
Finishing a call
Call disconnection also occurs through messages sent on the D-channel.
The message which conveys this information is the DISC, which also carries a cause
code.
A DISC may occur because one of the users terminates the call (by hanging up the phone,
for instance). The cause code will be 'normal call clearing'. A disconnection also may
happen before the call has been completed, for instance with cause code 'destination
busy', or for some other reason.
This diagram shows the interaction at the end of a successful call.
Receiving calls
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