COMs are essentially embedded computers built on a single circuit board. What differentiates the COM from a conventional single-board computer (SBC) is that it lacks the standard connectors needed to directly connect external I/O devices. Hence, the module would be mounted onto a carrier card or baseboard that breaks the system and I/O buses out to allow for connection to standard peripherals. That carrier card can also break out to custom I/O if needed for a particular application.