The system of Classes of Service (COS) helps defining rights for one or another extension in the PBX or Centrex systems. For example, few groups require more space for storing voice messages, while other need the redirection of calls to cell phones, the third does not have to make calls outside of the office network. With the help of this system one can change and configure settings.
Citel Technologies , A Voice over IP Phone company that provides VoIP Business Phone Systems. Its Main products include EXTender, PBXgateway, Upgraded Hardware Products, PBX platforms etc.