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Re : [SLUG] ISDN (OnRamp/Home) experience, anyone?

>So, the question: has anyone used Linux to dial out on the
>digital link of one of these beasties?  The connection is just
>RS-232, so it must be a simple matter of software...

>Clues?  Things to read?  URLs?

There has been some discussion of this on the [Oz-ISP] mailing list. Below
is a mail that has some details about the device. As [Oz-ISP] is a public
mailing list I assume it fine for me to repost it here, not like its a
private mail.

Some pictures are also available at http://users.rendrag.net/~damien/orhh/


---------- Forwarded message ----------
To: Karl Ferguson <karl@xxxxxxxxxx>
Cc: Damien Gardner Jnr <rendrag@xxxxxxxxxxx>, aussie-isp@xxxxxxxxxx
Subject: Re: [Oz-ISP] OnRamp HomeHighway install.. 
Date: Fri, 07 Jul 2000 01:37:11 +0930
From: Leigh Hart <hart@xxxxxxxxx>
Sender: majordomo-owner@xxxxxxxxxxxxxxxx
Precedence: bulk


some facts about ORHH:

The NTU for ORHH is a "smart" ISDN network termination unit.  It
plugs into the U sock (the Telstra copper line that connects to
the IDSN switch linecard at the exchange).  This protocol is
identical to plain old OnRamp2, only the tarrif and NTU are

The NTU is made by the Open Group, NZ.

The NTU has:

an RS232 port capable of 115.2Kbit/sec async;
two POTS ports; and
one S/T port.

The S/T (or S-BUS) port is for connecting traditional ISDN gear
eg: ISDN routers (Cisco 1603, Ascend Pipeline, etc) or PCI cards
that talk ETSI ISDN, etc.

The POTS ports are mapped in the exchange and in the NTU to ring
or originate voice calls on each of the respective two telephone
numbers you have been assigned with the ORHH service.

The RS232 port is the fun one.  This is an interface into a Hayes
style AT command set that looks like a modem to your PC.

It comes with Windows software and "modem" drivers for MS Dialup
Networking to use, along with a program to select what "mode" you
want to use (all of which is manually selectable using a terminal
program and a swag of AT commands) one of:

64k PPP, 128k MPPP, 128k MPPP Dynamic Voice Override.

The unit itself runs PPP back to your PC, from there, depending 
on the option selected above, it will dial either a PPP or MPPP
session to your ISP.  If MPPP, *IT* does the MPPP to PPP adaption
and rate adapts down from 128Kbit/sec SYNC to 115.2Kbit/sec ASYNC.

Why anyone would spend the extra $$ on making a 128k SYNC call only
to have it rate adapted down to 115.2k async is beyond me - that's
only ever going to allow 10.2KBytes/sec into your PC, if your PC's
UARTS can cope with that speed.

But, the feature is there nontheless.

Considering how *new* this device is in the Open Group's range, I'm
surprised it doesn't have the 235Kbit/sec RS232 UARTs on board, but
alas, most PC's don't support that anyway.

The Dynamic Voice Override (DVO) feature allows both an incoming or
outgoing voice call to occur while you are running at 128k (ok, at
10.2Kbytes/sec then).  The NTU does this by detecting the incoming
signal on the D channel, then dropping one of the two MPPP channels
freeing up a line and then returning a signal back to the Telstra
switch to say "proceed with that call, Jeeves!" - or if making an
outgoing call, as soon as the handset is lifted, it does the same
thing (apart from signalling the exchange at that point, of course).

Once the voice call (incoming or outgoing) is finished, the NTU will
try to re-establish the second MPPP channel (all transparently to 
your PC's plain ole PPP session to *THE NTU*.

That should be enough for now - more technical analysis will come
when mine is actually installed early next week :-)

"Karl Ferguson" <karl@xxxxxxxxxx> wrote:
> > The NT1Plus is somewhat larger than a standard NT1 (a couple of
> > pics at http://users.rendrag.net/~damien/orhh/), has a row of
> > RJ45 connectors on the back for the 'U' cable in, S-bus out,
> > rs-232 out (This is a mac-serial style connector), and the two
> > voice lines (Tel1/Tel2) out.
> The NT1Plus is just an ISDN modem with a few add ons (the words from a
> Telstra tech I talked to today).  You don't need an ISDN modem/router to
> plug into the ISDN port either (which eliminates a cost straight away) -
> mereley connect your serial port to that Mac-style connector and dial out
> like a modem (aparantly).  The charging rate is a data call and it only uses
> one B channel aparantly (he couldn't confirm that).
> Quite a good idea actually.


| "By the time they had diminished | Leigh Hart, hart@xxxxxxxxx |
|  from 50 to 8, the other dwarves | CCNA: http://www.cisco.com |
|  began to suspect 'Hungry' ..."  | PO Box 3057 Newton SA 5074 |
|   -- Gary Larson, "The Far Side" | http://www.dotat.com/hart/ |
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