At 09:40 27/08/99 +0800, you wrote:
>Hi All,
>        I have been asked by some Morse coders to explore the possibility
>of using a micro to set an AT-command style modem into 300 baud to
>communicate via a hand operated Morse key.
>
>  At the moment these guys are using dumb modems to send Morse to each
>other all over Australia,  dumb 300 baud modems are getting harder to come
>by so they are looking at using smart modems with a 'little black box' to
>handle setting the right mode and interfacing to the key and sounder.
>
> If anyone has some time to spend on this let me know.  I am sure lots of
>people
>have done some sort of telemetry over a modem and have some handy routines
>to
>simplify this task.
>
>  My one concern is that today's smart modems are not going to like sending
>or
>receiving data that is not framed correctly.  If anyone has some direct
>experience of
>any brands that will be good or bad, or ways around this please don't stay
>quiet!
>
>  As many 'dumb' modems are already in use and hooked up, compatibility
>between
>the smart and dumb versions needs to be maintained.  e.g.. no packets of
>'key on' 'key off'
>
>
> Any comments truly appreciated,  I have played with 16C84's a while ago
>but fairly open to other options.  Cost is significant as most of the users
>are
>on a pension.
>
>
>        cya,    Andrew...
>
>


I suspect that you are after BELL 103 as the comms rate. This is something
that most modems will do and assuming a standard AT command set, you can
use things like AT&F to set default connections and then set the nominal
connect rate eg ATB1 etc. Unfortunatly, there are some modems that now use
a differnt method to setting the speed/connection type (Banksia for
example) I suppose that the okd NETCOM may be the best bet (Has a good
manual too!) The MNPT type correction protocols can be turned off and the
thingo will operate like a dumb modem.

No on this matter a bit more, In fact you can save the configuration in the
NETCOMS and it will come up in this mode each time, except for the ATH and
ATA and ATD commands that will be required to get the things to connect. In
general, this should be a simple task, 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).

For the small extra cost I would put on a universal modem chip (Could also
use things like Exar tone decoders and generators etc.) an put the entire
thing into a small box (Most universal modems are a bit of a current
sucker) but the entire thing could be done for around $40 (Cost only)

Dennis