[asterisk-bugs] [Asterisk 0017318]: [patch] FXS Polarity Reversal on Hangup or Answer

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=17318 
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Reported By:                armeniki
Assigned To:                alecdavis
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Project:                    Asterisk
Issue ID:                   17318
Category:                   NewFeature
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     assigned
Asterisk Version:           I did not set the version :( 
JIRA:                        
Regression:                 No 
Reviewboard Link:           https://reviewboard.asterisk.org/r/797/ 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2010-05-11 06:12 CDT
Last Modified:              2010-09-07 02:16 CDT
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Summary:                    [patch] FXS Polarity Reversal on Hangup or Answer
Description: 
FXS lines normally connect to a telephone.  However, when FXS lines are
routed to an external PBX or Key System to act as "external" or "CO" lines,
it is extremely difficult, if not impossible for the external PBX to know
when the call has been disconnected without receiving a polarity reversal
on the line.

DAHDI/Asterisk should have a feature to allow a setting someplace, perhaps
in chan_dahdi.conf, to allow a FXS channel to provide a polarity reversal
on channel hangup.
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Relationships       ID      Summary
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related to          0017724 [patch] Race condition in handling writ...
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 (0126654) alecdavis (manager) - 2010-09-07 02:16
 https://issues.asterisk.org/view.php?id=17318#c126654 
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Additional Note: In a setup where an FXO port is connected to a Telco, and
an inbound call to an IVR where a message may be taken.

In testing, we have found that our telco only reverses the line polarity
on the outbound call's 'answer' and 'hangup' events, not an inbound call.
So when your called, and answer the call, you cannot rely on a polarity
reversal if the remote party hangs up first, as is the case when a message
is being taken by voicemail.

chan_dahdi.conf required on the Telco connected FXO port
busydetect=yes
busycount=4
busypattern=250,250 

Issue History 
Date Modified    Username       Field                    Change               
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2010-09-07 02:16 alecdavis      Note Added: 0126654                          
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