asterisk users - Oct 2006 - disabling hardware echo can on tdm2400p

Hey list,

Short version:
I have a need to disable the hardware can on the tdm24xxp I have.  I 
figure it's something in zconfig.h in the zaptel directory, but I'll be 
damned if I can figure it out.

Long version:
I have a tdm2403e card which is experiencing an odd problem;  When 
several lines are in use, there is a "bleeding" of lines.  My users
call
it the 'ghost'.  Regardless, they can hear other people's
conversation
on different lines.  I've been told this has to do with the hardware 
echo can I have on there, and that I should disable it if I continue 
having problems.  So that's where I stand.

Answers and opinions welcome. 

Sean

Sean Kennedy wrote:
> Hey list,
> 
> Short version:
> I have a need to disable the hardware can on the tdm24xxp I have.  I 
> figure it's something in zconfig.h in the zaptel directory, but
I'll be
> damned if I can figure it out.
> 
> Long version:
> I have a tdm2403e card which is experiencing an odd problem;  When 
> several lines are in use, there is a "bleeding" of lines.  My
users call
> it the 'ghost'.  Regardless, they can hear other people's
conversation
> on different lines.  I've been told this has to do with the hardware 
> echo can I have on there, and that I should disable it if I continue 
> having problems.  So that's where I stand.
> 
> Answers and opinions welcome.
Crosstalk is not an Echo Cancel issue.  It is usually caused by a wiring 
issue.  Search the archives or look at the Zaptel README for the module 
option to disable the echo canceler.

Hi.  

I don't believe this course of action will fix your issue.  It sounds like
crosstalk, where stray signals from one pair are transmitted onto another.

My standard voice quality troubleshooting fix is as follows.

1.  If the zaptel module is ancient, install the new release.
2.  Stop asterisk and run 'fxotune -I 5'.  This takes a while, 3-4
minutes
per line.
3.  Add 'fxotune -s' to /etc/init.d/asterisk
4.  Ask the Telco for the number to a milliwatt test line and use the
"correct" procedure to set the incoming gain in zaptel.conf.
5.  Loop two lines and use the "correct" procedure to set the outgoing
gain
in zaptel.conf.
6.  Reset all the echo cancelling and training settings to default.

Fxotune does some magic that matches the internal settings of the zaptel
card to the lines.
Setting the gain properly in the zaptel.conf puts the incoming signal into
the optimal range of the echo filters.
Resetting the echocanceler and training settings back to default pulls
everything back to a known value, which usually works well.

This has fixed it for me every time except once.  In the case of the
"once",
a cheap phone cable (flat, not twisted) was run 35 feet around the edges of
the room, under space heaters, from the NID to the closet, butt-spliced and
hooked to the 66block, and then to the PBX.  Replacing this cable with a
category 5 cable run under the house (I didn't have any Cat3) fixed it.

Ejay Hire

-----Original Message-----
From: asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Sean Kennedy
Sent: Saturday, October 07, 2006 5:31 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: [asterisk-users] disabling hardware echo can on tdm2400p

Hey list,

Short version:
I have a need to disable the hardware can on the tdm24xxp I have.  I figure
it's something in zconfig.h in the zaptel directory, but I'll be damned
if I
can figure it out.

Long version:
I have a tdm2403e card which is experiencing an odd problem;  When several
lines are in use, there is a "bleeding" of lines.  My users call it
the
'ghost'.  Regardless, they can hear other people's conversation on
different
lines.  I've been told this has to do with the hardware echo can I have on
there, and that I should disable it if I continue having problems.  So
that's where I stand.

Answers and opinions welcome. 

Sean

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