Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mdisea!mdivax1!van-bc!sl
From: sl@wimsey.bc.ca (Stuart Lynne)
Newsgroups: comp.dcom.fax
Subject: Re: fax/phone switches ?
Message-ID: <1991Jun07.184109.1367@wimsey.bc.ca>
Date: 7 Jun 91 18:41:09 GMT
References: <1991Jun5.145752.16042@uni-paderborn.de> <1991Jun6.000911.14780@athena.mit.edu> <1005@goblin.ntg.com>
Organization: Wimsey Associates
Lines: 31

In article <1005@goblin.ntg.com> dplatt@ntg.com (Dave Platt) writes:
>In article <1991Jun6.000911.14780@athena.mit.edu> caserta@athena.mit.edu (Francesco Caserta) writes:
>
>> No problem at all. Modems and faxes send acoustic signals that are
>> specified in worldwide accepted standards. Depending on the signal they
>> hear, they will switch to the right device. (There is some exception for
>> some old equipment.)
>
>Actually, I think it _is_ a problem.  It's true that faxes (Group 3, at
>least) do send a specific tone every few seconds after they dial, and
>that a fax-aware answering machine or switch can use this tone to route
>the call to a fax machine.

This is called CNG and is not a mandatory part of the G3 (aka T.30) standard in
North America (it is mandatory in many European countries I'm told).

So many fax machines sold in NA have CNG disabled. Usually it can be re-enabled. But
given consumers that have a tough time selecting FINE mode over STD it's not
apparent that it would be to easy to get a machine that's calling you fixed. Also it
is sometimes not too easy. For example I've got a little Fujistu Dex Ten, to turn
CNG on I had to phone Fujistu Canada, track down a support engineer and he fax'd me
some pages from the Service manual. It just wasn't in the Users manual at all.

I've been told by the people who design modems that there is currently no way to
accuratly determine the difference between data modems and fax modems. If there was
they would be rushing to get it into the standards. It's certainly a hot topic at
the standards meetings.

-- 
Stuart Lynne	Computer Signal Corporation, Canada
		...!van-bc!sl 604-937-7785 604-937-7718(fax) sl@wimsey.bc.ca