[sllug-members]: T1, Carriers And Info

[Chris Brown]

Adam,

  Fax machines WILL work, with caveats.  When using G.711 codec (the
industry standard for "good" voice quality), faxes work more or less
ok.  Often one or two pages will go without trouble, but when sending a
20 pager it's likely to encounter a failure.

  However, if using the T.38 protocol faxes can be very reliable.  With
T.38 the ATA device (must be one that supports T.38, such as SPA-2102,
Audiocodes, Quintum, etc) the ATA device decodes (rather than encoding
like G.711) the Fax signal and sends the resulting data to the distant
end SIP termination device (which must also support T.38).

  Another related protocol, T.37, is store and forward.  While the T.38
protocol is a real-time streaming of the Fax data to the far end
termination device, T.37 completely receives the fax, then forwards the
data to the far end T.37 terminate to resend out the PSTN.  This
protocol is less common.  The advantage of T.38 is that the two fax
machines can communicate and agree to the best common features (such as
higher resolution, color, etc) while T.37 only uses the lowest normal
features since it has no idea what the far end device can support.

  On private networks I've been very successful with T.38 devices. 
Shameless Plug: Layer-4 (local VoIP provider, see below) can support
T.38 endpoints to ensure quality fax delivery.  They/we also provide
inbound Fax-to-Email such that all inbound faxes are received as emails
if you so choose.

Chris Brown
Layer-4, (801)990-3988
CCI Intellisys, (801)975-7466
Arrivaltel, (801)990-3990
cell: (801)949-0300


Adam Barrett wrote:
> I also have a follow up question about VoIP and Fax Machines.
>
> Are there any known problems? Will Fax machines work with VoIP?
>
> Thanks again!
>
> On 2/28/07, Adam Barrett <dragen at gmail.com> wrote:
>> Hey All,
>>
>> I have recently taken a position with a small company, we are looking
>> into moving our phones to VoIP, for all the good reasons, and I was
>> talking with my current carrier and as best I can tell I have a single
>> T1 line, currently running 6 phone lines.
>>
>> I was hoping that I could find some help here on Asterisk, as well as
>> what the heck I need to know to handle phones on my own, or in
>> conjunction with my carrier of choice.
>>
>> Does anyone have a decent site that explains the steps, tools, methods
>> for working with T1 lines, and the accompanying equipment?
>>
>> Can anyone suggest a good carrier who might support Asterisk in Utah?
>>
>> Can anyone suggest some books I should be reading before even
>> attempting this feat?
>>
>> I appreciate all the help you guys have offered in the past, and I
>> look forward to helping people too someday :D I just haven't settled
>> in my knowledges yet.
>>
>> Thanks!
>>
>> -- 
>> Adam Barrett
>> dragen at gmail.com
>> ______________________________________________________________________
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>
>