[kwlug-disc] VOIP and Direct Detect (offtopic)

john at netdirect.ca john at netdirect.ca
Sat Feb 20 08:12:12 EST 2010

This customer had an ATA, probably a sipura (it was a while ago) that connected the fax to an asterisk box. 

I think it generally worked because the LAN between the two was not heavily used (two PCs and two servers). 

What would have worked better is a telephony card in the Asterisk box or a dedicated ethernet connection. 

A solution like a fax machine connected to a telephony card in asterisk connected to the PSTN through a telephony card would work very well. Render a movie on the asterisk box and I bet you'd kill the fax connection. Pass the fax connection through a loaded network and it would affect the fax. In other words add any inconsistent delay and it affects the fax. 

There is a VoIP protocol for sending faxes over a network. I haven't checked lately to see if asterisk supports it yet. Fax is slowly dying in favour of email and scanned document attachments. So I'm not looking to innovate there myself. 

John Van Ostrand , CTO, co-CEO
Net Direct Inc.
564 Weber St. N. Unit 12
Waterloo, ON N2L 5C6
Ph: 519-883-1172
Fx: 519-883-8533

----- Original Message -----
From: unsolicited [unsolicited at swiz.ca]
Sent: 02/19/2010 11:52 PM EST
To: KWLUG discussion <kwlug-disc at kwlug.org>
Subject: Re: [kwlug-disc] VOIP and Direct Detect (offtopic)

John, in the case you mentioned:
- what were they using to connect the fax to asterisk? (A board, a ???)
- in your experience, did the fax work because of asterisk, or did it 
just work? i.e. With the SPA-3102 'directly connected' to unlimitel, 
should faxing also have worked, or did asterisk make something happy?

john at netdirect.ca wrote, On 02/19/2010 5:57 PM:
> kwlug-disc-bounces at kwlug.org wrote on 02/19/2010 04:54:17 PM:
>> I know this is off topic, but since there are a few VOIP experts here,
>> I am humbly requesting any advice I can get.
>> I am moving into a new house in a couple weeks and was just thrown a
>> curve-ball. I just found out that the Kitchener won't give us an
>> occupancy permit unless we have this direct detect service:
>> http://www.kitchener.ca/city_hall/departments/devtech_services/fire/
>> direct_detect/residential_monitoring.html
>> Of course, they "say" that it only works with a Bell phone line.
>> Apparently it is just a device that dials out when the smoke alarm goes
>> off. I have convinced them to let me "try" it with my voip ata.
>> I'm going to get DSL service at the house on the first, and our
>> inspection is on the second, so I need this thing to work right away or
>> problems will ensue.
>> I'm considering involving my lawyer if this delays our occupancy
>> permit, but I'd like to know if anyone here has used this system with a
>> voip ata? Any chance this will simply work?
>> note: I'm using a linksys spa-2102 with Acanac and have been using it
>> for over a year, so it's already configured correctly for phone use.
> It would depend on how the detect-direct data communications is happening.
> Typically modems and faxes don't work reliably on VoIP systems. The 
> modulation requires predictable timing that VoIP can't reliably provide. 
> Also I've read that the echo cancellation also effects the signal. I've 
> read it's possible to dial a #99 prefix or something like that on some 
> ATAs to remove echo can, but I doubt the detect-direct box will know to do 
> that.
> That said, we've had customers use faxes connected to ATAs using an 
> Asterisk box on the same LAN fairly reliably. I say "fairly" because they 
> did have some problems but we never nailed it down to the VoIP before they 
> stopped doing business. I would expect trying to fax over VoIP through the 
> Internet would fail reliably.
> If the communications relies on touch tone signals it should work as long 
> as you have the proper DTMF support configured. Some configurations like 
> to eat DTMF so careful configuration may be needed.
> It sucks that you are paying for something that your taxes should already 
> be paying for.

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