1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0G0!.$G0G0)3$./0%2!4)/. G0G0.5-“%2). G0G02/54).G0G0!.$G0G0-/“),%3%26)#%30%$).G0G050G0G04(%G0G0%34!“,)3(-%.4G0G0!.$#,%!2).G0G0/&G0G00(/4/4%,%2!0(G0G0#!,3)45G134G0G0RecommendationG0G0% (Ext
2、ract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation E.320 was published in Fascicle II.2 of the Blue Book. This file is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Bl
3、ue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication
4、 may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle II.2 - Rec. E.320 1Recommendation E.320Fascicle II.2 - Rec. E.320SPEEDING UP THE ESTABLISHMENT AND CLEARINGOF PHOTOTELEGRAPH
5、CALLSWhen international phototelegraph calls are sent over telephone circuits, the total time of occupation of thecircuit 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 therefo
6、re recommends to Administrations to bear the following directives in mind whenever it istechnically practicable:1 Telephone circuits intended for phototelegraph transmissions should, at terminal repeater stations, pass throughpanels at the international phototelegraph position (IPP) enabling these c
7、ircuits to be disconnected from the telephoneservice equipment and interconnected or connected to phototelegraph stations. Before switching on this circuit, it mustbe ensured that no telephone calls are in progress1). If there are calls, the circuit must be blocked as soon as thetelephone call is ov
8、er (preliminary blocking).2 The calling phototelegraph position must be ready to call the corresponding phototelegraph position over thetelephone circuit as soon as it notes that the chosen circuit has been cleared. The calling signal should automaticallydisconnect the telephone equipment from the c
9、ircuit at the called end. The circuit is thus immediately available for theestablishment of a phototelegraph call.3 If the called phototelegraph position has to be obtained through a transit phototelegraph position, the procedureoutlined above is applied successively to the two circuits which are to
10、 be interconnected.4 The same signal (see 2 above) can also be used to invite the incoming, and possibly the transit, IPP to enterthe line: if there are difficulties, or to signal the end of transmission.Note The calling frequency f2used for phototelegraphy should be different from that used for tel
11、ephonesignalling f1. In the case of automatic or semiautomatic telephone circuits, frequency 500/20 Hz will be adopted as thesignalling f2frequency for phototelegraphy._1)At the time agreed upon with the telephone service, if such a previous agreement is considered to be necessary by the telephoneoperating services.
