ITU-T U 44-1988 MULTI-ADDRESS CALLS IN REAL TIME FOR BROADCAST PURPOSES IN THE INTERNATIONAL TELEX SERVICE《国际用户电报业务中供广播用的实时多址呼叫》.pdf

1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 5 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(G0G037)4#().0!24)#5,!2G0G03).!,).G0G0 amended at Melbourne, 1988)The CCITT,considering(a) the definitions of multi-address and broadcast calls; (Supplement No. 2 to F-Series Recommendations)(b) that n

2、ew systems are capable of providing broadcast facilities, thereby permitting a telex subscriber to setup a call to a list of destinations such that signals transmitted by the originating subscriber are received virtuallysimultaneously by the called subscribers;(c) that one, or more, of the destinati

3、ons could be an international destination;(d) the provisions of Recommendation F.61 1 relating to the chargeable duration;(e) the provisions of Recommendation D.61 for charging and accounting purposes;(f) the provisions of Recommendation U.15 on signalling interworking rules;(g) the provision of Rec

4、ommendation U.l on the receipt of text before or after the answerback code;(h) the provisions of Recommendation U.41 on changed address interception and call redirection,and further recognizingthat the calling and clearing procedures to be used in the originating exchange are a national matter,unani

5、mously recommendsthat the following general principles be adopted when setting up broadcast calls in the international telexservice:1 The setting-up of the various outgoing calls in a broadcast call by the originating exchange preferably be doneconcurrently rather than sequentially in order to minim

6、ize the holding time of international circuits.Where, however, calls are set up sequentially, then priority shall be given to the establishment of the nationalcalls first.2 The answerback codes of each called subscriber shall be returned to the originating exchange in accordancewith the relevant Ser

7、ies U Recommendations. How the received sequence of answerback codes is to be sent to thecalling subscriber is a national matter.Receipt of a service signal shall be handled in a similar manner. The method of informing the callingsubscriber of the received service signals, including the indication o

8、f any additional information received in accordancewith 10.1.2 of Recommendation U.1 is a national matter. This also applies to the RDI condition, in which case thecall will not be extended to a redirected subscriber.3 The standard text BCT MOM, in accordance with Recommendation F.60 2, should be tr

9、ansmitted by thecalling exchange to each called subscriber 150 ms after receipt of the respective answerback codes.4 Should the national network of the calling subscriber also provide a camp-on service, then this service shouldbe disabled in the case of broadcast calls.5 The maximum number of intern

10、ational addresses in a broadcast call shall be limited to 5.6 a) Having returned the list of received answerback codes (or service signals), the originating exchange shalladvise the calling subscriber to commence the transmission of the message by the return of the standardtext, GA, to his terminal

11、in accordance with Recommendation F.60 2.The broadcast call should now be through-connected from the calling subscriber to all called parties.2 Fascicle VII.2 - Rec. U.44b) It is recommended that the calling subscriber commence the transmission by forwarding his ownanswerback sequence to all called

12、parties using the Here Is key on his terminal.c) Alternatively, the originating exchange, if it can be so programmed, shall cause the transmission of thecalling subscribers answerback sequence to all called subscribers prior to the return of the GA signal.7 It shall be possible for any of the called

13、 subscribers to clear his individual connection in accordance with therelevant Series U Recommendations.Should all called subscribers clear their connections, then the originating exchange shall return the clearingsignal to the calling subscriber.8 However, it shall not be possible for any of the ca

14、lled subscribers to interrupt the transmission of signals fromthe calling subscriber to the other called parties.9 The access by subscribers to an exchange in another country for the purpose of setting-up a broadcast call shallnot be permitted. The provisions of Recommendation U.6 shall apply.10 Eac

15、h individual international connection shall be charged in accordance with the provisions ofRecommendation F.61 1.11 Clearing of a broadcast call, in response to the clear signal from the originating subscriber, shall comply withthe relevant U-Series Recommendations.For new systems, and as far as pos

16、sible for existing ones, should the originating subscriber wish to know thoseparties who cleared prematurely (and, by implication, those who received the complete message) then this should besignalled by terminating the transmitted text with the letter shift MMMM. The originating exchange will then

17、clearforward in the normal way, list those subscriber, if any, who cleared early to the originating subscriber and clearbackwards.Note Application of this procedure to destinations which use code conversion facilities is a matter for furtherstudy.References1 CCITT Recommendation The chargeable duration of a telex call, Rec. F.61.2 CCITT Recommendation Operational provisions for the international telex service, Rec. F.60.