ITU-T E.320-1988 加速建立和清除传真电报呼叫 Speeding up the establishment and clearing of phototelegraph calls

pdf标准 ITU-T E.320-1988 加速建立和清除传真电报呼叫 Speeding up the establishment and clearing of phototelegraph calls

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国外分类,ITU,ITU-T(电信标准分局),itu,加速,建立,清除,传真,电报,传真电报,呼叫,speeding,up,the,establishment,and,clearing,of,phototelegraph,calls

INTERNATIONAL TELECOMMUNICATION UNION )45 4 % TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU 4%,%0(/.% .%47/2+ !.$ )3$. /0%2!4)/. .5-"%2).' 2/54).' !.$ -/"),% 3%26)#% 30%%$).' 50 4(% %34!",)3(-%.4 !.$ #,%!2).' /& 0(/4/4%,%'2!0( #!,,3 )45 4 Recommendation % (Extract from the "LUE "OOK) NOTES 1 ITU-T Recommendation E.320 was published in Fascicle II.2 of the Blue Book. This file is an extract from the Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, the contents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below). 2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. © ITU 1988, 1993 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 writing from the ITU. Recommendation E.320 Fascicle II.2 - Rec. E.320 SPEEDING UP THE ESTABLISHMENT AND CLEARING OF PHOTOTELEGRAPH CALLS When international phototelegraph calls are sent over telephone circuits, the total time of occupation of the circuit often greatly exceeds the duration of the phototelegraph call itself. It is also important that telephone circuits should be held for as short a time as possible. The CCITT therefore recommends to Administrations to bear the following directives in mind whenever it is technically practicable: 1 Telephone circuits intended for phototelegraph transmissions should, at terminal repeater stations, pass through panels at the international phototelegraph position (IPP) enabling these circuits to be disconnected from the telephone service equipment and interconnected or connected to phototelegraph stations. Before switching on this circuit, it must be ensured that no telephone calls are in progress1). If there are calls, the circuit must be blocked as soon as the telephone call is over (preliminary blocking). 2 The calling phototelegraph position must be ready to call the corresponding phototelegraph position over the telephone circuit as soon as it notes that the chosen circuit has been cleared. The calling signal should automatically disconnect the telephone equipment from the circuit at the called end. The circuit is thus immediately available for the establishment of a phototelegraph call. 3 If the called phototelegraph position has to be obtained through a transit phototelegraph position, the procedure outlined above is applied successively to the two circuits which are to be interconnected. 4 The same signal (see § 2 above) can also be used to invite the incoming, and possibly the transit, IPP to enter the line: − if there are difficulties, or − to signal the end of transmission. Note – The calling frequency f2 used for phototelegraphy should be different from that used for telephone signalling f1. In the case of automatic or semiautomatic telephone circuits, frequency 500/20 Hz will be adopted as the signalling f2 frequency for phototelegraphy. _______________ 1) At the time agreed upon with the telephone service, if such a previous agreement is considered to be necessary by the telephone operating services. Fascicle II.2 - Rec. E.320 1

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