Voice API Programming Guide — June 2005 55
Call Progress Analysis
7.6 Media Tone Detection on DM3 Boards
Media tone detection in call progress analysis is discussed in the following topics:
•Positive Voice Detection (PVD)
•Positive Answering Machine Detection (PAMD)

7.6.1 Positive Voice Detection (PVD)

Positive voice detection (PVD) can detect when a call has been answered by determining whether
an audio signal is present that has the characteristics of a live or recorded human voice. This
provides a very precise method for identifying when a connect occurs.
The ca_intflg field in DX_CAP enables/disables PVD. For information on enabling PVD, see
Section 7.4.3, “Setting Up Call Progress Analysis Parameters in DX_CAP”, on page 48.
PVD is especially useful in those situations where no other method of answer supervision is
available, and where the cadence is not clearly broken for cadence detection to identify a connect
(for example, when the nonsilence of the cadence is immediately followed by the nonsilence of
speech).
If the ATDX_CONNTYPE( ) function returns CON_PVD, the connect was due to positive voice
detection.

7.6.2 Positive Answering Machine Detection (PAMD)

Whenever PAMD is enabled, positive voice detection (PVD) is also enabled.
The ca_intflg field in DX_CAP enables/disables PAMD and PVD. For information on enabling
PAMD, see Section7.4.3, “Setting Up Call Progress Analysis Parameters in DX_CAP”, on
page 48.
When enabled, detection of an answering machine will result in the termination of call analysis
with the reason CR_CNCT (connected); the connection type returned by the
ATDX_CONNTYPE( ) function will be CON_PAMD.
The following DX_CAP fields govern positive answering machine detection:
ca_pamd_spdval
PAMD Speed Value: To distinguish between a greeting by a live human and one by an
answering machine, use one of the following settings:
•PAMD_FULL – look at the greeting (long method). The long method looks at the full
greeting to determine whether it came from a human or a machine. Using PAMD_FULL
gives a very accurate determination; however, in situations where a fast decision is more
important than accuracy, PAMD_QUICK might be preferred.
•PAMD_QUICK – look at connect only (quick method). The quick method examines only
the events surrounding the connect time and makes a rapid judgment as to whether or not
an answering machine is involved.
•PAMD_ACCU – look at the greeting (long method) and use the most accuracy for
detecting an answering machine. This setting provides the most accurate evaluation. It