asterisk users - Dec 2004 - NewBie Question Modem Telephone -PSTN

Hello, I'm really new on Asterisk.
Is it possible to use a telephone machine connected to a modem as an asterisk
voice input output device? I do not need PSTN connection.
The scheme i'm  thinking about is;

user -> phone -> modem -> asterisk -> ip -> vice versa.

If it is possible can a user dial another asterisk user via the phone?

 I've searched astersik lists but couldnot find any help on this issue.

Sorry for bothering and thanks alot.

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