ABB TB820V2 INDUSTRIAL PLC SUPERIOR QUALITY PRODUCT FREE SHIPPING WORLDWIDEThe TB820V2 ModuleBus Modem is a fiber optic interface to the ModuleBus. The ModuleBus Modem has an electric and an optical interface which are logically the same bus. A maximum of 12 I/O modules can be connected to the electrical ModuleBus and up to seven clusters can be connected to the fiber optic ModuleBus.