Dymec models 5843 and 5844 are hardened fiber optic Link/Repeaters that convert RS232 or TTL level copper to amplitude based fiber output. Supports data rates from dc to 250k bps, DCE or DTE port configuration and a diagnostic/test mode that allows testing of the copper and fiber connections before the connected IED is active in the network. By simply setting a few switches, the Dymec 5843 and 5844 Link/Repeaters can be configured for point to-point, star, optical bus, or loop networks, and permit quick, easy connection of devices. For example, an extensive multi-drop network - where two or more intelligent electrical devices are connected and communicating-can be constructed simply by connecting the devices through Link/Repeaters. Dymec 5843 and 5844 Link/Repeaters may optically connect devices of different formats, eliminating the need for format converters. For example, an RS232 IED may be connected to a model 5844 which is optically connected to a model 5846, which, in turn, can communicate electrically to its IED in EIA 485.