using V.24 circuits 106 and 133 is opti
44、onal (see 6.2.12N.25 ter). Image data with the same ordinal values of DCl (l/l) or DC3 (1/3) shall not be interpreted as flow control commands. The DTE may turn off the above specified flow control methods, but some other method shall be used to avoid overrun of the DCE buffer. The credit method can
45、 be implemented using the transparent data command character pair (see 8.3.3.9). In the receive direction, the DTE can use delayed Packet Protocol acknowledge characters for flow control. Transmitted data Received data The response time of the DCE to indication of a DTE-not-ready condition are for f
46、urther study. These times shall not exceed 64 character times, as measured from the instant the DTE asserted the not-ready condition. The DCE shall further be prepared to accept at least 64 additional characters on circuit 103 at the instant it asserts a not-ready condition to the DTE. The mechanism
47、 to identify and select the flow control mechanism is defined in 6.2.12N.25 ter (+IFC). parameter in 8.5.3.2. NOTE - A facsimile DCE may provide additional data buffering beyond the needs of flow control. See the +FBS 5.4 Serial data interchange circuits 5.4.1 Mandatory circuits The required circuit
48、s are shown in Table 1. TABLE 1.32 Mandatory serial data interchange circuits 5.4.2 Optional circuits The optional circuits are shown in Table 2. Provision of additional circuits is optional. 5.4.3 Optional circuit behaviour The behaviour of circuits 105, 106 and 133 is described in 6.9 and 6.2.12N.
49、25 ter. The behaviour of circuit 108/2 is described in 6.7. The behaviour of circuit 125 is described in 6.5. When the DCE switches to +FCLASS= operation (including upon issuing a +FDM response when a data modem is detected during adaptive answering), th the the high order bit is ignored. Upper case characters are equivalent to lower case characters. For Phase C data transmission or reception, the data is binary (not Recommendation TSO), transferred using 8 data bits without parity (RecommendationV.4). It is therefore preferable to use character formattin
