[Asterisk-Users] Re: Echo and other reasons to migrate to BRI

[Paul Davidson]

Brent-

There is no good way to say what changing the hardware and PSTN hookup will
probably do for the echo problems.  I'm not sure if you mentioned (lost in
the past history of your post now) what sort of hardware you're using for
PSTN connection now- TDMs, X100s, ATA's, etc- but that could also be a
potential cause. I've heard tell of aftermarket X100s and certain ATA's
being very finicky with echo- and age of hardware can sometimes make a
difference.  I personally use and recommend the Cisco handsets- it's hard
(IMHO) to get echo generated there.  Adjusting the gains, as you've already
done, is generally step two, and should be done with caution, but it sounds
like you've got that part down.

I will say that, if you have generally poor audio quality on your PSTN
circuits- (and I would measure the difference between 'through the 7960' and
'through an analog handset plugged into the line' by ear to confirm- you may
have already done this), it is definitely time to start looking for
alternate PSTN termination.  Each new method, however, brings with it
additional chances for echo problems- however, if you're working with a
single Asterisk box, all lines and handsets terminated to it, a digital
circuit directly to it (via Digium TDM card) presents the *smallest*
possible chance for echo problems- you're left with network issues, or
possible server performance issues.

Instead of BRI (which has more complicated hardware and channel drivers),
you might consider a fractional PRI, or an Integrated Access circuit, where
you're bringing in the full T1, but paying only for a few channels.  I know
that that's available here in Illinois, at very competitive pricing to BRI
circuits.  You may also want to switch to 100% VoIP provided termination,
porting your number to a carrier (I'm recently a fan of NuFone, and they're
relatively local to you, with centers in Michigan and Chicago- but YMMV), as
you know that's an echo free solution.

-Paul Davidson
 PlanCommunications, LLC

          Date: Tue, 28 Feb 2006 09:52:02 -0600

From: "Brent Torrenga" <lists at torrenga.com>
Subject: [Asterisk-Users] Re: Echo and other reasons to migrate to BRI
       from    POTS? Was (Echo on PRI/BRI?)
To: <asterisk-users at lists.digium.com>
Message-ID: <000b01c63c7e$eae0ba60$7200a8c0

@oscar>
Content-Type: text/plain;       charset="us-ascii"

Paul,

Ah, I see. Our echo is largly under control now. It took me a while to
figure out the gains and get them tuned, and now the echo only leaves very
small artifacts. Nonetheless, this still provokes the odd complaint here and
there. We use VOIP for outgoing calls when our POTS lines are congested, and
we find zero echo during those calls. Therefore, I assume that our handsets
(Cisco _79[46]0's) handle echo properly, and the source is our local loop.

I suppose then I cannot promise that migrating to a pair of BRI circuits (4
channels) will eliminate echo. It would be safe to say that echo would
PROBABLY be eliminated?

Other reasons to migrate: eliminate static/line noise (from our local loop,
can't do anything about the other end), speed up call setup time, eliminate
the 1 in 1000 chance that you will accidentally "answer" an incoming call
when trying to place an outgoing call.

Reasons not to migrate: more costly (about $15/month/channel), harder to
configure (I'm a bit intimidated - can't have downtime), if the * server
blows up one cannot simply plug in a $10 handset from Walmart to get some
bit of functionality - MUST use ISDN hardware.

Any experianced opinions on this?

>Brent-

>Echo can occur for all sorts of reasons- analog conversions as someone else
>already mentioned, 4 wire to 2 wire in particular- but could also occur in
>the IP path due to network issues, and can occur on any sort of digital or
>analog circuit due to various electrical or audio components. (one of the
>more commonly neglected causes is poor handsets, that do a bad job of
>isolating the speaker and microphone, or attempt to add sidetone
incorrectly
>(sidetone is the slight echo you should hear of your own voice- it's very
>hard to hear, but without it, you get the feeling that you're talking to a
>dead wire).  Conversion to BRI/PRI is a last step only, in my opinion,
>unless you have other compelling reasons to do so- there's a lot of other
>places to look first.

>If you could describe more of your particular setup, I'd be happy to give
>more detailed description of where the problems might lie.

>-Paul Davidson
> PlanCommunications, LLC


Sincerely,

Brent A. Torrenga
brent.torrenga at torrenga.com

Torrenga Engineering, Inc.
907 Ridge Road
Munster, Indiana 46321-1771

219.836.8918x325 Voice
219.836.1138 Facsimile
www.torrenga.com



>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20060228/7b212bd1/attachment.htm