[asterisk-bugs] [DAHDI-linux 0015311]: Call to a FXS DAHDI channel with Panasonic KX-TG4000 connected drops in 8 seconds randomly

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=15311 
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Reported By:                vmikhelson
Assigned To:                
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Project:                    DAHDI-linux
Issue ID:                   15311
Category:                   dahdi (the module)
Reproducibility:            random
Severity:                   major
Priority:                   normal
Status:                     new
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Date Submitted:             2009-06-11 00:49 CDT
Last Modified:              2009-06-14 05:23 CDT
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Summary:                    Call to a FXS DAHDI channel with Panasonic KX-TG4000
connected drops in 8 seconds randomly
Description: 
More often than not a call placed to a DAHDI channel with Panasonic
KX-TG4000 connected would drop on its own in exactly 8 seconds after being
answered. Before being disconnected two (2) clicks are being heard in
succession. The second click kills the connection.
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 (0106372) alecdavis (reporter) - 2009-06-14 05:23
 https://issues.asterisk.org/view.php?id=15311#c106372 
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Vladimir:
If it is indeed the same problem I had experienced. DAHDI trunk, doesn't
exhibit this problem even on the TDM400P, checked tonight.

The fix for DAHDI 2.1.x (untested as I don't have an Asterisk NOW box):
On Debian in /etc/modprobe.d we add the line 
options wctdm reversepolarity=1 boostringer=1

Summary:
I believe the key to fixing this is the 'reversepolarity=1' module option
for the wctdm, how it's achieved in Centos I'm not sure.

Detail:
As I understand it, on the FXS module (Si3215), the line voltage is
reversed while ringing, and when you answer the line, it stays reversed for
6 seconds (ohttimer), then is switched back to normal, hence the click.

The workaround, operates the FXS line in reversepolarity, so ringing
doesn't have to reverse it, thus after 6 seconds of it being answered it
doesn't have to switch back to 'normal' polarity. 

Issue History 
Date Modified    Username       Field                    Change               
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2009-06-14 05:23 alecdavis      Note Added: 0106372                          
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