Recommendation U.44

MULTI-ADDRESS CALLS IN REAL TIME FOR BROADCAST PURPOSES

IN THE INTERNATIONAL TELEX SERVICE

(Malaga-Torremolinos, 1984; 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 new systems are capable of providing broadcast facilities, thereby permitting a telex subscriber to set up a call to a list of destinations such that signals transmitted by the originating subscriber are received virtually simultaneously by the called subscribers;

(c)	that one, or more, of the destinations 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 Recommendation U.1 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 recognizing

that the calling and clearing procedures to be used in the originating exchange are a national matter,

unanimously recommends

that the following general principles be adopted when setting up broadcast calls in the international telex service:

1	The setting-up of the various outgoing calls in a broadcast call by the originating exchange preferably be done concurrently rather than sequentially in order to minimize the holding time of international circuits.

Where, however, calls are set up sequentially, then priority shall be given to the establishment of the national calls first.

2	The answerback codes of each called subscriber shall be returned to the originating exchange in accordance with the relevant Series U Recommendations. How the received sequence of answerback codes is to be sent to the calling subscriber is a national matter.

Receipt of a service signal shall be handled in a similar manner. The method of informing the calling subscriber of the received service signals, including the indication of any additional information received in

accordance with S 10.1.2 of Recommendation U.1 is a national matter. This also applies to the RDI condition, in which case the call will not be extended to a redirected subscriber.

3	The standard text BCT MOM, in accordance with Recommendation F.60 [2], should be transmitted by the calling 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 should be disabled in the case of broadcast calls.

5	The maximum number of international 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 shall advise the calling subscriber to commence the transmission of the message by the return of the standard text, GA, to his terminal in accordance with Recommendation F.60 [2].

The broadcast call should now be through-connected from the calling subscriber to all called parties.

b)	It is recommended that the calling subscriber commence the transmission by forwarding his own answerback sequence to all called 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 the calling subscriber's answerback sequence to all called subscribers prior to the return of the GA signal.

7	It shall be possible for any of the called subscribers to clear his individual connection in accordance with the relevant Series U Recommendations.

Should all called subscribers clear their connections, then the originating exchange shall return the clearing signal to the calling subscriber.

8	However, it shall not be possible for any of the called subscribers to interrupt the transmission of signals from the 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 shall not be permitted. The provisions of Recommendation U.6 shall apply.

10	Each individual international connection shall be charged in accordance with the provisions of Recommendation F.61 [1].

11	Clearing of a broadcast call, in response to the clear signal from the originating subscriber, shall comply with the relevant U-Series Recommendations.

For new systems, and as far as possible for existing ones, should the originating subscriber wish to know those parties who cleared prematurely (and, by implication, those who received the complete message) then this should be signalled by terminating the transmitted text with the letter shift MMMM. The originating exchange will then clear forward in the normal way, list those subscriber, if any, who cleared early to the originating subscriber and clear backwards.

Note - Application of this procedure to destinations which use code conversion facilities is a matter for further study.

References

[1]	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.