[asterisk-dev] chan_dahdi problem using FXOs with lines that do a polarity reversal on seizure, causes immediate answer or hangup

Alec Davis sivad.a at paradise.net.nz
Fri Nov 7 15:20:39 CST 2008

The problem is noticed under the following conditions when use an FXO
module/card operating on analog lines that do a line polarity reversal on

	answeronpolarityswitch=yes in chan_dahdi.conf the sympton is that the audio
is immediately connected with the caller, which can be a long pause as the
call is setup, then finaaly ring is heard from the remote telco.

	hanguponpolarityswitch=yes in chan_dahdi.conf the symptom is that the call
is immediately terminated when the line is seized, thus unable to make a

I have re structured the polarity reversal checking code in chan_dahdi but
initially reported the bug http://bugs.digium.com/view.php?id=13716 as 1.6.0
but forgot to set branch as TRUNK, this patch still applies and works with
current trunk. Is it possible to change the branch to trunk, or do I open a
new bug report with correct details, referencing this bug.

This problem I have seen using 3 Ericsson F250m, but could further test it
on a Jtec (Panaseer) ALEM2 card that has options for battery reversal at any
stage of the call.

Alec Davis

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