Voice API Programming Guide — June 2005 45
Call Progress Analysis
•positive answering machine detection (post-connect part of call progress analysis)
•fax tone detection (post-connect part of call progress analysis)
Figure 2 illustrates the components of basic call progress analysis. Figure 3 illustrates the
components of PerfectCall call progress analysis. These components can all operate
simultaneously.
In basic call progress analysis, cadence detection is the sole means of detecting a no ringback, busy,
or no answer. PerfectCall call progress analysis uses cadence detection plus frequency detection to
identify all of these signals plus fax machine tones. A connect can be detected through the
complementary methods of cadence detection, frequency detection, loop current detection, positive
voice detection, and positive answering machine detection.
Figure 2. Basic Call Progress Analysis Components
Incoming
Signal
Frequency
Detection
Cadence
Detection
Loop
Current
Detection
Positive
Voice
Detection
Intercept
(SIT) No
Ringback Busy No
Answer Connect