Hub expansion module 2x hub 100 BASE-TX The POWERLINK bus controller X20BC8083 and the stand-alone hubs X20HB8880 and X20HB8815 are equipped with a modular hub expansion. An additional 1 or 2 slots are available. depending on the bus base used. The X20HB2880 hub expansion module can be operated in these slots. The status of the module and network are indicated by LEDs