Includes Mediant 1000B chassis, one Active/Standby pair of GE interfaces, including one module with 4 spans E1/T1 and 60 VoIP channels for PSTN Fallback/Lifeline configuration, single AC power supply and fans. Chassis can be expanded with any Mediant 1000 Voice modules such as FXS/FXO/BRI or T1/E1. Order M1KB-SWX module for additional 2 pairs of Active/Standby GE interfaces.