Voice API Programming Guide — June 2005 81
Call Progress Analysis
7.16.4 Outcomes of Cadence Detection
Cadence detection can identify the following conditions during the period used to establish the
cadence or after the cadence has been established:
•No Ringback
•Connect
•Busy
•No Answer
Although loop current detection and positive voice detection provide complementary means of
detecting a connect, cadence detection provides the only way in basic call progress analysis to
detect a no ringback, busy, or no answer.
Cadence detection can identify the following conditions during the period used to establish the
cadence:
No Ringback
While the cadence is being established, cadence detection determines whether the signal is
continuous silence or nonsilence. In this case, cadence detection returns a no ringback,
indicating there is a problem in completing the call.
Connect
While the cadence is being established, cadence detection determines whether the audio signal
departs from acceptable network standards for busy or ring signals. In this case, cadence
detection returns a connect, indicating that there was a “break” from general cadence
standards.
Cadence detection can identify the following conditions after the cadence has been established:
Connect
After the cadence has been established, cadence detection determines whether the audio signal
departs from the established cadence. In this case, cadence detection returns a connect,
indicating that there was a break in the established cadence.
No Answer
After the cadence has been established, cadence detection determines whether the cadence
belongs to a single or double ring. In this case, cadence detection can return a no answer,
indicating there was no break in the ring cadence for a specified number of times.
Busy
After the cadence has been established, cadence detection determines whether the cadence
belongs to a slow busy signal. In this case, cadence detection can return a busy, indicating that
the busy cadence was repeated for a specified number of times.
To determine whether the ring cadence is a double or single ring, compare the value returned by the
ATDX_SHORTLOW( ) function to the DX_CAP field ca_lo2rmin. If the
ATDX_SHORTLOW( ) value is less than ca_lo2rmin, the cadence is a double ring; otherwise, it
is a single ring.