Mediant 500 VoIP Gateway and Enterprise Session Border Controller (E-SBC) with 1 E1/T1 voice interface upgradable with software license for SBC sessions. Includes Mediant 500 chassis, single E1/T1 voice interface, 4 GE ports, a single AC power supply. Software license for SBC sessions may be purchased separately. For information on the maximum supported SBC sessions refer to the Mediant 500 Release Notes.