Voice API Programming Guide — June 2005 53
Call Progress Analysis
To enable ringback detection, turn on SIT frequency detection in the DX_CAP ca_intflg field. For
details, see Section 7.4.3, “Setting Up Call Progress Analysis Parameters in DX_CAP”, on
page 48.
The following DX_CAP fields govern ringback behavior on DM3 boards:
ca_cnosig
Continuous No Signal: the maximum length of silence (no signal) allowed immediately after
the ca_stdely period (in 10 msec units). If this duration is exceeded, call progress analysis is
terminated with the reason CR_NORB (no ringback detected). Default value: 4000 (40
seconds).
ca_noanswer
No Answer: the length of time to wait after the first ringback before deciding that the call is
not answered (in 10 msec units). If this duration is exceeded, call progress analysis is
terminated with the reason CR_NOANS (no answer). Default value: 3000 (30 seconds).
7.5.4 Busy Tone Detection
Call progress analysis specifies two busy tones: TID_BUSY1 and TID_BUSY2. If either of them is
detected while frequency detection and cadence detection are active, then call progress is
terminated with the reason CR_BUSY. ATDX_CRTNID() identifies which busy tone was
detected.
To enable busy tone detection, turn on SIT frequency detection in the DX_CAP ca_intflg field. For
details, see Section 7.4.3, “Setting Up Call Progress Analysis Parameters in DX_CAP”, on
page 48.
7.5.5 Fax or Modem Tone Detection
Call progress analysis specifies two tones: TID_FAX1 and TID_FAX2. If either of these tones is
detected while frequency detection and cadence detection are active, then call progress is
terminated with the reason CR_FAXTONE. ATDX_CRTNID() identifies which fax or modem
tone was detected.
To enable fax or modem tone detection, use the ca_intflg field of the DX_CAP structure. For
details, see Section 7.4.3, “Setting Up Call Progress Analysis Parameters in DX_CAP”, on
page 48.
7.5.6 SIT Frequency Detection
Special Information Tone (SIT) frequency detection is a component of call progress analysis. On
DM3 boards, SIT sequences are defined as standard tone IDs.
To enable SIT frequency detection, use the ca_intflg field of the DX_CAP structure. For more
information, see Section 7.4.3, “Setting Up Call Progress Analysis Parameters in DX_CAP”, on
page 48.