Combination Output Interface (COI) With Connectors | 80-911-0119-00Combination Output Interface (COI) with connectors 80 911 0119 00 The Combination Output Interface (COI) combines multiple input and output devices in to one module, offering a compact and intelligent replacement for traditional DC fuse boxes and circuit breaker panels with digital switching technology. Mastervolt is a pioneer in digital switching, a proven CANbus technology where a single data cable is used to operate clusters of switches. In large