Re: flexfax: HylaFax (fwd)

[David Woolley <david@djwhome.demon.co.uk>]

> 
> 
> Hi again,
> Can someone help me. I am trying to solve the problem of Multi fax's (over 10)
> to a receiver. Someone told me to change ModemClass to 1, but when I did
> most of the faxes that queued did not go.

There are two basic possibilities:

The modem/phone line is sending a distorted/noisy signal;

You are getting corruption of the data between the computer and the modem
which in turn could be:

  - flow control failures;
  - electrical problems (these will be most severe at very high DCE/DTE
    speeds - when using a Comtrol Rocket card with one modem brand we had
    to wind back the speed a couple of notches - this was PPP not fax);
  - I have reason to believe that the Linux serial driver handles the UART
    in a way which causes some implementations of the UART hardware to 
    misbehave when interrupts are turned off on the fly, to stop output
    (this is not necessary on 8250 family (i.e. 8250, 16450, 16550, and
    their ASIC clones) UARTs).

Combining on and offline discussion from before, retransmitting is probably
the correct action from a standards point of view, but may not be the best
pragmatic solution, as many receivers use errors in the digital data, not
the underlying analogue quality, to decide whether a retrain is needed, so
will issue retrains for systematic digital errors, or for corruption whilst
in the digital domain.