[TUHS] Anyone have a modem wired up?

[Dan Cross]

On Wed, Oct 27, 2021 at 2:31 PM John Floren <john at jfloren.net> wrote:

> On Wednesday, October 27th, 2021 at 11:17 AM, Chris Hanson <
> cmhanson at eschatologist.net> wrote:
>
> > Obihai makes some decent, cheap-on-eBay, unlockable/hackable analog VoIP
> boxes that work just fine with not-super-fast modems. You won’t get 56K or
> even 33.6, but 9600-14.4K should be fine and a Telebit Trailblazer probably
> would be too if you want to use UUCP over dialup…
> >
> > — Chris
>
> I've got a Grandstream HT801 through my ISP (Sonic.net) which works fine
> for voice, and it previously did ok with the modem, but now when I try, I
> start to get garbage soon after the connection establishes (see
> http://jfloren.net/noise.jpg for an example). It happens regardless of
> who I connect to, and seemingly without regard for the connection
> speed--although at 9600, the garbage fills up the screen quite rapidly
> compared to a rather sedate trickle at 4800.
>

My guess is that the codec it uses is optimized for human speech and gets
confused by the range and levels of data modulation.

My modem-fu is rather weak, so if anyone recognizes what's going on, please
> let me know. I worry that it's just a noisy phone connection, but I was
> under the impression that modems had some sort of error-correction built in
> (this is a SupraFaxModem 288).
>

This depends very much on the modem. It might be painful, but I wonder what
would happen if you tried it at 1200 or even 300 baud (assuming those are
simple AFSK using two tones as in Bell 103 and 202 schemes).

        - Dan C.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://minnie.tuhs.org/pipermail/tuhs/attachments/20211027/7ae32e85/attachment.htm>