74 Voice API Programming Guide — June 2005
Call Progress Analysis
3. After a SIT sequence is detected, ATDX_CPTERM( ) will return CR_CEPT to indicate an
operator intercept, and you can determine which SIT sequence was detected by obtaining the
actual detected frequency and duration for the tri-tone sequence using extended attribute
functions. These functions are described in detail in the Voice API Library Reference.
The following fields in the DX_CAP are used for frequency detection on voice boards. Frequencies
are specified in Hertz, and time is specified in 10 msec units. To enable detection of the second and
third tones, you must set the frequency detection range and time for each tone.
General
The following field in the DX_CAP is used for frequency detection on voice boards.
ca_stdely
Start Delay. The delay after dialing has been completed and before starting frequency
detection. This parameter also determines the start of cadence detection and positive voice
detection. Note that this can affect detection of the first element of an operator intercept tone.
Default: 25 (10 msec units).
First Tone
The following fields in the DX_CAP are used for frequency detection for the first tone.
Frequencies are specified in Hertz, and time is specified in 10 msec units.
ca_lowerfrq
Lower bound for first tone in Hz.
Default: 900.
ca_upperfrq
Upper bound for first tone in Hz. Adjust higher for additional operator intercept tones.
Default: 1000.
ca_timefrq
Minimum time for first tone to remain in bounds. The minimum amount of time required for
the audio signal to remain within the frequency detection range for it to be detected. The audio
signal must not be greater than ca_upperfrq or lower than ca_lowerfrq for at least the time
interval specified in ca_timefrq.
Default:5 (1 0 msec units).
ca_mxtimefrq
Maximum allowable time for first tone to be present.
Default: 0 (10 msec units).
Second Tone
The following fields in the DX_CAP are used for frequency detection for the second tone.
Frequencies are specified in Hertz, and time is specified in 10 msec units. To enable detection of
the second and third tones, you must set the frequency detection range and time for each tone.
Note: This tone is disabled initially and must be activated by the application using these variables.