We have a dial-up connection that is set to automatically shutdown after 1 h of usage.
I am to extend this to a longer period. Where is this setting usually stored, i.e. which file should I edit?

I think there are few options
what dialer are you using?

I wish I knew...
The only thing I know it is a FreeBSD server. I can login and su into it, but the dialer was set up by an other guy whose help is unavailable.
Then how can I determine the dialer first?

How exactly do you login, in X or in a term?

In term with SSH.

Just reading the ssh man and it sounds like you edit the config file and change KeepAlive to 'yes'. You can also enter verbose or ssh -v to see what happens to kill your connection after the hour.

I do not think this is a question of an SSH setting, since even those guys who do not use SSH just browse the internet via that dial-up connection are disconnected when the one hour is over.
Or do you rather mean that SSH can somehow keep alive a dial-up connection even if the connection termination is programmed somewhere else? I suspect that this is a hard limit, that cannot be overridden by keep-alive requests.
However, I may give it a try tommorrow when the next connection is due...

I have heard of some whacky internet providers doing things like that, if you haven't talked to them about it, or read your contract, then that might be your problem too.

you need to check dialin config like wvdial.conf, or
in /etc/ppp/ there are bunch of configs, all depends how do you dialout, ( with what program)

I found /etc/ppp/ppp.conf on the machine (and there is no vwdial.conf or conf files of any other dial-out programs - at least so far as I can judge).

So, is /etc/ppp/ppp.conf the place where a timed shutdown of dial-out connection (after 1h) can be given?

How?

I just came to the idea that there may be a unix command that establishes a ppp connection, and an other that disconnects it. If so these may be given e.g. in the root user's crontab. Am I right?

P.S.
I have to make pre-fabricated ideas, because the daily one-hour ON state of that connection is short and so slow via SSH that I hardly have time to anything once connected.

Just look at it. If you don't want to bring ppp.conf up in an editor, enter this:

less ppp.conf

You can look at the file without altering it in any way. If you see something that looks like a timing control entry, then get out of the file by hitting the "q" key. Then open it up in your favorite editor.