🚀 go-pugleaf

Stefan Haller <stefan.haller@ascom.ch> wrote:
> I have to send a voice message to the local police if some alert in our
> central application appears. This message should be repeated until the
> person on the phone hangs up. Additionally to that, a Fax has to be sent
> to the police, too.

Ideally, we could make so that the user must press 1 if he acknowledges
the message.

> Other alarms are sent via Fax or pager to the service personel of the
> customer.


> I don't understand how I can do that. mgetty has to run as a daemon,
> doesn't it?
> How can I access the device with a paging application without disturbing
> the daemon?

lock files. Your application creates a lock file, open the /dev/ttySx
device, and mgetty shuts up and doesn't access the device until the
lock file is removed. message.sh does exactly that (well, vm
does). Also sendfax does that. Only incoming calls are handled
by mgetty/vgetty.

> Mgetty itself should not reply to any incoming calls.

If absolutely no incoming calls happens, then there is no need for
mgetty/vgetty in any inittab: outgoing faxes are handled by sendfax,
and outgoing voicemail by a vm script.

> We had an application that supported paging and fax, hylafax, but it
> does not offer any voice functionality. And it runs as a daemon as well.

If it uses proper locking strategies (that is usually no problem), it
will interoperate.

> What do you mean with "proper"? What do I have to look for in those
> applications?

- Use the same device name everywhere (call-out and call-in), on
  Linux this is /dev/ttySx
- Check that lock file locations are the same for all software.

With packaged software (e.g. debian or SuSE), this is usually OK with
recent (ie less than 2-3 years) distribution. The only thing you want to
do is to download the latest 1.1.21 mgetty release, maybe apply some
vgetty patches, and compile yourself -----> beware of lock files
and stuff.

> For the customer installation, we'll have to buy a new modem.
> But for these first testing steps, I'll use the USR. But thanks for your
> advice.

I mean, if you really want this to work, even a very bad modem should
be ok (most of the problems are that firmware upgrades sometimes change
the command set, etc).

One thing which I know for sure doesn't work is the hang down detection
(ie the caller HAS answered the phone). The ZyXEL supports that.
For most US Robotics, you are lucky since we already implemented a
work-around (in the latest vgetty patches), using ring-back delay
(ie the time that there was NO ring).

> Data Modems over the public phone network (PSTN) reached data transfer
> ratios around 4800bps at most(!), depending on their geographical
> location. Could that have any serious effects on the application itself?

For voice, no, except maybe some quality degradation. For data or
fax applications, it depends, you may have hangups, or slowdown.

PS: there IS a SMS application in mgetty, called tap/, but it's
    specific to germany.