From: alansar@ccs.northeastern.edu (Mohammad Al-Ansari)
Subject: Re: Telephone Fax Switch, CNG Signal, FaxModem Software
Organization: College of CS, Northeastern U
Date: Thu, 5 Nov 1992 22:18:22 GMT

In article <HXsPTB1w164w@wolferts.ka.sub.org> dkw@wolferts.ka.sub.org (Dr. Klaus Wolferts) writes:
>
>In <H.bpqHL9qENDw@moko.saar.de>, micha@moko.saar.de (Michael Bongartz) writes:
>> In <BwzDv3.n34@wimsey.bc.ca>, Stuart Lynne writes:
>> > In article <H.WkL1VZ9XpMo@moko.saar.de> micha@moko.saar.de writes:
>> > >In <1992Oct26.050119.7848@random.ccs.northeastern.edu>, Mohammad Al-Ansari writes:
>> > >
>> > >> The problem with this approach is that it relies on the CNG tones.
>> > >
>> > >I thaught, that all fax machines use CNG tones!
>> > 
>> > It is required in some countries. But not in North America. And for some reason
>> > some manufacturers took the opportunity to make it into and option. Some even
>> > went farther and made it default to off.  :-(
>>                    ^^^^^^^^^^^^^^^^^^^^^^
>> That's not nice for fax switches :-(
>

[...]

>
>And here several modem fax software packages fail too:
>
>I have tried BitFax Class 1 V3.09A, DosFax lite V2.00 and WinFax Lite 
>V2.0. They DON'T start a transmission with the CNG tone but wait for the 
>CED signal of the called station. 
>

This is strange since I have WinFax Lite which came with my SupraFaxModem
and it *does* generate CNG tones when it initiates a call. 

Incidently, the Supra modem has an option that can be used with the ATD
command which is the character ^.  If you dial using a command like
ATDT^123-4567, the modem would start sending CNG commands just as it begins
dialing, and it continues to do that until it connects.  I think that the
software uses this kind of command to generate the CNG tones.

Might it be that you modem does not support this command? Or maybe your
version of WinFax Lite is not doing this. Try this command (or any similar one
that might be documented for you particular modem) from a comm program and see
what happens.

>Then, if the called station is combo machine with fax + phone (+ answering 
>device) or a (human or automatic) fax/phone switch, these sw packages 
>are unable to send a fax because the switch on the receiving side never 
>gets a signal showing them an incoming fax is pending. Without calling 
>the receiving party before and announcing the pending fax transmission, 
>you don't have a chance to send your faxes! 
>
>In the meantime I have trained some of my fax partners with devices like 
>those mentioned to start their fax machines when they get calls with no 
>signal to hear on the line which will get the fax through. But if an 
>uninformed person picks up the phone, there is no chance again.
>
>Klaus
>
>
> ____    __  __  __    __   __
>|    \  |  |/ / |  | /|  | / / Dr.-Ing. Klaus Wolferts: dkw@wolferts.ka.sub.org
>
>|  |  | |  | /  |  |/ |  |/ / Ing'Buro f. EDV + Elektronik  
>| d|  | | k| \  | w| /|  | / Mitteltorstr. 45,            Phone: +49 721 706016
>|____/  |__|\_\ |__|/ |__|/ D-7500 Karlsruhe 31, Germany,  49x03'02"N 8x22'58"E


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Mohammad Al-Ansari                      | alansar@damon.ccs.northeastern.edu
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