The C1220 is an ISA PC interface card designed for Beckhoff Lightbus. It connects a PC to the Lightbus fiber optic network, enabling fast processing of process images from sensors and actuators. The Lightbus system uses a fiber optic ring structure, providing high immunity to interference and a data transfer rate of 2.5 Mbaud. Communication with the PC is handled via DPRAM for efficient data exchange. The Lightbus protocol is optimized for speed and simplicity, with integrated diagnostics for ring error detection and correction