Includes Mediant 1000B chassis, 1 Active/Standby pairs of GE interfaces, three modules of 2 E1/T1 spans, 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.