> >Mike A. Harris <mharris@ican.net> wrote:
> >> from thereon of course one needs to enter AT commands, but as
> >> soon as +++ is entered, the modem instantly responds with "OK".
> >ATS2=255 or modem equivalent. Hangup only on DTR dropping.
> It isn't clear to me what you are trying to point out here. I
> was just stating that when I type "+++" on any modems around here
> with any terminal emulator running, I get an "OK" greeting from
> the modem. The modem happily responds to any AT commands i give
> it, and stays online. An "ATO" switches back to data mode,
> however an ATO will kill the connection on some connection types.
> I believe one of the error correction modes disconnected on an
> ATO in command mode while online. MNP5? I dunno...
There are three basic modem types you are likely to encounter.
The first is the "Hayes patented" escape sequence:
<delay> + + + <delay>
Where <delay> is typically 10 seconds.
When Hayes started trying to enforce their patend on the time
delimited escape sequence, modem manufactures came up with "ties" (Time
Independent Escape Sequence). This eliminated the delay and just triggered
on the "+ + +".
That gives use the second (and most ANNOYING) class of modems:
+ + +
That gets tripped over A LOT! Best thing there is to kill the
escape character by setting S2 to 255 (or 127 - some modems will not
accept anything >= 128 there).
The next "improvement" to "ties" was to require an AT sequence
to follow the + + +. That gives this:
+ + + A T [valid AT Command]
This is much more "noise immune" than the simple + + + which can crop
up in encoded data all too easily.
For a while, Hayes employees where signing their E-Mail with a
signature block which included "+ + + A T H 0" at the end of one of the lines.
Guess what that was for... :-) (ATH0 says to hang up the phone).
Sooo... Your milage WILL vary on these tests depending on which
of the three general classes your modem falls in. A simple "+ + +" will
only bust the lamest class. A "+ + + A T H 0" will take out that and the
next but leave the true Hayes compatibles alone...
Note: Spaces inserted in all of the modem commands listed above
to avoid random acts of terrorism... :-)
> --
> Mike A. Harris Linux advocate GNU advocate
> Computer Consultant Open Source advocate
>
> News for nerds, stuff that matters: http://slashdot.org
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.rutgers.edu
> Please read the FAQ at http://www.tux.org/lkml/
>
-- Michael H. Warfield | (770) 985-6132 | mhw@WittsEnd.com (The Mad Wizard) | (770) 925-8248 | http://www.wittsend.com/mhw/ NIC whois: MHW9 | An optimist believes we live in the best of all PGP Key: 0xDF1DD471 | possible worlds. A pessimist is sure of it!- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/