[Asterisk-Users] ISDN2e card

[Pauline Middelink]

On Thu, 08 May 2003 around 14:52:28 +0200, Patrick wrote:
> On Thu, 2003-05-08 at 09:36, Pauline Middelink wrote:
> [snip]
> > 
> > Than have a look at all the cards isdn4linux supports.
> > They are available from 35 euros up into the 300 euro
> > range (all depending if you want an active card, or
> > a card with a capi driver so you can use kapejods
> > chan_capi)
> > 
> >     Met vriendelijke groet,
> >         Pauline Middelink
> 
> My personal experience with a cheap $25 HFC chipset based passive ISDN
> card is that the echo is horrible and unusable in a production
> environment. I have asked a question about it on this list but there
> doesn't seem to be a simple solution other than to buy an active ISDN
> card and use chan_capi. Iirc only these brands are supported by
> chan_capi: Eicon Diva Server Series and AVM B1. Good luck!

The problem is not with the card, its with the interface to
asterisk. The i4l driver handles the isdn line like sa serial
link (modem alike). This will get the data through, but introduces
latency. Latency == echo. So we need a echo canceler. Which
wont work because echo canceling works by subtracting the
outgoing signal from the incoming. So we need to know
precisly what the other party is hearing when we send. This
we dont know because of all the serial buffers inbetween.
So no echo canceler, so bigtime echo.

You still wonder why you get any sound from your card??? :)

Anyway, if you use the card for an IVR system all is well.
So its full up to the situation you are going to use it for.

PS. The best way is to just take the hfcpci driver from i4l
    and interface it to the zaptel module. This will deliver
    3 channels, 1 D and 2 B. Than adjust libpri to do TEI
    negociations and you are home free. A ISDN2 card (which
    can probably act as a NT1 too with a small terminator
    and powersupply), instant echo support and all the other
    features the chan_zap delivers without hurting your feed.
    Or hand or whatever you were using kicking your computer :)

Oh yes, did i mention the about 2 weeks full time effort it
would take to do this? Nah? :)

    Met vriendelijke groet,
        Pauline Middelink
-- 
GPG Key fingerprint = 2D5B 87A7 DDA6 0378 5DEA  BD3B 9A50 B416 E2D0 C3C2
For more details look at my website http://www.polyware.nl/~middelink
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