Unidentified subject!

[searchen]

I would like to know how I can configure my Linux-server so that I can call on 
it. The server is not always connected to the internet. I'm using ISDN to call 
in on my provider. So the server has a ISDN (Teles 16.3) card. 
I want to be able to use another computer with a modem or ISDN card to login on 
the server. (I want to be able to login using Linux or Windows). 
Can anybody tell my how I can do this???