[Asterisk-Users] Application Faxing using SIP

[Phil Blundell]

On Sat, 2006-02-18 at 22:04 -0800, Lee Howard wrote:
> Traditional faxing (not T.38) pretty much requires a lossless audio 
> channel.  Normally the best way to get this is with PSTN channels/lines 
> through a Zap device.  That said, VoIP channels can be configured such 
> that they are also lossless.  IAXmodem, for example, functions on the 
> premise that an IAX2 channel passing over the loopback device will be 
> lossless.  I have also seen lossless SIP and IAX channels running over a 
> WAN, but they were very specificially configured, and I wouldn't expect 
> most connections with traditional VoIP providers to be anything near the 
> kind of losslessness that is required for this to work well.

I have a PRI terminated in a TE110XP card on my Asterisk box.  Right now
we are using a separate analog line for faxing, but (for a variety of
reasons) I would like to switch to sending and receiving faxes over the
PRI via Asterisk.

What's the recommended way to do this?  The three obvious options I can
think of are:

1. Connect the fax machine to an ATA and have it speak SIP or IAX to *

2. Fit a TDM400P with FXS linecard into the * box and connect the fax
machine to it directly.

3. Replace the TE110XP with a multispan E1 card, connect a channel bank
to the second span, and plug the fax machine into that.

Option 3 can be ruled out immediately for us due to cost.  Option 2 is
quite appealing, but I've previously been told that running multiple Zap
cards in a single machine is not a good idea.  Option 1 seems like the
cheapest and easiest, but I have no idea how reliably faxing will work
over an ATA.

Thanks for any insight.

p.