Help on setting terminal lines (secure)

[Peter Eckhardt]

Does anyone know, how to specify dial in security on a
terminal line? I would like to set up the following
security scheme
    - our employees, should not be allowed to dial in but
      should be allowed to log in at our company ( on a
      terminal not a modem line )
   - our customers should be allowed to dial in ( and get
      a secure environment = Application Program, no shell)
   - i want to log in ( via modem ) and want to be called
     back by the system.

Is there anyone out, who tried anything like that ???
Any help is appreciated
Thanks

Peter Eckhardt