44 Voice API Programming Guide — June 2005
Call Progress Analysis
There are two forms of call progress analysis:
PerfectCall call progress analysis
Also called enhanced call progress analysis. Uses an improved method of signal identification
and can detect fax machines and answering machines. You should design all new applications
using PerfectCall call progress analysis. DM3 boards support PerfectCall call progress
analysis only.
Note: In this document, the term call progress analysis refers to PerfectCall call progress
analysis unless stated otherwise.
Basic call progress analysis
Provides backward compatibility for older applications written before PerfectCall call progress
analysis became available. It is strongly recommended that you do not design new applications
using basic call progress analysis.
Caution: If your application also uses the Global Call API, see the Global Call documentation set for call
progress analysis considerations specific to Global Call. The Global Call API is a common
signaling interface for network-enabled applications, regardless of the signaling protocol needed to
connect to the local telephone network. Call progress analysis support varies with the protocol
used.
7.2 Call Progress and Call Analysis Terminology
On DM3 boards, a distinction is made between activity that occurs before a call is connected and
after a call is connected. The following terms are used:
call progress (pre-connect)
This term refers to activity to determine the status of a call connection, such as busy, no
ringback, no dial tone, and can also include the frequency detection of Special Information
Tones (SIT), such as operator intercept. This activity occurs before a call is connected.
call analysis (post-connect)
This term refers to activity to determine the destination party’s media type, such as voice
detection, answering machine detection, fax tone detection, modem, and so on. This activity
occurs after a call is connected.
call progress analysis
This term refers to the feature set that encompasses both call progress and call analysis.
7.3 Call Progress Analysis Components
Call progress analysis uses the following techniques or components to determine the progress of a
call as applicable:
•cadence detection (pre-connect part of call progress analysis)
•frequency detection (pre-connect part of call progress analysis)
•loop current detection (pre-connect part of call progress analysis)
•positive voice detection (post-connect part of call progress analysis)