From: curt@oasys.dt.navy.mil (Curt Welch)
Newsgroups: comp.dcom.isdn
Subject: Re: The ISDN network
Date: 16 Dec 92 17:17:40 GMT
Reply-To: curt@oasys.dt.navy.mil (Curt Welch)
Organization: Carderock Division, NSWC, Bethesda, MD

In a previous article deej@cbnewsf.cb.att.com (david.g.lewis) writes:
>2. It could use a multiple-call method, first attempting a 64UDI call, and
>if that is cleared by the network or the called customer, reattempting using
>3.1kHz audio.

In comp.dcom.isdn, bcapps@atlastele.com (Brent Capps) writes:
>Be serious.  Given the low number of successful terminations ISDN is
>going to achieve, you've effectively doubled the user's phone bill.

Not.

>These are very big systems with phone bills in the hundreds of
>thousands per month.  More likely we'll try POTS first, and if we
>can't connect that way we'll punt and point the finger at the terminating
>equipment.  Sooner or later they'll get the message that ISDN is costing
>them more trouble than it's worth and go back to POTS.

First, I don't know how ISDN charges work, but I doubt that you will be
charged anything for trying to place the 64K UDI call.  The network
will just return an error - like a busy signal - if the destination
can't answer that type of call.  At most, I'd expect that you would be
charged $.10.

The Fax will just automatically do this (so the user doesn't have to
try to fax everything twice - once G4 and then once G3).  It will first
try to use G4, and if that fails, it will use G3.

Question for the ISDN experts: Can an ISDN call request a 64UDI
service, but specify that a voice grade service is OK if 64UDI is not
available?  Or would it have to try 64UDI, and then if that failed, try
voice (assuming this neat sounding line database service wasn't
available).

And why would you go to the trouble of using a G4 fax and trying it
first?  Because G3 faxes uses 9600 baud modems.  G4 use 64000.  That's
over 6 times faster.  And I think G4 includes more advanced compression
algorithms, which could give you an even greater speed up.  All this
will (one day) add up to a great cost reduction in the price of sending
a fax.  Right now however, because of the limited avalibility of ISDN,
and the over inflated prices for the service, I think it still costs more.

In a few years, we will start seeing G4 ISDN fax machines that also
work as a laser printer, copier, and scaner.  On the NextStep TV show,
I saw a segment that talked about just such a machine (but G3 not G4)
that was just announced by one of the big computer printer
manufacturers.

Once you switch to G4 fax, you can get 400 dpi resolution (higher
resolution the the current de facto 300 dpi laser printer standard.)
So if you have these G4 fax/printer/copier/scaners, the best way to
connect them to your computer is not through a local LAN, but through
the phone system.

If you use the phone system as your LAN, then you can not only print
files on your local office printer, but you will be able to print them
on any G4 fax (i.e. printer) in the world.

Some computers - like the NeXT - are already set up to do this (but
they have only limted G4 support at this point).  On the NeXT, the
print panel that all applications share, has a Fax button.  Any
application that can print to a laser printer can also send it's output
to a fax.  When my laser printer was broken, I used my fax machine as a
printer.  Because the fax was G3, and used standard sucky fax paper,
this wasn't a great alternative, but it worked.

Once G4 faxes and ISDN become available, it will not only be possible
to use your fax as your printer, it won't make much sense to do it any
other way. (well actually - there is still yet another protocol problem
here that needs to be solved.  Even at 64K, a 400 dpi page can take a
few minutes to transfer - which is too slow.  For general use as a
computer printer there needs to be a standard way to send printer page
description languages like PostScript to these printer/faxes over the
ISDN link.  Technically this is simple, but the protocol needs to
defined first, and this is what takes so much time.)

Curt Welch
Newsgroups: comp.dcom.isdn