Re: [hylafax-users] MultiTech ZBA

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

On 2003.10.08 14:20 An Intrepid HylaFax User wrote:
> I have a MultiTech ZBA V.92 super-duper ($$$$) modem coming in the
> mail.
>
> It claims to support Class 2.1 - is this something I should use?

The only significant advantage of Class 2.1 over Class 2.0 is V.34 
support.  I'd recommend you run some real-world tests to determine 
which one will be better for your application.

> I'd
> like
> to exploit 2-D MMR if possible as I imagine most modern business fax
> equipment supports that.

Class 2.0 supports MMR, also.

> How are these modems best driven for outbound fax reliability?

They've been good for me.

> The
> HylaFAQ
> has Multitech all over it as a "recommended" modem - I hope I've not
> picked
> a turkey.
>
> Most of my outbound fax destinations are overseas, where quality of
> telephony may be marginal.  Is ECM a hindrance or a boon to such
> places?

It depends on your faxing goals.  If you want to ensure the remote has 
a perfect image at all costs then ECM is a must and V.34 should not be 
used as CTC attempts are not allowed in V.34 calls.  However, it will 
almost always (except, perhaps with the benefit of MMR and/or V.34) 
take longer to send than without ECM.  If you're trying to send a lot 
of faxes quickly, then you'll need to determine what is best for you.  
ECM does have an option to "minimize" lengthy calls by eliminating CTC 
attempts.  This can cause some destinations to receive incomplete 
images, when the line is very noisy, but it will only be to those 
destinations which were having trouble receiving data properly.  To 
those destinations you'd have to send without ECM to make the 
transmission quickly since it will likely accept more readily the data 
with partial errors.

Anyway, you'll need to test.

> Are there S-register settings for noise-floor and/or sensitivity that
> might
> benefit from some tuning?

The only one that you should need to consider is the AT+FRY command 
which enables/disables CTC in ECM.

Lee.

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