When in-band tones/announcements are not provided, the DISCONNECT message does not contain progress indicator No.8 in-band information or appropriate pattern now available. The network shall initiate clearing by sending the DISCONNECT message; start timer T305; disconnects the B-channel and enters the Disconnect Indication state.
On the receipt of the DISCONNECT message without progress indicator No. 8, the user shall disconnect the B-channel; send a RELEASE message; start timer T308, and enter the Release Request state.
On receipt of the RELEASE message, the network shall stop timer T305; release the B-channel; send a RELEASE COMPLETE message; release the call reference, and return to the Null state.
If timer T305 expires, the network shall send a RELEASE message to the user with the cause number originally contained in the DISCONNECT message; start timer T308, and enter the Release Request state. In addition to the original clearing cause, the RELEASE message may contain a second Cause information element with cause No. 102, recovery on timer expiry.