Voice API Programming Guide — June 2005 51
Call Progress Analysis
7.5 Call Progress Analysis Tone Detection on DM3 Boards
The following topics discuss tone detection used in call progress analysis on DM3 boards:
•Tone Detection Overview
•Types of Tones
•Ringback Detection
•Busy Tone Detection
•Fax or Modem Tone Detection
•SIT Frequency Detection

7.5.1 Tone Detection Overview

Call progress analysis uses a combination of cadence detection and frequency detection to identify
certain signals during the course of an outgoing call. Cadence detection identifies repeating
patterns of sound and silence, and frequency detection determines the pitch of the signal. Together,
the cadence and frequency of a signal make up its “tone definition”.

7.5.2 Types of Tones

Tone definitions are used to identify several kinds of signals.
The following defined tones and tone identifiers are provided by the voice library for DM3 boards.
Tone identifiers are returned by the ATDX_CRTNID() function.
TID_BUSY1
First signal busy
TID_BUSY2
Second signal busy
TID_DIAL_INTL
International dial tone
TID_DIAL_LCL
Local dial tone
TID_DISCONNECT
Disconnect tone (post-connect)
TID_FAX1
First fax or modem tone
TID_FAX2
Second fax or modem tone
TID_RNGBK1
Ringback (detected as single tone)