Re: [hylafax-users] Clear Channel faxes

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

Brian Postow wrote:
> I've been trying (unsuccessfully) to use T38modem to have hylafax talk 
> to a Mediatrix FOIP box. The guy who sold me the box suggested that 
> T38 is a bad technology, and I should try Clear Channel. My google fu 
> is weak, and only comes up with radio stations and billboards.
>
> Does anyone know of a program that will simulate a tty for hylafax to 
> talk to and then send clear channel out the IP? I'm using a Mac, but 
> anything  unix SHOULD work, I think.

By "clear channel" the guy probably means using G.711 (VoIP) instead of 
T.38 (FoIP).  The difference being that G.711 communicates audio data 
and T.38 communicates fax data.  t38modem does not talk "clear channel", 
so to accomplish this you'd need to probably do something like use 
Asterisk and IAXmodem instead.

While it may be true that the T.38 functionality of the Mediatrix box or 
the T.38 compatibility between the Mediatrix and t38modem is so poor 
that it would be better to use G.711 instead of T.38, this is not a good 
recommendation more generally.  VoIP jitter interferes with the ability 
for the fax-modem DSP to demodulate the audio accurately all of the 
time.  T.38 compensates for jitter by transmitting packets in duplicate, 
triplicate, or quadruplicate (depending on configuration).

See: http://hylafax.sourceforge.net/docs/fax-over-voip.pdf

So if your Mediatrix box is receiving faxes via TDM then using VoIP on a 
short LAN network to get it to HylaFAX may work.  Likewise if the 
Mediatrix can work as a T.38 gateway and the leg between the provider 
and the Mediatrix is T.38 you may also get away with this guy's 
recommendation.  However, there are numerous reasons why it wouldn't 
work, and if it doesn't work reliably, and if the T.38 doesn't work 
reliably, then you may be out of luck with the Mediatrix involvement.

Thanks,

Lee.


____________________ HylaFAX(tm) Users Mailing List _______________________
 To subscribe/unsubscribe, click http://lists.hylafax.org/cgi-bin/lsg2.cgi
On UNIX: mail -s unsubscribe hylafax-users-request@xxxxxxxxxxx < /dev/null
 *To learn about commercial HylaFAX(tm) support, mail sales@xxxxxxxxx*