#define CAUSE_NORMAL 16
#define CAUSE_BUSY 17
#define CAUSE_NOANSWER 19
#define CAUSE_OUTOFORDER 27
#define CAUSE_INVALNUMBER 28
#define CAUSE_NOCHANNEL 34
#define CAUSE_TEMPFAIL 41
#define CAUSE_INVALCALLREF 81
const char *cause_name(int cause);