[asterisk-bugs] [Asterisk 0013917]: [patch] fxo modules incorrectly believes channel is answered, if telco reverses line polarity at off hook.

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=13917 
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Reported By:                alecdavis
Assigned To:                jpeeler
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Project:                    Asterisk
Issue ID:                   13917
Category:                   Channels/chan_dahdi
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     closed
Asterisk Version:           SVN 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases):  trunk 
SVN Revision (number only!): 155671 
Request Review:              
Resolution:                 fixed
Fixed in Version:           
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Date Submitted:             2008-11-18 01:22 CST
Last Modified:              2009-06-26 14:28 CDT
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Summary:                    [patch] fxo modules incorrectly believes channel is
answered, if telco reverses line polarity at off hook.
Description: 
With answeronpolarityswitch=yes in chan_dahdi.conf
In our setup channels 63-65 in attached chan_dahdi.conf

When fxo modules are connected to analog lines that reverse polarity when
the line is picked up, the fxo driver (wcdtm) sends a polarity reversal
event, causing the channel to be answered, which is incorrect, as the call
is yet to be dialled.

The caller hears a very short ring, then silence for a while as the call
is set up, then finally remote ringing. This is very off putting for the
unaware user.

The attached patch chan_dahdi.diff.txt patch, sets the polaritydelaytv at
call setup, then uses the same sytle of checking mechnism as is used for
hanguponpolarityswitch=yes.

The DAHDI_EVENT_POLARITY in dahdi_handle_event has been reworked, from
using IF/ELSE statements with multiple OR's to easier to read SWITCH
statements.

Has been on a production box for nearly a month with around 100 calls out
of the fxo channels a day, with clean sounding ringing, with audio passed
as soon as the called party answers.



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Relationships       ID      Summary
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related to          0013716 [patch] Prevent false answer of channel...
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 (0107035) svnbot (reporter) - 2009-06-26 14:28
 https://issues.asterisk.org/view.php?id=13917#c107035 
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Repository: asterisk
Revision: 203700

_U  branches/1.6.1/
U   branches/1.6.1/channels/chan_dahdi.c

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r203700 | jpeeler | 2009-06-26 14:28:24 -0500 (Fri, 26 Jun 2009) | 23
lines

Merged revisions 203672 via svnmerge from 
https://origsvn.digium.com/svn/asterisk/trunk

........
  r203672 | jpeeler | 2009-06-26 14:03:25 -0500 (Fri, 26 Jun 2009) | 16
lines
  
  Check if polarityonanswerdelay has elapsed before setting a channel as
answered
  after a polarity reversal.
  
  Previously on a polarity switch event chan_dahdi would set the channel
  immediately as answered. This would cause problems if a polarity
reversal
  occurred when the line was picked up as the dial would not have yet
occurred. 
  Now if the polarity reversal occurs before delay has elapsed after
coming off
  hook or an answer, it is ignored. Also, some refactoring was done in
  _handle_event.
  
  (closes issue https://issues.asterisk.org/view.php?id=13917)
  Reported by: alecdavis
  Patches:
        chan_dahdi.bug13917.feb09.diff2.txt uploaded by alecdavis (license
585)
  Tested by: alecdavis
........

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http://svn.digium.com/view/asterisk?view=rev&revision=203700 

Issue History 
Date Modified    Username       Field                    Change               
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2009-06-26 14:28 svnbot         Checkin                                      
2009-06-26 14:28 svnbot         Note Added: 0107035                          
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