80 Voice API Programming Guide — June 2005
Call Progress Analysis
Figure 9. Cadence Detection
Once the cadence is established, the cadence values can be retrieved using the following extended
attribute functions:
ATDX_SIZEHI( )
length of the nonsilence period (in 10 msec units) for the detected cadence
ATDX_SHORTLOW( )
length of the shortest silence period for the detected cadence (in 10 msec units)
ATDX_LONGLOW( )
length of the longest silence period for the detected cadence (in 10 msec units).
Only one nonsilence period is used to define the cadence because the nonsilence periods have the
same duration.
Figure 10 shows the elements of an established cadence.
Figure 10. Elements of Established Cadence
The durations of subsequent states are compared with these fields to see if the cadence has been
broken.
nonsilence
silence
Dialing
Complete
Period Used to
Establish Cadence
Periods Compared to the
Established Cadence
The timings are given in units of 10ms.
nonsilence
silence
ATDX_LONGLOW
≈
50 50
25
ATDX_SHORTLOWATDX_SIZEHIGH
225