1、 . ITU-T RECNN*S.ZL 93 4862591 058b175 TL3 = INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD I ZAT I ON SECTOR OF ITU TELEGRAPHY ALPHABETICAL TELEGRAPH TERMINAL EQUIPMENT s.21 (03/93) USE OF DISPLAY SCREENS IN TELEX MACHINES ITU-T Recommendation S.21 (Previously “CCITT Recomm
2、endation”) _ ITU-T RECMN+S*ZL 93 D 4862593 0586376 95T = FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The IT-T is responsible for studying technical, operating and tariff questions and issuing Recommendations o
3、n them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Re
4、commendation S.21 was revised by the ITU-T Study Group IX (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCIT ceased to exist as of 28 February 1993. In its place, the IT
5、Telecommunication Standardization Sector (ITU-T) was created as of i March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text to references c
6、ontaining the acronyms “CCIT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a recognized operating agency. In t
7、his Recommendation, the expression “Administration” is used for conciseness to indicate both a O IT 1994 All 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 w
8、riting from .the ITU. ITU-T RECHN*S-ZL 93 W 48b259L 058bL77 896 Recommendation 5.21 USE OF DISPLAY SCREENS IN TELEX MACHINES (Geneva 1980; modijed at Helsinki, 1993) The CCITT considering (a) requirements laid down in Recommendations F.60 l, S.3, S.4, S.6, S.8 and S.9; that any terminal machine conn
9、ected to the telex network should meet the basic operational and technical (b) that a visual display screen facilitates message preparation and automatic calling in the telex service; (cl that it is important that the operator should not be interrupted in his work of preparing messages by an incomin
10、g call, except that the operator may need to be alerted if combination No. 10 in figure-shift in International Telegraph Alphabet No. 2 is received on the incoming line; (4 telex terminal should be recorded in a permanent form, that customer confidence in correct delivery of a telexed message requir
11、es that all signals sent or received by a unanimously declares the following views 1 Transmission of the answer-back should be in accordance with Recommendations S.6 and S.9. 2 line. Such signals do not necessarily need to be presented on the display screen. It is essential that any telex terminal i
12、nclude a printer that records at least ail the signais sent or received on the 3 the local printer. It should be possible to transmit a message prepared on the screen automatically to line and simultaneously to 4 When a call is received, the operator should be able to prepare or to continue preparin
13、g a message by means of the keyboard, the display screen and, possibly, storage equipment. All characters received from or transmitted to line should be printed. 5 subsequently appear on the page copy of the calling and called subscribers printers. The format and content of the message appearing on
14、the screen should be identical to those that will 6 message may be All the lines on the screen, except in a possible reserved area, should be available to display a message. This a) a message being prepared; b) c) NOTES a message already stored in a memory; a message incoming from the line. 1 In cas
15、es a) and b) the screen should constitute a window that the operator can move line by line over the message or the stored part of the message. It is highly desirable that the movement of the window over the message should stop automatically when there are no more stored characters, the last recorded
16、 line being visible at the top of the screen. 2 In case c) it is desirable that: - - the message received, apart from being printed, can be stored in the memory at the end of the call; that the operator can converse with his correspondent, all the characters transmitted or received being visible on
17、the screen. Recommendation S.21 (03/93) 1 ITU-T RECMN*S=21 93 YB62591 0586378 722 w 7 operator: A reserved area of the screen, where the operator cannot write anything, may be set aside in order to warn the a) that the memory is almost exhausted; or b) that the visible portion of the message does no
18、t include the beginning of the message. 8 The display screen and its memory should employ a line length of 69 printing characters. NOTE - This number of characters may not be strictly equivalent to the number sent to line, because the code used in the memory may not be the one used in telex calls. 9
19、 automatically at the end of transmission, so that the operator can send the same message to other addressees. It is very important that it should be possible to erase the message only at the command of the operator and not Reference 11 CCITT Recommendation Operational provisions for the international telex service, Rec. F.60. 2 Recommendation S.21 (03/93)
