User's Manual

84 Voice API Programming Guide — June 2005
Call Progress Analysis
ca_nsbusy
Nonsilence Busy: the number of nonsilence periods in addition to ca_nbrdna to wait before
returning a busy. Default: 0. ca_nsbusy is added to ca_nbrdna to give the actual number of
busy cadences at which to return busy. Note that even though ca_nsbusy is declared as an
unsigned variable, it can be a small negative number.
Do not allow ca_nbrdna + ca_nsbusy to equal 2. This is a foible of the 2’s complement bit
mapping of a small negative number to an unsigned variable.
7.16.5.4 Cadence Detection Parameters Affecting a Connect
You can cause cadence detection to measure the length of the salutation when the phone is
answered. The salutation is the greeting when a person answers the phone, or an announcement
when an answering machine or computer answers the phone.
By examining the length of the greeting or salutation you receive when the phone is answered, you
may be able to distinguish between an answer at home, at a business, or by an answering machine.
The length of the salutation is returned by the ATDX_ANSRSIZ( ) function. By examining the
value returned, you can estimate the kind of answer that was received.
Normally, a person at home will answer the phone with a brief salutation that lasts about 1 second,
such as “Hello” or “Smith Residence.” A business will usually answer the phone with a longer
greeting that lasts from 1.5 to 3 seconds, such as “Good afternoon, Intel Corporation.” An
answering machine or computer will usually play an extended message that lasts more than 3 or 4
seconds.
This method is not 100% accurate, for the following reasons:
• The length of the salutation can vary greatly.
• A pause in the middle of the salutation can cause a premature connect event.
• If the phone is picked up in the middle of a ringback, the ringback tone may be considered part
of the salutation, making the ATDX_ANSRSIZ( ) return value inaccurate.
In the last case, if someone answers the phone in the middle of a ring and quickly says “Hello”, the
nonsilence of the ring will be indistinguishable from the nonsilence of voice that immediately
follows, and the resulting ATDX_ANSRSIZ( ) return value may include both the partial ring and
the voice. In this case, the return value may deviate from the actual salutation by 0 to +1.8 seconds.
The salutation would appear to be the same as when someone answers the phone after a full ring
and says two words.
Note: A return value of 180 to 480 may deviate from the actual length of the salutation by 0 to +1.8
seconds.