A network call admission control system receives a call and determines a call characteristic requirement and a network characteristic parameter. And, a vacuum system is provided with only the quadrupole mass spectrometer which measures partial pressure strength according to a gas type in the vacuum system from an ion current intensity and does not have an ionization vacuum gauge other than the quadrupole mass spectrometer. The graphical user interfaces are also suitable for previewing or purchasing media items in an on-line manner. A heater is provided on the underside of the bottom plate for heating the vapor.