ISDN Revisted

[Simon Griffiths]

Thanks Brian that now a great deal more sence.

> -----Original Message-----
> From: Brian Somers [mailto:brian at Awfulhak.org]
> Sent: 02 April 2001 16:11
> To: Simon Griffiths
> Cc: Brian Somers; brian at Awfulhak.org
> Subject: Re: ISDN Revisted 
> 
> 
> > Excellent.  I'll see if BT would kindly swap the external t/a for the
> > internal version.
> > 
> > BTW is ISDN just like another com-port which you dump AT 
> commands to or is
> > there alott more to it ?  I was kinda naively under the 
> impression it was
> > exactly the same as using a standard modem.
> 
> Not really.  I'm no expert, but I'll say what I know.
> 
> ISDN is implemented as a ``bus'' with a control channel.  Data comes 
> in and goes out in packets - similar to the way you read and write 
> packets on an ethernet.
> 
> With an isdn card, the wire that you plug into the back of your 
> machine is the isdn bus.  You can connect other things to the bus too, 
> such as phones and terminal adapters.
> 
> A Terminal Adapter is an isdn device that presents a serial port on 
> the other side (the more expensive types may give you one or more 
> analogue phone jacks too so that you can use a regular analogue phone 
> with your ISDN setup).
> 
> I have a TA here that I use to receive incoming fax.  I do this 
> because there's no software support in FreeBSD to automatically 
> present the digital isdn stream as analogue data (I think that's 
> called v.35 or v.110 or something).  I plug a modem into the analogue 
> socket on my TA.
> 
> I also have an isdn card which I use for connecting to the 'net.  If 
> you use a TA to do multilink ppp (most TAs will hide the multi-link 
> stuff from the serial port so that you can use both isdn channels) 
> you end up with a 128k physical link and a 115200bit serial 
> connection - a pretty lousy setup when you think about it.  Instead, 
> it's best to use an ISDN card so that you can use the entire 
> available bandwidth.
> 
> I hope this makes some sense :)
> 
> > Si.
> 
> -- 
> Brian <brian at freebsd-services.co.uk>              <brian at Awfulhak.org>
>       http://www.freebsd-services.co.uk/      <brian@[uk.]FreeBSD.org>
> Don't _EVER_ lose your sense of humour !      <brian@[uk.]OpenBSD.org>
> 
>