[asterisk-users] question about PSTN pickup

[James FitzGibbon]

On 10/12/07, Yair Hakak <yair at hakak.com> wrote:
>
>  you'll have to excuse the ignorance (i'm a software guy, not a telcom
> guy..)
>  Is there any way to know if a channel has been answered by an automatic
> system (like voicemail) rather than a human being?
>  Specifically, I want to use a .call to make a call on a channel and only
> do something if a person answers, not a machine of any kind. Is this even
> possible, or is an answered channel an answered channel?
>

Asterisk 1.4 has the AMD() application that uses several thresholds (which
you can vary) to determine if the other end is a human or machine:

  -= Info about application 'AMD' =-

[Synopsis]
Attempts to detect answering machines

[Description]
  AMD([initialSilence][|greeting][|afterGreetingSilence][|totalAnalysisTime]
      [|minimumWordLength][|betweenWordsSilence][|maximumNumberOfWords]
      [|silenceThreshold])
  This application attempts to detect answering machines at the beginning
  of outbound calls.  Simply call this application after the call
  has been answered (outbound only, of course).
  When loaded, AMD reads amd.conf and uses the parameters specified as
  default values. Those default values get overwritten when calling AMD
  with parameters.
- 'initialSilence' is the maximum silence duration before the greeting. If
   exceeded then MACHINE.
- 'greeting' is the maximum length of a greeting. If exceeded then MACHINE.
- 'afterGreetingSilence' is the silence after detecting a greeting.
   If exceeded then HUMAN.
- 'totalAnalysisTime' is the maximum time allowed for the algorithm to
decide
   on a HUMAN or MACHINE.
- 'minimumWordLength'is the minimum duration of Voice to considered as a
word.
- 'betweenWordsSilence' is the minimum duration of silence after a word to
   consider the audio that follows as a new word.
- 'maximumNumberOfWords'is the maximum number of words in the greeting.
   If exceeded then MACHINE.
- 'silenceThreshold' is the silence threshold.
This application sets the following channel variable upon completion:
    AMDSTATUS - This is the status of the answering machine detection.
                Possible values are:
                MACHINE | HUMAN | NOTSURE | HANGUP
    AMDCAUSE - Indicates the cause that led to the conclusion.
               Possible values are:
               TOOLONG-<%d total_time>
               INITIALSILENCE-<%d silenceDuration>-<%d initialSilence>
               HUMAN-<%d silenceDuration>-<%d afterGreetingSilence>
               MAXWORDS-<%d wordsCount>-<%d maximumNumberOfWords>
               LONGGREETING-<%d voiceDuration>-<%d greeting>

-- 
j.
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