When the SETUP message is delivered by a broadcast data link the channel selection procedure, provided in 5.2.3.1, is not applicable. The network sends a SETUP message with the Channel identification information element indicating one of the following:
a) channel indicated, no alternative is accepTable [i.e. channel is indicated by the information channel selection field of octet 3 (bits 2-1) and, if applicable, octet 3.3, and the preferred/exclusive field (bit 4 of octet 3) is set to "1" in the Channel identification information element]; or
b) no channel available [i.e. the information channel field (bits 2 and 1 of octet 3) of the Channel identification information element set to "00"].
The network starts timers T303 and T312.
In case a), if the user can accept the call on the indicated channel, the user shall send the appropriate message (see 5.2.4 and 5.2.5). If the user cannot accept the call on the indicated channel,the user shall send a RELEASE COMPLETE message with cause No. 44, requested circuit/channel not available.
The user, in any case, must not connect to the channel until a CONNECT ACKNOWLEDGE message has been received.
In case b), the user not controlling any channel shall send a RELEASE COMPLETE message with cause No. 34, no circuit/channel available. Unless the procedures of the Call Waiting supplementary service (see Recommendation Q.953 [84]) are followed, the user wishing to re-use a B-channel it has already allocated to another call (e.g. by multiplexing packet calls) shall send the appropriate message containing the Channel identification information element, coded as channel is indicated,no alternative acceptable.