1、INTERNATIONAL TELECOMMUN ICATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TERMINALS FOR TELEMATIC SERVICES T.0 (07/96) CLASSIFICATION OF FACSIMILE TERMINALS FOR DOCUMENT TRANSMISSION OVER THE PUBLIC NETWORKS ITU=T Recommendation T.0 (Previously “CCIlT Recommendation“) ITU-T RECMN
2、*T=O 96 4862591 Ob1bLL5 OTO FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to stan
3、dardizing 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
4、 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 T.0, was revised by ITU-T Study Group 8 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 3rd of July 1996. NOTE In this Recommendat
5、ion, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1996 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, includi
6、ng photocopying and microfilm, without permission in writing from the ITU. ITU-T RECMNxT-O 96 m 4862573 ObLbLLb T37 SUMMARY Recommendations T.2 and T.3 define Group 1 and Group 2 facsimile terminals respectively; such stand-alone terminals have not been manufactured for many years and Group 3 facsim
7、ile terminals are the only type being used on the GSTN. In recognition of this market situation, Study Group 8 has agreed to delete references to Groups 1 and 2 in Recommendations T.4 and T.30. In order to be consistent and to minimize the possibility of any confusion, it is proposed that this Recom
8、mendation be amended to delete references to Group 1 and Group 2 terminals and also to use consistent terminology. Recommendation T.0 (W96) i Recommendation T.0 CLASSIFICATION OF FACSIMILE TERMINALS FOR DOCUMENT TRANSMISSION OVER THE PUBLIC NETWORKS (Geneva, 1976; amended at Geneva, 1980; Malaga-Tor
9、remolinos, 1984, Melbourne, 1988 and in 1996) 1 need for providing sufficient operating speeds to meet users requirements. 2 of document facsimile terminal. For document facsimile transmission by international communications carried on the public networks there is a Users requirements may best be se
10、rved at the present time by classifying the following four basic categories 2.1 Group 3 (see Note) A terminal which incorporates means for reducing the redundant information in the document signal prior to the modulation process and which can achieve a transmission time less than 1 minute for a typi
11、cal typescript document of IS0 A4 size via a telephone-type circuit. The terminal may incorporate bandwidth compression of the line signal. Terminais for use over the public telephone network NOTE - This terminal has been standardized in Recommendation T.4. 2.2 Group 4 (see Note) A terminal which in
12、corporates means for reducing the redundant information in the document signal prior to transmission mainly via Public Data Networks (PDNs). The apparatus will utilize procedures applicable to the PDN and will assure an essentially error-free reception of the document. Terminals for use over the pub
13、lic data networks NOTE - This terminal has been standardized in Recommendations T.6, T.503, T.521 and T.563. The users will choose among these terminals, in accordance with their needs and the facilities afforded by the 3 connection and the network. 4 in accordance with Recommendation T.30. 5 T.62,
14、T.62 bis, T.70 and T.90. 6 terminals. Procedures for Group 3 document facsimile transmission in the public switched telephone network should be Procedures for Group 4 document facsimile transmission should be in accordance with Recommendations Annex A contains definitions for terms used in the T-Ser
15、ies Recommendations applicable to facsimile Annex A Definitions for terms used in the T-Series Recommendations applicable to facsimile terminals (This annex forms an integral part of this Recommendation) The following definitions apply to Recommendations T.l and T.4: A.l which cannot be used for pic
16、ture signal transmission. A.2 its diameter. dead sector (Recommendation T.1): In drum terminals, that portion of the drum surface the scanning time of drum factor (Recommendation T. 1): In drum terminals, the ratio of the usable scanning length of the drum to Recommendation T.0 (07/96) 1 ITU-T RECMN
17、*T-O 96 4862593 ObLb339 746 A.3 facsimile (Series T): The process of scanning a document (page), converting the image scanned into electrical signals for transmission to a remote receiver and the conversion of the received signals to produce a copy of the image originally scanned. A.4 density. AS sc
18、anned line by line. A.6 index of cooperation (Recommendation T.1): Quotient of the factor of cooperation divided by the quantity x. In the case of a drum terminal, the index of cooperation is also equal to the product of the drum diameter and the scanning density. A.7 on the reproduced picture, slig
19、ht waviness or breaks in lines that are regular on the original document. factor of cooperation (Recommendation T. i): The product of the total scanning line length and the scanning flat-bed transmitter (Recommendation T.1): A terminal in which the original document is placed flat and judder, longit
20、udinal (Recommendation T.1): Effect due to the irregular rotation of the drum or helix causing, A.8 concurrent overlapping and underlapping in the reproduced picture. A.9 (white). A.10 judder, transverse (Recommendation T.1): Effect due to irregularity of the scanning pitch resulting in nominal blac
21、k (white) (Recommendation T. 1): Level or frequency of the signal corresponding to a pure black pel (Series T): A contraction of “picture element”. A.ll phasing (Recommendation T.1): At the receiver, ensuring the exact coincidence of the midpoint of the scanning field, with the corresponding point a
22、t the transmitter so as to ensure the correct positioning of the picture on the recording medium. A.12 interruption corresponding to the white (black) is sent during the lost time. A.13 intended for the reproduction of graded tonal densities and in which a photographic process is used at the receive
23、r. A.14 picture element (Recommendation T.4): phasing signal (Recommendation T.1): A signal sent by the transmitter for phasing purposes. NOTE - Phasing is known as “phase white (black)” if the phasing signal is a black (white) signal of which a short phototelegraphy (Recommendation T. 1): Method of
24、 reception of facsimile telegraphy which is chiefly a) at transmission: The part of the area of the original document which coincides with the scanning spot at a given instant and which is of one intensity only, with no distinction of the details that may be included. b) at reception: The area of th
25、e finest detail that can be effectively reproduced on the recording medium. A.15 the corresponding dimensions of the original document. A.16 resolution (Series T): A measure of the capability for delineating picture detail. In Group 3 and Group 4 facsimile transmission resolution is expressed as pic
26、ture elements or pels per mm (horizontal resolution) and lines per mm (vertical resolution). reproduction ratio (Recommendation T.1): The ratio of the linear dimensions of the reproduced document to A.17 A.18 the other of the scanning field. A.19 scanning lines. A.20 scanning direction are inclined
27、to it, owing to a difference between the scanning speeds at transmission and reception. A.21 transmitter and receiver. scanning density (Recommendation T.1): Number of scanning pitches per unit length. scanning line (Recommendation T.1): The area explored by the scanning spot in one sweep from one s
28、ide to scanning pitch (Recommendation T.1): The distance between the corresponding edges of two consecutive skew (Recommendation T.4): A defect in reproduction in which lines that should be at right-angles to the synchronization (Recommendation T. 1): The establishment of equal scanning line frequencies at the 2 Recommendation T.0 (07/96)
