[asterisk-bugs] [DAHDI-linux 0017318]: FXS Polarity Reversal on Hangup

[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:                
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Project:                    DAHDI-linux
Issue ID:                   17318
Category:                   NewFeature
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
JIRA:                        
Reviewboard Link:            
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Date Submitted:             2010-05-11 06:12 CDT
Last Modified:              2010-06-17 09:18 CDT
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Summary:                    FXS Polarity Reversal on Hangup
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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 (0123533) armeniki (reporter) - 2010-06-17 09:18
 https://issues.asterisk.org/view.php?id=17318#c123533 
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alecdavis: I'm afraid there's a misunderstanding someplace, as I am
completely aware of that feature/functionality.

As described, this issue is happening on a FXS channel, there are no FXO
channels involves in this situation.

Let me go through this again in more detail:

This is how the system is setup:

1) Linux box running Asterisk with a TDM400P and 4 *FXS* ports... not
FXO.
2) Several SIP trunks are connected to this box via Ethernet for various
lines in/out.
3) These FXS ports are then connected to the INPUT (or CO LINE CONNECTION)
to a large PBX system.

4) Normally, telco lines would be going to this PBX which would provide
ROD/ROI, however this is not the case as the Asterisk box is used to serve
the PBX with trunks/lines.

5) Since these FXS lines are being used as incoming/outgoing lines to the
PBX, they require to provide ROD/ROI so that the PBX knows when calls have
been disconnected.

I hope this makes it clearer.  

If anyone has played with a Linksys PAP2 ATA, this feature is also
included in that little box and is called either "reverse on hangup or
reverse on connect".

davidw: We're in Australia and it has nothing to do with the phones, but
the PBX which happens to be manufactured by Nortel and has its region set
to Australia.

So, in conclusion, what needs to happen is that when a call is
disconnected and the "Hangup" message appears in the Asterisk CLI - a
reorder tone is played AND a temporary reversal of the line is made.

Cheers,
Armen 

Issue History 
Date Modified    Username       Field                    Change               
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2010-06-17 09:18 armeniki       Note Added: 0123533                          
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