Dennis Plunkett wrote:

> ... but when you say dumb modem I think that you mean very dumb in
> that a MARK on the input generates MARK, ansd a SPACE generates SPACE
> (Not framed as most serial stuff does).

  He does mean that and therefore *no* "smart" modem of any description
will behave this way.  They are all character-buffered; anything other
than a proper ASCII character cannot be interpreted and will, if
transmitted, be trashed.

  They must do this as it is necessary for the modem first to decode the
character to ASCII, see if corresponds to an element of an AT command
sequence, and pass it to the line according to this.  This process
guarantees no time coherence, only character coherence, and a "break" is
the command to go into command mode in any case.
--
  Cheers,
        Paul B.